Campagnolo 12 speed cassette compatibility

Discuss light weight issues concerning road bikes & parts.
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Calnago
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by Calnago

Yes, my bad... .006” = 0.15mm, not 0.015mm, a virtual Grand Canyon when talking about things like bearings etc. I don’t know why I kept typing 0.015mm in my previous post. Typo corrected.
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gwerziou
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by gwerziou

Calnago wrote:
Fri Sep 27, 2019 5:51 pm

I don't agree with most things SRAM is doing these days on the road side of things to be sure
It's a bit off-tangent for this thread, but SRAM really seems to have sh!t the bed with their road development. For instance, what I and probanly most other more CX/gravel type riders were hoping for was just a mechanical road brifter that would make an Eagle-type derailleur shift across some nice 12 speed cassettes. How hard could that be for them? Not very. But no, what we got instead was super-proprietary, super expensive, electronic only, and those cranks are just the ugliest on the market. OK rant over, back to discussion of Campy 12 speed!

by Weenie


DaveS
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by DaveS

A couple of things to consider. Bike chains are based on an English standard #40 drive chain, not anything metric. They have a 1/2 pitch and the maximum roller diameter is .306 inch. The new SRAM chain fits the English standard for a #41 drive chain, with a maximum roller diameter of 5/16 or .3125 inch. I measured an actual diameter of .311 inch, compared to .305 for a Campy chain. The difference in the radius is a little less than the thickness of your average notebook paper.

Just today, I took a 5/16 inch drill bit shank that measured .311 inch and used it as a gage to look for that nasty 2-point contact. I didn't see any in the radii of my 34T cog. If there had been I would have seen light showing under the contact area with the drill bit shank. It supports the idea the the sprocket radii are made enough larger on Campy sprockets to work just fine with the AXS chain.

FWIW, I worked for over 20 years in the machine shop business and 10 of those were developing processes to machine nuclear weapons components. Those components have dual dimensions in both English and metric units, but the threads are all English. It makes no difference what system you use, as long as you make the correct conversion.

graeme_f_k
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by graeme_f_k

joejack951 wrote:
Mon Sep 23, 2019 8:10 pm
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.
You need to factor in the difference in sprocket spacings in 11s, for an 11-up, a 12-up.
The mean tooth centre-line spacings on the smallest three sprockets are not the same for an 11-up as they are for a 12-up.
This is a critical difference if you are trying to match a SH / SRAM standard cassette to a Campag system.

The redesign of the two 12s RDs have (almost) eliminated the need for this differential. Life is also made alittle simpler by only having to deal with an 11-up cassette.
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graeme_f_k
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by graeme_f_k

DaveS wrote:
Fri Sep 27, 2019 10:57 pm
A couple of things to consider. Bike chains are based on an English standard #40 drive chain, not anything metric. They have a 1/2 pitch and the maximum roller diameter is .306 inch. The new SRAM chain fits the English standard for a #41 drive chain, with a maximum roller diameter of 5/16 or .3125 inch. I measured an actual diameter of .311 inch, compared to .305 for a Campy chain. The difference in the radius is a little less than the thickness of your average notebook paper.

Just today, I took a 5/16 inch drill bit shank that measured .311 inch and used it as a gage to look for that nasty 2-point contact. I didn't see any in the radii of my 34T cog. If there had been I would have seen light showing under the contact area with the drill bit shank. It supports the idea the the sprocket radii are made enough larger on Campy sprockets to work just fine with the AXS chain.

FWIW, I worked for over 20 years in the machine shop business and 10 of those were developing processes to machine nuclear weapons components. Those components have dual dimensions in both English and metric units, but the threads are all English. It makes no difference what system you use, as long as you make the correct conversion.
This rather depends on the manufacturing tolerances.
You don't know if you had a 34T sprocket spot on nominal, or towards either end of the manufacturing tolerance.
You'd need to measure multiple rollers in order to get an average roller diameter as well, since they might vary (quite easily) by 0.01" plus.

I don't think Campag made their teeth deliberately to work with an AXS chain, TBH. I rather suspect it's a happy coincidence of manufacturing tolerance and a recognition that there will be variation in roller diameter from new as well as a gradual change in roller to tooth valley fit as wear and tear starts to take effect, that means that it's close enough not to matter too much ... logically if you have a tooth valley that exactly accommodates a .311" roller and you interface it with a .305" roller (as in your measurement examples), you'd have point, not surface, contact, anyway ...

