Popeyecahn

So in trying to coax a more useful gear range for me on the Vitus, I found a 13-34 cassette to slap on the back. I thought my Ultegra RD-6500 long cage would do, but as was pointed out by member T-Mar in another thread, it will not because there is more at play than just wrapping the chain around a cog.

So I started looking at the MTB range of RDs and the best I could come up with were: RD-M700 (6 spd I think but maybe the H/L adjusters could be tweaked to 7spd?), M560, M570/571, M730, M737, M751 and M761. These were the only ones I found that positively indicated a 34t capability. I'm also guessing these are all top normal as well.

I'm guessing anyone will do more of less depending on whether or not likes how it functions and looks. Obviously the Deerhead M700 would be the most gratifying looks wise, but right now I need function over form, though maybe a compromise is possible (or necessary?) with any of them.

I sure I missed something along the way, but my question is this: Has anyone else done similar and what did you do, and/or are there any thoughts, suggestions or infinite wisdom anyone might care to bestow upon my ever grateful soul?

cyclotoine

i suggest using a 32T large cog cassette to maintain looks?

ThermionicScott 

I can't speak to the other models, but the M550/560 is all but guaranteed to work, and work well. In action on a 7-speed "K" cassette (13-34):



Given the range you're asking it to shift, I can't see the non-slant parallelogram of the Deerhead doing as good of a job.

Popeyecahn

Point taken and that has crossed my mind, except that I would need to get a new CR to get the same gear ratio I'm looking for in addition to the cassette and another RD. The "K" unit I have covers the ranges.

The great firewall at work won't let me see the pic, but thank you very much for the info, I'll have a look at home. I did find some M550's, but the info on Velobase indicates 32T max. so I'll keep a look out for the 560 at 36T.

Jeff Wills

Shimano's "limits" are always very conservative. I used M550 Deore derailleurs with 34 tooth cogs on a couple bikes- never had a problem.

Popeyecahn

Thanks! I found some in the usual finding place for a reasonable price (unlike the assorted NOS varients I find for $125!). On toward wallet reduction exercise!

Popeyecahn

Success! Installed the 550, K cassette and new chain, adjusted for quail and rocked on down the road. Shifts fine and my legs are thanking me already lol Thanks again for the info

Popeyecahn

Well on closer inspection this morning, I noticed that the upper jockey wheel was contacting the teeth on the 34 cog and creating a bumpy motion, so either the chain is too short, or something else needs adjustment that I'm not aware of...?

Fiddling about with some other aspects than the limit screws increased the distance between the 2 gears enough to reduce the bumping noise. Hmmm... wait the bike is upside down right now, maybe gravity is playing into this, because I didn't notice is yesterday on the stand?

balindamood

I have had issues with Shimano derailleurs taking a 34T cog, although it is mostly the early 1990's models with this problem. The first adjustment is to run the B screw (at the top of the derailleur behind the mounting bolt) all the way in. On early 1990's Deore DX derailleurs, this still is not enough. On those, as well as some newer Ultegra 6500/6600 SGS models, I take the B screw out, and run it in from the back side (the head of the screw rests on the drop out). I have been running two bikes with 34T cogs this way for years without any issues.

Popeyecahn

Thanks, I'll give that a go!