Question RE Shimano 10 Speed...12-34 cassette

[Ralph]

Any of you successfully using a 12-34 10's cassette with a 34-50 and med cage RD? If so....which RD....105 or Ultegra....or does it matter. A friend is thinking about this for some hill climbing. I have Campy experience, not Shimano. But I can make it work, if it works. Believe a 34 with med cage is a little out of Shimano specs. Do you have to run the chain tight to make upper pulley clear, etc. Reverse B screw? Thanks

[eddief]

no worries with 9 speed mountain long cage...maybe medium cage too. good hardware store should have longer bscrew.

[Ed-B]

The Deore XT M772 GS (mid cage) shadow derailleur works very well with 11-34 and 12-34 ten speed cassettes, 34/50 cranksets and STI controls (but not the 4700 with new cable pull ratio). And the XT CS-M771 10 speed cassettes are available in 11-32, 11-34, 11-36 ratios. I have this configuration on several bikes. You will need an adjuster on your cable stop, or an inline adjuster somewhere.

[Ralph]

Also....After thinking about it...like Eddief says above.....I seem to remember that a Mtn bike 9 speed long cage works with 10 speed road shifters (but not a 10 speed mtn long cage). If med cage 10's road RD won't work.

[Ed-B]

Originally Posted by Ralph

Also....After thinking about it...like Eddief says above.....I seem to remember that a Mtn bike 9 speed long cage works with 10 speed road shifters (but not a 10 speed mtn long cage). If med cage 10's road RD won't work.

That's right. The M772 above is actually an mtb 9 speed mechanism. The various 10 speed road derailleurs weren't designed for anything beyond 27-30 tooth cogs.

[rccardr]

Originally Posted by Ed-B

That's right. The M772 above is actually an mtb 9 speed mechanism. The various 10 speed road derailleurs weren't designed for anything beyond 27-30 tooth cogs.

Correct.
Actually, pretty much ANY Deore RD from 6 speed thru 9 speed will play nicely with a 10 speed 34 tooth big cog and a compact crank. EG:

[dddd]

Originally Posted by rccardr

Correct.
Actually, pretty much ANY Deore RD from 6 speed thru 9 speed will play nicely with a 10 speed 34 tooth big cog and a compact crank. EG:

Not if you'll be wanting it to index.

Use of the 6s series derailers results in very inaccurate indexing going up to the largest cog of any 8s or wider cassette, and even the 7s models leave something to be desired in this regard as the actuation ratio trails off toward the largest cogs.

When using an indexed shifter of greater than 9 speeds, an older 8s derailer's upper guide pulley should ideally be revised to one with less float.