April 25, 2009

Old-school bike designs suck!


So a friend is thinking about having me build his wife a bike, and he has this design from some shop in Cali, using what’s obviously a generic bike drawing from quite a while ago.

I have a few complaints about this kind of “design”, which I see all the time, even from fittings done in the present day, by people who should know what they’re doing. Here are a few of the problems with this specific design:

-The saddle nose to bars measurement is useless. I hate to state the obvious, but saddles *aren’t all the same shape*. Some have long noses, some have short ones. And I have no info on this design indicating what saddle will be used, so I can’t even get the saddle and measure it.

Just give me a measurement to the seatpost clamp, which is an actual known quantity! Sheesh!

-While head angle is specified, no mention is made of fork rake. The designer in this case takes the easy way out and assumes 650c wheels, when in fact she’d fit just fine on 700c, even with a non-custom fork. Give people options!

-Rear end geometry and bottom bracket drop are ignored. This is fine in this case, since they don’t directly affect the fit of the bike, and I can decide (if I end up building the bike) how to proceed with chainstay length, bottom bracket drop, etc. But many people get these fits done as a guide to purchasing a mass-produced bike – and they should have some information about what to look for in terms of BB drop/height and chainstays. Both are VERY important to the handling of the bike. I’m guessing this fitting cost $150+. How hard is it to write a few notes about – “look for a bike with a bb around X height” or “look for longer chainstays if you can find them”, or whatever?

-This design looks suspiciously like it was partially stolen from existing ones. Does she really need a 75 degree seat tube angle? In my experience, that’s usually a way for a bike company to make a bike *appear* smaller and reduce toe overlap (check out the “small” and “medium” sizes of production 29ers sometime and see what their wheelbases are – you’ll get quite a surprise!) Of course, with this steep seat angle, to get the proper saddle position, many people will have to run a setback post and a shorter stem, effectively making the bike the same size as the next frame size up.

Of course, it’s possible that 75 degrees is just right – but consider that a 75 degree seat angle, 49.3cm TT frame (this one) is equivalent to a 73 degree STA, 51cm frame – that’s a significant difference. I’m suspicious that someone just looked at the “industry standard” geometry for small folks and pulled this seat tube angle from there. Not cool.

As a final note, I’ll say that the best fittings/designs I get from outside folks are from Sean Madsen at the Boulder Center for Sports Medicine. Sean knows his stuff, and he’s worked with everyone from pro studs to commuters (he also races with the pros in our local Wednesday night STXC series). And he gives me numbers I can actually use without making guesses about saddle noses, or wondering if the fitter had any idea what they were doing. So I guess this is a plug – if you want the *best* fit available, give Sean a call. I’ve built a lot of bikes for Sean’s clients, and I’ve never heard a complaint.