Maybe a long shot here, but want to see if anyone else has run into this. Sorry for the novel here…
Has anyone measured chainline on their Oiz? Anyone had issues using a BBInfinite Bottom Bracket? PF92/BB92 one piece in this case.
Here’s the back story. Did Lutsen which was a mudfest, pulled off the cranks for inspection when I got home, and there was a little muddy water in there, and I tore one of the o-rings that seals around the cranks in the process. Stock SRAM BB. Decided to replace the BB with a BB92 from BBInfinite. I am running SRAM DUB-SL Cranks - 8 Bolt with the Quarq Dzero Spider PM and XSync2 Chainrings.
On re-assembly, best I can tell is that the chainring is now closer to a 55mm chainline than a 52mm chainline (52 is the spec). My chain guide (which isn’t adjustable in/out without shimming) had to be shimmed 2mm outboard so the chain wouldn’t interfere. Which proves that the chainring is now sitting at least 2mm further out board to me.
My chain guide was not shimmed out at all, no washers behind it before I started testing, which the Oiz documentation seems to call for 1mm.
I’ve been trading messages with BBInifinte, but so far no resolution. I seems like the Drive Side spacer they provide is too big, but supposedly is designed per the spec… They’re focused on finding out what I did wrong (not saying it didn’t happen) but all of the easy stuff I think we’ve checked.
Any issues running it at a 54-55mm chainline? Could theoretically cause efficiency and shifting issues in my 52T, right?
Any ideas? Taking a shot in the dark here because I need to get this thing fixed. Will probably haul it in to the LBS tomorrow morning (JRA Cycles for those of you local) for a second opinion. I need this thing running again even if it means having them rip this one out and put a stock one back in.
measure the back of the crank arms to the downtube to figure out if your crank is centered.
on Dub, there’s a spacer that goes between the spider and the BB bearing that determines the chainline.
What crank is this? Is it an OEM crank model?
exact chainline isn’t as important as function. Eye up the cogs with the chainring. You probably need to take the chain off the ring. What cog lines up with the ring?
did you go from a direct mount ring to a spider mounted one? Does the ring offset 3mm back toward the bike or is it a flat one?
SRAM and Shimano have 52& 55 boost cranks, so it should work fine if your chainstay isnt super short. 52mm is a narrow q-factor hard trail and XC std. 55mm compromises Q factor but gives the rear suspension more room. Both work with the same boost spacing in the back.
Pics?
Yes, absolutely. Good idea on the downtube, hadn’t thought of that! Best I can tell is that crank is ~1.5-2mm too far to the drive side. Measuring to the downtube, and to centerline of my water bottle bolts (using steel rulers as reference) agrees. And, it was easy to see at first as my chain guide made it obvious.
SRAM DUB SL, XX1 8 Bolt Crank Arms, Quarq PM Spider, XSync2 Chainring. I’ve been using this setup for the last year. All that changed was to pull out the OEM SRAM BB, and Replace with BBInfinite and their recommended spacers. Install went easy, no issues until I saw the chain guide. The issue is, the spacers they send don’t allow adjustment as is. So far the dude I talked with was acting a little Snarky - “I know the Math.”
No clearance issues, rough test once I shim the chain guide out I can shift through all the gears. My 52 seems a little rough, but I may need to adjust everything anyways.
Am I making a big deal out of nothing? I am off-center by 2mm or so, and it is further outboard than with the OEM SRAM BB. The OCD / Perfectionist side of me wants this perfect how it was
Was going to take it into the shop in a couple hours and see what they think. I could have BBInfinite send me a slightly shorter Drive Side Spacer, and add a little more to the non drive side.
The Dub BB spacer I had was cupped on one side about 1-2mm. Maybe have a look and try flipping it around.
Don’t mind the dude on the phone. The first step is always clarifying the problem and reviewing the initial diagnosis.
Is 1-2mm a big deal? Not really, is making sure you’ve got it right a big deal? Yes.
My Chisel with Shimano’s OEM non-boost thru Superboost MT-511 crank was like 5-6mm offset overall. They put spacers to eat up the one-size-fits-all spindle. How many threads are there about people complaint about this offset? 0. It’s really not noticeable
The spacers I have are directional, so unfortunately, no flipping. Basically I’d need to sand / grind one down, and add another to the other side. (Or have them send me one)
I think easiest thing is get my shop to check my work first. I think I can ride it as is for the time being if need be, especially seeing my weekend rides are mainly faster gravel in the smaller cogs right now.
What’s in the back of my mind though is that the gear that will be impacted the most by moving the chainring outboard is my 52T. And, I’m racing Leadville in 4.5 weeks so am going to spend a decent amount of time there that day!
Don’t sand or grind. You need flatness there. Get an extra seal or live with the spacing. Those bb30/dub single bolt cranks are always going to be 1-2mm off because of the preload adjustment.
Sounding like I may just have to live with it unless they can provide me different spacers. Here’s a quick and easy solution. An extra pedal washer on the left side to balance out the distance to centerline and then give all of the shifting a check / tune to make sure it’s good?
