Magnesium BB Shell: Low Torque, LocTite Red?

[(PeteCresswell)]

Looks like I'm getting a warranty replacement on the magnesium Maverick monolink
BB shell whose threads I managed to tear out the other day.

Had a chance to opt for a redesigned version in Alu, but that would have
required a new (wider) spindle and also moved the cranks about an inch
forward; so I stuck with the older magnesium version.

From what I've heard so far, magnesium is a step below Alu in toughness and is
significantly more susceptible to corrosion from salt water/salt air.

Given that, I'm thinking:
---------------------------------------------------------------------
1) Ignore Shimano's (rather high 50-70nm) torque specs when
installing the spindle.

2) Set both drive side and the plastic cup on the non-drive side in
LocTite Red.

3) Torque to maybe 30nm and let the LocTite go off overnite.
----------------------------------------------------------------------

Rationale:
----------------------------------------------------------------------
- The Red LocTite will counterbalance the reduced torque

- The Red LocTite will seal it better - preventing infiltration by water
into the threads.

- If/when I need to remove it, a little careful application of heat should
break down the LocTite.
-----------------------------------------------------------------------

Anybody have some thoughts on this?
--
PeteCresswell

 

[jim beam]

(PeteCresswell) wrote:
> Looks like I'm getting a warranty replacement on the magnesium Maverick monolink
> BB shell whose threads I managed to tear out the other day.
>
> Had a chance to opt for a redesigned version in Alu, but that would have
> required a new (wider) spindle and also moved the cranks about an inch
> forward; so I stuck with the older magnesium version.
>
> From what I've heard so far, magnesium is a step below Alu in toughness and is
> significantly more susceptible to corrosion from salt water/salt air.
>
> Given that, I'm thinking:
> ---------------------------------------------------------------------
> 1) Ignore Shimano's (rather high 50-70nm) torque specs when
> installing the spindle.
>
> 2) Set both drive side and the plastic cup on the non-drive side in
> LocTite Red.
>
> 3) Torque to maybe 30nm and let the LocTite go off overnite.
> ----------------------------------------------------------------------
>
> Rationale:
> ----------------------------------------------------------------------
> - The Red LocTite will counterbalance the reduced torque
>
> - The Red LocTite will seal it better - preventing infiltration by water
> into the threads.
>
> - If/when I need to remove it, a little careful application of heat should
> break down the LocTite.
> -----------------------------------------------------------------------
>
> Anybody have some thoughts on this?

yes, get the alu frame and spring a few bucks for the wider bb.

 

[Werehatrack]

On Fri, 24 Feb 2006 21:16:43 -0500, "(PeteCresswell)" <[email protected]>
wrote:

>Looks like I'm getting a warranty replacement on the magnesium Maverick monolink
>BB shell whose threads I managed to tear out the other day.
>
>Had a chance to opt for a redesigned version in Alu, but that would have
>required a new (wider) spindle and also moved the cranks about an inch
>forward; so I stuck with the older magnesium version.

I think you would have been better advised to take the aluminum frame.

>From what I've heard so far, magnesium is a step below Alu in toughness and is
>significantly more susceptible to corrosion from salt water/salt air.

It's also more likely to crack from cyclic flexure.

>Given that, I'm thinking:
>---------------------------------------------------------------------
>1) Ignore Shimano's (rather high 50-70nm) torque specs when
> installing the spindle.
>
>2) Set both drive side and the plastic cup on the non-drive side in
> LocTite Red.
>
>3) Torque to maybe 30nm and let the LocTite go off overnite.
>----------------------------------------------------------------------
>
>Rationale:
>----------------------------------------------------------------------
>- The Red LocTite will counterbalance the reduced torque
>
>- The Red LocTite will seal it better - preventing infiltration by water
> into the threads.
>
>- If/when I need to remove it, a little careful application of heat should
> break down the LocTite.
>-----------------------------------------------------------------------
>
>Anybody have some thoughts on this?

