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Looking at possible used bike buy as I fancy a full suspension, unfortunately nearly all seem large but and this seems a big but most of the couple of year old models in a large seem pretty much the same sizing as a modern medium. Say a 2 year old orange four has same reach as a new bird 120 iirc. Looked at that many I'm confused now
But other than a degree or two in the seat angle and perhaps seat tube length it looks on paper as I now miraculously fit a large at just over 5'9
How much difference in seat to stem length does a degree or two make ta
Looked at that many I’m confused now
the letters are meaningless really, what you need is the geometry chart that has the measurements on it.
Compare it to something you have ridden and go from there.
Well a new bird 120 is 23mm longer in reach than current bike. But with a 35 mm stem on it it will be 8mm longer same as an older orange four. Which is nowt. But reach doesn't seem to take into account where the seat sits which is important when seated climbing but I don't know how much a degree or two slacker seat tube transfers the seat back thus lengthening the cockpit when seated. Bloody bikes haha
If you are of reasonably average size, a degree difference on the seat tube at 74 cm saddle height will be (from arc of a circle)
2*3.14*(1/360)*74 = 1.3 cm
about the same for head angle.
So a degree is about 1cm, front and back.
Saddle rails should be able to cope with that 1cm difference, so slam it forward and you’ve got the de rigeur steeper seat angle at the same time. BOSH! Job done.
At 5'9 you won't be a large on a current Bird full suspension imho- probably a medium large. My medium Bird 1.5 is still a good fit at 5'10, although I am looking forward to the roomier AM9. Bird said a large would be to big for me.
Just back from town sat on a couple of large oranges and whytes the reach felt OK on both sizes on a sat on test but the frames were too big on large. It appears although the reach has increased in recent years the frame sizes remain constant cheers all
I'm 5"9/10ish. Just bought a used T129 in large. Reach feels good, 125 Reverb is as low as it will go and it pedals ok. I might cut a few mm off the seat tube if I feel it's too high at some point.
Sizing has gone to pot recently.
Edit: I have longish legs for my height though.
I'd almost be tempted to say ignore geometry numbers and trust sizing - you've got people buying Medium Birds when they're 6' and should be on a Large just because the geo numbers scare them.. If you're Medium height, buy a Medium. If you're Large height, buy a Large. It's not rocket science..!