My Fat bike has been off the road, hasn’t bothered me too much as the little one is getting too big for the Macride now... but with the next one coming and the current weather I could use it.
It suffered from snapped chainrings (SRAM X5), not worn out, but snapped on the chainring bolts. Twice on the outer and the inner turned oval and came off as well.
Anyway I wanted to replace like for like, but finding 32/22 chainrings (appropriately ramped) was problematic, so in the end I’ve found a whole X5 (34/22) crankset brand new for £50. I went for it as the chainring failure’s made me suspect that there was a problem I couldn’t find with the crankset. But the price was also cheaper than I could find just the outer chainring for anyway.
On fitting the new crankset i find this ~5mm gap between the RHS bearing cover and the RHS spider. Where ~5mm of axle is showing. I’ve refitted the old one to check and it’s the same, I never built the original, and never noticed it before. You can’t push it through further as the LH bearing limits the axle movement.
It doesn’t feel right, the RHS bearing cover can come loose and slide up the axle. I can do it by hand.
I’m undecided what to do, SRAM install instructions , seems to suggest this is correct (although it’s not clear). But the RHS bearing cover is clearly going to come loose.
Options I have.
1) leave it. I rode it today and it was fine although I’m worried about water into the BB. When the cover moves.
2) add spacers between the BB shell and BB. There is quite lot of engaged thread, and adding some to the LHS would bring the chainline in and improve it. Although ~5mm is a lot, and quite a bit of lost tread. Plus I don’t have any suitable spacers.
3) I have a spindle spacer from a hollowtech crankset. I could put this between the RHS bb bearing cover and the RHS crank, it fits but it’s a tad two thick and the spindle is not pushing up against the LHS bearing. I think there could be too much load from the left crank on the left bearing, or not enough engagement on the left crank to left spindle. I could file this spacer down.
4) I could buy a new BB, get a SRAM one and see if it resolves maybe the external cups/spacers dimensions are different..... I cannot see the brand of the one installed. It has no internal tube for the spindle, and the RHS outer external part is damaged where the ovalled inner ring tried to take it off as well. Maybe this damage, is not encouraging the bearing cover to say in place. But The bearings are fine and you can still get a BB removal tool on it.
I’m probably going to try 4) as although I brought this bike on a whim, Its been really useful with the kids, so it’s got a few more years to go now!. And wondering before I spend £40 on a SRAM BB and find myself in the same position, if anyone has seen this, and if this gap is perfectly fine.
At the moment I fully expect to buy a new BB and find myself in the same position...
SRAM GXP BSA RHS spacer.
Re: SRAM GXP BSA RHS spacer.
The RHS bearing cover cannot (quite) come out far enough that it come completely free from the BB. If it did there would be play in the crankset/BB as the bearing cover slides in and make the crankset spindle sit flush. Without it there would be maybe 1mm play in the crankset/BB.
I really don’t think this piece should move.
I really don’t think this piece should move.
Re: SRAM GXP BSA RHS spacer.
I think that there is meant to be a spacer and a wave washer. But often this seems to be missing from both the BB assy and the chainset, so you need to get the correct parts or to improvise.
I have often used spacers and packing shims on the spindle, so that there is some preload on the RH bearing when the axle shoulder contacts the LH bearing.
If you push the spindle briskly leftwards you will hear/feel a clunk as the shoulder contact the LH bearing. If you used a thick spacer to get it within 1mm and then add 0.1mm (beer can) shims one at a time, then the first time you don't hear the clunk (or one shim more than this), is usually the correct setting.
If the RHS plastic 'top hat' bushing is worn so that it is free to move as you describe, it will soon knacker itself unless you (through it) add preload to the RH bearing, and if it is worn enough it'll carry on wearing anyway, no matter what you do.
cheers
I have often used spacers and packing shims on the spindle, so that there is some preload on the RH bearing when the axle shoulder contacts the LH bearing.
If you push the spindle briskly leftwards you will hear/feel a clunk as the shoulder contact the LH bearing. If you used a thick spacer to get it within 1mm and then add 0.1mm (beer can) shims one at a time, then the first time you don't hear the clunk (or one shim more than this), is usually the correct setting.
