Campagnolo 12 speed cassette compatibility

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XCProMD
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by XCProMD

I just tried yesterday a SRAM 12 s wheel on an otherwise Campag SR EPS 12s bike. Shifting is spot on. Chain was Campag 12s. 160 km, 1500 m climb, 0 issues.

One might argue the shifting is slightly smoother with a Campag cassette but not faster. EPS V4 is nothing short of otherworldly anyway.


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by Weenie


DaveS
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by DaveS

Good info. I assume that a Campy chain was used with the sram cassette?

XCProMD
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by XCProMD

Yes, Campag 12s chain. BTW frame is a Sarto Seta. I guess some dropouts can make it harder for the RD to move to the 10T cog, but clearance was plenty in all 3D with this one.


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Last edited by XCProMD on Sun Sep 22, 2019 3:08 pm, edited 1 time in total.

fehguy
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by fehguy

@XCProMD same here! Last night I hooked up my EPS shifters and tested against a SRAM 10-28 cassette. They work perfectly.

I don't have my frame ready to finish up the build, so I will send more details when it's done in a couple weeks. But for those interested, I ran a couple experiments...

* There is plenty of range between the bottom and top cog for SRAM 12 speed cassettes, even though the entire width is slightly greater than Campy
* The EPS controller seems to evenly divide the range for each of the cogs. That means you could even run a narrower 12 speed cassette with the EPS if it existed.

Overall I'm thrilled that it works, and I don't have to cobble something else together. Bravo Campy for doing the right (and obvious) thing regarding spacing and adjustment of the EPS shifters :)

octav
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by octav

Would it work with mechanical? :D It would be nice...

DaveS
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by DaveS

octav wrote:
Mon Sep 23, 2019 8:46 am
Would it work with mechanical? :D It would be nice...
It should, since the overall stack length is closer than 11 speed mismatched cassettes, that most users think works just fine. It's an assumption that eps might actually adapt to changes in the overall travel.

gwerziou
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by gwerziou

I thought I had seen a post where someone ran a SRAM flattop chain with a 12 speed Campy drivetrain and it worked perfectly. Can anyone confirm that?
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joejack951
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by joejack951

fehguy wrote:
Tue Sep 03, 2019 9:13 pm
@miller yes, English measurements in the states, and for traditional machining, it'll probably never change...
Couple of things...

1. It's been about 20 years since I've defaulted to designing in inches. I guess it depends on which industries you tend to work for.

2. I happen to be sitting here with a Campy Record 11 cassette so I took some measurements to see how it differs from the new 12 speed stuff. First, some metric conversions to make things easier for the majority (the ROW and a big chunk of the US that sees the metric system for the better way that it is :)):

.057" = 1.45mm (Campy 12 cog thickness, as posted)
.080" = 2.03mm (Campy 12 cog spacing, as posted)
1.61" = 40.89mm (Campy 12 cassette overall width, as posted)
.07" = 1.79mm (Campy 12 cassette overhang, as posted)

My measurements:
1.6mm (Campy 11 cog nominal thickness)
2.25mm (Campy 11 cog nominal spacing)
40.6mm (Campy 11 cassette overall width)
1.4mm (Campy 11 cassette overhang)

Note that if you add up my cog and spacing measurements and the same Campy 12 measurements they don't properly add up to the overall width measurement. In the case of Campy 11 this is because the 12T cog (of my 12-25 cassette) measures 1.8mm (0.2mm thicker than nominal) and has a built in spacer thickness of 2.5mm (0.25mm thicker than nominal). Perhaps the OP can double check the 11 and 12T cogs of his cassette so that a proper comparison to SRAM's cassettes can be done.

My bet is on the 11 and 12T cogs measuring around 1.75mm thick and their spacers being about 2.2mm. Using 1.5mm per cog and 2mm spacing then the total thickness number works out.

Also, note that Campy played the same 'trick' of overhanging cogs on the freehub body with the 11 speed cassettes as they did with the new 12s, just slightly less so.

