Technische veelgestelde vragen: fietsframe van profs, kniepijn en supersnelle bewegingen

Technische veelgestelde vragen: fietsframe van profs, kniepijn en supersnelle bewegingen

maart 22, 2020 0 Door admin


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The superstars of some pro cycling teams are catered-to by their bike sponsors, at least to give them a psychological edge of thinking that they have a special bike—if not an actual performance advantage.

Have a question for Lennard? Please email us to be included in Technical FAQ.

Dear Lennard,
I don’t ride carbon bikes any more, preferring steel or titanium (though I am open to being convinced), but I just wondered if the frames the pros ride are off-the-shelf frames from the big manufacturers, or are they specially hand prepared with extra love and attention knowing what their destination will be?

Dear Louis,
In general, most pros are riding on the same frames you can buy in a bike shop, although they may be a season ahead in model. That said, the superstars of some pro cycling teams are more catered-to by their bike sponsors, at least to give them a psychological edge of thinking that they have a special bike, if not an actual performance advantage.

Other than when working on a completely new model bicycle that will be available in a subsequent season, when a manufacturer does make a custom frame for a rider, the frame will still come out of the same mold as all of the other frames of that model sold in that size. Thus, there will be no change in geometry or frame shape; rather, any changes will be to the “layup.” In other words, the only things that will change between what the pros are currently riding, and what you could be riding will be the specific types of pre-preg carbon fabric and the shape, number, and orientation of the cut pieces of fabric laid into the mold.

The shapes of many carbon bikes are unique and distinctive, some of them even iconic, and these shapes are formed in a mold. To make a custom frame with the unique characteristics which a rider is looking for, while also mimicking the shape of the stock frame is a big ask. While mass-produced carbon frames come out of a mold, fully custom carbon frames are made with tube-to-tube construction (tubes mitered to “fish-mouth” around the adjacent tube like a metal frame would be, with carbon tape wrapped around the joint replacing welding as the means of attachment of the tubes). The distinctive shape of the mass-produced frame model cannot be replicated with this method.
― Lennard

Dear Lennard,
I have been having some problems with pain in my left knee joint when initiating sprints or starting a hill climb, and I was hoping you might have sage advice!

Most of the time, when pedaling normally or at easy pace, there is no pain at all, but sharp pains come and go on the downward leg motion engaging the knee more forcefully. As I say, these are only intermittent pains, and my knee is otherwise fine most of the time. I also then notice the pain walking downstairs for a week afterward.

My cleat is positioned the same for both feet, but the knee pain only affects me in the left knee (I am right footed). Cleat positioning is directly below the joint between my big toe and my second toe.

Can you offer any advice?

Dear Simon,
I checked with world-famous fit guru Dr. Andy Pruitt about your situation, and this is what he said:

“Well Simon, we can’t comment on cleat position without actually seeing you, as cleat set up is anatomical/biomechanical. But from my experience, you are describing patella femoral pain, or, in other words, pain from behind your knee cap. The patella is the fulcrum in the knee lever system; as you apply more pressure/work/watts, the patella is under great pressure, initiating your pain. The same is true for descending stairs, as it is an eccentric load, where the patella acts as a brake in the system, requiring much more pressure than climbing.

So, yes, bike fit is where you should start; saddle position and shoe/insole/cleat set up are crucial in preventing patella femoral pain. If that fails to resolve the situation, then a visit to your local sports medicine doctor would be in order.”

I suggest you see a bike-fit professional. You don’t want to exacerbate that condition. It takes a long time to rehab it if it gets highly inflamed.
― Lennard

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is a custom frame builder and purveyor of non-custom huge bikes, a former U.S. national team rider, co-author of The Haywire Heart, and author of many bicycle books including Zinn and the Art of Road Bike Maintenance (DVD), as well as Zinn and the Art of Triathlon Bikes and Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn

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