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Suntour index shifting issues

Old 12-28-19, 08:57 PM
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Suntour index shifting issues

I know there have been a lot of threads like this, so thanks for reading.

I decided I wanted to switch to indexed bar end shifters (from friction) because my commute can be quite hectic and having my hands off the brakes for a long time is worrisome (only got doored once this summer!).

My bike is 3x6-speed so I picked up some 6-speed suntour accushift bar end shifters. I found out my derailleur was not modern enough to run indexed (suntour mountech) and it didn't work all that great anyway (pulleys froze after 5 hours in the rain and got chewed up) so I replaced it with a suntour xc pro long cage. I had my LBS do a quick install of the rd because I needed a rear cable anyway, but it came home shifting poorly.

Granted I'm probably twice as old as the kid who installed it (and I'm not old), but after tinkering with it for an hour (tension, limit screws) I'm wondering if the freewheel is actually the issue - it's a suntour pro compe, but it seems it might be an ultra (5mm spacing). Would this matter, or do you see some other compatibility issue, or should it be working and there must be another problem (bent cage, bad rd, or something else)?

To recap: suntour 6-speed indexed barcons, suntour xc pro rd, suntour 6-speed pro compe freewheel (two prong, 13t small cog with ~5mm spacing), not shifting well, new rd cable and housing.

Thanks!




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Old 12-28-19, 09:19 PM
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If your freewheel is indeed an Ultra-6, the spacing is pretty much the same as 7-speed and you would need shifters that pull 7-speed cable length per shift. According to Sheldon Brown's website, Sun Tour and Shimano 6-speed standard freewheels are spaced 5.5 mm and Ultra-6 and 7-speed are 5.0 mm. Sounds like that's what you have and you need 7-speed shifters.
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Old 12-28-19, 09:20 PM
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It sure looks to me that the FW is a non indexed design. So no wonder that a system that failed in the market with all the right parts might work poorly with the wrong part. SunTour's Acushift system was cable tension focused and the spacing between cogs was not consistent across the cog set. So modern, equally spaced cog sets won't also match up well. Is that a Sedis Sport chain too? If so then also pre index spec. The last bit is the large amount of open chain between the cogs undersides and the guide pulley. Andy
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Old 12-28-19, 10:37 PM
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Scroll down just a bit-
https://www.sheldonbrown.com/cribsheet-spacing.html

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Old 12-29-19, 06:41 AM
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Originally Posted by HillRider View Post
If your freewheel is indeed an Ultra-6, the spacing is pretty much the same as 7-speed and you would need shifters that pull 7-speed cable length per shift. According to Sheldon Brown's website, Sun Tour and Shimano 6-speed standard freewheels are spaced 5.5 mm and Ultra-6 and 7-speed are 5.0 mm. Sounds like that's what you have and you need 7-speed shifters.
Ok, I think it will be easier to replace the freewheel. If i get a "standard" 6-speed suntour freewheel, will that work?
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Old 12-29-19, 09:10 AM
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Originally Posted by sixer View Post
Ok, I think it will be easier to replace the freewheel. If i get a "standard" 6-speed suntour freewheel, will that work?
Probably a lot better.
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Old 12-29-19, 11:31 AM
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IIRC SunTour gave up on their unique cog spacing and cable pull ratios and began producing Shimano spec parts. So a modern ST 6 speed freewheel is likely to be still not spaced the way that the rest of your system wants. Even when all is well matched the ST Acushift never was as responsive and positive a shift as the then current Shimano was. There's a good reason why Acushift left the market. I would suggest moving on and go to a full Shimano spec system (or Microshift if you dislike Shimano). Andy
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Old 12-29-19, 02:25 PM
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Suntour and index is like ice cream and ketchup...
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Old 12-29-19, 04:35 PM
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Originally Posted by wheelreason View Post
Suntour and index is like ice cream and ketchup...

