Posts tagged #Cranks

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.




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 .

New Crankset From Sugino


The Road OX801D
          Sugino, the Japanese company famed for making some of the best crank sets to grace bikes through the decades have come up with yet another innovative design that is both stylish and addresses a common problem when choosing a gear combination. Lack of choice.
The MTB ZX801D
           The new OX801D for road and the ZX801D for MTB features a 110 and a smaller 74mm bolt circle diameter that enables the use of rings only usually obtainable on a triple. This new design and the selection of rings available gives you 13 possible combinations. Perfect for those looking for the ultimate touring setup or a cross racer looking for a tweak to the standard configurations. Mtb  options for running a wide gap for a low climbing gear on a tough or muddy course. The choice is yours.
Close-up Showing the 74mm. BCD for mounting  the smaller rings
           The build quality is superb, typical Sugino, and the outboard bearing bottom bracket configuration is very stiff. The setup also gives you the lowest Q factor available when using the lower 74mm mount rings at 145mm for the road and 156mm for the mtb. Let us know what your gear requirements are and we can put together the best combination for you.
Posted on December 6, 2012 .