When does one try a different derailleur?
 

I'm riding a 79 Nishiki outfitted with Suntour Cyclone. It's all in good shape, but I feel like I'm fishing for the sweet spots on the RD and there's a been a few starts at traffic lights or pedaling through turns where I unexpectedly drop a gear in the back. I checked the chain tension and it seems a-ok. Haven't checked the cable tension yet though. The Cyclone stuff is good, so it's probably an issue with tuning?

How do you decide: I'm going to see what x or y derailleur performs like now?

Slipping a gear might be an issue with your shift lever rather than with your derailleur. What shifters are you running?

Neal

OTIS! My man! They're the Suntours that I believe the bike came equipped with. Double cutouts on them so I'd imagine they were good stuff at the time. They're a bit tight to shift but I figured that would prevent any slipping.

You say it drops a gear on starts, and in corners. Take a look at your shifter cables (not just tension). If you have a flexy frame, they might be binding under the bottom bracket as the BB deflects. Clean and grease the cable guides, replace the cables if necessary.

Could also be a worn chain...but I bet you already checked that

Operator error? Friction deraillers are a linear system, ie, they're centered on the cog when the rider places them correctly. Typical to overshift then trim back a hair to fine tune. Usually you can tell by a little telltale clicking that its not quite right; clean and lubed it should be silent when pedaling. Shifting by itself could be loose shiftlever D rings..

A Suntour Cyclone, unless there's something wrong with it, should shift as well as any friction derailleur. If you don't like it, you probably don't like friction shifting. Check the stuff others have mentioned; also inspect your freewheel; maybe it's time for a replacement.

Actually I haven't checked for chain wear. Not sure I know how. I degreased and regreased when I got it but that's it. Do I check the lateral flex between links?

I'll check the freewheel closer. Now that I think of it, There's a bit of a clunk when I go from coasting back to pedaling. It's pretty damn loud too so I maybe would replace it regardless.

And as far as friction shifting...I love it! I picked up a Basso with Campy STIs and it's not nearly as fun. Same kind of direct connection that driving manual provides, I think

I'm with you on the friction shifting, but then again I haven't even tried the newfangled stuff. I figure if it was good enough for someone to win the tour on 30 years ago it's good enough for me now. I have one bike with a Cyclone RD and it shifts really smoothly - just as nice as my Campy Nuovo Record. I've heard others say the same. My guess is the derailleur itself isn't your problem. Go through the repair pages on the Park Tool website. You'll probably be able to figure it out.

I'd pull the back wheel off and clean and inspect the freewheel for wear on the teeth. Also clean and lube your chain, and check for stretch. Pull it tight next to a ruler. Put the end of the ruler on a rivet; the 12" mark should be on a rivet. If the closest rivet is more than 1/8" past the 12" mark, put a new chain on.

An easy way is to shift to the big chainring, then grab the chain somewhere along the front edge of the ring and lift. If you can pull the chain enough to expose a full tooth, then it's stretched.

The more accurate way is to use a chain-stretch gauge, but if you had one of those, you'd know it.

EDIT: Umm, right. Rulers. Also perfectly acceptable gauges, and much cheaper.

I will also say that there is a good chance the chain and or freewheel are shot... I bought a chain checker because it was only $10 and was surprised how many chains of mine were shot or close too it. Even the sram PC-68 that has only 3000kms on it was at 75% wear. I rode a KMC and cheepo shimano cassette for about 7000kms but I am sure it was way way past shot. The old 3/32" road chain on my fixed gear... well you know how if the checker hits the bushing and doesn't go in it is considered new or zero wear... well mine wouldn't go in because it was hitting the opposite bushing!!! damn...

I'd guess an alloy chainring would wear out before a chain stretched enough to be a problem...

the first thing i would inspect for would be a stretched or worn chain, second would be to check that the derailleur hanger and/or derailleur cage aren't bent or misaligned.

Most bike shops will check for chain wear for free.

In the words of The Dude: new **** has come to light, man!

Ugh. I think I've caused the problem. I was trying to disassemble the RD 2 weeks ago and got a little stumped since the cage isn't two separate pieces like the shimano RDs I'm used to. I loosened the allen bolt that's wrapped in a spring inside the cylinder that joins the upper arms to the pulley cage, and that didn't free the upper pulley, but I did feel the spring in there tweaking and what not. Anyway, I think the slippage started after I did all this, so I must've mussed up the tension on the spring's return.

Anyone? It's not shot now, is it? Can I open that part up and fix?

No; yes.

It's a coil spring that fits in a slot, right? I once rebuilt an ARX RD and I somehow screwed up the coil and it slipped out after a while (I had sold the bike and the buyer called me up). I said drop it off and come back in 24hours... I'll either fix it or replace it. I took it apart and found the problem and I can remember how exactly but I used more of the spring to ensure it didn't slip out again. It resulted in an even tighter spring and it shifted great. The buyer never called back so I assumed it was good. That was the last time I took apart a suntour derailleur:p

Yellow Jersey had an exploded-view of the Cyclone GT which is mine in question. I took it apart this afternoon and there seems to be more spring back now in the cage cylinder. I did encounter a problem though - the metal caps or lipped-washers or whatever they're called that sit in the grooves on either side of the RD pulleys - one was cracked and bent. All I had were Shimano to cannibalize and they use a smaller one so I had to take one from a Simplex I had. The pulley's lobes aren't as deep as the Suntour or Shimanos but hopefully it won't be a problem. Maybe I'll check the LBS for a jacked-up old Cyclone.

Thanks for the help guys!