If the RHS plastic 'top hat' bushing is worn so that it is free to move as you describe, it will soon knacker itself unless you (through it) add preload to the RH bearing, and if it is worn enough it'll carry on wearing anyway, no matter what you do.
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: SRAM GXP BSA RHS spacer.
I got up early as this was bothering me and checked the BB shell sizing. It’s uniformly 100mm and the BB is sitting cleanly (with spacers)
I appreciate what your saying is logical. And the type of solution I would expect.
The SRAM install documents do not show this type of washer/spacer for the BSA threaded assembly. They do (but on the NDS) for the PF. I don’t think this is an oversight from SRAM. Possibly, but they would have corrected it by now surely.
Plus it’s such small potential adjustments required it doesn’t feel intuitive in the intended design. Too much spacer and I think you’ll overload both sets of bearings pretty quickly with the torque required in the NDS crank bolt.
I’m going to get a new BB and start from there. Look at an extra spacer on the NDS between the BB and the BB shell, ( if I think there is enough thread) as this will help the already maxed out FD reach. And see how the DS bearing cover sits, and then if needed get to work on some can shims (cider in my case). I don’t like the idea of thatchers gold being an integral part of my crankset...
I appreciate what your saying is logical. And the type of solution I would expect.
The SRAM install documents do not show this type of washer/spacer for the BSA threaded assembly. They do (but on the NDS) for the PF. I don’t think this is an oversight from SRAM. Possibly, but they would have corrected it by now surely.
Plus it’s such small potential adjustments required it doesn’t feel intuitive in the intended design. Too much spacer and I think you’ll overload both sets of bearings pretty quickly with the torque required in the NDS crank bolt.
I’m going to get a new BB and start from there. Look at an extra spacer on the NDS between the BB and the BB shell, ( if I think there is enough thread) as this will help the already maxed out FD reach. And see how the DS bearing cover sits, and then if needed get to work on some can shims (cider in my case). I don’t like the idea of thatchers gold being an integral part of my crankset...
Re: SRAM GXP BSA RHS spacer.
thatcher's gold? No just basic engineering. Mot people (including yourself, it seems) are perfectly happy putting spacers behind the cups but not on the spindle? Double standards at work for sure.
Buying a new BB means that you are 100% at the mercy of the assembled length matching that of the BB spindle. I'd go far as to say that this cannot work properly unless a wave washer or shims are included. I have seen lots (assembled with neither) that have failed prematurely.
cheers
Buying a new BB means that you are 100% at the mercy of the assembled length matching that of the BB spindle. I'd go far as to say that this cannot work properly unless a wave washer or shims are included. I have seen lots (assembled with neither) that have failed prematurely.
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: SRAM GXP BSA RHS spacer.
Ok, so I’ve taken it apart again this has enabled me to get accurate measurements.
I’ve worked out the gap is exactly 5mm.
I believe the bearings are designed to sit on the silver bands on the spindle. In which case there is 105mm between the inside of the BB cups. 100mm shell + 2x2.5mm spacers.. which is what I have and I what I believe is the SRAM spec (although they just show spacers, not the actual size).
If I push the DS BB cup right up to the spider it becomes 110mm gap, which would imply 2x5mm spacers. I don’t think this is correct, as I think the bearing match with the bands.
I believe 2.5mm spacer is the correct spec, but it does leave 5mm between DS crank and the BB cup.
on removing and having a good look at it i’ve decided the damage to the DS BB is worst than cosmetic and water can get between the bearing cover and the bearing. So I’m going to get a new BB. And recover the bearing and covers from this one while they are still good.
I’m fully expecting the new BB to arrive with 2x 2.5mm spacers. (If it comes with 5mm I will be surprised). As I think the design is bearing on the silver sleeves, I won’t be adding additional spacers, and will leave me in the same position, with 5mm between BB cup and DS spider. so I’ve also ordered some M24 wave washers. For the cost of them I’m not going to mess around with my own.
Not sure they are in the original design, but given they will only provide a touch of load on the bearings if I’m careful they shouldn’t damage them... and if they do I’ve got a spare set (in theory)...
Gap between DS spider and Bearing cover as I think the bearing/bb should sit.
Silver marks for bearing to sit.
Damage to DS BB
I’ve worked out the gap is exactly 5mm.
