Posts tagged #Technical

Hydraulic Brakes. Make Them Like New Again.

Hydraulic Brakes are one of those components that everyone wants to have and then, when things go wrong, they bail and become anti fluid and pro cable actuated. I will admit that there are some good cable actuated discs out there that are very good, the Avid BB7 for instance, however, nothing comes close to the feel and operation of a good hydraulic system. That is why it is a shame when people ditch them. Even some bike shops are more than happy to sell the hydro's but don't want to mess with them afterwards for service. A hydraulic brake system can be ordered as a kit, hoses attached and filled with fluid. You can always tell a system that has come this way as it will have 3 feet of extra hose in a big loop off the bar, just waiting to be snagged by a passing Moose or even a tree limb. Now sometimes this is just laziness on the part of the mechanic but often it is fear of cracking the system open. So here is a little primer on the hydraulic disc brake system...

I have already mentioned Avid above, apart from making the BB7 they also make some great hydraulic units, the older Juicy and Code plus the newer series of Elixir and Trail. All of these models are easy to service and durable apart from working very well. Shimano also make a range that are popular and again easy'ish to service and repair. Other companies that we are fans of are Formula and Hope, both of these produce disc systems that also qualify as works of art, sadly they also  have price tags similar to a minor work from Rembrandt...

So, back to my point. What do you do when things start to go sideways? Well you service them.  Below I have taken some pictures of the complete internals of a set of Avid Juicy levers and calipers. These brakes recently came to us from a customer at the Lake of the Ozarks and they were in dire need of some TLC. These brakes are very common but basically all hydraulic brake units are following the same principles, so with a spec sheet of your particular make and model you will be in good shape.

These particular units had developed one of the common issues of older neglected sets. They had developed the sticky lever syndrome. Another common issue is a soft lever which means air is in the system either through the need of a good bleed or the hose has developed a hole or an o ring has failed on a bleed port. The sticky lever however means that the internal plunger in the lever is in need of replacing or that the caliper pistons are beginning to stick and corrode. My rule is; do both, if one end is gummed up and failing the other ain't far behind.

Wear gloves as DOT fluid is not something you want to be bathing in all afternoon and a pair of safety glasses, you would be amazed at how often I have shot myself in the face with a full syringe of this stuff.

I usually start with the lever first and, with a new bag of the correct internals, start cracking it apart. Below is what you end up with, again this is a Juicy so you will have a different looking pile of bits but they will be doing the same job.
Once the lever blade is removed it will reveal the circlip that needs to be removed to slide out the reach adjust mechanism and the plunger.

Reach adjust mech is next. If yours is a more basic model this will be missing.
In this case the parts were worn
All the parts laid out ready to clean. In this instance everything is being replaced except the body the blade and the reservoir cap.
The main culprit of the sluggish lever return is the plunger unit, in the above picture it is the thing with the spring attached to it. However when you are pulling it apart you may as well replace all the bits as they are all in the rebuild kit anyway.

Once the lever is rebuilt I attack the caliper. Again disconnect the hose first. The only way to get into the pistons is to split the caliper body in half. this is achieved by undoing the three bolts. Once you have the body in two the fun begins. The way to get the pistons out of their press fit home is with the use of compressed air. You cannot get them out any other way so don't be jamming screwdrivers in there or you will damage the body itself and you will get fluid leaking out and the whole unit will become a paperweight. The compressed air does a great job of popping them out. Warning; Make sure you don't have the thing aimed at anything soft and fleshy, it will hurt...
Waiting to be cracked open like a walnut...
The main culprits in here are the quad rings (the square edged rubber washers) and the round pistons.All of which will be replaced.
Once the caliper has been rebuilt all that is left is to run new hose, to the correct length as mentioned earlier to avoid lassoing stray Moose... Also never re-use banjo fittings or crush washers. Once they have been tightened up they have to be replaced. That's it, job done. Go ride.
Good as new.



Posted on April 13, 2014 .

Square Taper Crankset Woes.

The method of affixing crank arms to a bottom bracket spindle using a square taper system has been around for many, many years now and even though we have had lots of designs since it is a method we still see a lot especially on the comforts and hybrids and anything that comes from a box store.

Because we see a lot of these cranks on the cheaper bikes does not mean that it is a bad method, White Industries make a very high end crank set that uses a square taper fit and Phil Woods produce some of the most expensive bottom bracket cartridges ever in square taper format.

