Aluminium sprocket wear
 

Hi guys, so I fitted a renthal aluminium sprocket just over 1200 miles ago and this is how it looks already...

http://s16.postimg.org/cmaoi8p79/20160405_150618.jpg

I have a scottoiler and as you can see there is plenty of oil getting on the teeth after a ride

http://s22.postimg.org/4pv7jjhw1/20160405_150804.jpg

There are also aluminium shards on the chain which i found by wiping my finger on it. Is this normal wear? Should I be concerned?

Thanks in advance!

Generally hard anodised 7075-T6 aluminium sprockets last half as long as good quality steel sprockets. I would suggest that the sort of wear you're experiencing is very definitely abnormal. There is no way even an aluminium sprocket should hook up like that in just 1200 miles; even on a poorly maintained bike or one ridden in sand you'd expect to get more life out of it than that. It must by a duff sprocket or maybe even a fake Renthal of which there are quite a few being leaked on to the market at the moment by unscrupulous ebay sellers.

I take it your chain is OK and not stretched?

Thanks for the quick reply Pleiades. I just jacked up the rear wheel to double check and the chain is still in the correct adjustment (around 50mm) with no tight spots. I purchased the kit from B & C Express who seem to have a good reputation. I regularly check the chain for lubrication and keep my scottoiler topped up. Also the front sprocket shows no sign of wear. I do drive pretty hard opening the throttle quickly and doing 100+ mph from time to time but still that's what these things are made for right?

If you bought it from B&C then it'll be genuine, so we can rule a fake sprocket out. Personally I would contact them and show them you photos and see if you can wangle a replacement out of them. There's a small chance you've got a duff one that missed out on the hardening or anodising process. I would expect to see at least 6000 miles out of a Renthal aluminium sprocket and even then I wouldn't expect it to look as bad as yours does at the moment.

I don't think his problem is down to the fact it's aluminium. Yes, you can expect half the mileage of a steel sprocket, there's no dispute that they don't last as long, but 1200 miles is plain ridiculous!

Thanks Pleiades I will contact them and see what they say. I can't see any reason why it would wear so quickly especially as the other sprocket and chain are just fine. I too expect much more from renthal as they have a good reputation for making sprockets.

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OK so I spoke to B&C Express and they said that just by looking at the hooking on the teeth they have determined that the chain is too loose. I argued the point with them that actually it is within the manufacturers specifications and they eventually agreed that if I send it back to them they will have a look at it and if necessary send it back to renthal for inspection but that it is unlikely that they will come to any other conclusion. I am pretty disappointed at this response and have never heard of a loose chain causing this kind of wear. They did sell me a new steel JT sprocket with free postage so that I can replace the renthal one which is a small consolation. Hopefully I will have better luck with that one.

Not so sure about it being caused by a loose chain? Even if it was I still wouldn't have expected it to hook that badly in 1200 miles.

Still worth enquiring though. Might be worth contacting Renthal directly and see what they say - after all, they do have a reputation to up hold. You never know, you still might get a refund from B&C down the line if it does turn out to be faulty. Keep us posted.

Yes I definitely will keep you updated thanks.

OK so mystery solved, I think. I fitted my new chain and sprockets today and upon inspection of the old chain it seems that I tightened one of the rivets on the master link too tight as it was very stiff. I am assuming that this is what caused the premature wear on the Renthal sprockets. I checked and double checked the master link on the new chain after riveting and it seems as flexible as the others so hopefully I will not get the same problem again. If I do it will be endless chains for me from now on even if it does mean I have to remove the swingarm to fit them! It was my first time riveting a chain however and I feel confident that I have done it properly this time so I doubt I will have to resort to that.