Brandon"monkeyman"Ives wrote:
> >Sprinting and Keirins bring out the conservative in any rider. 200 lb
>>riders who can squat lift 400 lbs and more do strange things to bikes.
>>Every bit of rigidity obtainable can make a difference in how squirrely the
>>bike is in the final turn. How the bike tracks through this turn makes all
>>the difference in determining possible lines, effect of rules and finishing
>>strategy. There is also a psychological component in having complete
>>confidence in the bike.
> >Joe
>
>Sorry Sheldon but Joe is 100% right-on about the need for really strong
>bikes on the track.
I never said anything to the contrary.
>I've watched just about every part on a track bike
>break just on the stresses exerted by the rider. Stems and forks snap,
>wheels and chainrings fold, seatposts and frame tubes twist. I know people
>who have replaced their bolt-on axles with QR axles (without the QR) to
>save weight but have always bent or broken the axles.
A QR axle _without_the_QR_ is certainly weaker. I'm not convinced,
however that a QR axle _with_ a good QR tightened properly is any
weaker in practice.
>If you use a QR on
>the track it WILL slip. If you watch someone like Marty Nothstein, Ken
>Carpenter, or my young friend Jason Vance pull on a pair of bars you will
>understand the use of overbuilt parts.
Again, I never said anything to imply that they don't need strong
parts--but, the drive train stress is inversely proportional to the
chainring size, and directly proportional to crank length. Thus even
behemouth sprinters who snap stems and bars like toothpicks aren't
pulling as hard on the chain with their 165 cranks and 48 tooth rings
as a mountain biker grinding a 24 tooth granny gear with 175 cranks.
>If all you do is cruse around town
>on a track/fixed bike lightweight parts are fine, but on a 48 degree bank
>at 30+mph they just won't cut the mustard.
Neither the top speed nor steepness of the banking have anything to do with the need for strength. Indeed, the greatest stresses on a sprint bike occur at the lowest speeds, at the beginning of a jump.
Sheldon "Campagnolo 1010 Dropouts Are Strong Enough For Anybody" Brown
Newtonville, Massachusetts
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772, 617-244-1040, FAX 617-244-1041
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