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.