I picked up a 1979 (from what I can tell) UO9 Super Sport (20 bucks) and am in the process of fixing it up. The rear derailleur is a Simplex SX410GT. I am finding out that this is the "long cage" version. One of the jockey pulleys has a few missing teeth. The front derailleur is not original, looks like a SunTour.

Can I replace the original derailleur with another Simplex model? What does the "long cage" version mean? Should I install a Shimano instead? I know the frame tubing is smaller, so installing the front derailleur could be a issue with current derailleurs.

Would like to keep everything french, but which is cheaper and more reliable? Looking to turn this into a leisure city bike for riding around the neighborhood and running errands close to home. Thanks for advice.

John

Why not just throw another jockey pulley on? Usually they are interchangeable.

+1 - pulleys should be fairly easy to find and cheap. Long cage refers the the length of the piece that holds the two pulleys - longer cage means more chain can be handled, which is needed for large rear sprockets. If you really want to you can certainly use another Simplex, or go with a period upgrade and put on Suntour or Shimano. I have an AO-8 with a Simplex rear (and SX100 - cheap newer version of the original Prestige) and Suntour front. I put on a Suntour rear (took no more than 15 minutes), and it shifted well but (I hate to say it) I liked the look of the Simplex better - I'll leave it there until it breaks or wears out, then put the Suntour back on.....

Lots of NOS low level Simplex derailleurs sitll come up at eBay as they made so much of them. Just avoid the ones with too much plastic (delrin) parts on them. You can also update to a model SX 610 that will shift much better than anything your bike originally came with. It will be a good investment for 40 to 60 bucks. How many teeth on the biggest rear cog on your bike?? the SX 610 might be able to handle up to 28 teeth. Long cage usually mean real big rear cogs though.

Chombi

You can buy original Simplex pulleys:

https://cgi.ebay.com/ORIGINAL-SIMPLEX...g_bikeparts_SR

There are also universal replacement pulleys available. I like these, but not at that price.

https://cgi.ebay.com/Bullseye-Deraill...ts_Accessories

Thanks for the info guys, much appreciated. How about this one, a SLJ 6600. I can not tell if it is a long cage or not. Would this work?

https://cgi.ebay.com/ws/eBayISAPI.dll...%3DI%26otn%3D2

Same seller has them down to $22.50 (purple) or red for $24.50
https://sporting-goods.shop.ebay.com/...=p3911.c0.m282

Blue or black are pushing $40. Cheap shipping though.

Chomi, Just counted, 28 teeth.

Uhmm......SLJ6600 = Big bucks! A short cage version will easily bring in about 200 bucks these days if it's NOS. Most of them sell to robo bidders with maximum bids set to trigger at the last few seconds of the auction. Don't bother with them if you are on a tight budget.
Check out the SX610 as it is mechanically identical with just some budget material substitutions.

Chombi

IMHO buy a new jockey wheel, it the cheapest fix and keeps the bike original. I sacrificed my Simplex to the spoke gods this spring and replaced it with a Suntour. Works great but I hate looking at it, it was nicer when it was all French and didn't work so well.....but it did work.....that is until it malfunctioned...never mind, but I'd still replace the jockey wheel.