20 yr old specialized rockhopper needs new crank gears Any help in what front pedal crank replacement gears to buy for my old Rockhopper.  It is a Altus A-10 crank.  I believe the crank to be fine but the gears look to be worn quite a bit.  Took it to a bike shop and they replaced the rear wheel gears, but still slips a little.
The "front pedal crank gears" are called chainrings. Just searching for the word should find several options.

There are several different bolt circle diameters for 5-bolt mountain bike chainrings. It's best to measure. Aftermarket parts from brands other than Shimano are fine, look for chainrings designed for 8 speeds or less and correct bolt circle diameter (BCD).

For changing the chainring, you need a chainring bolt tool to keep the other side of bolt from spinning.