Soo scheming on bmx geo… I am racing on the bike I built with regular ish geo…
I am wondering on longer faster tracks with a big start hills with decent starting speed. I am thinking longer and slacker head tube angles could be effective lower bb. Kinda getting in to some mtb geo thoughts. the long low idea.
72 deg hta 23.5 top tube length and running a super short stem big gearing… I need a longer bike anyway as I am 6’2"
thoughts??
Yay BMX race frames!
For reference I’m 6’ tall and ride OS20. I’ve hovered around 22” TT, though have liked a few 22.5” TT frames I’ve tried.
My first frame build I dropped the BB to 10.8, which is a 0 drop on OS20. Daylights and a few others run around a 10.8 on regular 20 frames. I wanted something fast, low, stable, and something that would carve like a mfr. it did all that. It proved somewhat tricky to pull up and control over more technical rollers at Hardesty in OK.
I’m underway on frame 2, which will be stretched out at 23” TT, 16” CS, and 11” bb.
One more note, BMX people seem to be stuck on TT length. People’s eyes kind of glaze over when I mentioned reach, rider area, whatever, at least locally. I think theres value in exploring geometry the same way other cycling disciplines have. That’s kind of been my MO for getting into frame building. Excited to discuss this further and maybe even pick up ideas from the other non-bmx frame builders here!
My 8yo daughter has been doing some BMX sessions with our local club, she’s slowly building confidence and strength but she absolutely loves it. But I can’t for the life of me find any simple explanation to bike and wheel/tyre sizing. I rode BMX (flatland) a bit back in the day and I’d love to give racing a go (now I’m hitting my 40s!). 20 years ago I just went by TT length (18" for super-techy flatland, 19-19.5" if you like a bit of street stuff too), but race bikes seem to be a whole different breed these days - different wheel sizes which are all 20", cruisers, and juniors sizing just boggles my mind. Anyone know any decent websites to help me get the basics?
The weird wheel sizes are really only in the Micro/Mini/Junior sizes, at least that’s the way it was years ago. In adult sizes there’s a more traditional 20, some 22s, 24 and even some 26” cruisers. Some 29” wheeled cruisers too if you want to count those.
Did you build the frame?. Like you I was interested to see how low is too low and I have gone as low as 11.5,11.4 which I liked but more recently 11.2" (1.2" above axle line) and I think 11.2 is too low for me. I think the bike becomes harder to pump and not as lively when the BB is too low. I’m riding on jumps mostly not racing though.