TX3.0

sorry for the dumb question, but a search wasn't giving me what i needed.

i have some old suntour accushift downtube shifters, but no rear derailer for a bike i'm rebuilding. i want index shifting, so do i need an index specific RD? i may pick up an older shimano 600 RD (arabesque looking, not sure the numbers) if i can use it with my downtube shifter.

thanks in advance.

CV-6 

I think if you have a derailleur with a cable adjuster, it will work. I used an old Suntour V-Luxe with indexed Suntour levers on my Lejeune for years. But I also had a Suntour freewheel. YRMV.

leecycle

Although, the Shimano 600 RD may work, there's no way to know without trying it. The easiest way to ensure that your Suntour shifters work properly is to use it with an Accushift RD and freewheel. The Accushift RDs have a spring in the upper pivot, whereas the Suntour non-Accushift RDs don't. Note that the Accushift components can be used interchangeably (e.g., a Cyclone Accushift RD will work with Sprint Accushift shifters); the only exception being the Accushift 3000 shifters should be used with the 3000 RD, due to difference in the cable pull per shift. You also need an Accushift freewheel, since earlier Suntour freewheels had different distances between the cogs. Overall, in my experience, the Suntour index system is more finicky than the Shimano SIS and less tolerant of substitutions and mis-adjustment. Nevertheless, my Cannondale uses a Suntour 7s Accushift system and once adjusted properly, it works well.

RobbieTunes

I've used Suntour GPX 7-speed DT shifters on both RX100 and Light Action RD's, no problem. I'd probably use them on a 105 and a tri-color 600, but I wouldn't go any older just to err on the side of caution.

I've also used a Suntour GPX RD (7-speed) with a 9-speed cassette and DA 9-sp down tube shifters. After an hour of adjusting, it worked, but I did make sure I had a 9-speed chain.

jsmithepa

An index shifter+RD+cluster is matched precisely so a click on the shifter produces a precised amount of cable travel, which produces a precise amount of RD travel that precisely matches the spacing between the cogs.

That is, if u want the whole "system" to work smooth, minimal noise etc. If yer on a budget and can put up with less than precise shifting as an indexed system is designed to do, hey go4it.

USAZorro

The pull on the rear derailleur is by far the least critical of the three components. Cog spacing and shifter indexing are very specific to the manufacturer (Campagnolo vs Shimano vs Sun Tour). The pull ratios of rear derailleurs are very close.