Raleigh Mercury chainring problem

ILM

Active Member
Hi

Raleigh Mercury, early 1990’s, pink and white 12 speed.

Bought this the other day second hand. Lovely bike, just need to change bar tape and fine tune gears.
I’ve just noticed a problem with the front chainrings though. When it spins it has some sideways movement, in other words it firstly catches the front derailleur when it spins and I’ve noticed that the small chainwheel has eaten into the paintwork on the chainstay tube. It is not loose as BB is fine and tight, it’s just that somehow it’s been ?bent with obvious sideways movement into and out of the bike frame.

How do I get the right size replacement to ensure it fits onto the BB without major changes needed??

Thanks

Ian


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TheDoctor

I've seen things you people wouldn't believe
Moderator
Location
Stevenage
With a bike that's over a decade old, I'd change the BB as well. A BB is only about a tenner, after all.
 
OP
ILM

ILM

Active Member
OK,

thanks for the advice, but is there a specific type/make/size double chainset I need?
 

accountantpete

Brexiteer
Basically you will need a crank extractor.

Get this (or borrow one) and take the crank off and then remove the chainring. Then put the crank on a piece of glass and you should find that one of the crank arms has been bent. If it isn't too much then you could try warming up that arm and then bending it back into shape.

On the other hand if the crank arms are ok then the axle in the BB is bent and you need a new BB and a BB tool to undo the existing one and possibly a different BB tool to tighten the new one! It's a big subject so suggest you ask further if this turns out to be the case.

Alternatively you can just sling the bike at a LBS and get them to sort it out.
 
ILM said:
OK,

thanks for the advice, but is there a specific type/make/size double chainset I need?
Are the chain rings bent?

Could be the BB is also too short and that that is the reason the rings are impacting the frame?
 
OP
ILM

ILM

Active Member
Hi
I've stripped the BB today and it's the old school Cup and Cone BB.

http://www.google.co.uk/imgres?imgu...a=N&rls=org.mozilla:en-US:official&tbs=isch:1

The axle is so thick I doubt it's that that's bent. I've re-greased the lot and put it back and looks/appears to be fine. I'll look at the chainrings, if I cannot bend them back how do I know what to buy to replace it so that it fits the same?? What I mean is that if its a different width compared to the first one I could have the same problems or it could be wider and then the derailleur may not work properly.

thanks

Ian
 
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