If the square taper crank to bottom bracket interface has ever had a problem it has been with installation and maintenance. The basic principle behind the method is that the crank arm gets tighter as it is drawn onto the square spindle because of the tapering. The most comon issue we see is the crank arm bolt coming loose or falling out completely and the bike is still ridden. Even though the crank arm is tightly fixed onto that spindle with the bolt gone the pedaling action will break the bond within a mile of riding. Now here is were it gets interesting. People just assume that a new bolt when they get home and a wrench to tighten it up will solve it. Wrong. When the arm gets loose and you continue to ride it the square hole in the crank arm just mushrooms out. The crank arms are made of soft aluminum and the spindle is steel. Once that crank arm hole becomes deformed it will never stay put, no matter how tight it feels when tightening it back up. The only cure is a new crank arm.
This is a typical example of a crank that became loose and was still ridden.
This is what they are supposed to look like
The above are pretty generic examples of the square taper cranks that you see on multiple bikes nowadays. Below is a picture of a White Industries VBC crankset and bottom bracket. This one was recently installed on a Ti Moots road frame and made a significant upgrade to the bike.
White Industries VBC crank set in anodized black.
The bottom bracket to match.
One slight issue that you have when using the white industries bottom brackets is the choice of spindle lengths or the lack of choices. In the event that a different length is needed then the Phil Woods bottom brackets are a great alternative.




Yearly Maintenance. (The Bottom Bracket)

 This is the time of the year when the workshop is full of bikes waiting for their annual check up. Mixed in with the bikes that we see every year are the bikes that have just been dragged out of the barn for the first time in 5 years and were put up wet in the first place. Those bikes are always interesting to pull apart and really highlight what can happen to bikes that have suffered some neglect.

However it is just not neglected bikes that have problems, any bike that is ridden regularly and hard throughout the year desperately needs that overhaul before the new season starts. Recently we had just such a bike in the workshop. This bike is one that has been overhauled by us before, not yearly I think we did a frame up rebuild on it 3 years ago, however the bike always is cleaned and lubed on the outside by the owner and kept inside.

Below is a picture of what we found inside the bottom bracket shell, once we had used a breaker bar and 2 of us to get the cartridge out!


 Keep in mind that this is an aluminum frame so that is not rust from the frame itself that you are seeing however aluminum does create a powder like substance under the right conditions. This is a mixture of sweat and moisture that finds its way down the seat tube and also the cartridge itself being steel bodied can supply some rust to the mix as well.

Moral of this story is. "If it looks good and clean on the outside, it doesn't necessarily mean everything is cool inside..."
 
This is a bottom bracket tap. The threads were so damaged after removal we had to re-cut them. Not an ideal scenario but the only option at this point.
This is the material that was removed in the re-tapping.       
Posted on April 2, 2014 .

How Not to Treat Carbon

             I have written many times on the subject of carbon fiber and rarely does a week go by without someone thrusting a scratched or damaged carbon doodad under my nose and asking is it OK.  Well last week we had a bike come in for a full overhaul and prep ready for the new race season with a couple of good examples of carbon fiber that is definitely NOT OK.

             The parts in question are a carbon drop bar and a full carbon seat post. These two components are the most common to suffer abuse and these examples are the most common way to kill them. Over tightening the clamping pressure. The handlebars have been squashed in the stem to the point of cracking through all the layers on both sides of the face plate. The seat post has suffered a similar fate by being  over torqued at the seat clamp. Both these components are dead and will fail in a spectacular fashion if used further.
             If you only buy one tool in your life let it be a torque wrench.
Again, probably twice the specified torque on the stem face plate to cause this.
Carbon has been squashed so hard it has made a peg in the carbon.
Posted on February 20, 2013 .

Raleigh Competition Renovation

Recently we had a renovation project come through the doors, a 1973 Raleigh "Competition". This bike had been owned since new by the present owner and he had decided that it was time for a makeover.

Before the new paint and decal job.
What started as a simple pull apart, service and rebuild turned into a pull apart and update everything to a modern Campagnolo group and a custom wheelset.

First the frame was treated to a blast and full repaint including a new original spec decal set and three coats of clear-coat. The frame then had the lugs highlighted with gold pin striping. A new custom wheel set hand-built by myself and sporting a set of Eldon rims and a matched set of high flange polished Velo-Orange hubs.
Back from paint.

The customer wanted the build rounded off with a 10 speed compact group from Campy.

The conversion was not without its headaches and a lot of small shims and add-ons had to be handmade to get the new technology to work. However the end result was definitely worth it.

Complete and ready to go.

High gloss and gold pinstripe, classic 70s...

Posted on February 17, 2013 .

Q-Factor

            The previous post on crank-sets made reference to a dimension called the "Q-Factor" This raised a few questions along the lines of 'What the hell is a q factor???' So, here is the definition and why it is important.
            The Q-Factor is the distance from the point of pedal contact on one crank arm to the other, measured parallel to the bottom bracket. The little illustration below shows the measurement.
             Some people of a certain vintage refer to this dimension as the crank-set  tread, but nowadays it is universally called q-factor.
             In most cases we want the smallest q factor that is possible. The more this dimension increases the less clearance we have when cornering and for most body types the further out the pedal is the more the angle of attack under pedaling force. Think of this when you are running say, your legs prefer to function by being directly under your hips. If you widen your stance greatly you start to rock and loose some power. Also it puts pressure and strain on knees and hip joints.
             Why then don't we just make skinny crank-sets? Well we have clearance issues when building frames. We have to widen chain-stays on mountain bikes to get clearance for big tires, the chain rings have to be allowed for. All these things dictate the minimum q factor. With the compact double road bikes with minimum tire clearance we can get crank-sets with the narrowest tread.
Posted on December 13, 2012 .

