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Evening, currently have a gt zaskar 9r 100 expert, looking at changing cranks arms. Currently has a SRAM S1400 2.2, OCT Hollow Forged 39/26T.
If I wanted to replace the bb how do I know which one I need, I.e gxp witdth? E.tc etc
Cheers
Ash
Yes and yes but by no means in good a nick as that!
I have knackered the front rings and figured I could get a replacement in the sales ready for summer, and possibly replace the bb.
So it is only gxp 68/73mm? Is that a multi or is it one particular size?
68/73 is a standard size and the difference between the two numbers is made up by spacers on the BB.
If you are replacing the BB you can move away from the SRAM/Truvativ GPX axle standard if you want.
I couldn't find any specifications on the bike to be able to tell if the BB is Press fit or an external one but an external one looks like this
[img] 
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If your looks like above pretty much any Hollowteck II or GPX crank should fit your bike with the matching BB.
Cheers rusty, I will probably stay with sram, bit can I get say a chris king bb to replace?
Not sure about King but Hope do GXP adapters for their BB's. Any 68/73 BB will fit the frame but the axle size may be an issue.
From memory the GXP axle is 23mm where Hollowtech 2 is 25mm the King BB's are designed to be used primarily with Hollowtech II hence needing the adapter to drop the size down for GXP axles.
Cheers rusty.
Why so many different versions! So probably easier to stick with gxp all the way.
So whats bb30?
If it was me i'd ditch the gxp and go with standard Hollowtech II stuff because i have not heard anything good about the gxp bottom brackets but you pays your money you makes your choice and go with what you want.
A quick look in the chris king website shows this
http://chrisking.com/bottombracket
COMPATIBILITY
We offer our bottom bracket cups in combination with a plastic center sleeve and three anodized 2.5mm chainline spacers for 24mm crank axle systems such as Shimano Hollowtech II. Only 108 grams.
Also available is the SRAM-compatible 24mm stepped axle configuration. The stepped axle Chris King bottom bracket makes use of a fit kit to match the crank axle to our standard cups and bearings but without use of chainline spacers. 125 grams.
So you could upgrade the BB to a Chris King then if you change the cranks at a later date you could remove the fit kit and re-use the BB.
So whats bb30?
Press Fit. BB is back enclosed in the frame but the BB housing is significantly larger to house it. Frame is not threaded BB cups are pressed into the frame.
But if ditch gxp ( which I have heard bad things about as well in fairness) could I still use sram truvativ? Being honest the whole thing confuses me.
So if I went for a normal bb I can still use sram, or would it be shimano?
Cheers rusty sorry for being such a spoon with this!
The King BB seems to be compatible with both.
If you went to the Hollowtech II standard you could use Shimano, Race Face, Middleburn and a host of others cranks but the gxp stuff would need n adapter to work as it is a smaller diameter axle.
Hope do an adaptor too for their HT11 bottom bracket so it works with GXP.