No way would I go that far in dissing ST's index efforts. They did work, just not as nicely as Shimano's. But like any system having all the parts in the same family of compatibility is VERY important. It's been so long since the inception of modern indexing (having started with Shimano's Positron in the 1970s) that many young ones don't know about how poor some of the early (and often the cheapest level) designs were, even from Shimano. That proper ST Acushift compatible parts haven't been produced for nearly 20 years it's no wonder that current attempts to service ST Acushift are usually met with frustration. Andy
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Old 12-29-19, 05:17 PM
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Originally Posted by wheelreason View Post
Suntour and index is like ice cream and ketchup...
If you remember back that far, Campagnolo's early indexing efforts were somewhat less than stellar too. Ask anyone who used them about "Syncro".
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Old 12-29-19, 09:12 PM
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sixer, you need a 4 prong Suntour freewheel to make that work . The 2 prong are not index compatable.
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Old 12-29-19, 09:26 PM
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I still have a Suntour 7 speed Accushift system. It is a complete group - shifters (bar ends), rear derailleur and freewheel. I specifically remember you needed the proper freewheel to make it work. I'll also agree - it does work just fine, but not as nicely, quickly and smoothly as Shimano's.
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Old 12-31-19, 11:48 PM
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Suntour gets a bad wrap in their index shifting. Would we have kicked the Wright Brothers to the curb because their first attempt at flight failed? The Shimano/Suntour war was like a cage match where Suntour slipped on the mat and Shimano kicked them while they were down. I have no doubt that Suntour would have bounced back fiercely if they had had the financial resources to stay in the fight. Shimano had deep pockets, and to their credit, a very good early effort that succeeded. Suntour was overwhelmed. That said, I still marvel at the quality they produced in their best products.
I have attached a .pdf many may find useful. There are pages in it that describe compatible components in their product line.
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Old 12-31-19, 11:51 PM
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Originally Posted by trainman999 View Post
sixer, you need a 4 prong Suntour freewheel to make that work . The 2 prong are not index compatable.
Very correct.
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Old 01-01-20, 09:44 AM
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Originally Posted by UKFan4Sure View Post
Suntour gets a bad wrap in their index shifting. Would we have kicked the Wright Brothers to the curb because their first attempt at flight failed? The Shimano/Suntour war was like a cage match where Suntour slipped on the mat and Shimano kicked them while they were down. I have no doubt that Suntour would have bounced back fiercely if they had had the financial resources to stay in the fight. Shimano had deep pockets, and to their credit, a very good early effort that succeeded. Suntour was overwhelmed. That said, I still marvel at the quality they produced in their best products.
I have attached a .pdf many may find useful. There are pages in it that describe compatible components in their product line.

Re bolded comment- I don't think that this analogy is accurate of what really went on. Shimano did nothing against the rules. They just were the bigger and better engineered company with a better marketing dept. Imagine David and Goliath where David has no sling. For as much as many of us wrenches liked SunTour (they did deliver us from poor shifting Euro made stuff before Shimano was a factor here in the US) I do admit that Shimano did the better effort in various areas overall. I once read that Shimano had more people studying old patents for ideas then SunTour had engineers of any kind. Shimano also had an auto industry arm that fueled a lot of their manufacturing ability. Andy
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Old 01-01-20, 09:58 AM
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Originally Posted by Andrew R Stewart View Post
Re bolded comment- I don't think that this analogy is accurate of what really went on. Shimano did nothing against the rules. They just were the bigger and better engineered company with a better marketing dept. Imagine David and Goliath where David has no sling. For as much as many of us wrenches liked SunTour (they did deliver us from poor shifting Euro made stuff before Shimano was a factor here in the US) I do admit that Shimano did the better effort in various areas overall. I once read that Shimano had more people studying old patents for ideas then SunTour had engineers of any kind. Shimano also had an auto industry arm that fueled a lot of their manufacturing ability. Andy
I agree my analogy was off.... I was trying to show exactly what you were saying. Shimano simply overpowered Suntour is what I guess I was trying to say. I am beginning to wonder if SRAM and Shimano don't have Campy next on their list.
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Old 01-01-20, 11:12 AM
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If I were SRAM or Shimano I'd be more concerned about maintaining the size of the pie, rather then the size of the slice. Andy
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Old 01-05-20, 07:50 PM
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FWIW I installed a 6-speed Shimano freewheel - MF-HG22 14-28t and it worked just fine - I haven't had it out on the road but was able to tune it well in all three front gears on the stand.

I was searching for a suitable Suntour freewheel but $40-$50 was the least expensive I could find and I didn't want to have something else laying around if it didn't work.
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Old 01-05-20, 08:50 PM
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The SunTour guide pulleys didn't have any float designed into them IIRC. So a small amount of off centering (of the pulley under the intended cog) can result in greater chance of chain catch/noise/auto shifting. Replacing that pulley with a float design can loosen up this sensitivity. Andy
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