davidad

Get a Shimano BB and be done with it.

Ghrumpy

Read the OP. It's badly cross-threaded, which is why there's a MAVIC in there in the first place.

@seagull.apollo, bummer about the bearings. I think I have one with a broken axle that I could harvest the bearings from if they're in decent shape. I'll PM you if I do.

ThermionicScott 

OP hasn't visited the forum (to say nothing of this thread) in 7 years.

Ghrumpy

Awesome. FWIW I've waited longer than for the right part before.

My offer is open to anyone who might need bearings for their BB.

kc0yef 

The bearings are 16x30x9mm apparently, not standard 6902 (15x28x7mm) or 6903 (30x17x7mm).
Supposidly? maybe _not sure_ SKF part # BB1-3507



retrobike has the manual
https://www.retrobike.co.uk/gallery2/...0URDManual.pdf
here are the tech sheets

fietsbob

FWIW, Schlumpf, 1.6x overdrive 2 speed geared cranks use the similar chamfered edge BB Shell modifications.

they're an integrated BB gear box combination .. a 34t chainring acts like a 54, in its overdrive range ,
chainring turns faster than the crank-arms.. but at same rate in low..

Threaded within themselves, to compress against the conic ends but not into the frame threads....



....

34505838

actually you don't even need washers can just use a rubber o-ring (same size that comes on one of the dust covers) and put on outside of each bearing (for if using 7mm wide bearings)

KJK

velocentrik

I think its important to put in a placeholder regarding these epic Mavic bottom brackets and "exactly" what taper they are...

There is a lot of misinformation out on the web in the early days of the internet (Sheldon Brown got it wrong), and in forums (Old Potatoe got it wrong), and even in the reference manuals of record (Sutherlands). There was a lesson here in that , a lot of the best go-to bike mechanics that haunted the Internet forums at times put bad info out there when they really didn't know, and even when faced with measurements and observations the cycling community wanted to believe the personalities that had become authorities on such things, even when they were factually wrong. It was a great case study in different personalities "remembering things incorrectly" and passing around bad information to each other then citing each other as references.

Silly argument over Mavic Bottom Bracket spindle standard

It is absolutely NOT the case that Mavic bottom brackets are JIS. Neither are they exactly ISO (but pretty much). Late 70s and early 80s things were a little more proprietary back then.

Remember the Campagnolo color charts that showed the compatibility of different Syncro indexing shift inserts with different freewheels as an example? It's kind of like that. Cycling used to not so much be standards based as more of an "A-fit" or "A-minus" or "B-fit" compatibility across some components. As an example the old Campagnolo charts are supposed to tell you which Syncro shift disks match the cog spacing of which freewheels, but the absence of standardizations across everything left all this nuance regarding which chain to use. To read the charts you had to reference the tiny little symbols represent compatibility with different chains just to see if your shift disk (yellow 6 speed or blue 7 speed) would work with a given Campy freewheel (say Record 6 speed or Victory Triomphe 7 speed). It was madness!

From this era that had a lack of defined and exacting standards, compatibility was a function of what worked with what. Mavic Bottom Brackets, are not JIS and not specifically ISO (predates the cycling industry adopting the ISO BB square taper standard), they were a proprietary taper like Campagnolo of the same era (in fact that was the non-standard standard of the Mavic BB) which is now referred to as the Campy/ISO standard.

When Kontact of the old Paceline Forum community actually reached out to Skip at Mavic, going directly to the source to try to settle the debate he found out that there never seemed to be any actual claim that the Mavic BB spindle was ISO. It most definitely was NOT a JIS spindle though. Skip related, per Kontact, "C-Record era Victory spindle was an A fit for the Starfish 631 crank, and a Nuovo Record spindle was an A-. Shimano was not even considered a B fit. This fits with the information out there that Campy wasn't technically ISO until post C-Record, and there was some minor variations in their spindle tapers."

Best recommendation is to use a Mavic crank or Campagnolo crank on a Mavic bottom bracket, or any other ISO crank. There will be A fit, A-minus fits, and fits that are not even B fits.

What is all this talk about bottom bracket spindle standard? From the Phil Wood website:



How to prep a BB shell for a Mavic BB:

Mavic tech advice pg 30 of catalog

3alarmer 

...because this comes up pretty high on Google as a reference, and because I finally got around to taking one of these BB's out so I could repaint the bike, here are some photos of a difficult extraction. When I got the lock rings loosened up and off, I somehow naively thought the BB unit would slide right out. It turns out that if you put an aluminum shelled sealed unit in slip fit proximity to a steel shell, you'll get some galvanic corrosion over the years. this is especially true if you tell people the BB will last forever.

Anyway, I managed to figure out a way to extract it without pounding on it, which I would suppose is not good for the bearings. I don't think I'll re-use it, because I'd like to rebuild this with a different Shimano crank that only marginally works with this spindle. But you never know what you'll run into down the line. the pulling unit is the the original locking nut for one side, reversed so you don't mess up the chamfered inner edge. The shims you use to gradually coax the unit loose are just a miscellaneous collection of standard, loose bearing BB lock nuts from the spares drawer.

Dan Burkhart 

Wow! So, is there any hope for the bottom bracket threads to fit a conventional cartridge, or will you need another threadless solution? I can't see through all the rust.

3alarmer 

...there is always hope. I wire brushed it, knocked out some of the sand and rust (there was so much that it blocked to lower end of the down tube like a plug), and have the frame hanging up outside filled up about halfway with Evapo-rust. There are definitely threads still there... I don't know why the Mavic was installed in the first place, because I've only had the bike for 8 years or so. I'll try to chase it out with some standard piloted taps, and if that doesn't get it to where a sealed cartridge BB from this century with JIS spindle ends installs securely, I'll either go with one of those Velo Orange threadless thingies, or maybe ream it a skosh and tap it Italian. I'm pretty sure I can make it work, but I'll definitely get this resolved for sure before I go to the trouble of repainting and stickering it.

I kind of had a hunch this was gonna be a PIA, which is why I've left it alone since it continued working (and still does.)

Interestingly, the majority of the observable rust is located within six inches in any direction of the BB shell, and lot of what got sacrificed in the galvanic erosion appears to have been from the aluminum. If those lock rings are yet another metal, (they might be), that only added to the problem

JohnDThompson 

Ooh, that's nasty. I had to deal with a Legnano that had a Phil cartridge in similar neglect. I ended up pounding it out, and it didn't matter about the bearings because they had already been destroyed by rust:



I picked up some new cartridge bearings for a bout $6/each and pressed them into the Phil cartridge. Looks like hell, but runs smoothly and no one will see the nasty outside of the cartridge.

fietsbob

Ah older Phil ,the sleeve is steel , not quite stainless, because it has enough iron content to rust ,
They used the same tubing on their hubs , I left a leather strip on the hubshell that kept it shiny..