merlinrkd

Early Specialized Hardrock. The frame has the rear brake next to the BB. The rear derailleur is a Shimano Altus A10. The jockey wheels are getting close to toothless. They have 10 teeth. Replacement wheels are 11 teeth. The bike is very suitable for it's current use. But some upgrades are in the works for spring. The jockey wheels are a place holder repair. Do 11T wheels work in place of the 10 tooth originals?

70sSanO

I would think you could use an 11t as long as you are not running a large cog too far beyond the max where there might be a clearance issue.

That A10 rear derailleur is from the early 90’s and I believe it is a 7 speed. It probably uses a standard/wide derailleur pulley and not an 8 speed that has narrow stamped on it.

If so, I’m guessing the derailleur pulley bolts are longer. I don’t see why you couldn’t put a thin washer on each side to get a better fit.

I’ve never done it with Shimano, but I have with an old Bullseye aluminum pulley.

John

hokiefyd 

You likely can run whatever size jockey wheels you like, within reason. I have a '97 Shimano STX derailleur (RD-MC34 I think) that has a 15t lower jockey wheel from a newer derailleur. Yeah, it looks weird, but I did it just to try it and see if I could tell any difference (none to speak of). There's plenty of clearance between the rear chain retention tab and the wheel. If your A10 derailleur is similar, and it looks like it is, the 11t jockey wheels should work just fine.

The larger you go with the top one, the tighter your B screw adjustment may need to be to keep the guide wheel out of the cassette, but 11t is similar enough to 10t that you probably won't have any problems.

Bill Kapaun

U brakes were 1986-89 for the most part. I think some small frame Specialized went until 1990 until they used up the previous years inventory.

merlinrkd

Yes, it has the U brake. And its a 6 speed so late 80's makes sense.

Bill Kapaun

Make that 1987-89.
My 86 Rockhopper didn't, but my 87 does.