gonesh9

This might be a stupid question, but would it work to just put my XT mountain bike cassette on my road bike? They're both 9 speeds...
The reason I ask is that there's a super hilly death ride this weekend, and my road cassette tops out at 25t. It would be nice to have some extra gears, a few of the climbs on this ride hit inclines around 25%.

HillRider

Assuming you have a Shimano road rear derailleur it probably won't allow a large cog bigger than 30T. Shimano rates their road derailleurs for 27T and experience has shown most will accept a 30T. A 32T cog sometimes works and a 34T almost never.

If you want to be sure a 32 or 34T large cog will work you need an MTB rear derailleur.

Also, your chain might not be long enough to allow big-big with the larger cassette cog if it it sized for the 25T. Going from a 25 to a 32T cog requires a chain 3-1/2 (really 4) half-links longer.

Now big-big isn't a recommended gear but, for mechanical reasons, the chain must allow it just in case you forget and shift into it.

johnny0

this is exactly what im planning to do this weekend to prepare my bike for a 4 day tour. swapping out the back cassette to a 11-32 and got a deore RD and new chain. only cost $65 total for parts.

i'll be too lazy to swap it back afterwards though. w

thirdin77

You'll need a mtb rear derailleur that's "top normal" for your shifters to work as they already do. You'll probably want the longer cage, the SGS, as it will handle as big or as small a cassette as you want to use.

I suggest you consider which cassette you're going to use. The 11-34 probably looks tempting but I've ridden one on the road and it has 4-tooth gaps between the larger cogs, as well as a 20T middle cog. That might be difficult to tolerate on some parts of the course that have more gradual changes. The 11-32, on the other hand, has more like 3-tooth gaps between the larger cogs and a 18T middle cog.

Check Sheldon Brown's gearing calculator with your tires & crankset to see if the 34 offers a low-enough low gear to justify riding with such big ratio gaps.

joejack951

The good news is that the Deore derailler will shift your road cassette just fine so swapping back and forth only requires a 5 minute cassette swap. No changing and reindexing deraillers necessary.

HillRider

Get master links for both chains and you can swap the cassettes and matching chains around in a couple of minutes. As joejack noted, the Deore rd will function perfectly with either.

alcanoe

I keep an 12/34 to replace my 12/27 for the mountains. I keep the chain links with a gold link and the cassette as a kit so the change-over is easy. However, to handle the total gearing range of both the rings and the cogs I have to keep an xt mountain bike rear derailleur on the bike.

Al

urbanknight

I have been told that some guy has an 11-34 9 speed cassette on his road derailleur and it works just fine. The only catch is you need to avoid cross shifting if it's a short cage. If you try this, I recommend doing it early and getting some rides in to make sure it works before you had to Death Valley without a backup plan.

Skipper

I just bought a Deore XTR (M971) rear derailleur to put on my road bike. I still need to get a chain of the proper length. Then I can choose between a 12-29 road cassette for "normal" riding and a 12-32 or 12-34 mountain cassette when I do something insane like the Dairyland Dare.
I am currently using a 12-29, slightly customized, road cassette with an Ultegra 6500 derailleur with no shifting problems whatsoever.

HillRider

Who makes a 12-29 9-speed cassette? The only 29t cogs I've seen are on Campy's 13x29 10-speed.

Shimano makes a 12x27 and SRAM makes a 12x26 but nobody I know of makes a 12x29.

Deanster04

This will work just fine. I have setup a number of friends like this for mountain tours like the Bicycle Tour of Colorado. An 11-34 will work as well. I have setup one friend who had one of the old 105 long cage road RD and that has worked just fine. Just so long as you match components sized properly it will work just fine. Even if you go back to your old cassette 11-25 you can leave the MTB RD with the new chain. If you use a chain with a quick link you can change out the chains easily.
I have a touring setup using campy 10spd ergo shifters and a SRAM 11-34 9spd cassette with a Centaur LC RD. Works just fine with the pitch on the cassette. I used Sheldon Brown's gear index tables to determine this setup. The campy 9spd will not work.
Give it a try and have fun. The low gearing is great to have when you need it.

oldster

Very interesting...Not to hijack this, but its in the same vein...
I have a Motta with a 10 sp hub, and right now, a 13-30 7sp indexed. I also have a 12-27, 10 sp casette and10sp. DTshifters. Will the 10 sp DT shifters shift the 9sp 11-34 casette you refered to??? Itwould be useful for the mtns as you said...Thanksfor any direction..
Bud

Skipper

I do. Read my post again and take note of where I attempted to point out that the 12-29 cassette is not stock. I can't remember if I used a 29 tooth Shimano cog or a Sram cog, but I really, really do have a 12-29 cassette.

Deanster04

If they are Campy DT 10spd shifters they will work just fine, but I didn't think Campy made 10spd DT shifters. I did setup the original experiment with 10 spd Campy bar end shifters before I moved to the ergos. They worked fine and I know that the Bar End shifters use the same indexing gear mechanism as the DTs. Give it a try...Why are you using DT shifters anyhow...Luddite (no offense intended). I have several sets of wheels and change between the Shimano 9spd 11-34 and campy 10spd cassettes by just readjusting the limit screws and a small tweek on the road until everything is perfect again. BTW I found the Centaur hub with the Shimano spline pattern (apparently made by campy) for the 11-34t. I have since found that there are some after market hub bodys that can be exchanged. A good source would be peter@vecchios.com. He has setup some touring bikes this way and knows where to buy the items.

alcanoe

He doesn't have a triple with a 22 small ring (22/36/46). A major function of the rear derailleur is to maintain chain tension. The rings play an important role in determining the need for a long-cage mountain bike RD.

Cross shifting is no additional problem (not a good idea in general) as the chain should be sized big enough so it fits the big ring and the big cog, otherwise you'll brake the chain if your forget. Small ring (22) to small cog (11 or 12) will cause the chain to rub on itself at the jockey wheels even with a long cage RD. That makes a noise which tells you that you are crossed, but it causes no damage or problems.

Al

oldster

The Shifters are Shimano DA, DT's, Hub is Ultegra,and the RD is a Megarange so it will shift the big rear gears...I was, and still am hoping, that I could come up with a 9 or 10 sp casette with a bigger low range than the 12-27 Ultegra for the hills..The Sram 10 sp are to much loot. Guess I am Gonna fool around with the crankset next...Thanks !
Bud

HillRider

I believe you, I just wondered how you got it.

I have a 13x27 9-speed Shimano cassette on one of my bikes and, no, Shimano didn't make it in that form, I did.

HillRider

Sure you can get a lower range than a 12x27. Shimano makes their MTB 9-speed cassettes in 12x32 and 11x32 and 11x34. Given the rd you have, any of these will work.

BTW, If you want REALLY low gears, I just saw a Velo News article saying that Shimano has just introduced a new CS-HG61 9-speed MTB cassette that's 12x[b]36[/]. It will work with Shimano's "Shadow" design rear derailleurs, what ever thay are.

urbanknight

My fault for assuming. The guy I'm walking about was on a compact double. I know all about chain wrap, cage length, and cross shifting.

laura*

Shadow = XTR RD-M972 or XT RD-M772 or SLX RD-M662

The derailleur body hides "behind" the cassette, i.e. in its shadow, so that it is less likely to hit trailside obstacles.

HillRider

Thank you. These trade and marketing names sneak up on me occasionally since I don't follow MTB components that closely.