woodrow5

Well, I have done many researches for upgrading my tandem. I bought 6603 10spd Shifters, Sram 10spd cassette, 10 spd chain. However it doesn't work with 10spd XT M780 Rear Derailleur.

With proper wire cable installation; I still couldn't shift the RD to last two biggest teeth sprockets. I have searched couple post and people said Ultegra 6603 doesn't work with any RD with Dyna Sys...

Do you guys have any solution ?

Thanks!!

jimc101

10 speed road and MTB Dynasys won't work, as they were never designed to be compatible.

You can use a Shimano road 10 speed RD, like a 5700 or 6700 GS version, I use a 5700 STI, 5700 GS rear with a SRAM 11-32 cassette, and have had no issues with it.

shelbyfv

What he said. Plus, you could also use a Shimano 9 speed mtn bike RD.

HillRider

Youe best bet is a 9-speed Shimano MTB rear derailleur. Shimano's road rear derailleurs are rated for 27 or 28T maximum rear cogs and, while you hear of some successes using 30 and even 32T cogs with them as jimc101 reported, it's not a reliable match. A 9-speed MTB rear derailleur is guaranteed to work.

IthaDan 

Any long cage shimano should do it. If you need more downward displacement of the RD you can either source a longer b-bolt, or take off the RD and flip the b-bolt around so the head is hitting the sharkfin on the RD hanger. Just an old trick to add to the repertoire.

mechBgon

I'd go with an XT RD-M771 for your setup.

HillRider

If you have to buy something, why not get the right design from the beginning? Yeah, if you alread have a road rd, you can try to jury rig the b-screw or make other adaptations to see if it works but if you are starting from scratch, get the correct part.

woodrow5

Thank you folks!

Road bike long cage rear derailleur may work on 11-32t. But it all depends on the drop out length.
But mount bike rear derailleur long cage will assure with no problem.

cycle_maven

Well, the 9-speed stuff has a tiny amount more float in the guide pulley- it moves side-to-side a slight amount more in the 9-speed than the guide pulley in the 10-speed rear derailleur. This leads to less than perfect shifts in the smaller cogs. I typically will file the spindle by about 1 mm when using 9-speed derailleurs in 10-speed systems to decrease the float, and get much crisper shifting.

HillRider

Interesting. I'm using a 9-speed Ultegra rd (RD-6503) on an otherwise Shimano 10-speed bike with a 12x27 cassette and, if the shifting is compromised, I sure can't tell. Compaired to an all 9-speed group and an all-Campy Chorus 10-speed group the shifting is just as good.

IthaDan 

Totally agreed. I guess just tossing out some of the tricks of the trade I'd picked up over the years. Plus, I wasn't really thinking when I posted that, hadn't had my coffee yet.