Oval chainrings eat Shimano clutches?

It’s very likely I’ve missed a common bit of MTB knowledge – did I miss the memo saying oval chainrings will eat through Shimano clutches?

Over last two years I’ve had three occasions to service (or on one occasion – have a shop service) the clutches on two different derailleurs – an XT and an XTR.

Is this a known/common issue, or just bad luck (timing of services needed anyway) or an effect of my admittedly lacking maintenance routine?

Not had any problem with mine on three bikes. I’ve heard other reports of this so it might be a problem in some cases but I don’t know what the common factor linking oval chainring and clutch mech is. Might just be plain old luck of the draw.

in for info
same setup here, oval ring xt mech

No, it’s just needs a service like it would with a round ring, it’s just that the oval gives you an audiable service indication warning, where as you’d be none the wiser with a round ring.

I don’t see much more mech movement with the oval ring than I did with a round one and it’s at a much lower frequency than the bump/chaingrowth induced movement from the suspension so I doubt it’s a factor.

As above, suspension is likely to cause more problems than oval rings.

Pedal an oval ring in the stand and you’ll see a little bit of movement in the cage. You’ll see a lot more on a full suspension bike and other things are much harder on rear mechs, like mud, rocks, 1×11(or 12) speed setups giving extreme chain lines.

Is this a known/common issue

maybe not common , but i have heard this issue raised a few times ( on other forums )

As to why , my guess would be the regular and constant ( twice per crank revolution ) pulsing effect of an oval chainring through the chain to the mech cage which may put additional wear on the clutch.

I doubt that rear suspension travel would replicate the same effect , even though this does produce mech cage movement in itself – but clearly not as detrimental.

regular service of the mech does noticably help from what i’ve read / heard.

only my 2p tho.

There’s no effective chain growth/shrink, at least with absolute black oval rings. The mech doesn’t really move when pedalling. Maybe about 1mm at the end of the mech, and much of that is probably down to the tolerances in the entire system (mech wiggles back and forth a bit just peddalling a conventional round ring when on the bike stand).

The “pulsing” – assume that’s ever so slightly faster/slower linear movement of the chain over the jockeywheels / cassette?  If so, then “pulsing” is pretty much what you do with your feet by pedalling and stopping.

I’ve run oval rings and shimano mechs for years. The only problem I’ve had was with an M8000 mech which had zero grease on the clutch assembly and the cage seized up mid-ride. A quick strip, clean and grease and it’s been right since. I’ve noticed M8000 mechs have an oil port on the bottom of the clutch housing, so a few drops of light oil in the hole every few months should go a long way to keeping it running smoothly.

There’s no effective chain growth/shrink, at least with absolute black oval rings. The mech doesn’t really move when pedalling. Maybe about 1mm at the end of the mech, and much of that is probably down to the tolerances in the entire system (mech wiggles back and forth a bit just peddalling a conventional round ring when on the bike stand).

Mirrors my experience. I think the mech waggle is down to system error and you only notice there’s movement of the mech when you’ve fitted an oval ring and wondered if it makes the mech move. It didn’t ever occur to you to check when you had a round ring and even if you noticed any you wouldn’t have thought anything about it as it was normal.

Having said that there may be more inluence on a small front ring/long mech combo as the chain divergence angle is greater and there is therefore a fair bit less than a 180 degree wrap around the front ring which may give a bit of room for movement.

Think it deserves and article. ;o)

Mirrors my experience. I think the mech waggle is down to system error and you only notice there’s movement of the mech when you’ve fitted an oval ring and wondered if it makes the mech move. It didn’t ever occur to you to check when you had a round ring and even if you noticed any you wouldn’t have thought anything about it as it was normal.

Mirrors my thoughts. Chain wrap around an oval or round ring is constant at any point, any change in mech position will be very minor.

was just about to say put some oil in that little bleed port, and then thought has anyone ever bothered on the clutch mechs.

well done mr walsh..

tbh at £45 a pop I’m more than content with my XT derailleurs. SRAM on the other hand Grrrrr..