I believe the bearings are designed to sit on the silver bands on the spindle. In which case there is 105mm between the inside of the BB cups. 100mm shell + 2x2.5mm spacers.. which is what I have and I what I believe is the SRAM spec (although they just show spacers, not the actual size).
If I push the DS BB cup right up to the spider it becomes 110mm gap, which would imply 2x5mm spacers. I don’t think this is correct, as I think the bearing match with the bands.
I believe 2.5mm spacer is the correct spec, but it does leave 5mm between DS crank and the BB cup.
on removing and having a good look at it i’ve decided the damage to the DS BB is worst than cosmetic and water can get between the bearing cover and the bearing. So I’m going to get a new BB. And recover the bearing and covers from this one while they are still good.
I’m fully expecting the new BB to arrive with 2x 2.5mm spacers. (If it comes with 5mm I will be surprised). As I think the design is bearing on the silver sleeves, I won’t be adding additional spacers, and will leave me in the same position, with 5mm between BB cup and DS spider. so I’ve also ordered some M24 wave washers. For the cost of them I’m not going to mess around with my own.
Not sure they are in the original design, but given they will only provide a touch of load on the bearings if I’m careful they shouldn’t damage them... and if they do I’ve got a spare set (in theory)...
Gap between DS spider and Bearing cover as I think the bearing/bb should sit.
Silver marks for bearing to sit.
Damage to DS BB
Re: SRAM GXP BSA RHS spacer.
it sounds like you have a plan.
One thing to note is that if you intend to use a (nested) stack of wave washers, the spring rate (stiffness) goes up pro rata with the number of washers. Another is that to work well against a plastic top hat spacer, the washers/spacers have to be able to bear against the centre part. This means the washers can't be a slack fit on the diameter and can't easily deform into a convex shape under load, else the top hat may start to bear against the snap ring (bad).
cheers
One thing to note is that if you intend to use a (nested) stack of wave washers, the spring rate (stiffness) goes up pro rata with the number of washers. Another is that to work well against a plastic top hat spacer, the washers/spacers have to be able to bear against the centre part. This means the washers can't be a slack fit on the diameter and can't easily deform into a convex shape under load, else the top hat may start to bear against the snap ring (bad).
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: SRAM GXP BSA RHS spacer.
I have a pack of wave washer ordered, 10 I think, but was only thinking to use one. They are ID 24mm, OD 30.5mm and 3.5mm ‘wide’. I’ll wait till they get here but was thinking 1 with a couple of old bearing covers at each side,( along with the actual bearing cover), might work. Otherwise will have to get my cider hat on..
Re: SRAM GXP BSA RHS spacer.
So i accidently ordered my GXP 100mm BB from the EU. 
it took a while - no fees though..
I decided as i was eyeing it all up and the frame is a decent Surly with resale value, that the new BB and the New Crankset would go to the LBS to be fitted.
I also remembered the Drive side was a bit tough to get out and back i again and didn't want to risk it, and thought they could look at it.
Anyway they didn't fancy spacing out the gap, and as i'd already taken out the old one and cleaned it up they did it while i waited. I had 2 extra teeth on the outer cog (it was the closest i could find - like for like) and it took them about 10mins and most of this was adjusting the FD.
I now have the 5mm gap. as per SRAM spec. the the drive side fitting was perfectly fine.
I have a Road one ready to go, which will replace the HT2 currently on the turbo when the times comes to cut the left crank arm off. On measuring up with the (new to me) crankset, there is no 5mm gap.
it took a while - no fees though.. I decided as i was eyeing it all up and the frame is a decent Surly with resale value, that the new BB and the New Crankset would go to the LBS to be fitted.
I also remembered the Drive side was a bit tough to get out and back i again and didn't want to risk it, and thought they could look at it.
Anyway they didn't fancy spacing out the gap, and as i'd already taken out the old one and cleaned it up they did it while i waited. I had 2 extra teeth on the outer cog (it was the closest i could find - like for like) and it took them about 10mins and most of this was adjusting the FD.
I now have the 5mm gap. as per SRAM spec. the the drive side fitting was perfectly fine.
I have a Road one ready to go, which will replace the HT2 currently on the turbo when the times comes to cut the left crank arm off. On measuring up with the (new to me) crankset, there is no 5mm gap.