Understanding Bike Sizes


Jul 30, 2010
I used to think I had this down but after trying a few more, newer bikes I'm not so sure any more. I used to think it was all about reach...

I used to own a small m9 with a 15.4 reach. I tried out a friend's medium DHR with exactly the same reach and it felt HUGE. I then tried out another friend's small DHR with an inch shorter reach (tiny) and it felt pretty good, i'd say a little bigger than my old small m9. I have a trek with exactly the same reach as the m9 and it feels a little bit smaller. I've parking lot tested a bunch of other bikes too but the whole "reach is real size" in DH doesn't seem consistent.

Size is a deal breaker with a lot of frames when shopping and it's hard to actually ride test most of the bikes we want to buy. Is there any real(er?) science out there to how "big" or "small" a bike feels?


Turbo Monkey
Apr 5, 2008
You have to consider handlebar width as well. Stem length should be pretty much the same on DH bikes these days, 35-55mm, but also a factor to consider.