Mavic 631 - removing the steel posts



J

James Thomson

Guest
I'd like to remove the steel posts from a Mavic 631 crank. Each post has a
5mm allen socket at its base, but using all the force I dare, nothing's
moving. I presume they're Loctited, and my next approach will be the careful
application of heat, but I wonder if anybody's done this before and can
enlighten.

James Thomson
 
T

Tim McNamara

Guest
In article <[email protected]>,
"James Thomson" <[email protected]> wrote:

> I'd like to remove the steel posts from a Mavic 631 crank. Each post has a
> 5mm allen socket at its base, but using all the force I dare, nothing's
> moving. I presume they're Loctited, and my next approach will be the careful
> application of heat, but I wonder if anybody's done this before and can
> enlighten.


Are these posts the ones the chainrings attach to? I've never look
closely at these cranks and have never taken one apart. From the
descriptions I can find, the chainrings are affixed on steel posts which
presumably thread into the crank spider.

I think that I would not use heat at all, given the potential risk of
weakening the aluminum. You'd basically be doing uncontrolled heat
treatment. Have you tried a penetrating oil and then tapping the posts
gently with a hammer?
 
J

JeffWills

Guest
James Thomson wrote:
> I'd like to remove the steel posts from a Mavic 631 crank. Each post has a
> 5mm allen socket at its base, but using all the force I dare, nothing's
> moving. I presume they're Loctited, and my next approach will be the careful
> application of heat, but I wonder if anybody's done this before and can
> enlighten.
>
> James Thomson


Any particular reason you want to do this? They're in there tight.

Anyway- find a good, tight-fitting hex wrench. Clamp it, short end
pointed up, in a bench vice. Place the post down over hex wrench (it's
probably a good idea to clean them out thoroughly first). Use the crank
for additional leverage to break them loose one by one. After they're
loose, remove them all the way normally.

Wear gloves while doing this. They can let go with a snap and there's
plent of parts that can bite.

Jeff
 
O

Ozark Bicycle

Guest
JeffWills wrote:
> James Thomson wrote:
> > I'd like to remove the steel posts from a Mavic 631 crank. Each post has a
> > 5mm allen socket at its base, but using all the force I dare, nothing's
> > moving. I presume they're Loctited, and my next approach will be the careful
> > application of heat, but I wonder if anybody's done this before and can
> > enlighten.
> >
> > James Thomson

>
> Any particular reason you want to do this?


I was wondering this myself; what's to be gained?

> They're in there tight.
>
> Anyway- find a good, tight-fitting hex wrench. Clamp it, short end
> pointed up, in a bench vice. Place the post down over hex wrench (it's
> probably a good idea to clean them out thoroughly first). Use the crank
> for additional leverage to break them loose one by one. After they're
> loose, remove them all the way normally.
>
> Wear gloves while doing this. They can let go with a snap and there's
> plent of parts that can bite.
>
> Jeff
 
J

James Thomson

Guest
"Tim McNamara" <[email protected]> a écrit:

> Are these posts the ones the chainrings attach to? I've never
> look closely at these cranks and have never taken one apart.


When I reread my my post I realised that my question would probably only be
immediately clear to someone capable of giving me an answer.

> I think that I would not use heat at all, given the potential risk of
> weakening the aluminum. You'd basically be doing uncontrolled
> heat treatment.


My idea of "careful application of heat" begins with boiling water, and ends
with the method frequently described to free stuck pedals.

> Have you tried a penetrating oil and then tapping the
> posts gently with a hammer?


Not yet.

"JeffWills" <[email protected]> a écrit:

> Any particular reason you want to do this?


Yep.

"Ozark Bicycle" <[email protected]> a écrit:

> I was wondering this myself; what's to be gained?


I'd like to run them as a low Q, narrow chainline single. With the posts
removed, a single chainring should bolt flush against the spider without
spacers, and I can use a shorter bottom bracket than I could get away with
if the posts were in situ.

James Thomson
 
J

James Thomson

Guest
"James Thomson" <[email protected]> a écrit:

> I'd like to remove the steel posts from a Mavic 631 crank. Each
> post has a 5mm allen socket at its base, but using all the force I dare,
> nothing's moving. I presume they're Loctited, and my next approach
> will be the careful application of heat, but I wonder if anybody's done
> this before and can enlighten.


Well, it turned out to be simple. I ran a kettle full of boiling water over
the crank. The posts then come out very easily, right hand threaded, and
show residues of a thread lock compound. The chainring then fits flush
against the spider using ordinary chainring bolts.

Thanks for the advice.

James Thomson
 
J

JeffWills

Guest
James Thomson wrote:

> > I was wondering this myself; what's to be gained?

>
> I'd like to run them as a low Q, narrow chainline single. With the posts
> removed, a single chainring should bolt flush against the spider without
> spacers, and I can use a shorter bottom bracket than I could get away with
> if the posts were in situ.


OK, that makes sense. The only problem you *might* run into is that
you're limited in your chainring choice. With the 631 arm, you can't
run a small-ish ring- I think 48 or 49 teeth is the smallest before the
chain runs into the spider.

Jeff
 
O

Ozark Bicycle

Guest
JeffWills wrote:
> James Thomson wrote:
>
> > > I was wondering this myself; what's to be gained?

> >
> > I'd like to run them as a low Q, narrow chainline single. With the posts
> > removed, a single chainring should bolt flush against the spider without
> > spacers, and I can use a shorter bottom bracket than I could get away with
> > if the posts were in situ.

