Wrong middle ring?

elyob said:

Just fitted a middle ring I bought .. however probably isn't the right
bit. I needed a Sora 42, but got some unnamed 39 instead. It seems off
centre so am wondering if it's from a double? Can I space it or should I
just go back and say "you sold me the wrong part".

It took me a moment to work this one out. By "off centre" I take it you mean "doesn't
seem to be equidistant between large and small rings" rather than eccentric on the crank
axle.

Well you've got 10% less than you had before for. If you wanted a replacement then you
certainly have the wrong bit and it ought to go back.

--
Peter Fox
Beer, dancing, cycling and lots more at www.eminent.demon.co.uk

elyob said:

Just fitted a middle ring I bought .. however probably isn't the
right bit. I needed a Sora 42, but got some unnamed 39 instead. It
seems off centre so am wondering if it's from a double? Can I space
it or should I just go back and say "you sold me the wrong part".

Generally (handy word, that:-), although they may not work quite as well,
double inner rings can be used as triple middle rings. I don't know
specifically about your chainset, etc.

But anyway, you wanted a 42 and got a 39, so you should get it changed for
exactly what you want.

~PB

In article <[email hidden]>, elyob
[email hidden] says...

Quoted message said:

Just fitted a middle ring I bought .. however probably isn't the right bit.
I needed a Sora 42, but got some unnamed 39 instead. It seems off centre so
am wondering if it's from a double? Can I space it or should I just go back
and say "you sold me the wrong part".

Shimming it out should work fine as long as the tubular nut that holds
the two larger rings on the spider is long enough that it still engages
with the big ring - you probably shouldn't rely on just the bolt
engaging with the recesses in the big ring. But if you bought it in a
"that will have to do" moment and are having second thoughts then you
should probably return it as not fit for purpose.