Light crankset with 24mm axle for BB92 frame

Discuss light weight issues concerning mountain bikes & parts.

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Jwh1978
Posts: 8
Joined: Tue Nov 24, 2020 9:47 pm

by Jwh1978

Hello

SO i'm looking for a light set of cranks to use ona BB92 frame.

I currently have a nice set of FSA slk carbon cranks which use a BB92 - to BB30 bottom braket - but as the bearings are so thin (61706 / 6706 bearings) they are not lasting very long.
One has last 15 hours :(

So ideally i'd like to get back to proper size bearings...

I know i could use a Sram DUB setup - but thats only a little better...

I know of the usual shimano range - xtr... but is ther anything else out there which has worked for you.

Or maybe a better bottom bracket option which i've missed.

Thanks

by Weenie


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02GF74
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Location: Sunny UK

by 02GF74

15 hours!!!???

If quality sealed bearings have been fitted and unless the BB is immersed in mud, that does not sound normal.

Have you checked the bearing are fitted correctly I. e.. square in the BB? There usually is a circlip which the bearings butt up against and keep them square the frame.

I seem to remember replacing the sealed bearings in an external bearing type shimano BB - they're not supposed to be serviceable but that is not the case. When I did this I fitted slightly wider bearings, namely because the correct ones cost more but I had to trim some plastic part so it all fitted. Unfortunately I don't remember any more details than that.

Jwh1978
Posts: 8
Joined: Tue Nov 24, 2020 9:47 pm

by Jwh1978

Yes 15hrs... 8hrs of that was a sole 8hr xc race! (granted in 8hrs of rain )

These are not the nice fat bearings in a hollowtech type bottom bracket - these are 30mmx37mmx4mm
As its a small bearing there are 4 of them to spread the load. 2 on each side. These sit inside the BB shell and are not external.

The others are fine, just one outer bearing on the drive side. There is no damage to the bearing seal and there was an outer cover as well as a wave washer.
I think is just a bad bearing -but having read reviews on enduro bearings - they aren't great.

The bottom bracket is a push fit - but the 2 halves screw together ( like a praxxis BB ) so the fitting should be square (ish).. although i've seen to many www.hambini.com videos

I think i'm going back to a proper shimano setup with some XTR crank so i can have a normal BB.

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robbosmans
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by robbosmans

I use sram xx1 gxp cranks, they weight 400g wo chainring

Jwh1978
Posts: 8
Joined: Tue Nov 24, 2020 9:47 pm

by Jwh1978

robbosmans wrote:
Thu Nov 26, 2020 5:33 pm
I use sram xx1 gxp cranks, they weight 400g wo chainring
In a BB92 style frame? If so what bottom bracket are you using

Jwh1978
Posts: 8
Joined: Tue Nov 24, 2020 9:47 pm

by Jwh1978

ive just googled them - gxp is 24mm... somehow with all their options i'd completly missed that one

jff
Posts: 22
Joined: Sun Aug 08, 2010 10:33 am

by jff

One small remark: the spindle of a gxp crank has a 24mm diameter on the drive side and on the non drive side it's 22mm. So either go for a specifc gxp bottom bracket or use an adaptor with a regular bb.

With a bb92 frame I would not go for the DUB cranksets though they are light.Mainly due to the reason you metioned yourself (small ball bearing size)

Jwh1978
Posts: 8
Joined: Tue Nov 24, 2020 9:47 pm

by Jwh1978

I've just re-weighed my current cranks FSA slk force and they are 460g with a 32t chainring and end boots... Hard to beat that weight

I've also tried to verify the bearings i bought and i'm thinking they may have been fake - which is why they did not last too long. Apparently fake bearings is big thing - who knew.

As its only used occasionally at the moment.. going to try one last set of bearings... if they don't survice then it will be either GXP setup or some XTR cranks - just beacuse there will be NO compatibility issues.

mr4fox
Posts: 276
Joined: Sat May 15, 2010 2:01 pm

by mr4fox

Improper bearing alignment might explain the premature wear.

I've just ordered an xx1 dub crankset with quarq power meter because the price was really good and it was stupid light. Putting it in a bb92 frame. I'm aware of the compromised bearing size, but I thought some manufacturers were now using double row bearing for this application? Hoping I get more than 15hrs at least. I'm considering a BBinfinate with ceramic bearings. Damn expensive for a BB but the bearing have a lifetime garantee.

Jwh1978
Posts: 8
Joined: Tue Nov 24, 2020 9:47 pm

by Jwh1978

mine had 2 rows of bearings each side.
When installed first time it would spin freely enough. No signs of issues - and previously with a BB92 and shimano cranks they seemed to last a normal amount of time

Sadly the BB92 to 30mm axle is massive comprimise.. the dub is slightly better.
Luckily its only my race bike... i don't use it very often and this year its only be raced once :(

Good luck with the power meter - i've toyed with the idea of getting one - but in short XC races i'm not sure riding to power would benifit me. Possibly on longer races

02GF74
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by 02GF74

jff wrote:
Thu Nov 26, 2020 9:47 pm
One small remark: the spindle of a gxp crank has a 24mm diameter on the drive side and on the non drive side it's 22mm. So either go for a specifc gxp bottom bracket or use an adaptor with a regular bb.
I made my own adapter, first version was a strip of 1mm thick aluminium. Then I discovered that one of the sealed bearings outer race I had, just replaced, once separated, is almost a perfect fit. If I remember correctly, I had to use a sanding disc in a dremel to dress the inside of the bearing race.

by Weenie


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weightminimalist
Posts: 11
Joined: Thu Dec 09, 2021 2:58 am

by weightminimalist

I also have been looking for lightweight crankset for my BB92 and came across to find a titanium crankset (400g arms & spindle, GXP direct mount ) with 24mm spindle that can be custom-made to your required spec at Aliexpress. I am discussing with the seller about my required spec.

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