DaveS
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by DaveS

gwerziou wrote:
Mon Sep 23, 2019 7:24 pm
I thought I had seen a post where someone ran a SRAM flattop chain with a 12 speed Campy drivetrain and it worked perfectly. Can anyone confirm that?
That was me. It works and the AXS chain seems quieter.

gwerziou
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by gwerziou

DaveS wrote:
Tue Sep 24, 2019 12:19 am
gwerziou wrote:
Mon Sep 23, 2019 7:24 pm
I thought I had seen a post where someone ran a SRAM flattop chain with a 12 speed Campy drivetrain and it worked perfectly. Can anyone confirm that?
That was me. It works and the AXS chain seems quieter.
So much for all the talk of the flattop chain's bigger roller diameter making it incompatible, then? Or could there be increased wear?
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Calnago
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by Calnago

I saw that thread where you guys are using a SRAM AXS chain with an otherwise Campy 12sp drive train and just couldn’t even bring myself to respond. But now that you’re in the Campy 12sp thread, here goes...
Of course there is going to be increased wear. The rollers are bigger in diameter than what Campy, or Shimano, or even regular non AXS cassettes are designed for. The reason they made them bigger is to get more surface area contact with the few teeth that are actually engaged (esp with the 10 tooth cog), and thus hopefully get better wear. What you guys are doing is exactly the opposite. You’re trying to stuff larger diameter rollers in the valleys between teeth on cogs made for smaller diameter rollers. That’s going to create two extreme pressure points since the rollers are too big to fit nicely into the valleys between the cogs’ teeth. So less, not more area of actual good solid contact, increasing wear. Versus the normal even wear that full and even distribution of contact between the rollers and teeth would entail. Enough said on that, why you would even want to do that is beyond me.

[edit]: I just realized that THIS is that thread I was referring to that I didn’t want to get involved in. I thought I was in the more general 12sp thread. My bad. Oh well, those are my thoughts on the AXS chain/ Campy cassette mish mash mosh pit.
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XCProMD
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by XCProMD

It’s not so simple Cal. For starters, there will never be two contact points as the teeth in bicycle multiple cog stacks are off the standard since the ‘70’s and nowadays they are waaaay off. All for a better shifting.

Teeth today have a far greater radius at the root than what the standard requires, and that radius is far bigger that the roller diameter. In top of that the difference between AXS and Shimano/Campag rollers is so small that it will not make any difference.

Then there’s the contact fatigue beast. Very complicated topic, but to simplify as much as possible there are three factor that drive wear: surface finish, hardness in the shear stressed layer and hardness under the shear stressed layer.

In designing a chain/cog system the fundamental values to set are limit design contact force and reference contact force. Those vary almost nothing with the small roller diameter change that SRAM has introduced, regardless of what they say.


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DaveS
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by DaveS

Predictions of problems with the AXS chain overlook the fact that you don't know the actual size of the radius on the cogs. The AXS chain roller radius is only .003 inch larger. The radius stamped or machined into the sprockets has to be slightly larger than the chain roller radius, by definition, but only the minimum radius is defined. I've seen no evidence of abnormal contact with the Campy sprockets or chain rings so far.

What causes sprockets to become unusable is use with chains that have a longer pitch. At some point, a new chain will skip when mated with old sprockets that are worn to fit a longer pitch. To avoid new-chain skip, I alternate the use of several chains with a cassette. Chains can then be used longer and new-chain skip will not occur.

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Calnago
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by Calnago

XCProMD wrote:
Fri Sep 27, 2019 11:23 am
It’s not so simple Cal. For starters, there will never be two contact points as the teeth in bicycle multiple cog stacks are off the standard since the ‘70’s and nowadays they are waaaay off. All for a better shifting.

Teeth today have a far greater radius at the root than what the standard requires, and that radius is far bigger that the roller diameter. In top of that the difference between AXS and Shimano/Campag rollers is so small that it will not make any difference.

Then there’s the contact fatigue beast. Very complicated topic, but to simplify as much as possible there are three factor that drive wear: surface finish, hardness in the shear stressed layer and hardness under the shear stressed layer.

