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Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sat Jan 26, 2019 6:45 pm
by Greenduck
Hey all...

I have a Pinarello Dogma 65.1 with a SRAM/Truvativ GXP ITA bottom bracket and a Quarq DZero power meter.

It seems there's a problem with the edge of the bottom bracket bearing cup on the drive-side is rubbing on the inside of the power meter.

According to installation instruction you shouldn't use any spacers or washers but can I install a wave washer on the drive-side to move the DS a tiny bit out and avoid further rubbing?

It's clear to see where the BB bearing cup has rubbed aganst the power meter.
Image

This is how the BB bearing cup look. This is a new one I'm going to install.
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Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sat Jan 26, 2019 6:45 pm
by Weenie

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sat Jan 26, 2019 7:14 pm
by pdlpsher1
You are missing the wavy washer on the DS. This is needed on all GXP installations. And you may also need spacers on the NDS but you won't know until you have torqued the crank bolt. When properly torqued if the wavy washer is not almost completely flattened then you need some spacers on the NDS. Keep adding a thin spacer, one at a time, and retorque the bolt. You will know when to stop adding spacers when the wave washer on the DS is almost completely flattened.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sat Jan 26, 2019 7:33 pm
by osw000
I understood that wavy washers are not needed when installing GXP on BSA BB either english or italian. I run the same BB with etap Red normal cranks without washers and apparently everything is fine.

See some controversy here: https://r.tapatalk.com/shareLink?url=ht ... are_type=t




Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sat Jan 26, 2019 7:40 pm
by osw000
Sram reference, see page 22 : https://www.sram.com/sites/default/file ... kets_0.pdf

Wavy washer only on Press fit BB'sImage

Enviado desde mi SM-J530F mediante Tapatalk


Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sat Jan 26, 2019 7:48 pm
by pdlpsher1
I just re-read the Sram installation manual and you are right, a wavy washer is not specificed on a BSA BB. But I think it's the only way to cure the OP's issue. Plus it will provide a good preload to the BB bearings. So I can't see why it would hurt.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 3:21 am
by TobinHatesYou
Installing a wave washer might save the inner surface of your DZero, but only because it’ll take over as the sacrificial friction surface. The wave washer isn’t going to shift the position of the crank...that’s not how GXP works. With GXP, the NDS bearing is the “origin” or anchor point for the crankset. The inner race is sandwiched between the step in the spindle and the NDS crankarm. The bearing is in a static position inside the external ITA BB cup, and that cup is static relative to the BB shell. The only way your system can really develop lateral play is if the NDS cartridge bearing itself develops play, which is bad.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 12:07 pm
by Greenduck
TobinHatesYou wrote:
Sun Jan 27, 2019 3:21 am
Installing a wave washer might save the inner surface of your DZero, but only because it’ll take over as the sacrificial friction surface. The wave washer isn’t going to shift the position of the crank...that’s not how GXP works. With GXP, the NDS bearing is the “origin” or anchor point for the crankset. The inner race is sandwiched between the step in the spindle and the NDS crankarm. The bearing is in a static position inside the external ITA BB cup, and that cup is static relative to the BB shell. The only way your system can really develop lateral play is if the NDS cartridge bearing itself develops play, which is bad.
Makes sense. I can't really feel any play in the old NDS bearing but forces are higher when pedalling. I will install the new BB with the wave washer.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 12:24 pm
by jlok
Is there any difference between GxP BB for MTB and RB?

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 1:46 pm
by TobinHatesYou
jlok wrote:
Sun Jan 27, 2019 12:24 pm
Is there any difference between GxP BB for MTB and RB?
The external cups are the same, just the MTB BB shell is 73mm instead of 68mm.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 1:56 pm
by mattr
Check the actual width of the bottom bracket shell. I've seen them up to half a mm over length. (and more than 1 mm under size!)
You might need to get it faced, just to take paint/lacquer/slither of material off.

It's not rubbing much, so it'll literally only need a tickle with the facing tool.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 2:20 pm
by TobinHatesYou
It might also be that the DS cup started to back out since Italian BBs aren't reverse threaded on DS...

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 2:29 pm
by mattr
Yeah, that is a valid point, DS cup needs a proper bit of torque on it on ITA bottom brackets. Also, i prefer copperslip/antiseize rather than grease.
Even had to resort to a light threadlock before now on some frames with badly cut threads.

Re: Issues with Quarq DZero power meter and GXP bottom bracket

Posted: Sun Jan 27, 2019 2:29 pm
by Weenie