Went this evening for a professional bike fit on a Serotta Size Cycle from a local fitter who came highly recommended (although more for road than tri fit, I thought it was worth it). The fitting confirmed what I already thought I knew (I don’t really know much of anything). My existing bike does not fit me. It is the “old school” Cervelo One (pre-dual), when it had a 78 degree seat tube, and the top tube is too long for me (even with a 60 stem that we tried). I feel way too stretched out, and this was confirmed.
So, armed with measurements, I will begin to poke around for bikes that, most importantly, fit me and secondly, are a good deal. Only one “real” tri bike shop in my city, and I choose not to patronize them, so I’ll look online (including used on EBay) for a frame and have my preferred local shop do all else.
So, wise STers, what are the “critical measurements” that I need to match up? Preferred TT length, distance from seat to bars, seat to BB? Something else? How do I know what will “fit” and what can be changed on a frame close to the right size?
If you know seattube angle, toptube length and head tube length of a given frame, you can determine if it will fit. These are the three critical frame measurements that you need. The other measurements that might be nice to know are seattube length, toptube rise (if it’s not parallel to the ground), headtube angle, trail, fork rake, and front center (although these last numbers speak more to handling then fit).
Top tube and head tube length are probably the most critical measurements. It would be in your best interest to try and find a shop who would match a bike with your measurements. Ask around, ask on the forum which on-line retailer would be best.
I say head tube length because if your fittr got you pretty low, you will need a head tube that will replicate your position.
You could also take your measurements to a reputable builder (Ves Mandaric, Yamaguchi, etc.) and get a nice custom bike.
Beware the geometry chart my friend. You must actually *measure *the bike you intend to buy instead of just conducting an on-line survey of the geometry charts. Here’s why:
Famous maker triathlon bike, frame size quoted as “51 cm”.
As quoted on factory website geometry chart: Seat tube= 51 cm. Actual center to top measurement:
Wait a minute, aw phooey- the darn glass company just called me to install my mirror wall at home.
On behalf of all forum members, Tom, I think I’ve figured out why you have problems with women. You’re a tease. Look at your above post. How can you (most highly respected for your fit expertise) start a post like that and just leave me hanging? Running out the door to tend to your own needs. If you do that to women, they’ll become bitter and vindictive (familiar with that?). Just leaving me on the edge like that is so wrong
I have seen three bikes with a seat tube measurement of 52 cm on their geometry chart. One was a centre to top of top tube of 52 (making the centre-to-centre measurement somewhere like 50cm), one was a centre to seatclamp of 52 (making the effective top tube something like a 48cm), one was dead-on 52cm centre-to-centre.
And I forgot one other thing- the “compact geometry” is another slippery slope. How the hell do you measure an accurate top tube measurement? I have seen the “trained professionals” screw it up more than once…