I'm still struggling to figure out why anyone would want to run a SRAM chain on a Campag system, mind you ...
Last edited by graeme_f_k on Fri Sep 27, 2019 11:46 pm, edited 2 times in total.
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Calnago
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by Calnago

@DaveS: The “two points” of increased pressure are just kind of a visual I tried to create in order to try and explain the situation that is created by the larger radius versus the radius we’ve had for like forever. I don’t doubt at all that you couldn’t see see daylight with your experiment today. For one, we are talking about small differences not visible to the naked eye and the very thickness of the cog would have meant any daylight that might have shown through could easily be obscured. If you could actually see the daylight, then we’d be talking huge gaps in this context.
Anyway, I have no qualms with you doing whatever works for you, a lot worse mish mashes than that have and do happen in the bike world. But as far as I’m concerned that’s one I’ll stay clear of.
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DaveS
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by DaveS

Roller diameter would be one dimension that would typically be held to an extremely tight tolerance. The rollers are undoubtedly made from precision centerless ground bar stock on a screw machine. That means a tolerance of less than .001 inch for the roller OD. The design calls for a maximum of .3125 inch, so just like Campy's chain, the rollers are at least .001 inch smaller than maximum.

SRAM claims that this new design is there longest lasting chain. If it's quieter, cheaper and lasts a long time, it's hard to complain about.

There are already aftermarket chainrings offered that work with both chains.

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Calnago
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by Calnago

DaveS wrote: ...SRAM claims that this new design is there longest lasting chain. If it's quieter, cheaper and lasts a long time, it's hard to complain about.
Does SRAM then say that it is perfectly fine to use their AXS chain on any of their road groups? I don’t know whether they do or they don’t, but if they don’t... well... uh... they probably have a reason. At least I would think they do.
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DaveS
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by DaveS

Calnago wrote:
Sat Sep 28, 2019 12:48 am
DaveS wrote: ...SRAM claims that this new design is there longest lasting chain. If it's quieter, cheaper and lasts a long time, it's hard to complain about.
Does SRAM then say that it is perfectly fine to use their AXS chain on any of their road groups? I don’t know whether they do or they don’t, but if they don’t... well... uh... they probably have a reason. At least I would think they do.
SRAM only makes AXS 12 speed road groups, that work with the AXS chain. 12 speed mountain groups use a wider chain, that follows the common #40 drive chain standard. Obviously, the axs chain would not be recommended for 11 speed drivetrains.

Nefarious86
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by Nefarious86

So then comes the really dirty Q.. AXS chain on a Shimano 11s group?

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DaveS
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by DaveS

Nefarious86 wrote:
Sun Sep 29, 2019 2:47 pm
So then comes the really dirty Q.. AXS chain on a Shimano 11s group? Image

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No point in that, with all of the 11 speed models available. The narrow chain width would be a disadvantage at the extreme angles. Use a chain that's appropriate for the sprocket thickness.

A wider sram eagle 12 would probably work, but there's really no point in that either.

AC0
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by AC0


DaveS wrote: A wider sram eagle 12 would probably work, but there's really no point in that either.
Anyone use an Eagle 12 quicklink on a campag 12 chain? Anyone measured and compared the critical dimensions?

AC


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talltales
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by talltales

Calnago wrote:
Fri Sep 27, 2019 5:51 pm
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.
Or its just marketing to make the customer think only a AXS chain will mesh with a AXS cassette, "cos the rollers are different". In any case in 10s land a shimano HG54 chain has rollers that are at least 0.1mm smaller than a KMC x10 73m but they both work fine on a shimano 10s cassette. - Its the shimano chain that has smaller than usual rollers. The KMC seem to adhere to standard bike roller diameter. No one ever gave that difference a second thourght.

DaveS
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by DaveS

AC0 wrote:
Mon Sep 30, 2019 4:16 am
DaveS wrote: A wider sram eagle 12 would probably work, but there's really no point in that either.
Anyone use an Eagle 12 quicklink on a campag 12 chain? Anyone measured and compared the critical dimensions?

AC


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The eagle quick link will work with a Campy 12 chain. It's narrower than a kmc 12. The link is directional. The hump goes up on the top or down on the lower section of chain.

by Weenie


gwerziou
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by gwerziou

So, would the Rotor 11-36 12-speed cassette work with a Campy system? Obviously there are 2 issues there with Campy cassettes only going to 34 ( and in theory then, the derailleurs only being able to handle so much of a range), as well as the spacing. Rotor claims their 12-speed cassette uses '12 speed standard' spacing.

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