I am attempting my first rebuild on a road bike. I bought a 1979 Raleigh Rampar R One. I did mechanical check and all components check out aside from needing a good cleaning and lube aside from the rear derailleur which is bent badly and has to be replaced. The. Ike is totally original parts and I want to try and keep it as original as I can but I am thinking of replacing the derailleur with a more modern one. So I am of the understanding that since it is friction shifting I have a lot of options. Does anyone have suggestions of a good replacement and do I need a long bracket or short? I am am. PT looking to spend a great deal of money to replace it. Thank you in advance.

Brian O'Connor

Brian; we know very little about your bike.

What RD was on it originally?
What is the freewheel/cassette range?
Number of cogs on the freewheel/cassette?

I had one of those, bought new. Short cage should be fine. I like the old Suntour open cage derailleurs--no need to break the chain to remove. Off the top of my head, these include the cyclone, vx, vgt luxe for sure. There might be others.

A lot of it depends on how modern, the type of look you want, and what you want to spend. If it were me, I'd probably go with at least a medium cage and possibly a long cage. Something like a Shimano MT60 might have the right look and it would be an upgrade.

John

Your understanding is correct. Your options are wide open since you don't have to worry about indexing.

Why replace the derailleur with a more modern one? New derailleurs aren't necessarily better; they're just compatible with indexed shifters.

SunTour derailleurs from the '70s and '80s worked really well and would look right at home on your bike. Here's an inexpensive Raleigh-branded SunTour 7 GT (long cage) on eBay:
SUNTOUR - RALEIGH - REAR DERAILLEUR | eBay

Whether you need a long cage derailleur depends on your bike's gearing, both front and rear. The bigger the difference between your lowest and highest gear, the more chain slack the derailleur needs to be able to handle, and generally that means a longer cage. A derailleur's ability to take up slack is measured by its "wrap capacity", typically expressed in a number of teeth. You can calculate the wrap capacity you need with a little math:

(big chainring - small chainring) + (big cog - small cog) = wrap capacity

Once you've done the math using your bike's gearing, you can compare that against published numbers for derailleurs you're looking at. Not every short/medium/long cage derailleur can handle the same capacity, but here are some numbers for reference:

1970s SunTour V series:
V (short cage) = 24 teeth
V-T (medium cage) = 28 teeth
V-GT (long cage) = 36 teeth

Shimano 105 5600 (circa 2006):
SS (short cage) = 29 teeth
GS (medium cage) = 37 teeth

Shimano Ultegra 6700 (circa 2009):
SS (short cage) = 33 teeth
GS (medium cage) = 39 teeth

Shimano SGS (long cage) derailleurs are typically only found in their mountain bike lineups.

like this one?
Rampar Road Bike - bike

the rear derailleur is a MID CAGE length... not a short cage... and a short cage der. would not like your freewheel.

get a suntour VT or VGT... there are a few on Ebay, usually. it will be similar to the stock part, and will work great... i've used several through the years...

count the number of teeth on the large gear of your freewheel, and get the appropriate length cage, as Skydog mentioned/listed.