# Road Derailleur on MTB?



## Baulz (Sep 16, 2005)

Last summer I realized that I don't have any use for my bigring. So I have removed it along with the front derailleur and shifter. I am currently using a XTR midcage derailleur (8spd) with a 12-32 cassette. Has anyone tried using an Ultegra or DuraAce short cage derailleur with a 32t cog? I have seen XT's with short cages, but my goal is obviously to save weight. 

Thanks


----------



## Cloxxki (Jan 11, 2004)

What's keeping the chain on the middle ring now?

I am (slowly) building a 1x9 setup mysel, for racing. The Ultegra derailer I have (2004 or so) seems to reach the 32t just fine. I will race the bike mostly with a 12-27 or 11-27 probably, 29" wheels and 36t chainring. But for some races with steep climbs out of hairpins, I may throw a 11-32 on. Have not tested it yet with a chain let alone my weight on the wheels, but some DH folks do it already. I think one factor is where your hanger sits below the axle. Lower being better for this purpose.
Shimano obviously says it doesn't work. My Ultegra without drilling or anything is now 207g, I refuse to pay XTR or X.0 money when what I've got works just fine and weighs more or less the same.
Don't buy a new derailer to save the weight, there's better ways to invest those bucks in grams, I'm sure.


----------



## Baulz (Sep 16, 2005)

Nothing is keeping the chain on right now! I am working on a couple ideas for a simple lightweight guide. Made a couple carboard prototypes so far...

The other thing I was wondering about was simply buying (or making) shorter cages for my XTR. Anyone done this before? Would the Ulegra derailleur cages even fit on an XTR derailleur.


----------



## nino (Jan 13, 2004)

Baulz said:


> Nothing is keeping the chain on right now! I am working on a couple ideas for a simple lightweight guide. Made a couple carboard prototypes so far...
> 
> The other thing I was wondering about was simply buying (or making) shorter cages for my XTR. Anyone done this before? Would the Ulegra derailleur cages even fit on an XTR derailleur.


short cages do just up to 28t on the cassette!

with a 32 you need at least a mid-cage like the one on the XTR. short road cages won't work!


----------



## Zanetti (Sep 18, 2005)

I'm currently running an eight speed XT rear derailleur with a nine speed Ultegra cage grafted on to it. My cassette is a 12-32 XTR eight speed. With proper chain length and a little fine tuning, this setup works fine. The guide pulley tracks really close to the 32 tooth cog though.


----------



## 21switchbacks (Sep 22, 2004)

nino said:


> short cages do just up to 28t on the cassette!
> 
> with a 32 you need at least a mid-cage like the one on the XTR. short road cages won't work!


I don't think this is right. There are two numbers or "capacities" associated with a rear derailleur. One is the amount of chain it will take up, i.e., the difference between the biggest and smallest gear that you run - this is associated with cage length. The other is how big of a rear cog you can run. This is more function of how far the top pulley is from the axle and has nothing to do with cage length. All Shimano road derailleurs are spec'd to run a max 27-tooth rear cog regardless of cage length. All Shimano MTB derailleurs are spec'd to run a max 34-tooth cog regardless of cage length. In short, cage length has nothing to do with how big of a cog you can run.

However, Shimano's specs are always conservative in this area. Their road derailleurs will work with a cog bigger than 27. I have run a road derailleur (short-cage, FWIW) with a MTB cassette and could use a 30-tough cog with no problem. When I shifted into the 34, the top pulley would ride along hitting the outside of the cog. I don't know how it would have done with a 32 but I don't think that would have been doable either.


----------



## Hosehead (May 4, 2005)

Regardless of whether or not Shimano recomends it, it will work. Choosing the correct chain length, and avoiding big-big and small-small gear combinations is critical for it to work properly.

I used an Ultegra derailleur on my 3x8 back in the mid nineties. 22-32-42 up front 11-28 out back. There are LOTS of people who still use roadie RDs on ther MTBs.


----------



## nino (Jan 13, 2004)

*sure - i do...*



Hosehead said:


> Regardless of whether or not Shimano recomends it, it will work. Choosing the correct chain length, and avoiding big-big and small-small gear combinations is critical for it to work properly.
> 
> I used an Ultegra derailleur on my 3x8 back in the mid nineties. 22-32-42 up front 11-28 out back. There are LOTS of people who still use roadie RDs on ther MTBs.


i'm using such derailleurs since about 6 years. no bigger than 28t with road derailleurs though! ...
http://light-bikes.com/bikegallery/BikeListing.asp?id=774


----------



## Boon Fly (Mar 3, 2004)

*9 spd DA*

A buddy of mine used to run a 9spd Dura Ace rear der with XTR Rapidfire. If I remember he used an 11-32 XTR cassette with a long cage der. He wasn't looking to save weight necessarily but he really preferred the stiffer spring rate of the D/A der. of that day. I think the new XTR has that stiffer spring rate but of course then your locked into Dual Control, but I digress...


----------



## eurorider (Feb 15, 2004)

21switchbacks said:


> All Shimano MTB derailleurs are spec'd to run a max 34-tooth cog regardless of cage length. In short, cage length has nothing to do with how big of a cog you can run.


Besides Shimano MTB derailleurs, I've been told that all the SRAM (long, medium _and_ short) MTB derailleurs are designed to clear 34t cogs. I guess you would agree with this as well?


----------



## Knut (Jan 12, 2004)

If you have trouble clearing a 32T cog with a road derailleur try screwing the B-tension screw out and insert it from the other side. The head will lift the pulley a bit farther away from the cassette.


----------

