So I changed the bearings on my bottom bracket (Sram DUB). The bearings spin freely when the crank is installed, but not torqed down. If I tighten the cranks they get very tight, they probably wouldn’t even move at all If I would torque it to spec.
I’ve looked it up online how to install these, and there should be a adjustable preload thingy you can turn with your hands. Mine only has the threads but not the thing to grab onto. Could it be that this is missing? If so, is there a other way to turn it? I gently tried turning it with a towel an pliers but it won’t move at all.
Any advice is appreciated
by Chefkoch257
3 Comments
You will need the threaded adjuster to install this correctly. Also, make sure you have the proper spacers for your bottom bracket shell and spindle length. Both road and MTB spacer charts in the links below.
[https://www.sram.com/globalassets/document-hierarchy/compatibility-map/road/dub-choose-a-road-bottom-bracket-compatibility-map.pdf](https://www.sram.com/globalassets/document-hierarchy/compatibility-map/road/dub-choose-a-road-bottom-bracket-compatibility-map.pdf)
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[https://www.sram.com/globalassets/document-hierarchy/compatibility-map/mtb/dub-mtb-bottom-bracket-compatibility-chart.pdf](https://www.sram.com/globalassets/document-hierarchy/compatibility-map/mtb/dub-mtb-bottom-bracket-compatibility-chart.pdf)
When you say you changed the bearings on the bottom bracket, do you mean you replaced the bottom bracket entirely (cups and all) or you **just** replaced the cartridge bearings?
Without the preload ring, you have no way to adjust preload and thus the system is left in a “worst-case” state, i.e. there is 0mm of lateral play removed whatsoever. This means that after you’ve torqued the crank bolt up to ~52Nm then they should spin very freely (too freely). But if yours are too tight after doing so, then this implies something else is amiss.
You need the adjustable preload collar because it allows you to remove any lateral play in the cranks and set the preload onto the bearings. Any minute amount of lateral play will cause additional wear on the bearings.
They sell replacement SRAM preload rings, or you can get ones from a third party in an anodized colour.
Yes, your cranks are missing the preload adjuster.
When you torque the cranks to spec, there should be at least a couple millimeters of play, assuming the preload is backed out completely and no plastic spacers are installed.
Can we get a pic of the installed bottom bracket? Most sram bottom brackets come with two metal spacers to use on a 68mm bottom bracket. If your BB is 73mm and you install the spacers, it will be too wide for the cranks.