I need to replace the Simplex rear derailleur on a vintage Raleigh Grand Prix 10 speed. I read that a Shimano Tourney Mega Range is a good fit. Does anyone have experience with this or recommend another. Also, can I use the Simplex claw or do I need to replace that also?

A megarange may be overkill as far as cage and body length but should work.

You can find derailleurs with claws, those should work fine, I am not sure if there is anything with the Simplex claw that would make it problematic for using it with another derailleur (threading etc on some components were unique backk in the day).

If you don't get a definitive answer here, you can also ask in Classic & Vintage.

The Simplex RD was such a piece of junk that anything would be an improvement. And the front was even worse than the rear. Look for a lower end Shimano, SRAM, or Sun Tour (off another bike or acquired used) with claw and it will fit right on with no problem.

No, you can't use the Simplex claw with other derailers.

Is the shifting indexed? If not do you have a bike shop that has used parts? Shimano 600 derailleurs are cool.

There's no such thing as indexed Simplex. That's one reason why they went out of business.

I'd say that the proper vintage replacement for that derailleur would be a Suntour VGT. At least that's what we used to put on when the Simplex derailleur body wore out. There has to be a few of those still about because they produced and sold them for a very long time and they were built to survive a nuclear attack.

If you just want to make the bike rideable, I'd go ahead and slap on the Tourney. It comes stock with it's own claw attached.

Thanks to all that responded to my question.
Since I am new to bicycle repair I assume the correct Shimano Tourney Mega Range Derailleur would be the TX50 adapter claw mount.

Yup, and it will work at least as well as that Simplex ever did.

Thanks. One last (I hope) question. Are there other parts I should consider replacing such as the shifting cable (It's is relatively new)? The bicycle has very little milage on it though the chain will likely need replacing as it binds in places; the sprockets show little wear.

1. You'll probably need a new shift cable because it's probably frayed on the end. For no more than new cables cost it's worth it not to have to fight with it. If the bike has as little mileage on it as you say, the cable housings are probably OK.

2. Chains, even if moderately neglected, generally last at least a couple thousand miles. If yours is doing funny things you probably have a stiff link somewhere. After you get your bike put back together, turn the pedals backward and watch where the chain passes through the derailleur pulleys. You'll see the arm "jump" when the stiff link passes. Flex that link sidewards with your hand or, if necessary, rework it with a chain tool.

The bike shop sent me a a model TX 71 and it has an adapter claw attached. The off set on the claw (distance from the center of the axle slot and the center of the derailleur attachment)hole is about 54 mm compared to an adapter claw I ordered for a TX 50 Derailleur (27mm offset). If this will work OK I will keep it otherwise I will return it. Your advive would be appreciated.

First mod I made on my Atala was to replace the Simplex with V-GT/Compe V.
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My chain was coming off when I hit bumps and I realized my Simplex rear derailleur had lost it's chain tension. I removed the derailleur and used an Allen key to open the upper spring housing. Inside is the coil spring that has both ends bent at right angles to create 1/4" pins which fit into the holes of the Simplex plastic housing and spring cover plate. The pin in the housing section had broken off and that's what caused the lack of chain tension. I wasn't going on a wild goose chase to find old Simplex RD's because the Delrin chain gears also fail because of age and wear. The repairman at the bike shop said that a Shimano Tourney should work but I'd need a longer chain because of the Shimano's larger gears. My old shift cable was too short and that also had to be replaced. After the parts were installed and gave it a test ride the chain was slipping off the smallest cog. The repair man said it was due to the wear on the cog. I then had the freewheel (with cogs) replaced. Here's the part list: Shimano Tourney TX-31 W/Hanger, new chain, shift cable, Shimano MF TZ20 6-cog freewheel. A washer was added on the freewheel side of the axle as a spacer for more chain clearance. I recommend replacing the old plastic shift levers. The new metal shifter has detents that align perfectly with the shift points. In the end, the failure of a spring coil in the Simplex derailleur required an almost complete replacement of the drive train but the results were well worth the cost. If you have a chain tool and some mechanical skill you can save the $50-60 in labor. The parts should run approx. $50-60. Avoid problems with chain slippage and replace the chain AND the freewheel. My Raleigh Grand Prix now shifts smoother and quieter than the original parts. I've replied to this old thread to provide a first-hand solution for Future searches to this RD replacement. Other RDs may work but this is what an experienced mechanic at one of Long Island's largest bike shops came up with. Happy riding! :-)

I guess the "Search" function is working. All of the posts above yours are from three years ago.

reference is rather dated too .. Shimano hasn't called a rear derailleur a tourney in over 20 years..

Just for the sake of someone doing a search for a replacement for a Simplex Prestige, I think that Retrogrouch was misremembering. The Suntour V-GT ia a long cage touring derailer. The V would be more appropriate.