Odd crank issue, help!

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ff119
Posts: 117
Joined: Sat May 08, 2021 9:49 pm

by ff119

I have a cervelo and the only one in stock was apex, I had fitted at the dealer a stages sram power meter, over a year and no issues

Had drivetrain changed in feb 2024, no issues

End of May I had some creaking, shop tightened up crank, said "order a bottom bracket"

No notice so went to a shop on my way today (new town) and asked when I need this BB. Now I'm told my stages is wrong, I need a new crank or a new crankset + bottom bracket. Spacers could work but they won't do it and the bike not safe to ride.

I went to shop 2, told need new crankset (which? they don't know) and they can only tighten to 25nm torque but it needs 40 and it "may be safe to ride"

I'm confused how I did 17,000km if the crank is not the right size?

Why do they say a spacer would fix the issue but they refuse to do it?

I'm left without knowing what to order and unsure if I'm supposed to believe the bike is unsafe

by Weenie


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repoman
Posts: 43
Joined: Mon Jun 10, 2024 3:28 pm

by repoman

What did they say was specifically the problem?
The bump on Stages meters will cause some issue with the NDS chainstay sometimes, usually just putting some spacers in there to increase Q/Spacing works fine...usually only need 2-3mm on wide stays.

ff119
Posts: 117
Joined: Sat May 08, 2021 9:49 pm

by ff119

They say if they tighten the crank to 50nm it won't spin.

Every website says it's the right crank and 17,000kms didn't happen because the bike couldn't be used.

Why are they against using spacers?

mikemelbrooks
Posts: 359
Joined: Wed Jun 16, 2010 10:58 pm

by mikemelbrooks

Is it a gxp crankset?

ff119
Posts: 117
Joined: Sat May 08, 2021 9:49 pm

by ff119

yes it is

Greeners
Posts: 34
Joined: Fri Apr 26, 2024 10:13 am

by Greeners

There are some dreadful shops/mechanics out there. This sounds really odd to me, in my experience, the large style crank axles & press fit type b/b bearings don't like being over tightened, causing creaking. I would disassemble, clean, re-grease everything & re-install (not too much preload) but tighten to spec.
Do not over look the other areas of the bike known for creaking, bars/stem, saddle interfaces/ pedals etc - these often confused with b/b creaks.

ff119
Posts: 117
Joined: Sat May 08, 2021 9:49 pm

by ff119

Greeners wrote:
Thu Jun 20, 2024 1:56 pm
There are some dreadful shops/mechanics out there. This sounds really odd to me, in my experience, the large style crank axles & press fit type b/b bearings don't like being over tightened, causing creaking. I would disassemble, clean, re-grease everything & re-install (not too much preload) but tighten to spec.
Do not over look the other areas of the bike known for creaking, bars/stem, saddle interfaces/ pedals etc - these often confused with b/b creaks.
there is no sound now, but they claim they can't get the crank to 50nm only 25nm

eins4eins
Posts: 812
Joined: Wed Sep 28, 2016 11:49 am

by eins4eins

Give some proper information. Which bike, whats parts are installed?

ff119
Posts: 117
Joined: Sat May 08, 2021 9:49 pm

by ff119

eins4eins wrote:
Thu Jun 20, 2024 2:53 pm
Give some proper information. Which bike, whats parts are installed?
Cervelo Aspero, apex groupset with a stages power meter

Does that help in some way?

toxin
Posts: 938
Joined: Tue Apr 18, 2023 5:56 pm

by toxin

Give some pictures at least

mikemelbrooks
Posts: 359
Joined: Wed Jun 16, 2010 10:58 pm

by mikemelbrooks

Ok on a gxp crankset when you tighten the crank it clamps to the non drive side bearing. If you place a spacer on the drive side or the distance between the bearings is too long, the cranks will not spin. You either need to make sure that the bottom bracket bearings are the right width apart or that nobody has fitted spacer on the drive side of the cranks.

Aeo
Posts: 701
Joined: Wed May 25, 2016 2:06 am

by Aeo

https://www.hambini.com/sram-gxp-an-engineering-guide/

GXP cranks are double jeopardy when it comes to tolerances. Maybe your DBCA (distance between crank arms) is towards the short end of the range
Giant TCR Adv Pro Disc '17 · BH Lynx Race Evo '19 · Seraph GR029 '21 · Canyon Inflite AL '14

eins4eins
Posts: 812
Joined: Wed Sep 28, 2016 11:49 am

by eins4eins

ff119 wrote:
Thu Jun 20, 2024 3:15 pm
eins4eins wrote:
Thu Jun 20, 2024 2:53 pm
Give some proper information. Which bike, whats parts are installed?
Cervelo Aspero, apex groupset with a stages power meter

Does that help in some way?
No, not really. With the very little info you give, its wild guessing.

By just installing a powermeter crank arm on the non drive side without changing anything else, nothing could go wrong with gxp. Its stupid simple. This was probably done right as you rode the bike without a problem for a long time.
I assume the two shops are clueless and all you might need is a fresh bottom bracket.

ff119
Posts: 117
Joined: Sat May 08, 2021 9:49 pm

by ff119

eins4eins wrote:
Fri Jun 21, 2024 6:13 am
ff119 wrote:
Thu Jun 20, 2024 3:15 pm
eins4eins wrote:
Thu Jun 20, 2024 2:53 pm
Give some proper information. Which bike, whats parts are installed?
Cervelo Aspero, apex groupset with a stages power meter

Does that help in some way?
No, not really. With the very little info you give, its wild guessing.

By just installing a powermeter crank arm on the non drive side without changing anything else, nothing could go wrong with gxp. Its stupid simple. This was probably done right as you rode the bike without a problem for a long time.
I assume the two shops are clueless and all you might need is a fresh bottom bracket.
That is possible, the "it is going to just fall off" I find odd.

So far the other shops I've tried are all too busy to help fix the issue, whatever that issue may even be

by Weenie


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repoman
Posts: 43
Joined: Mon Jun 10, 2024 3:28 pm

by repoman

mikemelbrooks wrote:
Thu Jun 20, 2024 4:57 pm
Ok on a gxp crankset when you tighten the crank it clamps to the non drive side bearing. If you place a spacer on the drive side or the distance between the bearings is too long, the cranks will not spin. You either need to make sure that the bottom bracket bearings are the right width apart or that nobody has fitted spacer on the drive side of the cranks.
How would placing spacers on there change the distance between the bearings? :shock:
SRAM literally sells GXP specific spacers...

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