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Shimano Chainset Clearance Issue (Square Taper)

desmojendesmojen Posts: 136
edited May 2013 in MTB workshop & tech
Hi all,
Looking for some guidance on this, not something I've come across before and I'm honestly a bit confused by it.

The bike in question belongs to my nephew, and was bought second hand recently. It's a Specialized Rockhopper, not sure what year so here is a picture.

20130526_113419_zpsa40830d5.jpg

It was brought to me to have a few jobs done as there was play in the crankset and the brake pads were worn out. I assumed the play was due to the BB being worn out and duly ordered a fresh one. All was disassembled and the new BB fitted without issue. I did notice that the old BB was not as worn feeling as it should have been for the amount of play the cranks had. While cleaning everything, I noticed some scoring around the BB shell, and some wear on the chainstay. The chainstay wear had clearly been caused by the big ring, and I cleaned it up and wrapped it.

20130526_113435_zps1bd2bfce.jpg

While cleaning the cranks up, I noticed that there was a little play between the spider and the crank arm itself, and thought perhaps that might explain the scoring on the chainstay and some of the play that had been felt. It wasn't really bad though so I decided to put it back on rather than replacing it. And that's where it got wierd.
When refitted, even before pulling the crank down onto the taper, the big ring was almost touching the taped area of the chainstay. An exploratory tighten made it touch, as it has looked like it would initially, but on trying to turn the crank it was locked solid. Only then did I notice that some tangs on the granny ring were touching the face of the BB shell. This explained the scoring around the shell, and honestly I cannot imagine how the previous owner ever got the cranks on!
I am now thinking that the crankset could not have been fully tightened down somehow when fitted, allowing it to move around a little and score up the chainstay. Here is a photo of the offending area. The tangs in question are the extended mountings on the granny ring, and the play is in the area where the splined joint is in the middle.

20130526_113514_zps421ae512.jpg

The thing is, what do I do about replacing it? The cranks are Shimano M460 and the big ring is 44 tooth. I can get an M442 crankset on CRC for £19.99, but is it going to fit?

Thanks for any help,
Jen.

Any ideas?

Posts

  • The RookieThe Rookie Posts: 27,802
    Sounds like someone has fitted an axle that is too narrow, check the techdocs to see what axle width that crankset needs and measure....
    Current steed - Whyte T129, 2013 frame, mongrel Revelations, Giant dropper, Stans S1 wheelset. 12, Magura Trail Sport brakes, 1x11. 12.8Kg
  • desmojendesmojen Posts: 136
    Thanks Beginner, you are spot on. I have got a 110mm BB and the one that came out (which was clearly also too narrow) was the 113mm version.
    I think I will get an M442 Chainset and the 122mm BB to go with it.

    Thanks again,
    Jen.
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