Bicycle Measurement

              You would think that the task of measuring a bike would be a very simple one but alas, as with most things in life, we have made it complex and ultimately very confusing. Over the years a few different ways of measuring frames, seat tube length specifically, have evolved. Sadly they have all become commonly used among the many frame manufactures out there, I have even dealt with manufacturers that have utilized 2 different methods of sizing within their range of bicycles. Needless to say this can get very confusing and needs to be kept in mind when purchasing a bike, especially when using an existing bikes measurement as the foundation for a new one. In my opinion buying a new bike in a size based solely on the fact that it is the size of the previous one is a bad way to go about things anyway but can be disastrous if the frames have been measured to different points.
 Today’s modern frames are designed very differently from the older, horizontal top tube, bikes of yesterday. The new geometry of compact frames with sloping top tubes are designed to have lots more visible seat post and can vary a lot from design to design so, again, sticking with the size of a previous one for the new and expecting it to fit like the old probably is not going to happen. Always get a new bike fit done on the bicycle style and design you are contemplating.
             The drawing below shows the various points that are used when quoting seat tube frame sizes. All have a starting point at the center of the bottom bracket but from there can be measured to the top of the top tube, the top of the seat tube itself or even to an imaginary line which represents the center of the top tube if it were a horizontal design
Click Image for full size.

There is actually another one that is only used by frame-builders when building custom frames and that is; to the center line of top tube where it will actually be. This is because we are building a bike to an individual’s body measurements and the tube dimensions are already factored in. We also work from center line dimensions when setting the frame jigs.


With all these methods you can see how varied the results can be. Looking at the frame in the picture you can see that there is quite a difference from   the shortest measurement to the longest on the same frame. I have always thought that the most important measurement on a production frame nowadays is the effective top tube length. When comparing a favorite frame to a possible new addition this is a good comparison measurement to start with, but again a proper fit is the way to go.

Posted on December 4, 2012 .

Alfine 11 Shifters.

                The recent post on the new Shimano 11 speed internal hub created quite a stir and I have had many questions regarding it. One of the main queries has been whether you can run it with a drop bar STI lever. Answer; yes you can. There has been a drop bar brake shifter around for a while as an option for the older 8 speed Alfine hubs and that manufacturer, 'Versa', produces a lever for the new 11 speed unit.
The Versa 11 speed cable actuated shift brake lever.
                However that is not the only choice, for those of you into the whole Di2 electronic shifting experience Simano produce a dedicated 'Alfine' specific electronic shifter.
The Shimano electronic Alfine 11 speed shifter and cable brake.
            Both of these options come with a matching left brake unit which is obviously just a brake.


Posted on December 2, 2012 .

Shimano Alfine 11

           As anyone who knows me will tell you, I am a big fan of internally geared hubs, from the old Sturmy Archer systems through to the new crop from Shimano, I think they are the best option for anyone who is a recreational rider, they are hassle free, need very little adjustment and are easy to keep clean. Another plus for people that transport bikes in the back of a car or pick-up is that there is no derailleur hanger to bend. Nothing screws up the shifting quite as quickly as a bent derailleur hanger.
          However, as much as I am a fan of internals for Recreational riding I have never recommended them for aggressive mountain bike applications. Except for one model, The Rohloff 14 speed internal hub. These hubs are in a completely different league and that goes for price as well, a Rohloff setup usually runs around $1400.
          Recently though Shimano has stepped up the game a little, the new Alfine 11 speed hub, although looking similar on the outside to the 7 and 8 that preceded it, are completely re-vamped internally. The 11s are even running an oil bath system just like the Rohloff. A sign that things have changed somewhat is the emergence of some cyclo-x rigs running the new Alfine 11. The hubs are also compatible with the new Gates belt drive setup. It is a bit soon to tell if these hubs have the durability required but initial feedback seems quite positive. We have a couple of projects in the workshop at the moment, which will feature a little later here on the blog, and an Alfine 11 is definitely on the short list as the drive choice.
Alfine 11. Total gear ratio of 409%.

Posted on November 19, 2012 .

