I have a Raleigh maybe 8 years old with shimano 15 gears. How do I reassemble the rear gearing after fitting new tyres? Everything seems to be in correct position but a small bolt with captive nut seems to fit in a triangular hole above the axle, on frame but this then throws the gear all out of position. Any ideas?
Sounds like you're placing the tire back into the wrong gear to begin with. Always remember what gear you left off on as it can ruin your entire setup in a matter of seconds.