Modern bottom bracket options for Stronglight 49d
 

Greetings C&V,

I have two similar cranksets (Stronglight 49D, Specialities T.A. Cyclotouriste (both doubles)) sitting in my parts bin that I'd finally like to use on a Gazelle Champion Mondial A-Frame that I am building up.

However, the main issue has always been finding either a.) a modern cartridge bottom bracket that would work with either crankset, which were originally designed for asymmetric spindles, or b.) definitive information, either on this forum or elsewhere online, regarding correct spindle length for a double crankset, should I decide to try and source a vintage/NOS BB.

Over the years, I have seen many users post pictures of their bikes here utilizing both of these cranksets, some even with fairly modern(-ish) builds. My question to you is: how have you addressed the spindle length issue? Is there there something that I am missing here? Maybe a modern BB intended for a triple crankset? A spacer inserted behind the driveside BB cup and the frame?

My attempts to make these cranksets work have been unsuccessful - either the drive side is too close to the BB shell/chainstay, or the ND side is much too asymmetrically offset compared to the driveside.

Ideally, I want to achieve a set up where I have a good chainline and both crank arms are symmetrical relative to the frame.

Any and all ideas/solutions/info would be appreciated!

Maybe check with vintage online resellers such as Marco Vintage Bikes, Purgatorio (velowizard.com) and other well known european vintage dealers where to source a new olds stock bottom bracket.

Here are Stronglight and TA's specs for bottom brackets:
https://cimg2.ibsrv.net/gimg/bikefor...faf9c99f32.jpg
https://cimg5.ibsrv.net/gimg/bikefor...3063e76e4f.jpg
Perhaps a cartridge with similar axle-end dimensions will work. Failing that, a cartridge like Phil Wood that allows lateral adjustability will let you set the chainlone where you need it.

I use Velo Orange bottom brackets with a spacer if necessary on the drive side. Phil BBs are good as well. I've never worried much about whether the crankarms have the same spacing from the frame -- it would only be a couple mm in any case.

I’ve also had success with V-O 118mm cartridge BBs on Stronglight and TA doubles.

I've got 49D + TA cyclotourist on my 1961 Holdsworth Cyclone.
Original axle: Brampton England BBA.285 cottered 129.61mm.
Had the same issue as you picking a BB, went with Tange LN 3922 (symmetric 68 x 115mm) with a 3mm spacer on DS.

rear drop out = 121mm
BB shell width = 67mm
With 52/36 TA rings there's 2mm clearance to the chain stay.
Chainline 43.05mm

On my 1979 PX10, I used a symmetrical 113mm Shimano bottom bracket, which allowed sufficient clearance for the chainrings and which positioned the pedals symmetrically about the bb shell.

The original front derailer falls just short of retracting far enough inward for a robust downshift however, so a 115mm bottom bracket would have been the better choice.

You can always go back and add a cup spacer if you find that you need an extra mm or two driveside offset.

Note that a bb having a JIS taper will be effectively 2.5mm longer ON EACH END versus any vintage Stronglight spindle having comparable L and R protruding lengths.
So a 118mm Stronglight spindle is like a 113mm JIS spindle being set up with similar ~1mm offset (i.e. one end protruding 2mm further than the other end).

The TA spindles that I've measured have a slightly thicker taper than vintage Stronglight, so would be slightly more similar to JIS taper thickness, i.e. about like vintage Campagnolo.

A JIS spindle gives a more shallow engagement with a non-JIS crankarm, but I have had no issues associated with this myself and just use a slightly shorter spindle when replacing a French original bottom bracket with a JIS bottom bracket.

One solution that not everyone will like is grinding some metal off the F.der. until it moves inward enough. Figure out where it hits, and remove just as much metal as needed

Wife's Litespeed has a stupidly-oversized seat tube (well, stupid for her, at her wattage, but I can maybe see it for a burly sprinter). The crankset is a triple with basically a double chainline, perfect shifting on all the rear cogs when in the outer two chainrings, with the granny rings only used on a few of the bigger rear cogs. That's an excellent drivetrain IMHO, but the fat seat tube made it difficult.

Luckily I have a Dynafile (small hand-held belt sander).

https://cimg0.ibsrv.net/gimg/bikefor...865131e632.jpg
https://cimg1.ibsrv.net/gimg/bikefor...773a4ddf01.jpg

I know it looks dicey, but she's had it like that for 10 years and she rides a lot, her mileage is twice mine.

Oh wait I just remembered, I didn't grind it for that bike! Before it was on the Litespeed, the same derailer was on our tandem, which also has the same inward-offset triple chainline. That seat tube is only 1-1/8" (i.e. not oversized) but it was ovalized, for side-to-side stiffness, same effect as far as the F.der.goes. The tandem was set up that way in about 1990, so that butchered derailer has been like that for at least 35 years.

I think it has passed the test.

I also use V-O bb's, and in one instance on a Stronglight 49, but I still worry about ISO crank arms on a JIS-taper bottom bracket.

Omniracer sells very nice cartridge bottom brackets in a variety of spindle lengths and have both ISO and JIS taper options. Not sure if they offer different threading or just BSC.

My vote is always to use bottom brackets and cranks from the same manufacturer and from the same era whenever possible. If there is not a compelling other reason to use a cartridge crank, I would source a Stronglight Competition (widely inexpensively available from EBay and COOPs), grease the bearings with plenty of PhilWood grease, and you will have 90% of the service life of a new Phil Wood cartridge (likely far more than that of a cheap, far eastern unit) without any of the incompatibility issues.