Forum menu
Gearing on my 26” HT is spot on and I want the same on my new 29er.
The 26er is as follows :-
2x11
Crank is 38/28
cassette is 11/40
Crank arm length will be 175mm and tyres the same brand/model/width on both bikes.
What chainrings and cassette do I want on the 29er to get the same gearing?
36/26 and 11/40?
34x 10-50?
Should cover all the bases
Sorry should have said I want to stick with 2x11
If it were me I'd start at 36/26 11-40
I suspect that your preferred 26r gearing won't necessarily be exactly what you need/want on the 29r anyway. Probably depends how finicky you are.
I have a 26" and 29" bike that run quite similar overall ratios but I am not convinced they really get used the same because the ride characteristics of the bikes are different.
YMMV.
garage-dweller makes a lot of good points about the practicalities.
The change in wheel size is about 10%, so if you keep the same 11-40 cassette then the chainrings need to get 10% smaller to give you the same gears: 34.2 and 25.2.
If you used an 11-42 cassette you would need 34.2 / 26.5.
Use these and think about what range you want.
If it were me, I'd probably go 24/36(or 38?) x 11-40 - keeps the cassette you like and makes use of the range available with 2x.
26 x 2.35 tyres, 90rpm 38x11: 24.7mph
29 x 2.35 tyres, 90rpm 35x11: 24.7mph
26 x 2.35 tyres, 90rpm 28x40: 5.0mph
29 x 2.35 tyres, 90rpm 26x40: 5.1mph
You could use the gear ratio calculator website.
I'd just keep the same ratio's and see how you get on, and then you'll know from experience where you want/need to make the changes...i.e. at the top end, bottom end or both. You never know you might even like the result on the 29" wheels.
As @bsims says, use the gear calculator site - http://gear-calculator.com/ - there's the option to compare two setups to make it easier for you. Alternatively there's the Sheldon Brown gear calculator - http://www.sheldonbrown.com/gear-calc.html .
I know you want to stick with 2x but bear with me. On a 1x system I've found that you get equivalent gearing between 26", 27.5" and 29" wheels if you remove two teeth from the chain ring for each increase in size. So a 34T on a 26" wheel is roughly the same as 32T on 27.5" and 30T on a 29". So if you want to stick with the same cassette then find a crankset with four teeth fewer. By that reckoning you want a 34/24 crankset, if such a thing exists. The figures aren't too far from @smiler's 10% calculations.
If you can't get a crankset that small then you'll need to use the calculators to work out what cassette size/range will suit you.