Have I got my big chainring on backwards?

robthehungrymonkey

hi,

I recently changed my chainset (knackered) but changed the chainrings back to my old ones as the sizes were what I wanted (they're not that worn).

Since then, I've had some problems with the chain coming off. Going straight past the big cog. This never happened before, and is quite frustrating.

Have I put the big ring on the wrong way round? How can I check this?

Thanks

will3

Any lettering would normally be on the outside, together with the peg to stop the chain dropping between the crank arm and the ring.
Inside often has short pins or similar features to aid shifting.
Did you replace like for like? Different brands have different dishing, ie the teeth may just be nearer than they were on the old ring.

robthehungrymonkey

will3 wrote:

Any lettering would normally be on the outside, together with the peg to stop the chain dropping between the crank arm and the ring.
Inside often has short pins or similar features to aid shifting.
Did you replace like for like? Different brands have different dishing, ie the teeth may just be nearer than they were on the old ring.

I replaced the new chainrings for the original ones (105 to Ultegra Cranks).
I needed new cranks and managed to get some ultegra ones in the chain reaction flood sale really cheap, but it had massive cogs on it! So i just put the old ones back on.
I'll check what you have suggested...

ColinJ

There should be a metal pin sticking out the side of the ring. This is to stop the chain getting stuck between the ring and the crank if the chain comes off. You should therefore have the pin sticking out next to the crank.

PS Curses - slow typing - beaten to it again!

I was with another rider on an audax once and I looked at his bike and spotted that he had the big ring on the wrong way round. I pointed out his mistake and he said that he'd swap the ring round when he got home. A couple of minutes later, his chain came off and got wedged down the side of the crank - QED!

SB75

It's a possibility that you've put your chainring on the wrong way round but unlikely. The holes for the chainring bolts are countersunk so it's fairly obvious. As previously mentioned, the chainring should be fitted so the peg sits behind the crank. I'd say what you're experiencing is a result of the Ultegra chainset being 'lower profile'. Both chainrings will probably be sitting closer to the chainstay. The way to stop shipping your chain is by using the limit screws on the front mech. There'll be plenty of advice on other threads about how to do this.

robthehungrymonkey

thanks for your help