>
> OK, that makes sense. The only problem you *might* run into is that
> you're limited in your chainring choice. With the 631 arm, you can't
> run a small-ish ring- I think 48 or 49 teeth is the smallest before the
> chain runs into the spider.
>


Based on experience, 49T is the limit, unless you want to "modify" the
spider..
 
J

James Thomson

Guest
"Ozark Bicycle" <[email protected]> a écrit:

> JeffWills wrote:


>> With the 631 arm, you can't run a small-ish ring- I think 48 or 49
>> teeth is the smallest before the chain runs into the spider.


> Based on experience, 49T is the limit, unless you want to "modify"
> the spider..


I have a 631 with a 48t big ring on my desk as I type this - there's ample
clearance between the chain and the tips of the spider.

I was guilty of an imprecision: the crank I'll be singlespeeding is a 631/2
with shorter arms and a 44t minimum big ring. I'll be using a 45.

James Thomson
 
O

Ozark Bicycle

Guest
James Thomson wrote:
> "Ozark Bicycle" <[email protected]> a écrit:
>
> > JeffWills wrote:

>
> >> With the 631 arm, you can't run a small-ish ring- I think 48 or 49
> >> teeth is the smallest before the chain runs into the spider.

>
> > Based on experience, 49T is the limit, unless you want to "modify"
> > the spider..

>
> I have a 631 with a 48t big ring on my desk as I type this - there's ample
> clearance between the chain and the tips of the spider.


I was wondering how this was possible....
>
> I was guilty of an imprecision: the crank I'll be singlespeeding is a 631/2
> with shorter arms and a 44t minimum big ring. I'll be using a 45.


......and this explains it all!
>
> James Thomson
 
J

James Thomson

Guest
"Ozark Bicycle" <[email protected]> a écrit:

James Thomson wrote:

> > I have a 631 with a 48t big ring on my desk as I type this - there's
> > ample clearance between the chain and the tips of the spider.


> I was wondering how this was possible....


> > I was guilty of an imprecision: the crank I'll be singlespeeding is a
> > 631/2 with shorter arms and a 44t minimum big ring. I'll be using a 45.


> .....and this explains it all!


No it doesn't.

I bought several complete sets of 631 and 631/2 cranks at a sale at the
weekend. The crank from which I removed the posts is a 631/2: I was
imprecise, but the difference wasn't relevant to my original question. The
631 crank on my desk is of the earlier design with the more extravagant
spider, and it has a 48t TA big ring fitted. Using the first chain that came
to hand, a SRAM PC59, the closest possible clearance between chain and
spider is 1.6mm.

James Thomson
 
O

Ozark Bicycle

Guest
James Thomson wrote:
> "Ozark Bicycle" <[email protected]> a écrit:
>
> James Thomson wrote:
>
> > > I have a 631 with a 48t big ring on my desk as I type this - there's
> > > ample clearance between the chain and the tips of the spider.

>
> > I was wondering how this was possible....

>
> > > I was guilty of an imprecision: the crank I'll be singlespeeding is a
> > > 631/2 with shorter arms and a 44t minimum big ring. I'll be using a 45.

>
> > .....and this explains it all!

>
> No it doesn't.
>
> I bought several complete sets of 631 and 631/2 cranks at a sale at the
> weekend. The crank from which I removed the posts is a 631/2: I was
> imprecise, but the difference wasn't relevant to my original question. The
> 631 crank on my desk is of the earlier design with the more extravagant
> spider, and it has a 48t TA big ring fitted. Using the first chain that came
> to hand, a SRAM PC59, the closest possible clearance between chain and
> spider is 1.6mm.
>


Way back in 1990, I put a 48T Mavic ring on a 631, it fouled the chain.
Absolutely. I had to eat the 48.
 
J

Johnny Sunset

Guest
Ozark Bicycle wrote:
>
> Way back in 1990, I put a 48T Mavic ring on a 631, it fouled the chain.
> Absolutely. I had to eat the 48.


What beer goes well with chainrings?

--
Tom Sherman - Post Free or Die!
 
O

Ozark Bicycle

Guest
Johnny Sunset wrote:
> Ozark Bicycle wrote:
> >
> > Way back in 1990, I put a 48T Mavic ring on a 631, it fouled the chain.
> > Absolutely. I had to eat the 48.

>
> What beer goes well with chainrings?
>


I had it with a fine Chianti.
 
J

James Thomson

Guest
"Ozark Bicycle" <[email protected]> a écrit:

>> > Way back in 1990, I put a 48T Mavic ring on a 631, it fouled the
>> > chain. Absolutely. I had to eat the 48.


> I had it with a fine Chianti.


Well there's your problem: Italian wine with French food. What were you
thinking?

My 631 cranks have 1992 and 1993 date codes (1994 and 1996 for the 631/2
sets). I won't enumerate the obvious possibilities.

James Thomson
 
O

Ozark Bicycle

Guest
James Thomson wrote:
> "Ozark Bicycle" <[email protected]> a écrit:
>
> >> > Way back in 1990, I put a 48T Mavic ring on a 631, it fouled the
> >> > chain. Absolutely. I had to eat the 48.

>
> > I had it with a fine Chianti.

>
> Well there's your problem: Italian wine with French food. What were you
> thinking?


International harmony?
>
> My 631 cranks have 1992 and 1993 date codes (1994 and 1996 for the 631/2
> sets). I won't enumerate the obvious possibilities.
>
>


Interestingly, when the 48T ring arrived (1990), it wasn't drilled for
the stud found on most outer chainrings. I thought this a bit; when I
put the ring on the crankarm, I saw why it wasn't there.
 

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