Osymteric chainrings

MattBridges

Hi,
i just installed an osymetric chainring onto my bike. However whenever I go into the 3/4 largest gears (Top of cassette) when the chainring goes round the chain falls onto the little ring. If I switch it back into the big ring and shift again so the front mech moves over slightly more, the chain rubs against the front mech but does not fall off. I've taken off and put on the crank again, tightened the rear mech hanger, lock ring etc but nothing is happening!?!?!? Any advice as to why?
Thanks

trailflow

What type of bottom bracket do you have ? Sounds like a chainline issue and the crank is too far out. Are there any spacers on the driveside bb that can be removed ?

What size teeth was the older chainring ? Does the new ring have the same number of teeth ? Could the chain be too short ?

Another thing to check.
What speed is your cassette and freehub ? If you are running a 10 speed cassette on an 11 speed freehub. It may need a spacer behind if it hasnt already. if not it might be worth experimenting with another spacer anyway and see how far towards the frame the cassette will go without the chain fouling the frame when on the smallest cog.

MattBridges

Hi,
It's a standard shimano 105 11spd bb. There are no spacers to remove but I'll reinstall the crank again.
The old chainring was 52 as is the new one. The chain is he correct length.
I'm running an 11spd cassette on 11spd hub :/I will take it to a bike shop when possible.
Thanks for replying

StillGoing

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19768271#p19768271]MattBridges[/url] wrote:

Hi,
It's a standard shimano 105 11spd bb. There are no spacers to remove but I'll reinstall the crank again.
The old chainring was 52 as is the new one. The chain is he correct length.
I'm running an 11spd cassette on 11spd hub :/I will take it to a bike shop when possible.
Thanks for replying

If you're saying your old chain ring was 52 so you've kept the length of the chain the same, it will be too short. The oval chain ring when on its largest rotation will be tightening the chain. If this isn't what you're saying, then my mistake. Make sure you have the ova chain rings the correct way around for mounting too.