Bottom Bracket Conversion

          A common problem that arises nowadays, with the influx of new bottom bracket standards is what, why and how to move from one system to another. With the threaded bottom brackets of old there was not many issues with a change to the newer outboard bearing systems but, with the move to frame specific systems, the switch is no longer as simple or, in some cases even possible.
          One of the most common issues is the press fit systems more specifically the PF30 and BB30 standard. Whilst both these systems are good and make for a solid crank interface often the issue arises because the frame has been purchased as an upgrade for a specific build kit already owned and the owner needs to convert the bottom bracket over to a threaded external system. There have always been a couple of options for this however, the good folk at Praxis Works, makers of our favorite chain-rings, have come up with a superb new conversion kit for the purpose.
         One of the biggest problems with conversions and even the press fit systems as a whole is that they tend to creak and groan. This is because the adaptors are, like the bearings, seperate from each other. With the Praxis system the cups are actually conected to each other by means of a threaded sleeve. This sleeve is very tightly machined but also as it is installed it flares out and takes care of any wiggle that may cause problems.
          If you are thinking of doing a conversion or have already performed a conversion with another product take a look at the Praxis system. It is the only way I will go in future. If you want more information or need a kit just let us know as we are Praxis dealers and use the full range of their products.

www.praxiscycles.com

Posted on November 14, 2012 .

Airless Tires in our Future

A Colorado engineer has come up with a new tire design. Not just another new tread pattern but a whole new approach. Instead of the usual threads encapsulated in rubber he has gone for the latest in carbon nano-tube technology. Result is a tire that mounts directly to the rim and requires no tube or air pressure to give it shape. The nano-tubes can be adjusted to give different ride characteristics, much like adjusting air pressure, and are covered in the rubber coating with the tread pattern. Not available as of yet but I am sure it will not be long before they are filtering through into the bike shops. In the meantime have a look at the video. If nothing else they look cool.


Posted on November 8, 2012 .

Watts to Horsepower

           
A good friend of mine recently posed a follow on question to the watts article that appeared here some time ago. He had recently read about a new small car that had an engine power output of 6.5hp. Now, Tom is keen to know if that kind of output could be supplied by pedals and a couple of willing and fit passengers. So this post is for you Tom.
            A good place to start is by looking at the definition of horsepower. Basically the answer is in the name. Back when the steam engine had just been invented there was born a need to be able to measure power. What was this boiler shaped thing, puffing steam capable of? It was all very well turning up at a mine with one in hand but unless you could say to the mine owner that this had the power of something that they already knew, it was always going to be a tough sell. Thus horsepower was born. A guy named Thomas Savery came up with the horse comparison around 1702. He used it to good effect and sold many a steam unit by saying how it did the work of 15 horses. A problem arose quite quickly however, with competing manufacturers adding an extra horse on the figures here and there. All I can fathom is either some out and out monstrous sized horses were around back in the day or the figures were being fudged a little. So along came a standardized measurement of an average horse's potential, devised by Mr. James Watt the Scottish engineer. Using a gathering of fit dray horses, a mill wheel and a measured weight they ended up with the following. It is still the standard today. They fathomed that the average horse could produce 33,000 foot pounds per minute. Anyone that knows horses will tell you that those figures are a little optimistic, especially for a longer, period but those are the numbers.
              So that is the horsepower figure and Toms little car is producing about six and a half cart horses worth. The more astute of you are probably seeing a problem already, but I will continue. How does a human stack up with a horse? And can we fit them all in the car?
              There is a basic conversion for watts into hp., I won’t bore you with it, suffice to say that 1hp is equivalent to roughly 745.5watts, sustained, therefore the 6.5hp car is equivalent to 4845.75 watts. Going back to the original post we can see that a guy of reasonable recreational rider fitness, weighing in around 185lbs will be able to sustain approximately 196.8 watts over a period of an hour or so. Looking at these figures we can see that the car will need to be the size of a school bus to accommodate our human engine. The figures look a lot better if we can convince a dozen or so tour guys to be the engine but even then it is going to get cramped and gas, although expensive, is still cheaper than steroids.
              Tom had already fathomed this out and his main question is. Would it be possible to power batteries by pedal power that in turn powers the car with the necessary wattage and equivalent hp? Answer; yes, hooray. Not so fast, yes it would be possible for pedals to charge the battery bank but it would take a long time.
Using Ohm's law (amps=power divided by voltage) we can see that the average person could quite reasonably produce a 10amp charge rate, requiring about 120watts output, this is about the same as your average car battery charger. So, looking around at some electric motors it seems that the average requirement for a 1hp output motor is around 1000 watts. I know I said that 1hp = 745 watts but there is no such thing as a 100percent efficient motor.  
Watts ÷ volts = amps. Therefore the above example would mean 1000 ÷ 12 =83.3. Your average car battery can supply about 50 to 80 amp hours of capacity each battery would then require 5 to 8 hours of charge time at your pedal power 10 amp charge rate (divide battery capacity in amp hours by the charge rate).
Our 6.5 hp car would need approximately 8 batteries. I will leave you to work out your charge routine… Now I shall go and lay down, all this math has given me a headache.
           

Posted on November 2, 2012 .

