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  • Sram GXP crank and BB install issues*pic heavy
  • dumbbot
    Member

    Hi, I have actually been running these for a few months before I noticed some play in the crank, took them off and was plain to see I had done something terribly wrong. It;s a standard 68mm BB with 2 spacers installed.

    Sram s1400 crankset

    With a Skyeye BB with the shim installed in the NON drive side.

    When i took the crank off I have managed to grind the face off the drive side BB.(impressive)

    Now according to this http://trailtiretv.blogspot.co.uk/2012/12/srams-gxp-bottom-bracket-how-it-differs.html

    Just so you know, If you ever install the SRAM GXP Bottom Bracket, the Drive Side seal SHOULD NOT!! come in contact with the crank arm or spider, a small gap there is a good thing…

    Now obviously this seems like a spacer issue, but as the cranks were secondhand they did not come with spacer of wave washer, and they only seem to be available for Pressfit BB30?

    To add to my confusion, the torque setting on the crank arm seem wrong,…if i were to crank the 8mm bolt to 40+nm the cranks wont’t move, where is the 10mm rating of 12-15nm seems about right for pre-loading bearings.

    anyone?

    parkesie
    Member

    If your cranks are stiff when torqued to 40nm you’ve got to much spacer somewhere.

    mikewsmith
    Member

    The text that this lip holds it on not the 40Nm of grunt is important.
    For me GXP with the hope adapter is the easiest thing in the world to install. It takes a minute and just do it up tight so there is no play and it spins.

    wzzzz
    Member

    I’ve been through this I feel your pain.

    You have what you call the “shim” installed wrong.

    The shim needs to go from the INSIDE of the non drive side bearing.

    So remove your non drive side cup, remove the shim and re insert the shim from the inside and reinstall the cup.

    This will shift the lot over by 3mm meaning your drive side no longer contacts and wears the bb cup.

    All adapted HTII BBs use a shim for GXP. Hope BBs use a split shim, others use a 1 piece shim that should be inserted form inside the cup. A proper Sram GXP BB doesn’t use a shim as the bearings are sized right.

    Make sure you have one BB spacer each side of the bb shell. If your chainline is way out (shouldn’t be) then move the drive side spacer to the non drive side meaning 2 on the non drive side, or get some 1mm bb spacers to fine tune.

    You will end up with a slight gap on the drive side between crank and bb cup, this is normal. Sram used to supply a “wave” washer to fill the gap and retain the seal, some people use an O ring but your BB may have a seal that stays put.

    When you tighten a GXP crank you are not preloading the bearing (as you do with HTII), your are just clamping the bearing inner race between the step in the axle and the non drive crank. Make sure you do it up to the spec or it will come loose and damage the splines.

    wzzzz
    Member

    See here this is an original GXP BB:

    Your “shim” is doing the job of the extended inner race on the non drive side bearing. So it needs to go on the INSIDE of your cup.

    See also the wave washer and “spindle spacers” filling the driveside gap.

    Premier Icon vincienup
    Subscriber

    ^ This. I’m sure that the interwebz stories about GXP BB’s being rubbish mostly boil down to people ‘knowing how to stick a BB and crankset on’ and not imagining there may be anything different about them.

    Although, you do find plenty of people that don’t quite seem to get Shimano BB preloading, either…

    dumbbot
    Member

    I have 2 spacers either side of the BB, and the shim was indeed on the wrong way, however this was me this morning taking things apart and reinstalling incorrectly..as i recall it was installed from the inside and i knocked it though by accident. I have now put that right, but the drive side is still seems dam close against the BB face.

    And this is with no where near the 40+nm torque recommended on the inner 8mmm bolt

    I hear you about the spindle spacers and wave washer, but as i said secondhand cranks never came with them…and the only ones i can see online seem to be for Pressfit BB?

    wzzzz
    Member

    can’t quite see from your pic, and not clear when you say 2 spacers either side.

    You should have just one 2.5mm spacer on the drive side and one 2.5mm spacer on the non drive side.

    If your drive side crank is still is hitting the BB cup preventing you torquing the crank then remove the spacer from the drive side cup, maybe look at replacing it with a 1mm spacer if you like.

