Old 04-08-13, 05:59 AM
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Join Date: Jul 2011
Location: Turku, Finland, Europe
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Bikes: 2011 Specialized crux comp, 2013 Specialized Rockhopper Pro

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Zinn represents a philosophy of fit, that's all. In my personal opinion it's the wrong one for many riders. And because it's my personal opinion I don't really need credentials

Now if I just open up some of the differences between my and zinns philosophies maybe all this will be a bit clearer. The first thing I find wrong with bikes that are bigger in every way is the speed aspect. Zinn's bikes may be perfect for people prefer just riding and looking at the scenery. Actually I'm completely ready to admit that they might be perfect for touring, since they enable enough reach with a relaxed drop. But those bikes are not for going fast. And I'm using the "going fast" as an ideal, not as an actual point of reference because in the end it's all about the rider.

First problem: Massively long cranks for achieveing kops. Just read some of his writings and found out that the longer cranks are especially for achieving kops without massive setback. It's a nice idea, but the problem arises when the crank is in the 12 o'clock position. That is when your knee is in it's highest position. Now in normal drops position that might not be a problem but when you're going hard in the drops and your back angle is almost in the negative the longer crank length is going to (heheheh...) kick you in the stomach. Also raising the leg too high might be detrimental to power output in general, even allowing for increased torque in the crank's maximum power position. If you have long femurs you might have to accept that you have to pedal a bit in front of kops (which is not really a problem since this seems to be fairly common in pro cycling) or sit over the rear wheel (which is also not so bad but I'll get there shortly)

Second problem is the weight distribution of a tall frame. Imagine a triangle consisting of the saddle, handlebar and rider shoulder. On a bike which has a zinnish fit with the handlebar level with the saddle the highest angle of the triangle sits more rearward on the bike and also, fairly high up. On the bike which has lots of drop the top of the triangle moves forward and down. On bikes with similiar components it's clear which bike has better rear forward weight distribution. Also the center of gravity is lower on the low drop bike. And lower center of gravity usually leads to faster and more secure handling. Now if the high zinnish bike has all the zinnish innovations (longer cranks etc) then the weight distribution might be ok since the rider is sitting more forward compared to the rear triangle. But then you have the crank problem described earlier. If you are sitting over the rear wheel one way is to bring some of your weight forward by more reach and especially drop. One should always keep in mind that the arm torso angle should be 90 degrees. A lot fo reach migh allow for a low position, but if the angle becomes aver 90 degrees by a big extent you are going to tire your arms and shoulders really fast. Try doing pushups with your hands in front of your head for an example. This is where drop comes in. You can move your torso lower and forward without worrying about your arm torso angle going awry. You can imagine it by thinking the drop creating a forward rotation of the upper body without moving the arm torso relation at all.

Secondly the rider sitting upright is less aerodynamic. Rider aerodynamics is by far the biggest factor in overall speed, if power output has been correctly achieved. I read a test where different rider positions had a difference of 100 watts (tops vs aerobar). All modern gadgets (deep dish wheel, aero frame, aerohelmet, skinsuit) combined do not even come close (although combined they too are a big help). The lower the rider the faster you go. One might say that it's possible to be low, even if your handlebar is higher. Yes, you can, but I find that actually having the bars lower helps, since you have less strain on the arms, you can't cheat (slowly unconciously straightening the arms and in the end sitting up again). Also you could say that the drops are for going low. Well yes, that too is true, but again I find that being on the hoods is more comfortable and the drops are reserved for situations where you need to go seriously low like descents.

Now like I said, I'm describing the idea of speed here, so if you are not for speed, ignore everything written in this post. Also different body types have different requirements and there are people who just need to go custom. Nothing to it. Now realize that even though this post might look like it's against Zinn it actually is not. I'm merely trying to point out the things his fitting philosophy got wrong in this one fairly narrow setting. Again, touring, randonneuring, leisure riding etc are things that do not concern me at the moment so those are not really things I can have a take on. But looking at pro cycling, no many of his ideas are flying. Some of it has to do with UCI rules, but for example some tall riders use custom frames. They have shorter head tubes, not longer. Tom Boonen used a specialized roubaix with a shortened head tube (I want one of those).

And to think this all started from "nah man, massive frames are not the only way! try smaller!"
I could have been a bit less eager and all of this could have been avoided...

Last edited by elcruxio; 04-08-13 at 06:12 AM.
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