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kross57 12-22-20 06:28 AM

Simplex SX410GT Rear DR?
I am wrenching on a 1978 Peugeot U09. I replaced the Simplex front derailleur and I'm considering if I need to replace the rear. It seems to be in good shape and functions correctly. But if it is bound to fail, I can replace it now. Any opinions are welcome.

bikemig 12-22-20 06:37 AM

If its working, its working. I'd leave it alone. It is not particularly prone to failure. If you want a better performing RD, get a suntour but these aren't bad and they look right on an old Peugeot.

Barrettscv 12-22-20 07:55 AM

I have this derailleur. Unless itís damaged, use it and smile. Unlike the front derailleur, these are not brittle.

kross57 12-22-20 08:25 AM

Thanks guys! Sounds like there is no need for immediate replacement.

denaffen 12-22-20 08:44 AM

My understanding is that the most failure-prone part of those old Simplex derailleurs is the pulley wheels, which have a habit of self-destructing. If that happens to you (or you're worried about it happening) Suntour pulleys can be used with the original Simplex bolts. That said, for my own Peugeot it was easier to just drop a Shimano in.

Oh ... and if you do want to replace it, you'll need a new hanger, too. The original one uses a different bolt size than Shimano or Suntour.

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