Brake Reach Pitfalls

           We have a vintage Raleigh "Competition" road bike in the workshop for a complete makeover at the moment. It is an interesting project and will probably feature again in this blog before the transformation is complete. One thing that has cropped up already and is very common when doing these kinds of makeovers is 'brake reach'. It is not however just a problem with older style bikes it can cause issues on modern frames too, especially on those catch all frames that are designed to be built up in a variety of styles and need to accommodate a wider range of tire widths than a standard 23 or 25.
            Brake reach is basically the distance between the caliper mounting hole on the bridge,  to the center of the brake wear track on the rim.

            On a modern standard road bike this distance is going to be around 39-49mm and a standard short reach caliper from the big 3 will work just fine. Lots of manufacturers nowadays though are producing frames that can be equiped in various formats, a bike for all seasons if you will. This is where the brake reach figure can differ from standard and purchasing a short reach caliper is probably not going to work. The pads will hit somewhere on the tire instaed of the rim. Another problem scenario is with the older style frames as we have mentioned, the mounting bridge on these guys are usually set for the older style center pull styles that had a reach of around 61mm. Therefore a standard 39-49 short reach is never going to work.  Even what we commonly refer to as medium reach will have trouble as their range usually runs from 47mm - 57mm. The last tool in the box for a modern caliper is a long reach 55mm - 73mm.
             All this goes to show that you can never take anything for granted when changing parts on your bike. Measure, measure and measure again.
Posted on October 30, 2012 .

Butyl versus Latex. The Great Debate



Every year, as sure as leaves turn and fall, the perennial debate of "what are better butyl or latex tubes?" rears its head in the store. This year is no exception, brought to life by a group of riders traveling across the country and looking for a mediator.  Now I have learnt long ago when to keep my head down and look busy and this was one of those times. The rest of their trip gives me a headache just thinking of it. Anyway I thought that I might offer my thoughts on the subject here, where it is quiet…
                Firstly a little history, back in the day, the only game in town was latex rubber, basically latex is the stuff you pull out of trees and plants that can be formed into a rubber. Most plants exude some form of latex when they are cut or injured in some way. One tree in particular ‘Hevea brasiliensis’ was found to have great potential for commercially made latex rubber. Now I am no chemist so I will cut the lesson short on manufacturing natural latex, suffice to say it is produced from trees.  I should say that natural latex is, as it can be synthetically manufactured as well but originally everything from gloves to tires to condoms were made of natural plant based latex. Now everything was progressing fine until the advent of WWII. Amid worries about supply of rubber for everything from tire tubes to condoms a push was made for a substitute. Along came butyl, proper name Isobutylene Isoprene Rubber. The basis for this compound was developed by the German company BASF in the early thirties but was developed into what we know as butyl today by a couple of guys at Standard oil just before the onset of the war. Anyway I think that covers the how and the why but what is the difference and benefits of the 2 when it comes to your bike.
                I will agree that there are benefits to a latex inner tube and paired with a suitable tire they can be felt by most competent riders. The benefit comes in the form of better rolling resistance due to better or faster elasticity. When rolling, the tube is compressed and then, as it rolls along it springs back to its original profile. At the contact point the tire has a portion of its profile squashed to the road, obviously tire pressure and profile all factor in but as it is rolling the section that is leaving contact has to bounce back, the quicker this happens the less contact patch there is and by default the less drag. Latex is like a huge tight spring and it snaps back quickly. Butyl on the other hand acts like a hydraulic shock and bounces back slowly and in a controlled way, the energy is absorbed along with the heat.
                Other benefits include better feel when generally riding, for the reasons mentioned above, the tube also benefits cornering and basic feel.

A few things to consider when running Latex tubes.

·         Compared to butyl air leeches out quicker from a latex tube. Get used to pumping them up before the event to ensure proper psi.
·         Because of the high permeation rate, as mentioned above, do not use CO2 to inflate them. CO2 permeates through latex much quicker than regular air which is predominantly nitrogen.
·         They are lighter than a regular butyl tube, although some of the ultra-lite butyl are comparable. I have never been a big fan of the ultra-lite butyl tubes, they are extremely flimsy and the failure rate on them is very high which in my opinion negates any gain, especially on race day. Latex tubes in comparison, despite their delicate nature are surprisingly durable. They will shrug off lots of abuse. They will find any weaknesses in your rim tape though so be careful to install good tape well.
A standard Latex tube.

A latex tube will be beneficial to any good road race tire to a certain degree. That gain can vary from about 1.2 watts to about 2.8watts. Using a supple, high thread count tire makes a big difference. On tires utilizing some form of protective aramid belt or a thicker rubber tread the benefit will be considerably less.
Over the years latex has been definitely pushed under a rock when it comes to bicycle inner tubes and, honestly, that is probably the best for most riders. Butyl is much more suitable to the needs of most cyclists. It is thick and offers a little more protection and durability than latex. Butyl holds air better, it still needs topping off regularly but compared to latex it is significantly less permeable.
 Latex still has a place though, for those riders looking for ultimate performance from body and machine latex tubes can be a benefit. At this level any performance gain is always minimal but it is there. Running a quality latex tube in a quality race tire on race day is another of those gains.
Posted on October 15, 2012 .

