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15+ year old Scott MTB. When changing gear from mid to large chain ring the chain gets pinched between the mech and the large chain ring. Tried adjusting the max min screws, problem persists. Old bike so wondering if the price to get a new chain set that will fit presumably non-standard bottom bracket will be worth it. Thanks in advance

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  • Check the teeth on the big ring for wear. I've had a similar issue solved by replacing the chainring
    – Andy P
    Commented Apr 2, 2019 at 11:24

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So what's happening is the chain is not climbing the inner edge of the big ring as the derailleur cage pushes it outboard.

I'd suspect worn chain and chainrings, but I'd work through a systematic front derailleur adjustment process to see if I could get it working before buying new parts. The derailleur may have been rotated, or the cage bent slightly. Park Tool has great videos for derailleur adjustment with a set of steps to go through, here is the front derailleur one.

You should be able to change chainrings, not the whole crankset. FYI the bottom bracket standard from 15 years ago was BSA threaded shells with cartridge bearings (outboard bearings just arriving at this time I think?) which is still very much in use and available.

If you do end up replacing chainrings and chain you should replace the cassette as well. And for good measure replace the cables and housings so you have a completely refreshed drivetrain that will shift well.

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  • Regarding the possibility of replacing crankset and bottom bracket: I have a 2005 Specialized Stumpjumper FSR that now has a new Shimano 2 piece crankset with outboard bearing bottom bracket. My late 90's Giant ATX sports a NOS Shimano Octalink crankset and bottom bracket. After purchasing the Octalink set-up, I stumbled across some new chainings, still in their retail packaging at a bike coop for a pittance. Point is there's not much change in MTB bottom bracket shell width and there remains a wide variety of options for replacement components.
    – Jeff
    Commented Jun 27, 2019 at 22:22
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This one has been here a while so I guess you will have fixed it. However, it could also be that the wrong chain is fitted i.e. a 12 speed instead of 8,9 or 10, whichever cassette is fitted. Also, if the front mech can slide up and down the tube rather that being on a fixed boss, the position could be wrong.

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