3speed

I've read people saying things like "Oh, to make that bike have indexed shifting, you have to swap to an indexing derailleur." This doesn't make sense to me. Wouldn't it be all in the shifters? Also, I took a Suntour VGT that was friction on my old Motobecane and it worked just fine with no skipping with newer Suntour *alpha symbol*2000 indexed shift levers. What would be the difference?

On a side note, are Suntour Accushift shifters for freewheels, cassettes, or are there two different versions?

miamijim

Inedxing deraileurs are desgned to move 'X' distance per 'Y" distance of shift lever movement. Movement is often referred to as 'throw'. Simply put the shift lever and RD must have the proper ratio of movement. Without the proper ratio your RD will either not travel far enough per lever click or travel to far per lever click.

Aside from needing the proper throw indexing RD's have built in barrel adjusters to adjust cable tension and have self aligning upper jockey wheels.

reverborama

Isn't it also true that for modern indexable derailleurs, the throw remains the same through entire range of movement for the derailleur? This was not true of many older units (particularly pre-slant parallelogram) making them unsuitable for ratcheting shifters that move the same amount of cable for each shift.

miamijim

Yes, I believe the throw remains the same.

Zaphod Beeblebrox 

Its true as long as you aren't talking about Dura-Ace and (although i've got no experience with them) certain modern 10 speed RD's.

BluesDaddy

I will add on about the jockey wheel (the upper wheel on the rear derailleur) which has maybe 1mm of built-in side-to-side play, which permits the chain the pass over it without skipping if it is slightly misaligned with the rear cog. The idler wheel (lower) is fixed and does not have any play.

miamijim

Your thinking of something different. DA throw is linear, its just not the same no DA products.

While all 8s cassettes have the same spacing...5mm I think, there're diffent ways of achieving 5mm of RD movement.

This is just and example:

If 1mm of shift lever movement per click = 5mm of RD movement you get 5mm total per 'click'
If 2 mm of shift lever movement = 2.5 mm of RD movement you get 5mm total per 'click'

3speed

So there really isn't anything so different from them other than the barrel adjuster. I didn't think it seemed like there could be anything terribly different. My Suntour ARX is supposedly non-indexing, but someone has put a barrel adjuster on it (it doesn't look original anyway). I just saw some older Suntour Accushift levers on the local CL. Think there's any chance they would work together?

clubman 

I think you're fortunate to get your Suntour Alpha drivetrain to index easily. They have a reputation for being very fussy to set up if you don't have all the matching bits.

I think there were at least 4 different generations of Suntour indexed systems, two for freewheels (6/7) and two for cassettes (7/8)?

tatfiend 

Rear indexing derailleuras are NOT totally linear as Frank Berto reported and diagrammed in his 1988 book on upgrading road bikes. He had extensive information on cable pull per click of early indexed shifters as actually measured and the shifters did not pull th same amount of cable per click over the whole range. I have also seen such actual measured info for a Shimano 8 speed system from someone who was trying to come up with a travel agent to allow a 8 speed Shimano brifter to operate a Nexus IGH.

Early Campagnolo attempts at indexed shifting did not work well as their rear derailleurs were not "early shifting". The formula for designing an early shifting rear derailleur seems to be the following requirements.

Dual spring loaded pivots.
Slant Parallelogram.
Correct location of the cage pivot in relation to the Jockey pulley.

The latter two items in conjunction give a jockey pully to sprocket gap that remains within a narrow range as the derailleur moves the jockey pulley in and out. These have become practically universal on all indexed derailleurs from all manufacturers.

frpax

As long as the derailleur moves the same distance with each click, it doesn't matter.

I think SRAM derailleurs have a different throw, and therefore are not compatible with anything but their shifters. (I could be wrong on this, though)

tatfiend 

Correct, at least for rear derailleurs. SRAM does make shifters in two versions, one for Shimano derailleurs and one for their own derailleurs. Campy has their own cable pull to derailleur movement ratio which is different from Shimano or SRAM too.

sailorbenjamin

Some of those old Suntour Freewheels had different spacing between the cogs, check Sheldon on this. Some of them even had one spacing on the big cogs and another on the smalls, I guess to compensate for ... I forget what they're compensating for.

Pompiere

A lot of people have gotten index shifters to work with supposedly incompatable derailleurs, some just require more fiddling to get adjusted. I put a Shimano grip shift on my daughter's bike with a Suntour derailleur. It works fine. In general, it is best to stay within the same brand and number of gears.

sykerocker 

And a lot of it is just plain chance and luck. Prime example: A couple of years ago I built up a Schwinn 564 with a set of Mailliard Helicomatic wheels and a Shimano 600 tricolor group, 7-speed SIS. The intention was to run the shifters in friction setting. Having everything together and adjusted on the work stand, I figured, "switch it to index and see what happens." What happened is that it shifted perfectly.

A fast look in Sheldon Brown and I discover that the cog spacing between 6-speed Helicomatic and 7-speed Shimano is almost identical. Not a perfect match, but what differences there are in spacing are so close that the levers don't notice. You just waste one click on the levers.

I have to admit that I'm very taken with Shimano because of the degree of interchangeability with all their components past a certain year (except for one or two well documented Dura-Ace exceptions) - if the shifters and freewheel/cassette matches, it works. Period. The same thinking has me completely uninterested in using modern Campagnolo. Every time I start looking at the chart of what works with what, and more importantly what doesn't work with what, my eyes glaze over.