Telkwa

Hi, guys & gals -
A co-worker bought a Scott Aspect 55 with Shimano Acera square taper crankset. He's already
worn out the riveted Acera chainrings. I told him I thought the easiest thing to do would be to
look around for an older Deore XT or LX square taper crankset and toss the Acera parts.

Would that be the easiest/best thing to do? Or would you suggest looking for an entire crankset
w/ BB? BB's confuse me. There are so dang many of them. Anyway, his is a Shimano BB UN-26.

Thanks!

reptilezs

what is his spindle length. you will probably need a new bb anyways. shimano alivio sq taper cranks are cheap

Bezalel

Scott seems to put a component mix on this model, the crankset he has is not part of the Acera grourset, Acera cranks are in th FC-M33x to M36x range and according to Bikepedia it has a FC-M191. You don't need to go to the Deore group to get replaceable chainrings, the FC-M361 Acera cranks have replacible chainrings.

According to the Shimano docs the FC-M191 should use a 122.5mm spindle and the FC-M361 should use a 123mm spindle so you should be able to reuse the BB.

Telkwa

Hey, thanks for the replies. How did you pull up the detailed info re: FC-M etc. etc.? I need to get up to speed on this stuff. I loaned him a Deore XT crankset off my old neon green Diamondback Axis Team race bike. The DB is 10 years old or thereabouts, so it's a square taper XT. I don't know anything about the newer Octalink sets.

Oh, OK, spindle length. The UN-26 BB is supposed to be a 73/123. According to Shimano and several websites. I know this is a really lame question, but does the 123 refer to the tips of the spindle shaft, or the width of the cartridge? The 73 refers to the diameter of the cartridge, right? Or the threaded cartridge pieces?

I suggested going with Deore stuff because he beat up on the cheap Acera chainrings in a matter of weeks. This guy isn't overweight, he's just been riding a lot on rocky, muddy Washington State logging roads and trails. It never even occurred to me that there were parts within the Acera line, and/or whatever lines exist between Acera and Deore, that have replaceable chainrings.

Replying to reptilezs' post, is the Alivio line markedly tougher than Acera? Basically what I'm asking here is what level would you recommend for a guy who's riding several times a week? ALong the same lines, I see FSA and other cranksets that seem like they might be compatible. Any thoughts on alternate brands that would be a bolt-on replacement?

Suburban Grind

The BB designation is shell width x spindle length in millimeters. The diameter and threads are standardized, unless otherwise noted. Make sure to get English threads - Italian does not work on most frames made for Shimano-spec parts. The square taper you're using is called JIS square taper, NOT ISO square taper.

If he's wearing out chainrings in a matter of weeks, he should be running a crank with replaceable chainrings.

You could see lots of possibilities on Google shopping if you searched on "bicycle crank square taper."

It took me 15 years of street use to wear out my Shimano Altus C90 crank - I replaced it with a Sugino XD-600. Also replaced my bottom bracket with a Shimano UN-54 68 x 118, supposedly a step up from UN-26? Or the darn marketing guys got me again.

Detailed specs on bikes can be found at https://www.bikepedia.com

Bezalel

123mm is the length of the spindle, this number is determined by the crankset you are using. 73mm is the width of the BB shell this number is determined by your frame. There aren't any options for the diameter of the cartridge so there is no reason to specify it.

Telkwa

Thanks again, guys. I lived on my bikes when I was a kid. But we had no internet in the '60's and '70's, so if you had a question about your bike you kinda had to figure it out for yourself or maybe one of your buddies in the neighbourhood knew. I don't ride much anymore, but now any and all questions can be resolved via the net.

Kinda weird.

I figured out the part about JIS, and a Sheldon Brown webpage explained chainline nicely. Bikepedia is pretty cool; didn't know about that and it hadn't popped up on previous searches. As you say, Suburban, this guy needs replaceable chainrings. That's the goal w/out putting too much cash into this bike.

Belazel, if you catch this post, could you please give me a link to the "Shimano docs" you referred to in first reply? I can't find that data...

Bezalel

https://techdocs.shimano.com I check these before I buy any Shimano component.