grahameinlondon

Any help would be most appreciated.

What new rear derailleur do I need to work with my current shifters and new cassette? Is there more than 1 option?

My 10 speed road bike. For hill climbing, I am upgrading my rear cassette from 11-28T to 11-34T (CS-HG500-10).

I have Ultegra ST-6600 shifters, which I would like to use. At present I have Shimano Ultegra Rear Derailleur RD-6600,

Front rings are SG-X 53B and SG-X 39B. Capacity of drivetrain is 37.

Many thanks Grahame

cxwrench

ANY 8 or 9 speed mtb derailleur that matches your needs. Most of the 'current' Shimano 9 speed mtb derailleurs only come in SGS (long cage). That will work fine for you. Some of the older GS (medium cage) derailleurs would probably work as well, just confirm the capacity spec.

Supercardplayer

Good question I have a 34 tooth cassette on my bike. so you have to good options get a medium cage road derailleur that will work with that cassete just fine . meanwhile my setup is a short cage dearllier with a wolf tooth road link dearlier extender that will work with a bigger cassete. the road link basically makes the derailleur hanger longer. another options is if you're running 9 speed road you can youse a mountain bike derailleur and it will work fine with that cassette if you're running a 9 speed setup. so those are you're options.

grahameinlondon

Thanks so much. But I don't understand how a 9 speed derailleur will work on a 10 speed? Where can I find the pull ratio for my ST6600 shifters?

Bill Kapaun

The difference in pull amount is in the shifter. 7-9 speed for road & mountain RDER's (with rare exception(s) you don't have to worry about) are all the same ratio.
As the number of cogs go up, cog spacing gets closer so the shifter pulls proportionately less.
The shifter is the master and the RDER is the slave.

cxwrench

No, there are no 10spd road derailleur that work w/ a 34t cog. And while a Wolftooth road link will allow the derailleur to clear a larger cog than it's made to work with it won't magically make the cage any longer so it won't wrap the extra chain needed for the larger cog. This info is posted on the WT site. You clearly don't understand how rear derailleurs work and what 'capacity' is. Stop giving advice til you know what you're talking about.

woodcraft

+1

$20 for the Road Link plus a new chain and you're in business.

Cyclist0108

My wife has a 10 speed road derailleur on her bike and an 11-36T (SRAM) cassette. I very much respect your knowledge and experience, and I realize what she has is out of official Shimano spec, but it does work perfectly fine and has done so for several years without incident (the shifting works well, even on the 36T cog). My own case is 11-speed, but my first-generation Ultegra Di2 medium cage is specced for 32T max, but it works fine on 36T and 34T and without any deterioration in shifting quality or component life. Shimano is very conservative with their recommendations.

woodcraft

I have a Force 10 sp medium cage RD that absolutely works with 11/34 cassette,

and have been running short cage RD/ Road link 11/34 & 34/48 for several years without issue (there is a little slack in small/small which I never use).

Lighten up on a new poster.

Bill Kapaun

Just because it works on YOUR bike with YOUR UNSPECIFIED RDER doesn't mean it'll work on someone else's bike.
RDER hangar geometry can vary between different bikes.
OP already has a MEDIUM cage RDER.
Why don't you specify EXACTLY WHICH medium cage RDER will work?
A 6600 lists a 27T max cog size. VERY unlikely it would even handle 32T, and 30T could be problematic.

HillRider

The rear derailleur doesn't know or care how many cogs you have, only how far it moves from a given cable pull. Shimano 7,8,9 and 10-speed road and 7,8 and 9-speed MTB derailleurs all use the same cable pull geometry so they will work with any Shimano 7,8,9 and 10-speed shift levers and cassettes with matching speed count. Your ST-6600 shifters are 10-speed and will work with a 10-speed cassette and any of the above compatible rear derailleur generations.

The rd compatibility breaks down at 10-speed MTB and all 11 and 12-speed components.

cxwrench

No. I'll give him crap as I see fit. It's always a good thing to know your limitations and if you don't then know them someone needs to point them out. In your case the Force med cage is spec'd for a 32. Some people, like you, will get it to work. Bear in mind the big problem isn't getting the derailleur to shift into the bigger cog, it's the fact that the pulley cage will only wrap so much chain. If you add the dreaded Road Link your pulley cage doesn't magically get longer. You can shift into the 34 or 36 or whatever over-spec cassette you put on but it doesn't mean things work correctly. You can size the chain long and maybe have a little droop in the small/small, or you can size it normally and risk ripping the derailleur off in big/big. ALL modern drivetrains are engineered to work big/big so you should be able to do that w/o wrecking anything.

Cyclist0108

What magical thinking explains my two cases?

cxwrench

Let me explain this differently than the others have. There are no 'clicks' in a derailleur. It will move smoothly from high limit to low limit. The 'indexing' lives in the shifter.The shifter and the geometry of the derailleur determine how much it moves when the shifter pulls a set amount of cable. The nice thing about the older Shimano stuff...up to 10 speed road and up to 9 speed mtb, is that they all used the same cable pull ratio. You can mix and match any of those parts and they'll work perfectly. Mtb cable pull ratios changed at 10 speed (Dyna-Sys) and again at 11 speed (Dyna-Sys ll) and road also changed at 11 speed so you can't use any of those w/ the older 7, 8, or 9 speed derailleurs. Make sense?

woodcraft

Someone that just joined, has 5 posts, gives better than many input, your own contribution is questionable,

and you bite his head off? Classy.

Bill Kapaun

I think post #10 explains it.

Cyclist0108

For the record, 34T is in fact within spec, according to Shimano for its Tiagra rear derailleur:




However, if I was the OP (and hadn't been put off by all the hemming and hawing), I would try the Shimano Ultegra Rear Derailleur RD-6600 first, and see if a B-screw adjustment would enable a 34T to be accommodated.

Bill Kapaun

The 4700 has a different cable pull ratio.

Siu Blue Wind

Yeah being brash doesn't sit well with me..

cxwrench

You might want to ignore list me cuz I'm pretty old and have been like this for a long time.

Homebrew01

People can change.

Bill Kapaun

A moderator is more likely to remove you than ignore you.

Cyclist0108

You could also have written:

The 10sp Tiagra rear derailleur will work with both road and mtn shifters, fwiw.

The assertion was
I was simply providing a counter-example.

But the 34T will in many cases (including mine) with an Ultegra medium cage derailleur.

Even if it can't, the same information can be conveyed, possibly in a more compelling manner, if it is presented in a way that doesn't include the stuff about incompetency and not being a member of the club.

Heck, I'm a scientist with zero social skills, and even I can work that out.

Supercardplayer

Ok ok I have experience in this topic and was showing how I got it to work with my setup . Don't make up a story and say I said it to make me look wrong .

Supercardplayer

Please me nice and don't be elitist telling everyone that there wrong even if your right . These are the thing I really don't like about bike forms ,