Dura Ace 7800 with 11/32 cassette?

[transform]

i am picking up a used EM 53/39 double with a Dura Ace 7800 rd and an Ultegra 11/23 cassette. i wish to change the cassette to a 11/32 and not sure if the DA rd will handle it. any suggestions on what i need to do to put a 11/32 on this EM?

[oldpotatoe]

[QUOTE=transform;1278308]i am picking up a used EM 53/39 double with a Dura Ace 7800 rd and an Ultegra 11/23 cassette. i wish to change the cassette to a 11/32 and not sure if the DA rd will handle it. any suggestions on what i


Probably Only if you make the chain artificially short so the top pulley clears the 32t. Depending, the chain will probably be too short for big-big combos. Better solution is to get a shimano 9s MTB rder..and not worry about. cannot use shimano 10s MTB RD, not compatibile with road 10s STI shifters.

[shovelhd]

30T, yes, 32T most likely not depending on the derailleur hanger and B screw. You can play with 10T jockey pulleys but no guarantees. I'd swap the RD out with a 105 GS or an MTB RD like oldpotato suggests.

[dave thompson]

The upper jockey wheel of the 7800 rear der won't clear the big cog on a 32t cassette, not even close. A long-cage road derailleur won't either. It's not a matter of cage length, it has to do with the length of the 'knuckle' of the derailleur, a part of its design.

As others have said, a Shimano 9-speed MTB rear derailleur will work and is a very common way to run a large cassette on a road bike without issue while using 10-speed shifters.

As an aside, I found that a 6700 or 7900 rear derailleur will clear a 32t cassette and operate well, at least on the 5 bikes that I've run that combo on. I wouldn't know if that would work on your bike until it was tried. Shimano did redesign their road derailleurs in the 5700/6700/7900 series with a slightly longer 'knuckle' which allows better compatibility with larger cassettes.

[transform]

thanks to all of you for sharing your info. i think i'm going to go with the shimano xls mtb deraillier along with a SRAM 11-32 cassette. my preference would have been to keep my current rd and use a Shimano 11-32, but since that's not possible as far as i can discern, the former will be the way to go...unless there are other possibilities i haven't discovered.

thanks again to all!!!:hello:

[godfrey1112000]

30T, yes, 32T most likely not depending on the derailleur hanger and B screw. You can play with 10T jockey pulleys but no guarantees. I'd swap the RD out with a 105 GS or an MTB RD like oldpotato suggests.

Extend the Hanger or move to the MTB RD, or both

My LBS did the Both for my Riding partner, with SRAM, also went from RED to Apex or Rival

[Chance]

thanks to all of you for sharing your info. i think i'm going to go with the shimano xls mtb deraillier along with a SRAM 11-32 cassette. my preference would have been to keep my current rd and use a Shimano 11-32, but since that's not possible as far as i can discern, the former will be the way to go...unless there are other possibilities i haven't discovered.

thanks again to all!!!:hello:

The only one that comes to mind is to try an inexpensive 11-28 to see if it meets your needs. It can be a simple and quick test. You may be stronger than you think.

[krismac23]

Invert the B screw if you need clearance. Making the chain shorter is a horrible idea. Won't solve your clearance issue and will only add more stress to the chain. Your problem is the top pulley not clearing the 32t. If the b screw trick doesn't work, maybe take your der. hanger to a local machine shop. Experimental prototype also does custom cassette machining if you email him on pricing. http://hellore.se/experimentalprototype/

[oldpotatoe]

Invert the B screw if you need clearance. Making the chain shorter is a horrible idea. Won't solve your clearance issue and will only add more stress to the chain. Your problem is the top pulley not clearing the 32t. If the b screw trick doesn't work, maybe take your der. hanger to a local machine shop. Experimental prototype also does custom cassette machining if you email him on pricing. http://hellore.se/experimentalprototype/

Well shortening the chain is a bad idea but will roll the RD away from the cogset enough to have the pulley clear the biggest, 32t, cog.

Won't add any stress to the chain, it will to the RD lower spring if the cage is pulled forward a lot(which rotates the pulley away from the cog).

Just my opinion but just using a MTB RD(or perhaps a 7803, 66/6703) seems easier than machining a longer der hanger.

If the 'EM' m3entioned is a steel one or some of the aluminum ones, no detachable der hanger anyway.

[Chance]

Probably Only if you make the chain artificially short so the top pulley clears the 32t. Depending, the chain will probably be too short for big-big combos. Better solution is to get a shimano 9s MTB rder..and not worry about. cannot use shimano 10s MTB RD, not compatibile with road 10s STI shifters.

If you make the chain that artificically short, what happens when rider is in the big ring? Obviously big-big won't work, but since the big ring is 14 teeth bigger than the small ring, will the big ring be usuable with the 28T cog? Or the 24T cog? Just how short would you make chain?

Personally don't know, but going outside manufacturers' specs can be risky, particularly if the rider doesn't understand equipment limitations extremely well.

[zandrrr]

This application sounds perfect for a compact crank.

[madcow]

Chance is right about shortening the chain, it will leave you with too many unusable gears while in the big ring (it also still wouldn't fix your problem with a 7800), and if you should happen to have a minute of inattentive shifting and end up in one of those gears... not good.

I've done a lot of experimenting with different setups because of the project builds we've done. First you have to realize that there is no golden rule because every frame and it's hanger length is different.

