SRAM DUB BSA BB & Crankset Binding

[scoobydrew]

Building up a new MTB (2020 ish Ibis DV9) at the moment. Per Ibis' specs (link, page 8), it has a BSA threaded BB that's 68mm despite it being a MTB.

I'm using a SRAM/Truvativ DUB crankset that has a 3mm offset chainring for "boost" spacing and 52mm chain line. Bought a SRAM DUB BSA bottom bracket to go with these.

Per SRAM's specs (link, page 7), for a MTB with a 68mm BB I need a 2.5mm spacer inside of each BB cup plus a 4.5mm spacer on the outside of the drive-side (right) BB cup.

When I put this all together, the cranks bind way before the 54 N-m torque spec. The preload adjuster on the NDS arm is backed out all the way.

Any ideas?

[mjf]

Originally Posted by scoobydrew

Building up a new MTB (2020 ish Ibis DV9) at the moment. Per Ibis' specs (link, page 8), it has a BSA threaded BB that's 68mm despite it being a MTB.

I'm using a SRAM/Truvativ DUB crankset that has a 3mm offset chainring for "boost" spacing and 52mm chain line. Bought a SRAM DUB BSA bottom bracket to go with these.

Per SRAM's specs (link, page 7), for a MTB with a 68mm BB I need a 2.5mm spacer inside of each BB cup plus a 4.5mm spacer on the outside of the drive-side (right) BB cup.

When I put this all together, the cranks bind way before the 54 N-m torque spec. The preload adjuster on the NDS arm is backed out all the way.

Any ideas?

If it's binding you have too many spacers.

TBH, I'm distrustful of a lot of product spec sheets from manufacturers, especially since every other site that I'm finding on the 2020 Ibis DV9 lists the BB as 73mm instead of 68mm.

EX:
https://www.jensonusa.com/Ibis-Dv9-Frame-2020-10
https://www.vitalmtb.com/product/gui.../DV9-XTR,27395
https://mbaction.com/the-new-ibis-dv9-hardtail/ - search 73mm

So to begin, remove the spacers from both sides of the BB. While you're at it, measure the BB. It's almost certainly 73mm, not 68mm.

With that in mind, reinstall the cups without the spacers, and you'll likely be fine.

[scoobydrew]

Thanks for the info. You're right! Just measured out the BB as 73mm. With just the 4.5mm spacer on the outside of the BB as specified by SRAM, the cranks spin freely.