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I have Shimano FC-MC19 22/32/42 175mm crankset on my MTB for 17 years and it's time to replace it but I find it difficult to figure out what new crankset will fit my bicycle.

Shimano FC-MC19

Two years ago I replaced the original bottom bracket (it was 110mm) for Shimano BB-UN26 110mm and everything worked perfect.

Now, I am wondering if I purchase Shimano Acera FC-M361 22/32/42 175mm crankset will it fit on my 110mm bottom bracket??? The specs of the Acera crankset that I am considering to purchase are literally the same as of the old crankset I am replacing but the new Acera crankset says that recomended bottom bracket is 123mm.

Shimano Acera FC-M361

I don't see why the new Acera crankset wouldn't work on 110mm bottom bracket as the old crankset did for 17 years!? Also, I measured the distance from the bottom of the old crankset crank arm (where the pedals are attached to the crank) to the bicycle frame (where the crank arm is the closest to hit the frame) and there is 1cm of space on both sides, so no touching should occur between crank arm and the frame even if the new crankset is mounted on current 110mm bottom bracket in my opinion.

What do you think? Should I add spacers and how many??? Would that help? I really don't want to purchase new bottom bracket if everything would work well with the current one of 110mm spindle length.

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The problem is not clearance between the crank arms and frame. You need to look at the clearance between the chainrings and frame, which is likely to be much tighter.

You also need to consider chainline - how for the nominal centers of the chainrings and sprocket cluster are from the centerline of the frame. You will be moving your cranks 6.5mm inboard, that's significant. I checked the specs of both cranks [here and here] and they both have a nominal chainline of 50mm, so you need the correct spindle length to get the correct chainline.

I think you'll probably get chainring - frame interference with the shorter axle, and I'd get a new bottom bracket with the correct axle length to avoid chainline problems anyway. A 17 year old bracket probably needs replacing in any case.

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  • The bottom bracket is not 17 years old, I replaced it 2 years ago which is why I don't want to buy new one if there is a chance the Acera FC-M361 crankset (the one I consider for purchase) can work with the current (2 years old) 110mm bottom bracket. As for the clearance between the chainrings and frame - it's a square taper crankset so doesn't the square-shaped spindle determines how close the chainrings will be to the frame? And the Acera crankset I consider for purchase is the exact same 22/32/42 size. I am really not sure what to do now. Many thanks for your reply!
    – C. Felipe
    May 3, 2019 at 14:49
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    Re: doesn't the square-shaped spindle determines how close the chainrings will be to the frame? Yes, but the FC-M361 has the chainrings a little further inboard relative to its square taper hole, which is why it needs a longer axle to place the chainrings on the 50mm chainline plane. Your options are to either replace the BB with one with the correct axle length or look for a crank that needs a 110mm axle.
    – Argenti Apparatus
    May 3, 2019 at 15:11
  • Ok. I think I understand it now. It seems that a whole geometry of Acera crankset is different then, right? If I add two 2mm spacers (for a total of 4mm) at bottom bracket would that work? Or it is not advisable to do that? Thanks again for sharing your knowledge, I appreciate it very much!
    – C. Felipe
    May 3, 2019 at 15:36
  • I'm confused by your spacers idea. You can't add spacers to the BB to make the axle longer, and you can't add spacers between the axle and crank at the square taper interface.
    – Argenti Apparatus
    May 3, 2019 at 16:23
  • I had an E-type front derailleur before (the one which is mounted on the bottom bracket but I replaced it for a normal derailleur (mounted on the seat post tube) which is why I added one spacer at the bottom bracket to keep the chainline straight as it was before. But now I am replacing a whole crankset so I thought adding a 2 spacers of 2mm width each (for a total of 4mm) would help move spindle to the right on the right side where the crankset is mounted.
    – C. Felipe
    May 3, 2019 at 16:32

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