Magnesium alloys are inherently brittle. Even if the BB is installed
with Loctite, the threads will still be under the same strains that
caused the first failure. The Loctite serves only to seal and to
prevent rotational loosening; it will do nothing to strengthen the
threads themselves, and the shearing forces that tore out the first BB
(probably one thread at a time until the whole thing peeled) will most
likely be duplicated in the new frame. If the BB is undertorqued, the
possibility that the shell will be able to move slightly will go up,
and I do not think that the Loctite will prevent this from happening.
What will occur, however, is that the BB will be much harder to remove
later on. In particular, in my opinion, it's unlikely that you could
apply enough heat to the shell to release the grip of the Loctite
without also having some effect on the metal itself.

If you're going to use the magnesium frame, I would scrupulously
follow the manufacturer's recommended policies with regard to BB
installation. If it fails then, it's much harder for them to try to
state that it's your fault.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

 

[G.T.]

"(PeteCresswell)" <[email protected]> wrote in message
news:[email protected]...
> Looks like I'm getting a warranty replacement on the magnesium Maverick
monolink
> BB shell whose threads I managed to tear out the other day.
>
> Had a chance to opt for a redesigned version in Alu, but that would have
> required a new (wider) spindle and also moved the cranks about an inch
> forward; so I stuck with the older magnesium version.
>
> From what I've heard so far, magnesium is a step below Alu in toughness
and is
> significantly more susceptible to corrosion from salt water/salt air.
>
> Given that, I'm thinking:
> ---------------------------------------------------------------------
> 1) Ignore Shimano's (rather high 50-70nm) torque specs when
> installing the spindle.
>
> 2) Set both drive side and the plastic cup on the non-drive side in
> LocTite Red.
>
> 3) Torque to maybe 30nm and let the LocTite go off overnite.
> ----------------------------------------------------------------------
>
> Rationale:
> ----------------------------------------------------------------------
> - The Red LocTite will counterbalance the reduced torque
>
> - The Red LocTite will seal it better - preventing infiltration by water
> into the threads.
>
> - If/when I need to remove it, a little careful application of heat should
> break down the LocTite.
> -----------------------------------------------------------------------
>
> Anybody have some thoughts on this?

Yeah, the above sounds good then I'd find someone to off-load this bike to
ASAP.

Greg

 

[Qui si parla Campagnolo]

(PeteCresswell) wrote:
> Looks like I'm getting a warranty replacement on the magnesium Maverick monolink
> BB shell whose threads I managed to tear out the other day.
>
> Had a chance to opt for a redesigned version in Alu, but that would have
> required a new (wider) spindle and also moved the cranks about an inch
> forward; so I stuck with the older magnesium version.
>
> From what I've heard so far, magnesium is a step below Alu in toughness and is
> significantly more susceptible to corrosion from salt water/salt air.
>
> Given that, I'm thinking:
> ---------------------------------------------------------------------
> 1) Ignore Shimano's (rather high 50-70nm) torque specs when
> installing the spindle.
>
> 2) Set both drive side and the plastic cup on the non-drive side in
> LocTite Red.
>
> 3) Torque to maybe 30nm and let the LocTite go off overnite.
> ----------------------------------------------------------------------
>
> Rationale:
> ----------------------------------------------------------------------
> - The Red LocTite will counterbalance the reduced torque
>
> - The Red LocTite will seal it better - preventing infiltration by water
> into the threads.
>
> - If/when I need to remove it, a little careful application of heat should
> break down the LocTite.
> -----------------------------------------------------------------------
>
> Anybody have some thoughts on this?


Yep. make sure the BB shell is prepped. Use antisieze and normal
torque.
> --
> PeteCresswell

 

[(PeteCresswell)]

Per Werehatrack:
>I think you would have been better advised to take the aluminum frame.

It's not a frame, just a suspension link that contains the BB shell.

What I've got out of this thread so far:
-------------------------------------------------------------
1) Forget the LocTite. No benefit, considerable cost.

2) If/when I decide to order a spare link, get the Alu one.
I probably will get a spare link - if only as insurance against
Maverick's going belly-up.
-------------------------------------------------------------
--
PeteCresswell