Bent middle chainring

Kerbdog

Hi all,

I noticed when sorting out my gears the other day that a section of my middle chainring is bent towards the small chainring by about 5-10mm.

I tried to straighten it using an adjustable spanner but couldn't get the spanner on to it properly. How easy is it to remove the chainring and/or cranks in order to get this straightened? My chainset is a 'Truvativ Firex 3.1 GXP'. Also do i need to use any special tools when removing or reinstalling these? Finally, is putting a chainset onto a bike something that needs precise aligning or anything, or is it just a case of screwing them on?

Cheers for you assistance.

Rob

nicklouse

easy no special tools. no set up needed. just align the dimples on the rings with the cranks arm when re fitting the rings.

cougie

Are you sure its bent ? Some rings are designed like that to aid shifting.

Kerbdog

Cheers for the speedy replys,

Yeah it is so bent that when using the lower half of the cassette when on the middle chainring the chain wants to skip to the small chainring.

I had the bike (Boardman Comp) back to Halfords when i first got it with the same problem and they said they had changed the middle chainring. They also put on a chain that was at least 4 links too short (after the 1st one snapped on the 2nd ride) which has now been changed. I have given up on taking it back to those jokers and started doing things myself. Even with the bent chainring i have managed to get the gears running pretty smoothly, at my first attempt. It kind of baffles me how these so called bike mechanics couldnt do it the 3 or so times i had the bike back to the shop! Could a short chain bend the chainring?

So do i need to take the cranks off or can i just remove the chainring?

Cheers.

nicklouse

yes cranks off.

undo bolt on the non drive side. should pull that arm off.

tap axle through the bb and pull the drive side out.

Maybe download the manual from srams webby,

Or have a read of parktools.

tsenior

i did the same thing, couldent work out how you bend the middle but not the outer (big) ring which would surely hit the ground first?!?

reckon all the skipping wore the chain out prematurely before i got round to sorting it though so will have to replace that as well.

Nick: parktools and others says you need a crank extractor, are they just trying to flog me another bit of kit?

nicklouse

tsenior
no it does not.

but if it is not a one key release system then yes it will need a puller.

bails87

I managed to bend the small chainring once. Think I did it lifting the bike up or down some concrete steps.

I tried to replace the chainset, but without a crank puller it took several hours and a big hammer to get it off, I'd say the tool is worth it, if you need it of course.

What's the chainset? If, on the non drive side crank it looks like there's a small bolt hidden behind a bigger one then you don't need the tool, just undo the small bolt and it'll push against the big one and pull the crank off. Then you can remove the ring and straighten/replace.

tsenior

so; in the words of shaggy:

"if you want the job done well you've got to use the correct tool"

dont think he was talkig about its 'octolink' type cranks though!