29er Gearing
March 25th, 2006 by Tim GrahlI was wondering how many riders (or manufacturers for that matter) set up their 29ers to have equal gear inches to a 26er. My first thought is to use a compact crank set-up with 20/30/40 rings. This would give you similar overall gearing to a 26er for super steep climbing, with the added bonus of greater ground clearance and a lighter drivetrain. Similar to putting monster mud tires on your 4X4 – you need a higher [numerical] axle ratio or more horsepower, or you will lose low-end torque at the wheel. This makes sense to me since I can’t push big gears up all the hills – I’ve always spun really well, though.
–Brian
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Brian: You are on the right track! Great analogy by the way. The only problem that some riders are finding is that not all bolt circle diameters (BCD) support those sizes of chainrings. Typically you need to find a set of old five arm compact ring crankarms to get the chainrings that you specified. Although, I’ve seen examples of four arm cranksets with close to that gearing. One more thing, the 40 tooth chainring might be a hard one to find. Lots of guys go with 20-30-42 cranksets with some guys subbing out a 29T for the 30T. Again, the 29″s are harder to find, and your cranks BCD may affect your choices greatly.
I’d like to see someone make a single nine speed compatible rear cog in a 36 tooth size that you could swap out on a cassette by leaving off the smallest loose cog. You would loose the 11 or 12t cog, but your low gear would be easier to match to a 26″er without alot of chainring swapping/ crank swapping going on. Remember when Ritchey introduced the 2X9 setup? That system added an extra low gear cog to and 8 speed cassette making it 9 speed. That’s kind of the idea I’d like to see for 29″er specific cassettes
Great idea Ted! Now who could be tricked into making that for us? Yes, Boone perhaps, for $2.50 per tooth ($90).
Who’ll call SRAM? They’re pretty big in 29″ supplying to Fisher, it could really improve their service a lot.
I’d love a 12-36 cassette. 13-36 would be even nicer for me. Lower wear, suptle gaps. 13-14-16-18-21-24-28-32-36
In the mean time, if you came from an 11-32 cassette, a 12-34 would already make you forget most of the (mostly mental) gearing difference.
How about the Surly cogs? Shifting would be slow, but you could make all sorts of craziness in the rear end with their cogs…
Personally, running a 1×8 with a 32t in the front seems to get me through most anything.
make it a SS for a while and then go back to gears. you won’t notice the difference.
Currently I have an 11-34 SRAM cassette and a 20-32-44 deus crankset, shifts normally.
Bike: Dos Niner.
That’s what you can do:
1. – Buy a 20 tooth sprocket, size 40 (half inch) at an industrial supply store.
2. – Using your 22 tooth sprocket as an example ask a machine shop to cut the 20 tooth sprocket to the same dimensions (Of the 22 tooth sprocket).
3. – After installing the 20 tooth sprocket in the crank arm, just file the 4 chainring bolts in the outside, where they contact the chain.
It will last.
My setup is a 2×9. I run an 11-34 on the rear, and a 22-34-bash ring up front. This gives me a pretty good range of gears. Bringing back the 5 arm crankset would be nice. Race Face are you listening? That what we can run a 20t upfront.
A 12-34 on the back should be enough. I find the difference between my old and sold 26″ is really only one cog in the rear.
My only complaint with or about 29rs is still weight overall.
I want to get 30t and 40t chainrings for my 104 bcd crankset. As correctly mentioned above, the old 5 arm cranksets have a wider range of rings that will fit. Middleburn still makes such 5 bolt cranksets. However, I have recently spotted Heather Irmiger (possibly in cyclingnews) and Julian Absalon (mtb action) using 30t and 40t Stronglight chainrings on their 104bcd 4 bolt cranks (albeit on 26er bikes) Anyone know US distributors for Stronglight or anyone else intelligent enough to sell these in a 104 bcd? Why are these perfect rings being kept so secret, lol? Yes, I know Extralite makes a 30t 104 bcd (see fairwheelbikes.com), but most of us aren’t forking over that much for one ring.
I’ve used the Extralite and it does the trick nicely but needs to have the spider arms filed down a bit so they don’t clash with the chain, and I don’t take to kindly to filing down my new XTRs or my Carbon cranks.
Middleburn has announced that they will soon be releasing a 27T front for there cranks.
If you only are concerned about getting your lower gears in sync with 26ers, here is an easy solution:
Action Tec (http://www.actiontec.us/) makes a 20t chainring in both 58mm 5 bolt and 64 mm 4 bolt configurations. They are $75, but last forever. I dropped a 20t into my XT crankset and presto, gearing in the granny chainring that is very close to my 26er. The only thing that slowed me down was having to do a bit of hand filing on the edges of the chainring bolts (otherwise they interfere just a bit with the trough of some of the cogs, just as described above by Luiggi). Seems the Action Tec chainrings should work for the newest generation of XTR cranks too (M970s).
Why worry about gears !
go SS, yes it will hurt the first year, but next year you will have the biggest grin on ya face as kick ya mates ass up hill’s down hill’s all the while not worring about what gear you are in.
cheers
I need a 40t 104/28t,64 9speed for my 29′er going to make a2,9 were can I find them need help