In designing a chain/cog system the fundamental values to set are limit design contact force and reference contact force. Those vary almost nothing with the small roller diameter change that SRAM has introduced, regardless of what they say.


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Many things are not quite so simple as they seem, for sure. But in this case I think it really is. I don't agree with most things SRAM is doing these days on the road side of things to be sure, but be that as it may, increasing the chain roller diameter along with whatever changes they've had to make in their AXS tooth profiles/geometry to mesh with the new chain is a step that could help to prolong the life of these consumables, particularly if they insist on going with smaller and smaller cogs/rings. It's the only valid reason I can think of for making the change in the first place. So, that's all fine. Have at it. But keep AXS with AXS. Even SRAM will tell you that. The issue of how the metals are hardened, special treatments, etc., is really not at issue here, as those things are equally applicable to any of the chains/cassettes. What's at issue is the physical meshing of the chain with cogs/rings.

But to throw that AXS chain with its increased roller diameter on cassettes and rings with tooth profiles and geometries not designed with the chain in mind, is something I am not about to even experiment with, or consider as a long term regular thing. Might I throw an AXS chain on my Campy bike if I was in Timbuktu and my Campy chain broke, and lo and behold, the only chain in the land happened to be an AXS chain (like that scenario would ever happen :) )?... sure, as you guys have discovered, it will get the job done for a while just fine. After all, at least the pitch is the same. And you say it's narrower to boot, so it might even be quieter although I have to say the Campy 12sp chain on the rear 12sp cassette is quiet as silk if properly adjusted, so if you have a noisy cassette/chain on Campy 12sp, then I'm going to guess it's not perfectly dialed in. Give it to me, I'll fix it.

The other argument that seems to be being made in this thread for the mish mash is that the increase in roller diameter is only 0.006" larger (and no, I'm not aware of anyone in the bike industry in the USA not using metric measurements, just look at the T47 "standard" as an example, country of origin... USA). So, let's keep things in metric measurements shall we, at least for discussion’s sake, we're not in Detroit, and we're not building Chryslers. The argument seems to be that 0.15mm (0.006") is nothing, or so small that it won't make a difference. Yes, it's small, but in the world of circular metal contacts, think bearings etc., that difference is far from insignificant. If it were insignificant, then there would be absolutely no reason to have made any change in the first place, although it is SRAM, so that argument may not be fully applicable here. Nonetheless, when I'm dealing with creaking bottom brackets etc., of much larger diameters and radiuses than a chain roller, hundreths of millimeters are indeed significant. In fact, a gap larger than 0.15mm is the cutoff where I might consider using a retaining compound a bit thicker than what I might normally use.

It's not like I've never done things knowing full well that perfect 100% functionality may be lost as a result, but I'm aware of the tradeoffs being made, and on balance, the result I'm trying to achieve outweighs perfect 100% functionality. And that may be a little bit similar to what you guys are trying to do in this thread, so kudos for that. But the difference is that I believe what you are doing will compromise wear on your precious components. And those kinds of tradeoffs are the ones that I am very reluctant to make, and if I did it would only be in an emergency situation for a very short term. Someone said that he sees no visible signs of abnormal wear so far. And I really doubt that any of that abnormal wear will be visible to the naked eye even when it is well worn. I suspect you may notice a difference if you go through your AXS chain, wearing it out, then try to put new Campy chain on. My thoughts would be that a new Campy chain going on a drive train where an AXS chain has been run through to wearing out, will be a whole lot sloppier than if you were replacing a worn out Campy chain that had been on the drive train from Day One.

Ok, keep experimenting as you wish, but this is one experiment I will opt out of from the beginning.
Last edited by Calnago on Fri Sep 27, 2019 5:51 pm, edited 3 times in total.
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by joejack951

.006" = 0.15mm

All this talk makes me want to draw up some cassette cogs (copying standard designs) so that I can see in detail how roller diameter and chain pitch affect the contact areas. Anyone do this already?

I worked with Chrysler as far back as 2001 and they were all metric then.

by Weenie


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