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So, I managed to pick up a Bianchi Grizzly frame for pretty cheap, with nearly all components included to build up. Included was nearly a full XTR groupset that has seen better days. I installed it all, but the cranks quickly gave out on me (they came somewhat stripped).

As far as replacing them, new XTR parts seem a bit expensive, and I had to use a shim for the front derailleur anyway, so the spacing for front shifting was a little weird. Any recommendations on where to start looking for a new crank/what specs I need to keep in mind to have the right spacing?

OG crankset on this bike was 110mm spindle BB, Raceface Progidy LP crank, and maybe Shimano Deore XT Rapidfire SL derailleurs? Should I base crankset spacing off of that? I'm also not sure if it is worth upgrading both the front derailleur and the crankset at the same time, to make sure the spacing works out?

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I looked at the Bicycle Blue Book page on the 2001 Bianchi Grizzly, and what you included in your question matches up - 110mm spindle BB, Raceface Progidy LP triple crank.

The important thing to get right with a new crank is the chainline. If that's correct the front derailleur range or movement should cover the chainrings properly.

Standard MTB triple chainline was 47.5mm (see this Sheldon Brown Page) and I think it's safe to assume that's what the Bianchi has (you can check it of course). Presumably you also have a rear dropout spacing of 135mm.

You can get a new crank that will fit on the existing bottom bracket, but different model cranks require a different length BB axle to get the right chainline, so you are probably better off replacing the bottom bracket along with the crank. I'm not sure if you have a square taper or one of the splined types, if the later a BB would probably be hard to find. Also, a 18 year old BB probably should be replaced.

If you are going with a Shimano crank, you just need to look up in the Shimano specifications what chainline potential candidates provide (and the intended rear dropout spacing). The Shimano specs typically tell you what BB and axle length you need also In current Shimano products believe only Tourney level cranks are available in 8/9 speed triple and will give you the right chainline, so you might need to look at older used cranks. Fortunately Shimano provides an archive of specification documents.

  • Thanks for the tips! Just to clarify, I bought the frame with the XTR group, but it wasn't installed. I think the previous owner was running it with XTR, or was planning to, but it definitely is not quite the right group for the bike, and the group is likely quite a bit newer than the frame. The current BB is an external, I think Hollowtech with the XTR crank mounted on a hollow, splined axle (I don't have much experience with this kind of crank/BB combo). – Chris Aug 9 at 16:39
  • What I'm slightly concerned about as well is the compatibility of the front derailleur, as I had to use a shim to mount it, would this also be designed for a specific chainline? Or would it probably be designed for the 47.5mm standard? (this is an XTR derailleur, I think part of the same groupset as the crank and BB) – Chris Aug 9 at 16:42
  • @Chris, if the group is newer than the frame you definitely could have compatibility problems. Do you know what year/series the XTR group is? If not can you add a photo of the shifters, crank/BB and derailleurs? Is the crank a double or triple? If the components are all from the same series the front derailleur should have the proper reach for the crank. My concern would be that you have mismatched components and/or a crank designed for a frame with >135mm rear spacing. – Argenti Apparatus Aug 9 at 17:44
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There are several sources for cranksets including eBay, Amazon, and most any bike shop will carry at least a few selections of 9 speed compatible cranksets. Sometimes the crankset deal will include the bottom bracket.

While not trying to endorse brands, I'll relate that the last 3 bikes I've reconditioned have gotten Shimano 9 speed set-ups, 2 Deore and the other Alivo. The parts have been a mix of used and new. The cranksets with bottom brackets took a lion's share of the budget. You'll need to know the width of your bottom bracket shell (it's gonna be 68 mm) and, if threaded, whether the threading is English or Italian. This, along with spindle length and type (splined or square taper) are what you need too know to shop for a cartridge bearing bottom bracket. (Side note: you can use the newer-style outboard bearing bottom brackets that will accept the newest 2 piece cranksets from Shimano and others. Did this to an '02 Specialized Stumpjumper, and it works great with otherwise original parts).

Example of a used crankset for sale

Brand New

This one includes bottom bracket and it's the new style Hollowtech 2. If you chose to go this route, the cautions Argenti brings up in his answer need consideration as your chainline is most likely 47.5 and rear dropout spacing is 135 mm. Hollowtech 2 bottom brackets come with washer-like shims that will need to be placed if your bottom bracket shell width is indeed 68 mm.

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