What's What With Watts...



A few days ago I published a post on choosing a power meter and, though it seems to have been well received, I have been asked some follow up questions.
Firstly it seems that there is some interest in knowing what kind of power output is attainable and how does your output compare to others. To try and answer this I have broken down some previously published data and averaged out the results into four rider groups. Lastly, so that it is possible to compare riders of differing weights, I have broken down the power output into watts per kilo of body weight
(a kilo =2.2lbs)

Rider
1 Minute Burst( watts per kilo)
Maintained (watts per kilo)
Pro Tour Rider
11.2
6.1
Cat 2 Rider
8.85
4.6
Cat 4 Rider
7.6
3.75
Regular Recreational Rider
5.85
2.4

The higher wattage figure in each category is what the average rider, in that group, can reasonably expect to sustain for 1 minute. The second, lower figure, is the average output for a usual distance ride in each group.
These figures are by no means written in stone and I have done my best to average everything out with the intent of giving you some kind of baseline in each group. There are plenty of riders, in every category, that produce figures well outside of the norm and if you want to compare your wattage to your favorite tour rider then a five minute search online will glean you a set of figures to use. Top sprinters are capable of producing around 1200 watts output over the last run to the line and top climbers are getting close to 525 watts on extended climbing stages. Tour guys love to show off their power figures I have found…


 
The Second questioned, that has been asked more than once. Is there a way to calculate watts without a power meter?
Well, kind of. The first thing to remember is all the variables that act against your forward motion, as mentioned in my original post, the terrain, weather, equipment etc; all act against you gaining an accurate set of data from anything other than a power-meter but, by choosing a flat course and a mild day with no adverse wind conditions, a fair judge of power output can be recorded.
Using the table below, again I have taken an average of many power output readings to try and lessen inaccuracies; you can see what kind of power is required to propel you along at a given speed. The data used in the calculations all came from drop bar road bikes using tires from 18 to 25 wide. There may possibly have been the odd 28 in there too but not enough to make much of a difference.
The following is the chart that was produced.

Speed,(kmh)                                     Watts
20                                                           78
25                                                           123
30                                                           186
35                                                           273
40                                                           378

It is interesting to see how the wattage required to increase your speed grows substantially the faster you go. At low speeds the wind resistance plays very little part in holding you back along with other resistance factors. However the faster you go the more wind plays a part. This is because the resistance increases in line with the square of the forward velocity. All pretty technical but this is the basic factor that we have battled with since we decided to start going places on something else other than our feet. The bottom line is that the better you get the harder it is to get even faster.
Posted on September 17, 2012 .

Choosing a Powermeter




First things first, what does a power-meter actually do and why do you need one? Traditionally cycling performance has been measured by using a basic sensor fitted to the bike which tracks and monitors speed, distance and, more recently, cadence. Within those features we also have average speeds, max speeds attained, etc. Whilst this information is good and for most people who just want to keep a general record of miles ridden and average speeds probably all that is necessary, however the data and feedback does not take into account ride conditions such as headwind, tailwind, altitude or gradients. More importantly there is no measure of effort from you, the rider.
                 Lots of riders nowadays use some form of cardiac feedback, usually in the form of a band with a sensor worn about the chest and, though this data is useful, it still has large gaps and omissions plus it is wildly inaccurate at times. Again, outside factors of terrain and climate, altitude, whether you had a late night or two shots of espresso before you started all have effects on your base line. There is also a significant lag between pedaling output and your hearts increased beat rate.
                 So this is where a power meter takes over. It really is the only accurate way to gauge and compare performance. Power-meters measure power output in wattage and, more importantly, remove all the variables from the data. As an example; you completed a ride last week in fair weather and kept up a steady output of 285 watts for two, twenty minute training intervals. Today you did the same ride, this time in driving rain and a headwind but still completed two, twenty minute intervals, your distance covered was much shorter but your power output was 288 watts. You did better, but your ordinary computer would show that as a bad day. With the power meter this is accurate usable data, no need to discount the day or make notes to allow for bad weather. Watts are an accurate measurement of your performance regardless of all the changing forces acting against you. The end result is a phenomenal training tool and record of improvement.
                 During racing and endurance events it is a great source of feedback for maintaining calorie intake to match output and also keeping a comfortable pace for a long endurance event.
               
