Campag EPS rear derailleur capacity

Discuss light weight issues concerning road bikes & parts.

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by naavt

I've always used a 52-36 with 12-29 cassetes on my mechanical Campag groupsets, just because I had the notion that Campag rear derailleurs didn't accept an 11-29 cassette with my chainring configuration.

I'm now assembling an EPS system on one of my bikes. Have read the EPS rear derailleur manual again and the cappacity stated there is 33 teeth. I've always used 12-29 since its the limit capacity mentioned by Campag (52-36=16 + 12-29=17 so 16+17=33 teeth).

Anyway, today I was watching a local born rider bike (Nelson's Oliveira) and came accross with a big surprise: The presenter mentions Oliveira's bike as having an 11-29 cassette.

Is he wrong or its just true?

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by audiojan

I have a 52/36 non round rings with 11-29 and it’s just fine SR11EPS
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by Mockenrue

I've used an 11-29 cassette with 52/36 and 53/39 chainsets with no problems whatsoever.

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by bm0p700f

53/39 with 11-29T is fine as is 52/36 and 50/34 will have marginal chain tension in 34/11. However try a 11-32T cassette and you wont have capasity to maintain chain tension even with a 53/39T

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by naavt

So that's great news, since EPS wont let you cross-chain anyway, right?

What cassette configuration are you running? 11-12-13-14-15-17-19-21-23-26-29 ?

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by Miller

It's only Di2 doesn't let you cross-chain, EPS lets you cross-chain to your heart's content. The useful cross-chain is big-big where you'll have plenty of chain tension.

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by graeme_f_k

bm0p700f wrote:
Wed Feb 13, 2019 3:44 pm
53/39 with 11-29T is fine as is 52/36 and 50/34 will have marginal chain tension in 34/11. However try a 11-32T cassette and you wont have capasity to maintain chain tension even with a 53/39T
I've written about this several times before.

To re-iterate:
It's not about chain wrap or chain tension and Campagnolo don't recommend 11-29 with EPS - running it voids warranty.

The problem is that with some dropouts in some frame geometries, that fall within the Campagnolo specifications, with 11-29, the chain can "skip" the 11 on upshift and jam between the frame and the sprocket.

This doesn't happen with a correctly set H screw on 11-27, 11-25 or 11-23 because the tracking angle of the RD is such that these smaller biggest sprockets allow the top jockey to stay close enough to the cassette to control the chain correctly when it reaches the 11 cog.

On some dropouts (depending on the length, the flexibility of the hanger and the exact position of the hanger "hook") and in some frames (depending on the rear triangle length and the exact entry / exit compound chain angle generated by the combination of chainring size, BB drop and chainstay length), 11-29 presents no problems. In other cases it does.

Hanger flexibility is not something that Campagnolo can specify so they make a "reasonable assumption" about that - but given a hanger flexibility that is within that reasonable expectation, within the dimensional specification envelope published by Campagnolo exist instances where 11-29 is OK and instances where it isn't.

Wear and tear and differing accuracies of set-up also need to be considered - hence the reason for the recommendation and also the reason for rejecting warranty claims, since jamming may cause knock-on damage that may cause a failure immediately, or later, in the life of the transmission components.

Techs who recall well, will know that in the early days of production EPS (v1 up until Feb 2012), the overshift function that is built into the RD behavious, when going from next-to-top to top gear was set at 0.5mm. This was reduced to 0.25mm in iterations after that date in order to maintain better control in this shift but still give fast shifting into the big ring x top sprocket gear under load. This change gives sufficient chain control in 12-29 (which size cassette was launched at the same time) but not in all cases, in 11-29.

Even if the hanger permits it or can be modified to permit it and / or the H screw setting permits it or can be modified to permit it, the problem is even worse in cases where 11-32 is run.

If it was as simple as all that, Campagnolo would have simply bowed to consumer demand and said "OK, run 11-32 with all of our 2009-2014 pattern 11s RDs" ... they didn't, because of the problems reported from extensive lab & field testing with amateurs and teams on a very wide variety of frame geos and exact set-ups. I aws peripherally involved with that so I know how extensive the testing was and actually rode some of the bikes under test. Some were OK, some were not.

I have also personally worked on bikes for amateurs and for professional teams where the shifting with 11-29 and 11-32 has been acceptable ... and instances where "awful" doesn't begin to describe it.
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by Calnago

Graeme... thanks once again. I always knew that the 11-29 combo was kind of a no no for EPS, but I’ve never been sure why, except that it must be due to things found during testing, exactly as you just describe. In any case, whenever I’ve set them up I’ve always kind of been extra cautious and test it out thoroughly down there, but I guess I’ve been lucky enough to never have come across a “bad scenario”. It’s not like I’m doing tons of these to have any kind of meaningful sample to go from. And even if I did, it only takes that one bike that ruins your day and then you go “Ok, so NOW I know why I shouldn’t have done that”.
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by LionelB

Thanks for the info. Can you comment on how this works with an F8 with EPS v2 ? I have a 11-27 there now and was actually thinking of trying 11-29.

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