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Old 06-12-08, 10:08 AM   #1
bellweatherman
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Shift probs switching 1 wheel w/ Shimano cassette, to another wheel w/ SRAM cassette

I did a race once and flatted, changed out my Shimano wheel, with another wheel that had someone else's Campy cassette on it. Had to adjust the adjusting barrel several times, but eventually got it to work decent to finish the race.

Now, I just want to know if I can get two race wheels dialed in so well, that I won't need to mess with the adjusting barrel on a wheel change. Using the same hub (Ultegra), and same rims (Mavic) even. The only difference in the two wheels is the cassette. For example...
  • Ultegra hubs, both wheels
  • Shimano Cassette on one wheel
  • SRAM cassette on another wheel

Would I have to add any extra spacers or do anything weird to get the distance from the frame to first cog the exact same? How perfect can I get it so that I can just bam, do the wheel change and not even touch the adjusting barrel any at all?
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Old 06-12-08, 10:15 AM   #2
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I've done it using all matching Shimano mountain bike components so I know that it's possible. I built a spare wheelset for a customer so she could switch from knobbies to slicks without having to adjust anything.

I wouldn't think that substituting a SRAM cassette would screw up the works but the ultimate proof is how they work on your bike.
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Old 06-12-08, 10:25 AM   #3
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Getting two different wheels, even with "identical" cassettes, to work flawlessly is partially a matter of luck. All cassettes and hubs have manufacturing tolerances that can add up to the point where a small amount of adjustment will be needed.

I recently overhauled one bike and replaced the worn Shimano 9-speed cassette and chain with identical new parts. I had to do a slight amount of tweaking of the cable tension and high limit screw to maintain the shifting quality.
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Old 06-12-08, 10:59 AM   #4
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It's called tolerance stacking.The more parts involved,the greater the difference can be.No luck involved,that's why they make measuring tools,measure the distance between the right lock nut and the first gear,make them both the same.There aren't that many parts,so I would think there wouldn't be that much difference.Nothing a shim can't cure.
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Old 06-12-08, 01:50 PM   #5
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Theoretically, they match. In practice, there might be a slight difference.
I'd just check both wheels on the bike and if an adjustment is needed, just remember which one.
I have wheel "A" on. If I have to swap to wheel "B", 1/2 turn CW or whatever you've predetermined..
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Old 06-12-08, 04:39 PM   #6
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It's called tolerance stacking.The more parts involved,the greater the difference can be.No luck involved,that's why they make measuring tools,measure the distance between the right lock nut and the first gear,make them both the same.There aren't that many parts,so I would think there wouldn't be that much difference.Nothing a shim can't cure.
Interesting. I'm going to check that out when I can. I have two wheelsets - different wheels (one Mavic, the other Reynolds), but they both have SRAM 12-26 9 speed cassettes. I thought it would be "turn key", and while the limits are right on, it does involve some index tweaking when I change wheels.

Maybe there is a tolerance difference in SRAM cassettes - One is a SRAM 950, the other 970. But both are fairly new - "older" one has only about 5-700 miles. Regardless of the cause, I have to adjust the barrel adjuster when I change wheels. Not much, but it's there.
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Old 06-12-08, 05:41 PM   #7
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Originally Posted by Camilo View Post
Interesting. I'm going to check that out when I can. I have two wheelsets - different wheels (one Mavic, the other Reynolds), but they both have SRAM 12-26 9 speed cassettes. I thought it would be "turn key", and while the limits are right on, it does involve some index tweaking when I change wheels.

Maybe there is a tolerance difference in SRAM cassettes - One is a SRAM 950, the other 970. But both are fairly new - "older" one has only about 5-700 miles. Regardless of the cause, I have to adjust the barrel adjuster when I change wheels. Not much, but it's there.

Do you think that maybe one of your hubs is a little bit wider than the other hub?
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Old 06-12-08, 10:37 PM   #8
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Do you think that maybe one of your hubs is a little bit wider than the other hub?
I'm going to check it out as best I can with the measuring devices I have. I'll let you know what I find. The tweaking required is not much, just a turn or so on the barrel adjuster, but it doesn't make sense to me unless there's some dimension that is different.
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Old 06-12-08, 11:03 PM   #9
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first step is to compare the cassetts off the hubs, hold them next to each other with the small cog on the top of one, the large cog on the top of the other, and you can see if the cogs are spaced the same. SRAM and Shimano are supposed to be interchangeable, but you need to check.

Second step is to place the cogs on the wheels, and meaure from the smallest cog to the axle cone that presses against the drop out on the drop side. The distance needs to be exactly the same....say within .01 inches or less....this is micrometer accuracy.

No other measurements, rims stuff, etc affects the interchangeability
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Old 06-13-08, 10:14 AM   #10
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man I must have gotten lucky. My bike has the crappy factoryspecialized/jalco wheelset with sram 950 and I bought a set of the mavic krysium wheelsets and threw on an ultegra group and everything is as it should be with no problems. guess I just got lucky
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Old 06-13-08, 11:46 AM   #11
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I've done this more than once switching between 9-speed Shimano and SRAM cassettes with Shimano hubs. I've never had a problem doing this on the road bike or the mountain bike. I did have to tweak a bit (about 1/2 turn) when I was switching between Mavic and Shimano hubs with Shimano cassettes though.
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Old 06-16-08, 12:26 PM   #12
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Originally Posted by Camilo View Post
I'm going to check it out as best I can with the measuring devices I have. I'll let you know what I find. The tweaking required is not much, just a turn or so on the barrel adjuster, but it doesn't make sense to me unless there's some dimension that is different.
I measured the two wheels - from outside edge of smallest cog to edge of the axle locknut (that sets the wheel in the dropout). There was an obvious difference between the two. The newer (Reynolds) wheel had less space in that dimension. On a hunch, I checked the torque on the Reynolds wheel's cassette locknut and found it was quite a bit below spec (40 nm). When I installed it, I only had a torque wrench that went to something like 20 nm so I used that, and then tightened "a little bit more", which obviously was not enough. I was thinking that proper torquing might seat the cassette further onto the freehub. I now have the ability to torque to 40 nm, so I did so. The torquing to spec did indeed seat the cassette further onto the free hub, because now the above measurement is now exactly the same between the two wheels, or very nearly so - when I change wheels the shifting doesn't require any adjustment.

Interesting learning experience.
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Old 06-16-08, 05:58 PM   #13
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I measured the two wheels - from outside edge of smallest cog to edge of the axle locknut (that sets the wheel in the dropout).

Since I am interested in racing and interchangability of complete wheels with immediate perfect shifting, I did some own research and measurement on this. I agree to the measurement above, or if the cassette is off, from the distance of the flange to which the cassette is pressed to the edge of the locknut. (Precise measurements with digital caliper are necessary). For simplicity I assume for a moment that only one kind of the same cassette type is used) Since I found that different hubs, particularly, if not the same kind or manufacture may vary up to +/-1-2 mm you then have to define your own standard (maybe from your favorite hub) and than adjust other hubs with ˝mm cassette spacers (found on eBay) or (or 1mm spacers) or even further by machining thinned spacers or by modifications of the hub. It is my impression, if distances are within 0.2 mm, shifting is acceptable ok.
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