Cervelo BBright 6805 bottom bracket bearings

[smul]

Ok so there is something I really cant understand.

I've got an R3 it has a standard Cervelo thread together bottom bracket (i think) with 6805 24RS bearings, and I run a 24mm rotor axle..bought the bike like that, never had a problem, no there are no plastic spacers to take up 1mm.

There is no huge of 1mm play in the bearing for the axle, therefore it is some sort of ~24mm hole. Not sure how that is possible as a 6805 is 25x37x7 bearing size.

Now, recently, I got an Aspero, bought a Wheels MFG 24mm bottom bracket which has MR2437 bearings (24x37x7), and I went to put my same rotor cranks in, and well, they fit horribly. Yes I can get them in, but it requires a hell of a lot of force...i.e. the bearings are slightly too small..

So my question is, what are these mystery Speed 6805 bearings in my R3 bottom bracket that fit my Rotor 24mm axle??

[Coolcat]

The first (original?) bearing has the designation 6805/24RS. I think this might be synonymous with 6805/24 2RS, which seems to have the dimensions (Google) 24x37x7 mm.

As for the tight fit through the Wheels MFG bearings: Rotor 24 mm crank axles seem to be a little wider than Shimano 24 mm. Tolerances. I have five Rotor 24 mm cranksets, and all are quite tight to fit in Shimano BBs. When removing the cranks, the drive side Shimano plastic seal is often pulled off from the bearing, stuck on the axle.

[timmerrr]

My DUB Wheels MFG BB is significantly tighter on the spindle than the stock Sram one and the BBinfinite one that i currently have going in the bike. I think the bearings that Wheels MGF uses are a little on small side of the spec.

[Karvalo]

Now, recently, I got an Aspero, bought a Wheels MFG 24mm bottom bracket which has MR2437 bearings (24x37x7), and I went to put my same rotor cranks in, and well, they fit horribly. Yes I can get them in, but it requires a hell of a lot of force...i.e. the bearings are slightly too small..

Sounds like it fits ok

So my question is, what are these mystery Speed 6805 bearings in my R3 bottom bracket that fit my Rotor 24mm axle??

That bearing literally has 24 written on it.

[smul]

Ok so I'm just captian idiot. I'm ok with that then...

I didn't know 6805/24RS meant a 24mm, I thought the 24RS was to do with the seal :/

Well ok then, I guess mystery solved:
- 6805/24RS = 24mm
- Rotor 24mm axle is a fat boy
- Wheels MFG just run very tight (Enduro) bearings

All good thanks team

[Coolcat]

Good questions, and that's what this forum is for.

[StevieB]

Ok so I'm just captian idiot. I'm ok with that then...

I didn't know 6805/24RS meant a 24mm, I thought the 24RS was to do with the seal :/

Well ok then, I guess mystery solved:
- 6805/24RS = 24mm
- Rotor 24mm axle is a fat boy
- Wheels MFG just run very tight (Enduro) bearings

All good thanks team

FWIW, I have these Wheels Mfg AC bearings in my Aspero (in the OEM, screw-together Cervelo shell) https://wheelsmfg.com/products/bearings ... aring.html.

Installed them after the original 6805/24RS bearings packed it in after an absurdly short tenure in pristine conditions. A common issue; Cervelo deserve a lot of grief for shipping such crap bearings in their bikes. In any case, my Shimano GRX 24mm crank spindle goes through the WM bearings easily by hand. Suspect 99% of the issue is that Rotor spindles run a bit on the large side, as noted by others. OK, just snug...

[jfranci3]

Tip: If you're just going to R&R the bearings... Trek's BB90 kit has NSK DD (contact seal) 6805 37 x 25 x 7 ABEC5 (BB86 PF86 Shimano size ) with the 1mm shim/reducer / shield included. This is for the same price you can get any qualilty bearing as a one-off.

https://www.trekbikes.com/us/en_US/equi ... rCode=grey

This would be the way to go for any BB86/BB92/BB90 BB bearing replacement if you've got a good shell, are not going with a Shimano off-the-shelf, and not going ceramic. I don't prefer the Enduro bearings because the 24mm inner race is hard steel on my crank spindle, when I'd rather have the shim in these solving any alignment issues.