Help: Mavic 631 triple adaptor question



Howdy folks.

I am just in the process of adding a granny to the Mavic crank on my
Riv and I have a question. I have the proper (and hard to find) Mavic
adaptor and a new Stronglight 30T ring. It looks to me like the ring
is supposed to sit down flush on the reduced diameter tip of the
adaptor, so the bolts aren't the only thing preventing the chainring
from turning. My granny ring doesn't fit down onto these (the holes
are just the diameter of the bolts). I suspect that a correct/original
Mavic granny would fit down flush. I am thinking I should drill out
the bolt holes until the ring just fist down onto the reduced diameter
area, but I don't want to ruin my ring. Anybody know for sure how this
is supposed to work? If you wouldn't mind, please e-mail a response in
addition to posting.

Thanks and happy holidays,
Doug
 
J

James Thomson

Guest
<[email protected]> wrote:

> I am just in the process of adding a granny to the Mavic crank
> on my Riv and I have a question. I have the proper (and hard
> to find) Mavic adaptor and a new Stronglight 30T ring. It looks
> to me like the ring is supposed to sit down flush on the reduced
> diameter tip of the adaptor, so the bolts aren't the only thing
> preventing the chainring from turning. My granny ring doesn't
> fit down onto these (the holes are just the diameter of the bolts).
> I suspect that a correct/original Mavic granny would fit down flush.
> I am thinking I should drill out the bolt holes until the ring just fits
> down onto the reduced diameter area, but I don't want to ruin my
> ring. Anybody know for sure how this is supposed to work?


I have a 631 adapter in front of me, with an original Mavic 38t (yes, 38t)
granny ring. The ring is drilled with 5 10mm holes on a 74mm circle. The
backs of the holes are recessed to accept the 12mm bolt heads. The ring is
intended to sit over the tips of the five pegs of the adapter, as you
guessed. Most granny rings (like your Stronglight) are drilled with 8mm
holes.

You could drill out your Stronglight chainring to 10mm, or grind the pegs
of the (hard to find) adapter to allow the ring to mount flush to the
broader portion. You could also try assembling the parts you have without
modification, though that might affect shifting between granny and middle,
and increase the risk of getting the chain trapped between the rings. My
inclination would be to drill the chainring - or to have it drilled.

> If you wouldn't mind, please e-mail a response in
> addition to posting.


Mailed and posted.

James Thomson
 

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