chiefkurtz

I keep seeing listings for 'conversion kit for Suntour pulleys', for about triple what pulleys for current models cost. Are newer derailleur pulleys not compatible for older style (70s - 80s) Suntour and Shimano derailleurs? Is this just a marketing trick to separate you from more of your money?

steelbikeguy

the main factor might be that the older pulleys were usually wider than the modern ones.
A secondary factor is that some modern pulleys are designed to be able to slide left and right a mm or two. I'm thinking mostly of the upper Shimano pulley... If you use this pulley on the bottom, for the tension pulley, it shouldn't have any effect on the shifting behavior.

Personally, I've used the Tacx T4000 sealed bearing pulleys in a SunTour Cyclone GT rear derailleur, and it is working fine. I got them for $13 from a seller on ebay. They were a bit shop worn, and they might be out of production (TBD), so I can't say if you'll have the same luck.

Steve in Peoria

smontanaro 

I believe it has to do with the diameter of the axle/bolt upon which the pulley spins. 5mm v 6mm, or something. I do remember Bullseye pulleys being sloppy on my SunTour Superbe derailleur BITD.

I'd just ask the seller why they felt the need. This is Love City Cycles, yes? They are the folks who reproduced the Simplex wing nuts (definitely useful), so I suspect they felt there was a niche which needed to be filled.

steelbikeguy

I was looking into replacement pulleys earlier this year and made some notes....
The Bullseye pulley has a 6mm ID. My SunTour Cyclone derailleur used M6 bolts, so it was a good fit. The Campy NR used a M5 bolt, though. Once the bolts are tightened, though, the Bullseye pulleys work fine on the Campy derailleur (based on the two or three bikes that I have equipped with them).

The Tacx pulleys are not as sexy as the vintage Bullseye, but the cartridge bearings are fine. Their website makes it hard to figure out what will work with vintage derailleurs, and I had to exchange a few e-mails with them before figuring out that the T4000 model is well suited the Campy, SunTour, etc.

Steve in Peoria

T-Mar

+1, it's the diameter of the bearing surface on the bolt. Shimano uses 5mm, while SunTour used 6mm. Consequently, a Shimano pulley won't fit on a SunTour bolt. I believe the conversion kits are Shimano pulleys with drilled out bushings and dust caps, to accommodate the larger diameter Sun Tour bolt.