Bike Problems

Zingaro

iv got a 1980s ralleigh kellogs pro tour, that has 12 gears, the chain is coming of the cassete an getting stuck between the wheel and the cassete, Just tonight it happened while going up a hill and i went straight over the handle bars, and because of my new clipless pedals, the bike came with me < Does ani1 know how to fix this, there is no (pie plate) or whatever that thing is called could i get a new 1 or what???

woodywmb

"Pie plate" doesn't come into it. The likelihood is that this is one of two simple problems.
1. The cables have stretched through time and the chain is over-reaching the cogs. Turn the L limit screw clockwise, half a turn at a time and check the chain performance each time you turn it. Stop as soon as the chain settles happily on the biggest cog without falling into spokes.
2. The rear mech could be bent. Check that it lines up totally straight under the relevant cog. Straighten it if it doesn't. Use a heavy duty shifting spanner. Attach it to the mech square on. Close in the jaw of the spanner and when you're sure it won't slip, use your wrist to bend the mech into position.

Try the two fixes in that order. No success? Come back on and explain more.

smidsy

As woody says assuming everything is in proper condition (not bent or otherwise damaged) it is likely to be a simple fix of adjusting the rear mech so that it does not overshift into the wheel. There are little adjustment screws on the mech (called high and low) that are designed for this purpose. One stops the mech going into the spokes and the other stops it dropping off the outside onto the frame.

Simply adjust the relevant screw so that the mech only shifts far enough to sit nicely under the big cog (for your spoke issue). Only need small adjustments and it is a good idea to count your turns so you can go back if it goes pete tong.

team47b

As woodywmb said, but if you want to watch someone doing this adjustment see this excellent bike radar vid...


http://www.bikeradar.com/mtb/news/artic ... eur-34227/

nicktheluddite

Might also be worth checking the spokes. The chain can gouge them all nicely when it jams like that so that they are weaker and at higher risk of breaking.

Monty Dog

As said, rear mech stop screw adjustment or bent gear hanger / alignment. It won't be the cables, unless of course you've got some cables which uniquely have got shorter in use - 'stretch' results in under-shifting, not over.
Neither is insurmountable and expect a decent mechanic will sort you out in no time - the fact that your bike is 30-odd years old would mean it's probably had it's fair share of knocks and abuse in that time