Posts tagged #Tip

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 .

Tire Sealant, Our Recommendations.


       Tire sealant has been around for a good many years now and has certainly improved greatly in that time. What started as a thick sludge suitable only for a lawn tractors or wheelbarrows has now progressed to a foaming lightweight liquid suitable for a race wheel tubular. When I was mountain biking regularly in England I had great success avoiding punctures by using a bottle of the green slime in each tube. When the tires wore out and were removed from the rims there had been so many punctures sealed that the tubes had welded themselves to the tires, made me a fan of the stuff for life. It is still sold today and is still Martian green and still works great in a tube setup.
        Basically all the sealants work in the same way. When the casing is breached air rushes out through the hole taking the sealant with it, as the sealant flows through the hole, particles in its formula seal the gap. Although the principle is the same throughout the range of products on the market we have found some of these potions are more successful than others at getting the job done.
        For a comfort on hybrid bike or even a fat tire mountain bike running regular tubes Slime is still hard to beat. It is easy to install in a Schrader tube and, with a little patience and a removable valve core, it can be used on skinny valves too. Although it can be put in road tubes I find that it does not work quite as well under high pressure. Although Slime is about the beat of the bunch when using a tube, making the switch to a tubeless system can offer up a whole new set of possibilities.
       When using a tubeless system, such as the one offered by Velocity or the similar Stan's method, we prefer to use the Cafe Latex brand of sealant and the Stan's sealant. When putting a tubeless mountain setup together we prefer the Stan's sealant. This stuff works great on big tires, it seals quickly almost any puncture from thorns to nails and helps seal any areas around the valve and along the beads. It will not seal a cut or slit, none of the brands will, and like other makes, it does lose its effectiveness over time. Any punctures sealed stay sealed but after around 3 months the mixture dries up considerably and ceases to work sealing new holes and needs replacing.
      When it comes to tubeless road systems we prefer the Cafe Latex brand. This stuff is great on high pressure skinnies and seals quickly and permanently any punctures. Like the Stan's it also helps seal values and beads however we do find that it tends to keep its effectiveness a little longer.
Posted on August 29, 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 .

Aero-Bars. Making the Leap.


           Anyone who rides a road or Drop Bar bicycle regularly has, at one time or another, thought of bolting on a set of aero-bars. For some it is an idea born on a ride but dismissed before the brake pads have cooled. For others, it is tried and met with lackluster results and, for a few, a turning point in comfort and performance.
The following guidelines and advice is for those of you thinking of taking the aero plunge or who have a set of bars on their bike and are not sure how to set them up. Before we begin I will say that there are a couple of ways to approach aero set-up. For a' Time Trial' professional or specialist it is going to be very different from the way we fit and position bars for the casual or club rider. It is the latter that I shall concentrate on here.
Firstly, I often see bars that people have positioned after reading a magazine or following strict parameters used by Time Tail experts. Unless you are training exclusively for the TT discipline, do not set your bars this way. The aim should be for you to transition from drops to aero without a drastic change to your upper body position. One of the biggest problems is the elbow and hip height. This is often quoted in articles as a golden rule. It kinda' is if you're Bradley Wiggins however, for us mere mortals, it is not so important. If, after installing the bars and setting them up you find that your hips are in line with your elbows, then great. But, if your natural road bike position is comfortable in a higher front end do not change that to achieve a lineup of hips and elbows. You will lose more than you will gain.
        So where to start, well bar choice is important, there are hundreds of bars and designs on the market and all of them have their merits. But and it is a big but, most of them are not going to work for you and here is why; Adjustability. You need a bar with a wide range of adjustment and also, you still need to be able to ride using the drops and, I bet you like to ride the bar tops and hoods once in a while, that means the arm rests need to flip up when not in use. We like the profile Design bars for these reasons.
You will want to set the cups behind the handlebars and set the angles to comfortably cradle your forearms in their natural position, do not draw in your shoulders and arms to match the cups, this will restrict your airflow.
        The length of the aero-bars should be set so that when using them your head, neck and back position remain more or less the same as when you are in the drops. Lastly, try to set the angle of the extensions somewhat neutral. Bars that tilt up steeply from the elbow to the hands put unnecessary pressure on the spine and neck, keeping them level or even tilted down, will remove that issue.
The extensions on most bars will usually end up being just a little past the furthest point of you brake levers.0
Posted on August 13, 2012 .

Tip for the Day.


     There are lots of choices when it comes to picking new cables for your bike. Galvanized, stainless, slick, we mainly use the Stainless Steel slick from Jagwire. These guys are pre-stretched and perform very well. Some time ago it became popular to coat the cables with a 'Teflon Coating'. While on the face of it this sounds like a terrific idea, like many things it falls way short in reality. Here's why: 
    The Teflon is a coating, it is put on the finished cable, it is nice and slick and I'm sure that if you wanted to, you could fry a rasher of bacon on it, all be it a very skinny one, but that coating does not like to be pulled and rubbed through housing and it starts to peel off, now we have strips of coating clogging up inside the housing and binding up the cables. 
     If someone brings in a bike with shifting problems and it has coated cables we clip them and run slick stainless with new housing. Problem Solved.
Posted on August 8, 2012 .