DUB Boost Eagle groupset mystery - please help
Discussion
Putting together a winter HT.
Frame is a new Commencal META HT (boost rear).
Groupset is (supposedly) a SRAM Boost NX, bought as OE from Alpkit.
All set up nicely as per SRAM recommendations. BAS 68 so I put x1 2.5mm spacer either side of the BB shell.
And then the 4.5mm spacer on the drive side.
Put the chain on and it jumps off the ring on the inside as soon as I shift to the largest but one cog on the cassette.
I then tried all manners of spacers configurations but the only way it will shift into those last two gears without dropping the chain is for the chain ring to almost foul the frame. And that's using a weird configuration of x1 2.5mm and the 4.5mm spacer on the non drive side. And even then I can't put any pre load or it does foul the frame.
What am I doing wrong ?
The only thing I can think of is that the cranks are super Boost rather than Boost. Not that I know if that even exists.
Am I right in thinking there is only ONE type of DUB bottom bracket for BSA and that using the spacers is correct, not that I can use both anyway...
Frame is a new Commencal META HT (boost rear).
Groupset is (supposedly) a SRAM Boost NX, bought as OE from Alpkit.
All set up nicely as per SRAM recommendations. BAS 68 so I put x1 2.5mm spacer either side of the BB shell.
And then the 4.5mm spacer on the drive side.
Put the chain on and it jumps off the ring on the inside as soon as I shift to the largest but one cog on the cassette.
I then tried all manners of spacers configurations but the only way it will shift into those last two gears without dropping the chain is for the chain ring to almost foul the frame. And that's using a weird configuration of x1 2.5mm and the 4.5mm spacer on the non drive side. And even then I can't put any pre load or it does foul the frame.
What am I doing wrong ?
The only thing I can think of is that the cranks are super Boost rather than Boost. Not that I know if that even exists.
Am I right in thinking there is only ONE type of DUB bottom bracket for BSA and that using the spacers is correct, not that I can use both anyway...
Thanks so much, it's a brand new full NX groupset so using 11-50 HG NX cassette. I did upgrade to a GX Eagle chain out of the box as the NX chain doesn't have surface treatment. The ring is the one that came on the crankset which is a 32t 3mm offset steel X sync 2 ring.
I have now managed to prevent the chain from falling off when in the 2 biggest cogs by putting the 4.5mm spacer on the wrong side (non drive side).
This means I have about 3 mm clearance between ring and chainstay but obviously the left hand crank sticks out more than the right hand away from the chainstay.
I checked the rear spacing and it is 148mm.
Not sure what else to check lol.
I could buy a 6mm offset ring I suppose which is non boost.
Maybe the frame is not well aligned if everything else checks out?
I have now managed to prevent the chain from falling off when in the 2 biggest cogs by putting the 4.5mm spacer on the wrong side (non drive side).
This means I have about 3 mm clearance between ring and chainstay but obviously the left hand crank sticks out more than the right hand away from the chainstay.
I checked the rear spacing and it is 148mm.
Not sure what else to check lol.
I could buy a 6mm offset ring I suppose which is non boost.
Maybe the frame is not well aligned if everything else checks out?
Edited by nickfrog on Sunday 13th November 11:48
Everything checks out then. You've got everything bang on if everything is as you think it is.
The only thing I can think of is that you've somehow got a superboost chainring but I'm not sure that's a thing with OE Sram gear.
Have you got another bike that's a known quantity that you can borrow the cranks/chainring off to try and find the issue?
The only thing I can think of is that you've somehow got a superboost chainring but I'm not sure that's a thing with OE Sram gear.
Have you got another bike that's a known quantity that you can borrow the cranks/chainring off to try and find the issue?
bobbo89 said:
Everything checks out then. You've got everything bang on if everything is as you think it is.
The only thing I can think of is that you've somehow got a superboost chainring but I'm not sure that's a thing with OE Sram gear.
Have you got another bike that's a known quantity that you can borrow the cranks/chainring off to try and find the issue?
Good point I might borrow a friend's with a GX set up. The only thing I can think of is that you've somehow got a superboost chainring but I'm not sure that's a thing with OE Sram gear.
Have you got another bike that's a known quantity that you can borrow the cranks/chainring off to try and find the issue?
The ring does say 3mm offset at the back, does that imply that it can't be a superboost?
What do you think of my idea of buying a 6mm offset ring ?
bobbo89 said:
Everything checks out then. You've got everything bang on if everything is as you think it is.
The only thing I can think of is that you've somehow got a superboost chainring but I'm not sure that's a thing with OE Sram gear.
Have you got another bike that's a known quantity that you can borrow the cranks/chainring off to try and find the issue?
Exactly. That's what's bothering me, I hate a bodge. The other possibility is that the cassette is not "straight" so I'll take that off and reinstall to see what happens. Perhaps the wheel is not dished properly.The only thing I can think of is that you've somehow got a superboost chainring but I'm not sure that's a thing with OE Sram gear.
Have you got another bike that's a known quantity that you can borrow the cranks/chainring off to try and find the issue?
BOR said:
I've got a feeling that the centre-lock chain rings are reversible, which sounds like it might bring the chainline back to where you want it in combination with the correct spacers?
That's a good idea. I might try that. Sounds like a bodge though.I might just revert to Shimano (there was a Deore groupset on this frame which worked perfectly albeit 10 speed), I never had any issues with them in 30 years, this is my first SRAM groupset.
nickfrog said:
I might just revert to Shimano (there was a Deore groupset on this frame which worked perfectly albeit 10 speed), I never had any issues with them in 30 years, this is my first SRAM groupset.
If you go Shimano, the Deore M5100 wide range 11-speed is great value and actually has a slightly wider gear range than NX Eagle (11-51t vs 11-50t).nickfrog said:
I might just revert to Shimano (there was a Deore groupset on this frame which worked perfectly albeit 10 speed), I never had any issues with them in 30 years, this is my first SRAM groupset.
I run 10 speed Shimano across all my bikes. Solid, reliable and stuff is cheap and easy to get your hands on.bobbo89 said:
I run 10 speed Shimano across all my bikes. Solid, reliable and stuff is cheap and easy to get your hands on.
Yes agreed. 10 speed was the peak of shifting quality too for me.I took everything off this morning in the sun and then put everything back on as per SRAM's guidelines with the 4.5mm spacer on the drive side.
And guess what, the chain doesn't drop off the ring anymore!!
It makes no sense but I must have got something wrong the first time round.
Chain line is around 52mm with 6 mm ring clearance to the chainstay and 10mm from chain to the 2.8 tyre. Arms are now equidistant to the stays.
Thanks for all the help!!!
Edited by nickfrog on Monday 14th November 12:00
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