Slodad

I recently purchased an older Nishiki with a Shimano 600 SIS rear derailleur. When the mounting screw is snug, the derailleur has some lateral play and is able to rock side to side. This causes it to skip gears and be noisy. I've not disassembled the unit and have never worked on one. Are there shims to eliminate the excess clearance, or perhaps something that may be replaced?

Panthers007

It sounds like the spring is worn out. With new rear-derailleurs being very affordable - at least some are - I would advise buying a new one. Such as a Shimano Sora - which will work very well on your Nishiki. Anyone else has suggestions?

https://www.bicyclebuys.com/item/1010059PART

Do shop around for the best price. By the way - derailleurs are very long-lived components. 20 years is actually common.

Slodad

Thank you. Does the Sora come in a 6 speed model, or does it matter?

Panthers007

Because a derailleur is called 10 spd doesn't mean it can only change the gears on a cassette with 10 cogs. It just means it has the range work with a cassette as deep as a 10 spd. The only thing that would have to be 6 spd. in your case would be indexed shifters - if you have indexed shifters. If you have friction-shifters, it will work regardless of how many gears are on the cassette/freewheel.

Slodad

OK. It does have indexed shifting now and there are 6 sprockets on the rear wheel. So in that case, is there a difference between a derailleur designed to work with 6 sprockets vs. one designed for more? Thanks.

Panthers007

The derailleur will do what the cable from the shifter tells it to do. As long as it's Shimano. If you toss a SRAM shifter or RD into the line-up, all bets are off. Shimano tends to work with Shimano when it comes to the power-train of a bicycle. SRAM requires different amounts of cable be pulled to result in a shift. But if your working with all Shimano - it should work fine.

Are the shifters in good condition?

Slodad

Shifters seem to be in good condition. They click when the levers are moved and they stay in position. Is there anything specific I should check for with them? Do they require disassembly, cleaning and lubrication periodically?

It sounds like the shifter is what controls the indexing, not the derailleur. Is that correct? If that's the case, then does the travel between detents determine the movement of the derailleur so that any Shimano derailleur will move the same amount for a given Shimano detent spacing? That would certainly make shopping easier. Are there any specifications to consider, such as range of motion?

meb

That's correct. Yes. Any modern Shimano SIS will index properly with those shifters and have adequate throw (range of motion).