So, now that we have covered what a power meter can do for you we shall take a quick look at your main choices.  The benchmark device is probably the SRM range of crank mounted power meters. Very reliable, accurate and the company has been producing meters for many years. Sadly though, what limits their popularity is the price. While any of these devices are not cheap, setting up a bike with an SRM unit is going to run around 3 grand. Ouch. 
Next in the line-up is Ergomo, these guys produce a solid, bottom bracket device which you can install with a crank-set of your choice. Accurate and the company produce the usual range of data analysis software. Ergomo is cheaper than the SRM meters but still a little more expensive for a full system setup than the third choice.
 Power-Tap from CycleOps is about the cheapest option for a reliable power meter system and, for that reason, it is this system I shall concentrate on here. Still not cheap but they do have an option below a $1000 which is considerably less than the SRM. Even the top of the line G3 ceramic is less than the next player in the market and for that reason alone Power tap has become a very popular choice.
I shall start at the top with the G3 ceramic. This hub is the world’s lightest power meter and the complete hubs weigh in at a mere 315g. Next we have the standard G3, basically the same hub but without the ceramic bearings. The weight is still excellent at 325g and you can always upgrade to a ceramic bearing at a later date if you feel the need. The G3 series hubs are a complete makeover from the original power tap hubs. They have a significantly reworked body and allow for much easier servicing. One of the main differences and to my mind the most important one is the increased gap between the flanges. This dimension is very important and affects greatly the final strength of the wheel. The G3 series hubs increase the gap by 5.6mm over the original models and this makes it possible to build a very stiff and strong wheel, the dimensions are much the same as any road race hub in fact.
The original design is still available; it is called the Power-Tap Pro. With a sticker price of less than 900 a hub it is by far the cheapest meter option out there. Each year it gets a basic makeover to keep the internals up to date but shape and external dimensions have changed little. The pro is a fine piece of equipment and has accuracy the same as the G series, all the hubs have great accuracy, to within +/- 1.5%, and the company produces a great range of analytical software, it is quite a bit heavier than the G3s but it is also a lot cheaper. Over the years we have built a lot of them up and I always recommend getting one with a higher spoke count. With the closeness of the flanges on this hub we need to get as much strength as we can from the spoke number. You are not going to be making massive weight savings opting for the 24 spoke, not when the hub itself is 450g, so do yourself a favor and opt for the 32. With a 2x pattern and maybe an offset rim or a deep V at least, it can be built up quite strong and stiff.
When used for training purposes and accurate performance recording the standard Power-Tap Pro is a fine choice however, if like many you are looking for a wheel to race with I would suggest opting for the G3 series. These hubs are much the same as any of the many race hubs that we use and with the extra flange width I can build a super race wheel that gives you feedback as well.
A final thought on some other options. Recently there have been some forays into the power meter market by a few well known players. Over the past few months I have read some interesting press releases with regard to pedal devices. On the face of it a pedal option sounds a good idea, easy to transfer from bike to bike for one. But some of the price points that I have seen are ludicrous and I would like to see them in action first with some good field testing and data collection behind them. Some of the accuracy reports I have seen are a little disappointing, but it is early days. For the moment I suggest the Power-Tap , for best accuracy and bang for the buck.
Posted on September 12, 2012 .

Campagnolo Ergoshifter Rebuild. It Can Be Done...


           Modern road brake lever shifter units are not cheap; in fact they are downright spendy. Head towards the upper range of any given companies offerings and the prices start to look like zip codes. So when we have a bike come in for repair that has a broken shifter, there are going to be tears. If that shifter happens to say Campagnolo we may need a cardiac crash cart.
So it was recently when a beautiful Colnago, lugged frame and dripping with Campy, came in for a full overhaul. All was going well until l strung new cables and found a dead shifter. The call was made to the owner and, to his credit, EMT's did not have to be called.
Torn apart (note broken index spring at top of 3rd column from right)
The good thing about Campy, actually there are a lot of good things about Campy, is that the shifter units are completely re-buildable. Shimano and Sram units can have certain parts replaced with success but I have never been totally happy with delving in too deep with them and even ones that have been factory overhauled never feel the same as a new one. However with the Campy units the end result is sometimes better than new.
Pulling one of these bad boys apart though is not something for the faint of heart and I get beads of sweat forming on my brow when I release the first spring. But, so far anyway, with some patience and some good technical drawings that l have acquired over the years, I have had great success with them and a rebuild with some new springs is a lot cheaper than a new shifter.
Back In Business...
So, if you have a set of Italian gear changers that need a service just give me a call. Hell I will even give your Rolex a spring clean too...
Posted on August 31, 2012 .

New Titanium Manufacturing Process.

       A huge leap forward in bicycle frame manufacturing happened, very quietly, in the English countryside recently. "Charge Bikes”, a builder of some very nice frames and arguably the best titanium cyclo x bike frame on the market at present, has teamed up with the European Aeronautics Defense and Space center and come up with a completely new manufacturing process for titanium.
      Basically the process uses a sophisticated 3D modeling program to create a layer by layer printed guide, which is then used to print onto powdered titanium. Each of these layers is fused into the powdered titanium, gradually building up the part. With this method they are able to produce designs that could not be produced by any other method.
      The video below shows the process in action producing some shaped, hollow, dropouts, for use on their new 'Freezer' cylo x bike. The possibilities are truly endless and I can see countless parts being manufactured this way. Another benefit is the lack of waste material. Traditionally, when we manufacture a part, we start with a block and whittle it away until we end up with the shape we need. Even casting, which is a little less wasteful, still has quite a bit of cleaning up and filing to complete. With this new ‘printing’ method only the powder that is printed and required is used.
       Check out the video and visit www.chargebikes.com

Posted on August 17, 2012 .