On most frames, a 7800 will not work with a 32 regardless of pulley size, or chain length. Moving to a longer cage derailleur of the same generation does not improve your situation as the problem does not stem from cage length but more from the parallelogram which is the same within years for most models. A longer cage would improve your chain wrap capacity which can also sometimes be an issue when running an mtb cassette on a road bike but does not really improve clearance. (though an increased chain wrap capacity can allow for more variation and therefor a shorter chain which does help a bit.)

The 7900 generation of derailleurs have longer parallelograms (this also includes the latest ultegra and Di2 derailleurs as well.) Moving to one of these is your best bet. A short cage with a 10t upper and some b-tension adjustment can handle it with room to spare.

With 7800 a 28t is a safe bet.

[oldpotatoe]

Chance is right about shortening the chain, it will leave you with too many unusable gears while in the big ring (it also still wouldn't fix your problem with a 7800), and if you should happen to have a minute of inattentive shifting and end up in one of those gears... not good.

I've done a lot of experimenting with different setups because of the project builds we've done. First you have to realize that there is no golden rule because every frame and it's hanger length is different.

On most frames, a 7800 will not work with a 32 regardless of pulley size, or chain length. Moving to a longer cage derailleur of the same generation does not improve your situation as the problem does not stem from cage length but more from the parallelogram which is the same within years for most models. A longer cage would improve your chain wrap capacity which can also sometimes be an issue when running an mtb cassette on a road bike but does not really improve clearance. (though an increased chain wrap capacity can allow for more variation and therefor a shorter chain which does help a bit.)

The 7900 generation of derailleurs have longer parallelograms (this also includes the latest ultegra and Di2 derailleurs as well.) Moving to one of these is your best bet. A short cage with a 10t upper and some b-tension adjustment can handle it with room to spare.

With 7800 a 28t is a safe bet.

I would hope so since shimano makes road 11-28 BUT, I have installed many shimano 10s STi and barends with 11-32/4/6 10s cogset using a MTB rear der and there is no clearance problem in small ring and pulley to big cog and plenty of chain for big-big combos.

7800, 7700(9s), 5600, 5700...etc.

Last one was a Waterford touring rig with 7800 STI, triple, Deore 9s MTB rear der, 11-36 10s cogset..worked just fine..

[Pete Mckeon]

with a 32. works fine for my riding. :) pardon the spelling fingerflub of mine above



Chance is right about shortening the chain, it will



leave you with too many unusable gears while in the big ring (it also still wouldn't fix your problem with a 7800), and if you should happen to have a minute of inattentive shifting and end up in one of those gears... not good.

I've done a lot of experimenting with different setups because of the project builds we've done. First you have to realize that there is no golden rule because every frame and it's hanger length is different.

On most frames, a 7800 will not work with a 32 regardless of pulley size, or chain length. Moving to a longer cage derailleur of the same generation does not improve your situation as the problem does not stem from cage length but more from the parallelogram which is the same within years for most models. A longer cage would improve your chain wrap capacity which can also sometimes be an issue when running an mtb cassette on a road bike but does not really improve clearance. (though an increased chain wrap capacity can allow for more variation and therefor a shorter chain which does help a bit.)

The 7900 generation of derailleurs have longer parallelograms (this also includes the latest ultegra and Di2 derailleurs as well.) Moving to one of these is your best bet. A short cage with a 10t upper and some b-tension adjustment can handle it with room to spare.

With 7800 a 28t is a safe bet.

[Chance]

I would hope so since shimano makes road 11-28 BUT, I have installed many shimano 10s STi and barends with 11-32/4/6 10s cogset using a MTB rear der and there is no clearance problem in small ring and pulley to big cog and plenty of chain for big-big combos.

7800, 7700(9s), 5600, 5700...etc.

Last one was a Waterford touring rig with 7800 STI, triple, Deore 9s MTB rear der, 11-36 10s cogset..worked just fine..

What you proposed initially is not comparable at all to using a standard 11-28 cassette with chain cut to the right length. That will undoubtedly work fine across all combinations including the 53/28 because it falls within Shimano specs. But the 11-32 with “artificially short” chain is a different animal altogether.

There are many options but using a very short chain should be put on the back burner in my opinion. He can install an 11-28 and try it out. That’s a quick and cheap test (of himself, not the bike). Or he can use an MTB derailleur with MTB size cassette as you also suggested, or he can install compact cranks (like zandrrr suggested) with an 11-28 cassette. There are lots of options that don’t risk a major screw-up.

[oldpotatoe]

What you proposed initially is not comparable at all to using a standard 11-28 cassette with chain cut to the right length. That will undoubtedly work fine across all combinations including the 53/28 because it falls within Shimano specs. But the 11-32 with “artificially short” chain is a different animal altogether.

There are many options but using a very short chain should be put on the back burner in my opinion. He can install an 11-28 and try it out. That’s a quick and cheap test (of himself, not the bike). Or he can use an MTB derailleur with MTB size cassette as you also suggested, or he can install compact cranks (like zandrrr suggested) with an 11-28 cassette. There are lots of options that don’t risk a major screw-up.

I was responding to the fairwheel bike guy's post..

I think I mentioned more than once that a too short chain, artificially short chain was a bad idea.

But if you stayed in the small ring, you could use a short cage RD and use a 11-32. I did this very thing for a lady for the Mt Evan's hill climb..8s DuraAce..MTB 8s cogset..made the chain really short, made her promise to stay in the small ring..she did and finished..then I installed the road cogset and new chain.