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Paging C-40 RE: Fit stuff.(3 posts)

Paging C-40 RE: Fit stuff.Zonic Man
Aug 21, 2003 9:42 AM
A couple of days ago you said this:

Two things still don't seem right to me. The 110mm head tube would have to be a lot longer if you really intend to keep the bars 5.5cm below the saddle. For reference, try measuring from the floor to the top of the bars. Mine are about 87cm above the floor on my Fondriest. The saddle is about 96cm above the floor, for a 9cm difference. The head tube is 105mm with a 3cm headset, a .5cm spacer and an 84 degree Ritchey WCS stem. To get the bars to the height that you've listed, the bars would be around 91cm above the floor. 4cm is a huge amount to make up. Flipping an 84 degree stem to 96 will only gain about 2cm. Don't make the mistake of buying a "custom" and end up with a high rise stem and 2cm of spacer.

The 72 degree head tube angle is definitely not criterium geometry. A 73 would be more like it, with 45mm of rake. I also wouldn't get 50mm of rake on the fork. Not many forks available with this much rake.

I called IF on this. You have to take into account the 30mm of spacers they are giving me to play with, and the 35mm stack height of the chris king headset that I'm going with...This should give the desired effect of being 5.5cm below the saddle...but I'm probably going to be going about 7cm below.

Regarding the geometry, on the smaller bikes, they run that head angle with the 50mm rake fork (custom for IF from Reynolds Carbon) to obtain the necessary "trail" on the bike.

He seemed pretty convinced that it would be the right geometry for me.
re: Paging C-40 RE: Fit stuff.gtx
Aug 21, 2003 10:24 AM
C40 doesn't seem to be taking bb height and seat tube angle into account. If his are different that yours the comparison between bikes is invalid.

Are they doing the 72 degree HTA and 50mm rake to prevent toe overlap? Merckx and Sachs use this rake and it seems to work fine. Might also make the fork a bit more comfy.
no surprises...C-40
Aug 21, 2003 3:58 PM
I did take into account the stack height of the headset (read more carefully, 3cm is in my comparison). Yes, it will take at least 3.5cm, maybe 4.5cm to get the bars to be 5.5cm below the saddle.

What I'm trying too tell you is that it looks STUPID to have 3cm+ of spacers, plus a stem with a significant rise. If you're a beginner who doesn't know what height he needs, the short headtube length will certainly give you the option to go very low with the bars. IF the saddle height that you posted is correct, you will be able to get the bars about 10cm below the saddle with no spacers and an 80 degrees.

As for the steering geometry, there's nothing wrong with it. It's a bit faster steering than a Colnago for instance, that might have the same 72 HTA and only 43mm of rake, but Colnagos have stage race geometry, with more trail than any brand on the market.

In case you want to know the amount of trail the formula is
(R/tanH) - (rake/sinH). Run the numbers with R=336 and you get a trail of 56.6cm. I'll change my statement after figuring the trail. 56cm is definitely on the quicker side, they just take an unusual route to get there. 50mm rake forks aren't that common.