Drive Train Woes.


                Never a week goes by without at least a half dozen bikes with shifting issues. Most of the time it is an easy fix, a slack cable or a tweak of the limit screws, (see a previous post). Sometimes a bent derailleur hanger is the culprit and, occasionally, it is a simple case of 'it is worn out’!
                If we have checked all the above and it still has not fixed the problem, then chain, cassette and chain-ring wear is likely' the problem. Checking chain wear is a relatively simple procedure, there are quite a few chain checkers on the market, none of which are necessary or even reliable, the best way to check a chain is to lay it lengthwise on a bench and measure it over 3ft using an ordinary yard stick that measures 3 feet in inches. Line the center of a chain pin on the 1 inch mark and pull it taught; now look at the 36 inch mark, a chain pin should be centered on it. A new chain has its pins exactly a half inch on center, if it is not, then, how far off is it. Here is my rule of thumb on chain wear.

⅟₁₆ inch past = Fine, absolute minimal wear. If you are one of those people who like to slap on new chains every five minutes, then now would be a good time. I, personally, am not a follower of that cult.
⅟₈ inch past = Still fine, lots of wear left, however you are probably past the point of just renewing a chain.
⅟₄ inch past = Time to renew the chain, cassette and chain rings.

As the chain wears and the rollers start to migrate away from each other they wear the teeth of your cassette cogs and rings to suit their new dimension. Once the chain has reached that ⅟₄ inch mark it has done a lot of reshaping and a new chain will have no chance of adapting to the new tooth profile and the old chain will be having a hard time hanging on to the teeth in your favorite gear combinations, the ones that are worn the most, under heavy pressure. So, end result, suck it up and open up the check book…
Just recently we had a Time Trial bike in for the very problem of slipping under pressure. This particular bike had lots of underlying issues as well and ended up taking a good deal of my Sunday afternoon, however, I will not bore you with them now. The bike did bring up an issue which surfaces from time to time though, especially among club riders and weekend racers who are prone to swapping wheels and cassettes from bike to bike. After I had addressed each of the underlying problems and adjusted the derailleurs the thing still gave me a fit shifting in certain gear combinations. The chain was showing minimal wear so I persevered with trying to fine tune it, to no avail. On closer inspection I found a Connex chain, which suggested a renewal at some point, a Sram cassette of a different vintage and chain rings of a Shimano system, which was probably original equipment After talking to the owner of the bike I learned that the cassette was recently borrowed from a friend, the chain was possibly renewed by the previous owner of the bike before it was sold and the crank and rings were, indeed, original.
The moral of this story is; keep track of your drive-train components. Swapping things around on bikes that wear at different rates causes mismatched parts. Modern, high end, gear systems are finicky, hell they barely get along with each other at the best of times and, they definitely prefer to stick to the components they know. Grab the chain off one bike and the cassette from another and there’s gonna be trouble, with a capital T…

Posted on August 16, 2012 .

Adjusting Front Derailleurs.


        Had an email from a guy yesterday telling of his recent success tuning his rear derailleur, following my recent post on the topic. However, his bike also has a front derailleur...
        So, with sincere apologies for neglecting the front end, here is how to whip those doubles and triples into shape.
        The procedures and adjustments are very similar to the rear but, we do have one rather important extra step. Unlike the rear, there is not just one single point of simple attachment. We have to set the height and angle using our own judgment.
        So, what we are looking for is clearance of the cage of the derailleur as it swings over the chain rings, while still keeping it low. A gap of about 1mm between the top of the big ring and the bottom of the outer cage plate is ideal; manually pivot the cage out to get a look at the gap.
        Next we need to set the angle. As you look down onto the chain rings the cage of the derailleur needs to run parallel with the rings.
       Now you have your derailleur mounted correctly we can set the limit screws. We start on the low limit screw first.
Change gear at the rear so the chain is on the lowest gear, biggest cog. Without a cable attached to the front derailleur, adjust the Low limit screw until there is clearance of about 1mm between the chain and the inner cage plate.
       Change gear at the rear to the high gear, small cog. Here is where it gets a little tricky. You now have to manually swing the front derailleur out while turning the crank to shift into the high gear, big ring. It might take you a couple of tries, the spring on the derailleur is pretty tough. Once you get it pushed out to its stop, adjust the High limit screw to get clearance between the chain and outer cage plate of 1mm, when you are happy, release hold of the derailleur and cycle the chain back to the small ring. Attach the cable making sure that the shifter is set on the low gear or number 1.
       Try it out. If you have a slack in the cable, just take it out using quarter turns on the barrel adjuster, until it works perfectly.     
Posted on August 9, 2012 .