    Or just go buy a proper sram gxp bb, they are £20

    dumbbot
    Member

    Sorry, 2 spacers installed, 1 either side of the BB, wasnt very clear there. I will try removing the drive side one..

    Shimano drivetrain next time

    wzzzz
    Member

    Well I think it might be the BB at fault not the crank!

    A proper Sram GXP BB would just work.

    I also have a similar bodge (HTII BB with a shim like yours) on one bike that I went through what you are going through with.
    I have a hope BB with their own split shim on another
    And two more that run proper GXP BBs.

    Only the bikes with sram bbs have perfect chainline.

    I like Sram cranksets better than shimano, on most (like yours) you can remove the chainring spider and run one of these direct mount chain rings like this.

    https://www.aliexpress.com/item/DECKAS-GXP-Bicycle-Chainwheel-Crankset-Mountain-Bike-32T-34T-Chainring-Aluminum-Parts-Gear-Scope-For-sram/32734894983.html

    dumbbot
    Member

    I was trying the avoid SRAM BB’s as they have a reputation for being shite, but if you’re saying even a hope BB/split shim isn’t great… It’s not ideal is it.

    I haven’t the money for a hope BB anyway, so I’ve ordered smaller spacer/wave washer..See how I go with that.

    Thanks for your input btw.

    Quick question.

    Can i fit a SRAM GXP crank in place of a shimano crank. Wanting to get some carbon SRAM cranks but wonder if i can fit them to my current hope press fit set up.

    wzzzz
    Member

    Can i fit a SRAM GXP crank in place of a shimano crank. Wanting to get some carbon SRAM cranks but wonder if i can fit them to my current hope press fit set up.

    Do you currently run 24mm axle shimano HTII cranks?

    If so then yes, you just need the hope GXP split shim adapter, £8 or so.

    wzzzz
    Member

    I was trying the avoid SRAM BB’s as they have a reputation for being shite, but if you’re saying even a hope BB/split shim isn’t great… It’s not ideal is it.

    well the BB you have used is not designed for GXP cranks, its for HTII so its the wrong part really. The hope bb and shim gives better chainline than the type of shim you have.

    The current sram BBs are much better. I think most of the reputation comes from early OEM BBs and Truvativ branded BBs. Get a new Sram GXP from CRC, they last well. When the bearings go, replace the bearings with these: http://www.enduroforkseals.com/id228.html

    dumbbot
    Member

    Roger that, thanks again man..very helpful.

    Yeah, just get a SRAM GXP BB, £15 when the bearings go, get a new kit like wizzzz said, if you ring mbbearings, and speak proper nice to them, they will supply you the same kit.

    The SRAM BBs can suffer ‘creaking’ it’s not your axle, it’s the bearings creaking in the cups as they Loctite them in the cups. I removed them, cleaned the Loctite with acetone and greaded and pressed them back in, no creakage.

    kelv123
    Member

    Hi all, this is an interesting post. I didn’t want to get the SRAM BB because of bad reviews, so tried to install a Quarq Power Meter GXP on my Hollowtech 2 BB (BB-R60) using a Chris King Conversion Kit (number 6).
    https://www.powermeter24.com/uk/chris-king-gxp-conversion-kit-6-7-road/mtb-842

    With the disc spring from the conversion kit fitted on the drive side, I could only get up to a torque of about 30Nm before the crank became stiff. Without the disc spring I could get up to the required torque (I tried 50Nm) without any problems but the crank is too close to the frame which caused a worse chain line, my gears were out of alignment and I guess my pedalling would be different too (and invalidate the bike fit I had).
    In the end I’ve fitted a GXP bottom bracket but would love to know how to properly fit a Hollowtech 2 and convert it.

    wzzzz
    Member

    what BB shell do you have? The linked king converter is for press fit BBs

    “86,5 mm, 89,5mm, 92mm bottombracket shell”

    I’ve used the hope converter on normal threaded BB shells just fine
    http://www.chainreactioncycles.com/hope-bottom-bracket-truvativ-gxp-converter/rp-prod26899

    Premier Icon bedmaker
    Subscriber

    Tick

    teasel
    Member

    A big thumbs up to Wzzzz for taking time to help folk understand shit. Without any ‘tude, too.

    Awesome.

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