Outer chain ring not running true?

mattrixdesign2

Hi

Not so long ago I bought a new compact chainset, it is an FSA carbon type with ISIS BB, which a bike shop fitted.

I have noticed there is some chain rub on the f/mech, if I look down when pedaling I can see the out chain ring is not running 100% true.

Now other than when it is in the top gear, with the chain running against the mech it is difficult to tell.

Should I just put up with this or try and narrow it down, I presume it could be the chain ring, or could it be something else (poor fitting?), other than that it runs smooth.

MikeM22

If you think it is only the outer CR then check the fitting first. I had this on my outer C/R and after removal and refitting things were fine....

The chainring is bolted to the spider on the crank, I suggest removing the CR, ensuring areas where the CR and the Spider meet are clean, clean up the bolts too.

While you have it off you can also ensure that the C/R is true (ie flat).

Then reassemble, ensuring that the bolts are torqued up to the same degree.

sungod

^this

if the ring is bent, with care you should be able to straighten it

markos1963

Be careful when trying to straighten a chainring as they are quite brittle and can crack or snap if forced too far, it happened to me

mattrixdesign2

Thanks, are the chain ring bolts a normal thread, the reason I ask is that these are as tight as hell, and want to be sure.

sungod

yep, normal thread

there are a few different styles, if yours take an allen key on the inside on the chainring, it can sometimes be easier to loosen that side first

if they won't budge, put a bit of penetrating oil on and leave to seep in

Herbsman

Yes, they are.