Screw in BB86 for 30mm spindle?

[Fixie82]

I have a new frame which is BB86 and am wanting to run my Rotor 3D crank. I've searched extensively for a new BB option as coming from BSA and wanting to avoid any potential creaking issues from the start I wanted to find something similar to the Praxis and Hope screw in BB's. These are offered for 24mm spindles not 30mm currently.

Does anyone know of a BB option for 30mm spindles that is not simply pressfit bearings such as the Rotor 41/30 kit?

The new Enduro TorqTite is only being made for BB386 evo which has a larger diameter so no go there.

Any help is greatly appreciated

[Fixie82]

Stupid Tapatalk - apologies for putting this in everything wheels. I swear I was in the road forum. Please move or delete as appropriate

[Calnago]

I don't understand why the TorqTite version for 30mm spindles wouldn't work. What do you mean it has a larger diameter? I think TorqTite has a solution for you. That's what I would try. I've heard good things about them but haven't installed one yet.

[Fixie82]

So had I, the issue is the BB86 41mm vs BB386 46mm diameter, the TorqTite is only made in 46mm hence not being an option.

[Calnago]

Ah, yes. I've dealt with so many BB "standards" lately, my head is spinning. Need to carry around a pocket guide to keep them all straight. Good luck.

[andrew9]

A 30mm spindle in BB86 leaves very little room, 5.5mm around the spindle.
Most adaptors for BB86 use 6706 bearings; at 37mm o.d. they only leave 2mm for the bearing cup.

It would be possible to make a cup that would then connect to a threaded collar inside the BB, but with only 2mm to connect too it would most likely have to be steel or titanium to be strong enough.
It would probably be a good idea, because a stronger bearing cup could prevent the crush problem with 6706 bearings. The crush problem is because the bearing races of a 6706 are so thin, that unless a good tolerance is maintained, the outer race will deform and make the bearing too tight.

I have a lightning crankset, with their BB86 to 30mm BB. The plastic cups needed polishing on a lathe to get proper fit. The O.D. was approx .03mm oversize for my frame.
I think the lightning BB is a good, lightweight product, but due to tolerances in frames, they may need fine tuning to get the 6706 bearings to run smooth.

The Rotor PF41 uses aluminium cups, they might be a good choice, it looks like the bearings may be replaceable also

Wheelsmfg make a really good looking BB, looks to have larger bearing than a 6706. I think that their bearings are not replaceable, you would need to replace the whole BB if it got rough, but it should last longer being bigger

http://wheelsmfg.com/bb86-to-30mm-ceram ... aring.html
here's another one, very similar to wheels
http://www.enduroforkseals.com/id375.html

[Fixie82]

Great info Andrew and thanks for the links. At this stage it looks like I might go with the Rotor 41/30 bearings and if in the future a screw in is developed swap it out. I've had confirmation that a manufacturer by the name of a Wishbone is developing one but have had no indication of a release date.

How have you found bearing life with reduced size?

[andrew9]

I've only done 1500km on my cranks, after the fiddly install they have been silent and smooth. I replaced the bearings during install with some $20 (for 4) ebay ones. The originals were a tiny bit notchy after being installed too tight, these are very fragile bearings. plus the new metal shielded bearings spin more freely, at the cost of poorer sealing than the rubber type.
I'm happy with the Lightning, but the install must be very precise, I found it a little fiddly, and I install bearings and machine stuff as an occupation.

On second look, I don't think the Rotor PF41 are a replaceable bearing, but it's hard to see from the photos. There seems to be a sleeve inside the bearing in addition to being in a cup, none of the other BB’s have that, it means the bearing must be even thinner to allow for that sleeve.

I'd get one of the Wheelsmfg or Enduro BB's they look to me like they would be the biggest bearing as they are mounted directly on both the inner and outer races, only judging from the photos

Raceface make a BB with aluminum cups and a tube to seal the inside, if you feel that would be helpful (maybe for mtb/cross)
They state that is has a replaceable bearing, but the number found (6806) is for a 42mm o.d. bearing, that obviously would not fit, so that must be a typo.
The raceface part number is BB419230B7, it's a bit cheaper too