Bottom Bracket for Stronglight 49D Cranks

[James Thomson]

I have a pair of Stronglight 49D cranks that I'd like to use with a single
3mm (1/8") TA chainring to drive a Fichtel & Sachs Torpedo hub (~40mm
chainline) and I'm looking for a suitable bottom bracket.

The cranks were bought in different places at different times. The left
(stamped F and 9 near the taper) was originally French threaded (I've
retapped it to BSC), and the right (A and 4) British. It seems that the
tapers are slightly different: the right crank comes close to bottoming on a
Campag axle and seems a good fit on a Shimano UN71, while the left crank
seems happier with the Campag taper. The right taper doesn't look worn.

This needs to fit an old French "porteur" bike, with French threaded bottom
bracket shell.

I don't currently own a Stronglight crank extractor, so I'd like to get this
right first time if possible.

Can anyone tell me what the original Stronglight spec would have been for a
bottom bracket for track or hub gear use?

Can anyone make a stab at a reasonable modern alternative for a French
threaded frame? I have some Spidel cups that will work with 30mm cartridge
bearings or a UN72.

Thanks,

James Thomson

 

[Nick Payne]

Shimano UN72 works for me. I think it's a 118mm with the crank setup as a
double on a bike with 126mm rear OLN spacing and 7-speed freewheel. But they
don't come in French threading. Phil Wood sell French thread BB cups for
their bottom brackets.

Nick

"James Thomson" <[email protected]> wrote in message
news:[email protected]...
>I have a pair of Stronglight 49D cranks that I'd like to use with a single
> 3mm (1/8") TA chainring to drive a Fichtel & Sachs Torpedo hub (~40mm
> chainline) and I'm looking for a suitable bottom bracket.
>
> The cranks were bought in different places at different times. The left
> (stamped F and 9 near the taper) was originally French threaded (I've
> retapped it to BSC), and the right (A and 4) British. It seems that the
> tapers are slightly different: the right crank comes close to bottoming on
> a
> Campag axle and seems a good fit on a Shimano UN71, while the left crank
> seems happier with the Campag taper. The right taper doesn't look worn.
>
> This needs to fit an old French "porteur" bike, with French threaded
> bottom
> bracket shell.
>
> I don't currently own a Stronglight crank extractor, so I'd like to get
> this
> right first time if possible.
>
> Can anyone tell me what the original Stronglight spec would have been for
> a
> bottom bracket for track or hub gear use?
>
> Can anyone make a stab at a reasonable modern alternative for a French
> threaded frame? I have some Spidel cups that will work with 30mm cartridge
> bearings or a UN72.

 

[A Muzi]

James Thomson wrote:
> I have a pair of Stronglight 49D cranks that I'd like to use with a single
> 3mm (1/8") TA chainring to drive a Fichtel & Sachs Torpedo hub (~40mm
> chainline) and I'm looking for a suitable bottom bracket.
>
> The cranks were bought in different places at different times. The left
> (stamped F and 9 near the taper) was originally French threaded (I've
> retapped it to BSC), and the right (A and 4) British. It seems that the
> tapers are slightly different: the right crank comes close to bottoming on a
> Campag axle and seems a good fit on a Shimano UN71, while the left crank
> seems happier with the Campag taper. The right taper doesn't look worn.
>
> This needs to fit an old French "porteur" bike, with French threaded bottom
> bracket shell.
>
> I don't currently own a Stronglight crank extractor, so I'd like to get this
> right first time if possible.
>
> Can anyone tell me what the original Stronglight spec would have been for a
> bottom bracket for track or hub gear use?
>
> Can anyone make a stab at a reasonable modern alternative for a French
> threaded frame? I have some Spidel cups that will work with 30mm cartridge
> bearings or a UN72.

The Stronglight track spindle, same as a TA #314 is asymmetric, about
3~4mm difference which is why your symmetric spindles seem long on the
left/short on the right.
The original series Phil Wood #2 cartridge works perfectly, still made.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

 

[James Thomson]

"A Muzi" <[email protected]> a écrit:

> The Stronglight track spindle, same as a TA #314 is asymmetric,
> about 3~4mm difference

Thanks. I found this diagram of a TA#314 that seems to show it very nearly
symmetrical - 21.5mm left side offset vs 22mm right. Was there more than one
model with that number?

http://sheldonbrown.com/harris/images/ta-bb-axles.gif

> which is why your symmetric spindles seem long on the left/short
> on the right.

There's also a taper difference, at least under hand pressure: the right
crank has about 3mm more engagement. I don't know whether the right crank
bore started out smaller and has been enlarged (though it doesn't look that
way) or if Stronglight tapers changed between the times these two cranks
were made, but the difference is clearly there.

> The original series Phil Wood #2 cartridge works perfectly, still made.

Thanks, though a little beyond my budget for the bike in question.

I think I'll be able to get close with a 110mm UN72 using the Spidel cups
with a spacer under the right cup.

James Thomson

 

[* * Chas]

"James Thomson" <[email protected]> wrote in message
news:[email protected]...
> "A Muzi" <[email protected]> a écrit:
>
> > The Stronglight track spindle, same as a TA #314 is asymmetric,
> > about 3~4mm difference
>
> Thanks. I found this diagram of a TA#314 that seems to show it very
nearly
> symmetrical - 21.5mm left side offset vs 22mm right. Was there more than
one
> model with that number?
>
> http://sheldonbrown.com/harris/images/ta-bb-axles.gif
>
> > which is why your symmetric spindles seem long on the left/short
> > on the right.
>
> There's also a taper difference, at least under hand pressure: the right
> crank has about 3mm more engagement. I don't know whether the right
crank
> bore started out smaller and has been enlarged (though it doesn't look
that
> way) or if Stronglight tapers changed between the times these two cranks
> were made, but the difference is clearly there.
>
> > The original series Phil Wood #2 cartridge works perfectly, still
made.
>
> Thanks, though a little beyond my budget for the bike in question.
>
> I think I'll be able to get close with a 110mm UN72 using the Spidel
cups
> with a spacer under the right cup.
>
> James Thomson
>
It's not uncommon for the tapers in the crank arms to expand from frequent
removal and replacement especially if the person reinstalling them has a
heavy hand and a long wrench.

If they have been stretched to the point where the crank arm bolt bottoms
out before it's tight that can be remedied with an additional washer under
the bolt that has a hole large enough to fit over the spindle.

Note that this can create a chain line problem on the right side if the
crank moves too far inward.

If they are really stretched and you are a large rider you may consider
using them for show only. Stronglight 49 crank arms come up on ebay all of
the time. BTW. they interchange with TA Cyclotouriste components. If you
need BB parts, TA cups and spindles were better quality than Stronglight.

With old cranks like yours periodically check them for cracks around the
spindle and pedals.

Chas.