Bicycle Mechanics - 105 Longcage + MTB Cassette?

Long story short,I'm looking to re-gear my Element cross bike for the street. I've got a new 11-34 SRAM cassette laying around and I'm considering swapping it for the stock 12-26. Rear spacing is fine and they're both 9sp. I can't find any info about the 9sp 105 derailleurs on Shimano's site. I know the short cage one's won't handle this cassette,but I think this one might. I measured the distance between the pulley spindles and it came to about 84mm. I also measured the one on my Coda which has a Deore XT and an 11-32 cassette,and it came to about 86mm. Think the 11-34 will work with the 105? Thanks in advance.

Cage length is all about chainwrap capacity. The largest possible cog is more about the derailleur's upper parallelagram. For cogs larger than 30 you will need a mountain bike type derailleur. Shimano road derailleurs, short and long cage, are rated to 27 tooth maximum cog size but will usually go to 30.

Al

I agree, if you really want a 34, then something like a Deore LX should do the job well.

Not all Shimano mountain RDs are rated for 34 teeth, so you should check whichever RD you get if you go that direction.

I have been looking at the same change. I have two Giants, an OCR-2 with Shimano 105 RD, 12-26Tooth cassette and a FCR-2 with a Shram X7 RD and also a 12-26 Tooth cassette. I want to switch to 11-32 or 34 tooth cog set. My smallest chainring is 30Tooth on both bikes. I'm just trying to get to lower than 1:1 ratio fo my lowest gear on at least one of these bikes. Will the Shram X7 handle the change any better than the Shimano 105? Will a MTB RD mount the same as the road bike RD?

I rode the Deathride last year with a 34 tooth cassette. I had to take off my 105 deraileur and use my XT deraileur because the jockey pulley hit the 34 tooth and made a racket. Seemed to work ok on 30 tooth cog though.

What is the range of the crank set you have. You can't calculate chain wrap capacity without taking the crank into consideration.
Subtract the small ring from the big wring on the cassette and the chain rings, then add these numbers.

Ex. (34-11) + (44-22) = 45 This is your chain wrap capacity.

After calculating this number, either ask your LBS to look up the derailleur and give you the CWP, or let me know and I'll look it up at work.

I'm not sure if SHimano would list this on their site or not.

I . I want to switch to 11-32 or 34 tooth cog set. My smallest chainring is 30Tooth on both bikes. . Will the Shram X7 handle the change any better than the Shimano 105? Will a MTB RD mount the same as the road bike RD?

Yes and no.

The SRAM X.7 has a 34 large rear cog capability and 45 tooth chain wrap capacity, so it'll handle the cassette. The ESP, however, is a 1:1 cable pull derailleur so it won't work with Shimano shifters.