Interesting Problem

[roadie7]

I recently switched from Campy to Shimano 105. This included changing the rear wheel to fit the Shimano cassette on the Kyseriam SL. During my first ride yesterday while in the big/small and flying down a hill, I heard this awful metal-on-metal racket. I saw that the chain had gone slack on the big chairn ring and was rubbing against the front derailleur and then was slipping into the small chain ring. Once I pedaled again the chain returned to the big chain ring.

I took it to the shop and while I on the stand under the same conditions the chain again went slack, much to the mechanic's surprise. He readily admitted he really didn't know the reason but thought it had to do with the new cassette.

Does anyone have any thoughts or experience with this problem?

Thanks.

[Cicli]

Freehub dragging? see if it only does it while coasting. If so, freehub.

[Peter P.]

Yeah; it's your cassette. Verify it was installed correctly, it's Shimano-specific, and it's compatible with your hub.

[oldpotatoe]

I recently switched from Campy to Shimano 105. This included changing the rear wheel to fit the Shimano cassette on the Kyseriam SL. During my first ride yesterday while in the big/small and flying down a hill, I heard this awful metal-on-metal racket. I saw that the chain had gone slack on the big chairn ring and was rubbing against the front derailleur and then was slipping into the small chain ring. Once I pedaled again the chain returned to the big chain ring.

I took it to the shop and while I on the stand under the same conditions the chain again went slack, much to the mechanic's surprise. He readily admitted he really didn't know the reason but thought it had to do with the new cassette.

Does anyone have any thoughts or experience with this problem?

Thanks.

Free hub body dragging.The noise and slack. Either take apart and lube with oil or replace. Since the wrench didnt suspect this, hope he knows how to service this wheel.

[Cicli]

Free hub body dragging.The noise and slack. Either take apart and lube with oil or replace. Since the wrench didnt suspect this, hope he knows how to service this wheel.

No kidding, find a new wrench.

[jh_on_the_cape]

I had this happen and it was freehub drag.
It was a different hub (King) so I serviced it and it solved the problem.
If the rear wheel is new, ask about a warranty.
If it is used, it needs service.
If you want to try a quick bandaid fix, remove the wheel and just try to spray a buttload of wd40 into some crevice around the freehub. careful not to get it on the braking surface.
otherwise google how to service it.

[oldpotatoe]

I had this happen and it was freehub drag.
It was a different hub (King) so I serviced it and it solved the problem.
If the rear wheel is new, ask about a warranty.
If it is used, it needs service.
If you want to try a quick bandaid fix, remove the wheel and just try to spray a buttload of wd40 into some crevice around the freehub. careful not to get it on the braking surface.
otherwise google how to service it.

Don't disagree with the spray stuff but WD-40 is a solvent and could very well kill the bearings in the hub. 2 5mm Allen's, lefty loosely, easy to take apart. VERY common problem with this, IMHO, really crappy rear hub.

[cmbicycles]

Make sure there is a 1mm washer/spacer between the freehub and outer hub bearings. If that got left off in the swap it could very much cause the cassette body to bind.