Quick question to the masses. Was running 1x10 on a 26" wheeled bike, 34 tooth front ring. Just swapped to a 29" bike, and again want to go 1x10. What chainring will give me the closest ratio, 32 or 30?
ta all 😀
It depends a bit on what size tyres you are running, but basically you want the expression
D * (f/r)
to be the same, where:
D=the diameter of the wheel (rim+tyre)
f=number of teeth on the front
r=number of teeth on the rear
You can think of that expression as giving you the diameter of the equivalent sized wheel on a penny farthing for the gear you are in!
Alternatively, just use Sheldon's neat gear calculator:
http://sheldonbrown.com/gears/
Basically 32/36 with a 56mm tyre on a 29er rim is close enough to 34/36 with a 60mm tyre on a 26" wheel.
34:what?
Don't know why people don't refer to gear inches more often in mtb.
32 will get you pretty close to the same ratios if you are using the same range of cassette.
(29-26)/26 = 11%
34-11%= 30(ish), but 30t is hard to come by as it won't fit on normal 4 bolt cranks. If you want/need it then I'd get a 32 and a 11-36 (or 12-36) cassette. 32t with whatever your existing cassette is will be aproximately half a gear higher.
Don't know why people don't refer to gear inches more often in mtb.
Because
a) it leads to arguments over whether it's measured as development or as a wehel size (it should be wheel size, development is usualy expressed in metric units)
b) it's fairly nominal as unlike road bikes with 23mm tyres, everyone picks a different tyre.
c) it's really most relavent on fixed/SS bikes (all my MTB SS's are 49-50")
I've heard/read that 29" wheel is roughly worth about 3 teeth on the chainring. I've not worked this out myself, but seems to pass the common sense test. I'm running 1x10 on my 29er with a 28 up front (so maybe equivalent to a 31 on a 26er) and the usual 11 - 36 cassette out back. It is low enough for me to tackle any steep climb but I do suffer a bit on the high end when i'm on a smooth track/road descent, but in those situations i'm not looking to power my way down. So all in all it gives me more than enough range for off road riding. I could probaly go for a 32T up front, but what's the point? I'd rather have the extra low gear to go into if I feel I need/want it.
I don't know why people get so obsessed with gear ratios. Just try a 34 and if it's too hard try a 32 etc...
Of course , that would be so much easier than having a formula to work out how many inches your current set up is and then replicate that .
Cheers all, didn't think I'd get any answers! Looks like the equivalent is in between 30 and 32, ta.