Great Article on Bike Fit

[fourflys]

I debated on posting this here or the bike fit discussion, but figured it would get more eyes here and it's not a specific person question..

Anyway, MyVeloFit posted a pretty interesting blog post this afternoon.. enjoy!

https://www.myvelofit.com/fit-academ...bike-geometry/

[benb]

That is a great article.

If I was at Trek/Specialized or some similar company that was big enough and powerful enough I'd start a program that incentivized dealers to upload anonymized fit data when they fit a rider to a given bike.

The article talks about the BMC Roadmachine having a curved line as you graph the stack:reach ratio across sizes.

A curved line might be much smarter than a straight line, because people don't scale linearly with height, and as much as they seem to want to deny it women are not linearly scaled smaller versions of men. But how do you decide how to shape that line?

The thing is how much data is out there on how people end up fitting? If they collected a lot of data they could probably optimize the stock sizes of the bikes in a more intelligent way.

Maybe they use some well known DB of body dimension averages.. but if those are from a non-cycling source are they ideal? Because say measurements of army recruits is your sample DB... does it actually have data that shows what kind of joint angles they can handle riding a road bike?

Maybe MyVeloFit is trying to build this kind of data from users and then sell it to bike companies.

But none of these online things really seem to have an intelligent way to input one rider's flexibility level versus another. Fitting one of these bikes depends on both your dimensions and where you fall in with the angles based on your flexibility and functional level.

[Likes2ridefar]

Reconfirms while i enjoy looking at the finishes of the crux and aethos they’ll never fit me. Even when I was racing competitively, I’d steer clear. I was fortunate the cervelo r5 was a team bike for a few years. Before that it was usually massive drop to the bar, a short stem/less spacers on a too large frame, or proper frame size and very not-pro spacers and stem setup. The year I purchased a roubaix was when i finally found a great fit not requiring a silly high stack or stem pointed up. It is why I only rode gravel bikes now since they tend to have that similar geometry. The 3t I have now looks like a race bike, kinda behaves like one, but fits like a roubaix…maybe my new favorite.

[benb]

The bike(s) they mention that get more aggressive as the size goes up seem the weirdest of all.

That does not seem to make sense, but I don't have data. It has never seemed like taller people trend towards shorter legs & longer torsos... it seems like it's the opposite.

My gut feeling would be an ideal curve would be for the smaller sizes bikes for men to have more reach and less stack proportionally and for the larger sizes to have more stack and less reach proportionally.

And then women would probably be different.

[Dave]

I didn't read everything because I've been using stack and reach for years now. I look for a stack in the 505-525 range, reach of 365-380 and a seat tube angle in the 73.5-74.5 range, I didn't read enough to see if STA was mentioned in the article, but that's the third dimension I look at to be sure of my seat post set back. I recently bought a Cervelo Rouvida with 524 stack, 370 reach and 74 degree STA, with the only stem angle -8 degree. The bike comes with a zero setback post that won't work for me and a stubby 90mm stem that's too short. You get what's sold with the bike with no substitutions at Mike's Bikes, Denver. This is the first pre-built bike I've bought in 34 years.

I cut over 30mm off the steerer, got a 110mm stem and 25mm setback post to correct my fit. The original seatpost sold quickly on eBay. I need to put the stem on eBay too, but they only work with Cervelo's special D shaped steerers.

The only situation where STA doesn't work might be an odd ball design with a curved seat tube that's placed forward of the BB centerline, with a straight portion for the seat post, like the Cervelo S5. Normal STA is just a straight centerline through the center of the BB.