sprocket compatibility within Shimano

[peetee]

Well done.
Now I bet you are hoping there is enough sprocket left to last a few rides before the chain slips!

[Raph]

That's amazing work - well done, a well-deserved success! I would have bet on that failing, and a pile of useless metal filings

Out of interest, did you try doing a two-down-one-up shift to get from 11-to-13T [i.e. across two larger cogs, then back one]? Irritating, I know, but I'm just curious, as I had no idea that the ramps etc made such a huge differnece.

I realise your lever may not allow this - I don't own fancy modern stuff, sorry!

Yes, shifting two then back one always worked fine, even with the mismatch, but in the heat of the moment, remembering to do that on that particular shift was impossible - I'd always get the clatter, swear a lot, then shift one further and shift back one, or abort and re-do the shift while holding the lever a bit further to force the shift, and occasionally even that would fail, in which case loads more swearing and I'd do what you said and shift two then back one, all the while with it clattering like a joke shop denture factory gone berserk... a complete pain in the derrière!

Well done.
Now I bet you are hoping there is enough sprocket left to last a few rides before the chain slips!

Well, I've only taken less than a millimetre off each tooth, and it's been more a case of reshaping the top rather than removing lots of metal... so no discernible difference to the running - though I did worry that if it didn't succeed straight away I'd be tempted to take more and more off till it worked, and end up with "gums" rather than "teeth"!

PS what DID seem to line up between ultegra and XT was the teeth themselves - at the point where the "gate" (aka tooth with a top missing) allows the chain to pass through, get pushed up by the next tooth and therefore lift off, the timing of the teeth is such that it lands squarely onto the teeth on the next cog, with the chain rollers landing smoothly in the gaps between teeth - that's almost as crucial as the ramping. I haven't looked to see whether the synchronising of the teeth would match between Shimano and Sram - I'll have to check that out but I suspect it might not.

[TheBomber]

I haven't looked to see whether the synchronising of the teeth would match between Shimano and Sram - I'll have to check that out but I suspect it might not.

As you have the tools and the skills to grind parts of cassette sprockets away it might be worth looking at the splines on the inside of the sprockets. I recall Brucey has previously described how, by removing part of the large spline, it is possible the rotate the orientation of sprockets so that the shifting gates better line up when combining sprockets from mismatched groups.

[Raph]

Hey I hadn't thought of that - if needed I'll definitely try it. Thanks!

[531colin]

Well done for beating the system and getting what YOU want!

Grinding the inside of the sprockets sounds pretty tricky, but a photo of what you did to the teeth would be of interest, to me at least!

[Raph]

Ultegra:XT mix by Raph Mizraki, on Flickr

The right hand arrow points to the "shift gate", the left hand arrow points to the tooth that's been flattened so it picks up the chain rather than lets it slip back. Due to the shininess of the steel it's difficult to see the angles of the surfaces so you'll have to take my word for it!

I should have put more of a slope on the right hand tooth - but by then I'd taken off enough metal, plus it was working fine, so I left it at that.

As you can see the timing of the teeth from the 3rd cog to the 4th is roughly the same as between the first three cogs which are all ultegra, the 4th being the first XT cog.

This cassette seems not quite as smooth as the Sram, but I'll do a couple of rides first to allow it to bed in before trying to re-instate the Sram. The whole bike has only done a couple of hundred miles so far so everything's still pretty new.

Just off for a 40-miler to see if it still performs as well as it did round the block yesterday.

[Raph]

Here's the scoop: that was 36 miles of shifting BLISS!


The following is only for the very nerdiest:

It took 20-odd miles to bed in beautifully, and as it did, the new cross-over shift from ultegra to XT became very slightly less perfect - but I mean really only slightly; it still never missed any shifts, but became gradually more ker-lunk than pure beautiful klunk. But tbh it was still so good, and in terms of reliability same as all the others, that I almost didn't bother doing the following - but I've taken a fraction more off the leading edge of the relevant teeth.

What I reckon is that now the chain has bedded in it sits slightly lower between the sprocket teeth, it has further to climb when de-railing whereas when it first went on, brand spanking new, it wasn't so snug to start with so was easier to lift off. The extra grind seems to have sorted that, though I have to go on yet another ride to confirm that!

NOTE: the metal I've taken off is mostly on the "non-business" corner of the tooth - i.e. if you look at the tooth from the gear side of the bike, the chain is pushing the teeth clockwise, so from the left as you're looking at the upper half of the sprocket - the corner to be flattened is on the right of the tooth. So in theory it hasn't taken any useful contact surface off the tooth.

It's possible that I've got the theory all wrong, but nevertheless in practice it's gone from unworkable with occasional total refusal to shift, to a shift from ultegra to XT as slick as all the others.

teeth by Raph Mizraki, on Flickr