mrmw

At this link is a table of cassette sprocket spacing https://sheldonbrown.com/k7.html useful when mixing rear drivetrain indexing components from different manufacturers.

For Suntour 7 speed, the spacing between sprockets is listed as

3 x 2.8 mm(L)
3 x 3.0 mm(H)

Question: Does '3 x 2.8 mm(L)' refer to the three smallest diameter sprockets or the three largest diameter sprockets?

My Suntour Accushift 7 speed shifters index well mated to a Shimano HG 7 speed cassette and Deore LX rear derailleur. Not perfectly, but very well. From the table at the above link, I noticed that if I use three eight speed spacers (width=3.0mm) in place of several seven speed spacers (width=3.15mm) I could hit the 4.8mm c-c sprocket width almost exactly--within 0.05mm.

It wasn't easy, but I found some eight speed spacers locally. I had guessed that 3 x 2.8 mm(L) meant the three largest diameter sprockets. When that didn't improve things, I tried the 8 speed spacers between the smallest sprockets. Same, no progress from vg before the changes to pure perfection.

Is it that the incremental improvement from vg to perfection given this set of components is just not possible?

masi61

Hi MRMW,

Good to see you are still at it analyzing the SunTour indexing .
I'm thinking that since there are 7 cogs, then it would make sense there would be 6 spaces between those cogs.
If you've noticed, the cog spacing between your smaller cogs (H) is thicker. I really didn't have the dimension committed to memory but 3.0 sounds right.
The larger cog spacers (L) are thinner 2.8mm.

I think what you're trying to do is interesting. I have no direct experience with it but am eager to know how it turns out.
If you have a woodworking disc sander you could lightly sand the 3.0 spacers. Be aware that one of the "spacers" is actually part of the outer locking cog so you might have to sand away some metal.
Personally, I would probably stick to all SunTour and not try to mix and match like that.
Too bad the parts are becoming so scarce.

Sheldon Brown

"L" stands for "Low," "H" stands for "High."

The low gears are the larger sprockets

Sheldon "Abbr." Brown

dooley

i'm glad someone else did this; now i can hijack it!

sheldon reckoned my xc pro rear mech wouldn't work with a 7 speed shimano freewheel and a some old 105 shifters. now loooking at the chart it seemed as though the most important measurment was the centre to centre one, which for both the shimano and the suntour were the same. why is it you didn't think it would work? i only ask because my shifting has gotten a little crappy lately

Bekologist

you guys are soooo retro.....for an authentic and easy retro fix, go friction shifters (downtube or barcon) and you can shift 5,6,7,8,9 and 10 speed cassettes in back with no worries.....heck, you could make a three speed casssette for the back and have it shift smoothly if the jumps weren't too much.

Steev

I'm surprised you find that combination to work. I have tried the same setup (Suntour Accushifts, Shimano RD and cassette) and found it to not work to any degree.
Did you do anything special in set-up to get it to work?
There was a thread discussing this fairly recently.
https://www.bikeforums.net/bicycle-mechanics/237355-suntour-rd-da-bar-ends-will-work.html

Sheldon Brown

Theoretically it should not work because Shimano systems use more cable travel per click than Sun Tour does (and less than Campagnolo)

Generally, you need to use the same brand of shifter as the rear derailer to get the correct travel.

One exception to this is using Sun Tour _6-speed_ shifters with a Shimano rear derailer and _7-speed_ cluster. In this instance the two mismatches cancel each other out.

As to the difference in spacing between Sun Tour and Shimano 7-speed clusters, this is more of an issue when you're using a Sun Tour freewheel. If you're using a Shimano freewheel or cassette, the superior Hyperglide sprocket design generally makes up for the small mismatch of using a Sun Tour derailer and Sun Tour 7-speed shifter.

The shifting quality of Sun Tour cassettes is very much inferior to Shimano Hyperglide, and slightly inferior to the older Shimano Uniglide.

Sheldon "Interchangeabilitude" Brown

mrmw

I was in a rush when putting up the OP. This morning clarity is upon me.

1. The hypothesis in the original post, i.e. that 7 speed perfection might be possible with the correct spacers was flawed...because of the current mix of Suntour 7 speed shifter with Shimano RD. I had neglected the issue of shifter cable pull matching to RD movement in response to that cable pull.
2. The corrected hypothesis: With Suntour 7 speed shifter, Suntour indexing RD and Shimano HG cassette, indexed perfection may well be attainable with a custom cassette with each sprocket spaced correctly center to center.

--HG 7 speed sprockets are 1.85 mm wide.
--HG 7 speed spacers are 3.15mm wide.
--HG 8 speed spacers are 3.0mm wide.
--HG 7 speed c-c width is 5.0 mm.
--Suntour 7 speed c-c width is 3@4.8mm(low) and 3@5.0mm(high).

That the Suntour 7 speed shifters, Deore RD and HG cassette index very well I take no credit for working out. I was able to google several past posts from reliable voices which reported that Suntour 7 speed shifters, Shimano 105 RD's and either Sachs or Shimano freewheels/cassettes indexed fine.

Now that I am custom cassette enabled, and have managed to get my hands on several 3.0 mm 8 speed spacers (no easy task!), testing the hyothesis is on hold until I can locate a Suntour indexing RD capable of wrapping 35 teeth in order to handle the 48-38-28 front 13-28 HG rear. If anyone has one, please PM me.

Now that I've thought it through, I'm pretty damn optimistic.

mrmw

nice link sheds a great deal more light on the subject

https://mitglied.lycos.de/fanfan/radzeug/suntour_en.html

dooley

ok, if i get some suntour shifters - say superbe pro 7spd indexed - they would work perfectly with my xc pro rear mech and shimano 7 speed freewheel?

masi61

Negative.
As people have been saying, the Suntour Winner freewheel doesn't have the same high to low spacing like the Shimano does. For a shot at perfection with these shifters and rear mech, go with the Accushift compatible Suntour freewheel.