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Help w/ understanding bike geometry
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Looking at a bunch of different Tri bikes it seems that is a wide range of frame geometry. I'm not so much talking about stack and reach as I am about chain stay length, wheel base, and head tube angle, fork rake and trail. How I understand it, is that stack and reach affect how a bike will fit, and the others affect how the bike will handle. So, can one tell by looking at the handling numbers(wheel base, chain stay length, fork rake, trail)if a bike is a legitimate tri bike? An example would be to look at the difference between a 52cm Cervelo P2k and a 52cm C'dale Ironman 2000. From what I've read both are great bikes but they have very different handling geometries. How do I know which one is better or will suit my needs? Again looking at the geometry of the C'dale it seems to be closer to some road bikes that I'm also looking at like the Giant TCR composite. In fact the Giant has a shorter chain stay and wheel base, it has the same head tube angle as well, I can't find the rake or trail numbers for the Giant so there could be a difference, but given those numbers it seems to me that the Giant could perform well as a tri bike. What else needs to be considered and what am I missing.
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Re: Help w/ understanding bike geometry [Luntzy] [ In reply to ]
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Luntzy, as far as I am concerned you get a solid "A" for your research. You have an excellent understand of fit and handling and the influence geometry exerts on it, and, you were able to articulate it better than I have seen before. Very good. There are two questions in your post as I perceive it:

1.Which is a legitimate tri bike? IMHO they both are but (as you point out) they ARE different and one will emerge as the clear "best choice" when your body measurements and the bike's dimensions and geometry are compared by an experienced fitter at your local triathlon shop.

2.How do you know which one will suit your needs? Another excellent question. I would take the recommendation of a fitter whose reputation, results and expereince you trust.

I know those are my generic answers but I think they are good ones. One thing that I don't really recommend is a test ride, unless the shop is willing to part with both bikes for at least two-three weeks and do fittings (including pedals, cranks, stems, bars and saddles)specifically for you on both ones so you can spend an appropriate time getting used to them and evaluating them only AFTER they have been properly configured specifically for you. Taking both out for an hour or two without sizing them specifically for you is not an effective evaluation process IMHO.

Tom Demerly
The Tri Shop.com
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Re: Help w/ understanding bike geometry [Luntzy] [ In reply to ]
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If you become too theoretical or technical you can drive yourself nuts thinking about this. Also consider that some bikes like the P2K have quite a wide number of adjustments from a 74-79 seat angle. On the other hand, the TCR is a road bike geometry and according to some on this forum can't be as fast as a steep angle tri bike, yet Luc VanLierde won IM Hawaii on one setting the fastest bike split.

What it really boils down to is that there are a lot of viable options to be had and they all seem to work. Some just work better for some people and not for others You just have to determine which one suits you best.
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Re: Help w/ understanding bike geometry [Tom Demerly] [ In reply to ]
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I am with Tom on this issue, go spend the time to see a tri specific store. If I recall you are based on the pacific northwest, why dont you take a weekend to visit some of the large outfits in Cal.

After some advice from both Tom and Dr Coggan a while back when they both told me my current bike did not fit (and they are right, ) I cracked, gave in to my wife's insistence and finally got round to visiting a tri friendly bike store. In fact I just got back from a sizing. Even on the size cycle the fit felt right, almost straight away, I did not want to get off. I am in shock to tell the truth.

I have spent so much time messing around with my road bike (btw it rides (and fits) great as a road bike, I am trying to keep it to road race on) and suffering through 3 IM races (most recently IMNZ), I am actually fairly pissed of at myself for all the trouble, time and money I wasted.

This store is owned by a hardcore triathlete who believes strongly in the tri position, and after some measurements he pointed me to a 54 P2. He does not carry Cannondales or many tri brands but after much discussion and the experience on the size cycle I will give him my buisness. That is if he can get a frame from Cervelo before May! I am racing IMC so would really ideally like to have some time to adapt to a new bike.



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Simple Simon
Where's the Fried Chicken??
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