So this question has been posed on here before, but I wanted the opinions of people with better understanding of bike geometry. I have a 2020 Orbea Occam, 29 inch front and rear, love the bike. I put an offset bushing in to slacken it 3 years ago and I like the way it rides, maybe the BB is a little low. First Pic is the geo change from the bushing. I was thinking about going 27.5 in the rear due to my super short legs, I frequently buzz my butt on the rear wheel on steep drops and tech, I had to shim down my dropper by 10mm to clear the seat, still buzz the seat a little bit on full compression. if I put in the offset bushing backwards to steepen the bike, it mostly cancels out the geo changes from the 29 to 27.5 wheel change. Would it be a good idea to go mullet on a non mullet bike with an offset bushing for my short ass legs? Will it make technical climbing on chunky stuff much harder? The only big change is BB offset, does that even do much? Thanks in advance!
here's the geo changes with a 27.5 rear wheel and backwards offset bushing and current geo with the correctly oriented offset bushing:
Reach: -1.5 mm
Stack: +1.1 mm
Top tube length: +9.8 mm
wheelbase: +8.4 mm
BB offset: +21.8 mmh
BB Height: +3.4 mm
chainstay: -0.9 mm
head tube angle: -0.1 degree
seat tube angle: -0.1 degree
by GunTotinVeganCyclist
4 Comments
I highly doubt you’d notice much change with the geo with increments being that small. However yes you will notice less tire buzzing your butt which is nice for shorter folks.
Seems like it should be totally fine w/ the geo numbers you’re showing. You might even remove the offset bushing and let the bike ride a hair slacker, or at least experiment with both.
If the BB feels low, swap to 160 or 165 cranks if you haven’t already, it’s all win in my experience (haven’t tried shorter yet).
In terms of 27.5 rear vs 29, it’s not a massive difference for climbing, your tire and tire pressure will still be more important. You’ll be a little worse on seated climbing probably due to rollover but if you tend to purposefully pick up and hop your rear wheel that will prolly get a little easier.
I’d go for it if I were you. 27.5 wheels tend to be cheap as if you are shopping used. I just bought a used front 27.5 for my beater hardtail, a 350 hub + EX511 rim for 50€ shipped.
Putting the offset bushing backwards is a bad idea. It will succumb to the compression forces and eventually rotate back into the shorter position
I think longer hair in the back will probably just make you shorter looking