Bicycle Mechanics - Suntour compatibility questions

I have an old road bike with ALL Suntour drivetrain. It has indexed downtube shifters with 6speed freewheel. I want to replace the freewheel because the gearing is too low.

1. Can I replace the freewheel with other brands like shimano or sram?
2. Can I replace the 6speed freewheel with a 7-speed? Would other brands work?
3. If I replace the freewheel with a 7 speed and I want to keep the index shifting, do I need to replace the shifters?

Thanks

I have an old road bike with ALL Suntour drivetrain. It has indexed downtube shifters with 6speed freewheel. I want to replace the freewheel because the gearing is too low.

1. Can I replace the freewheel with other brands like shimano or sram?
2. Can I replace the 6speed freewheel with a 7-speed? Would other brands work?
3. If I replace the freewheel with a 7 speed and I want to keep the index shifting, do I need to replace the shifters?

Thanks

Your bike has the Suntour disease. Like a cancer, it spreads through the whole bike.

Suntour cog spacing and indexing is just a tad different from Shimano and replacement parts are unavailable through normal channels. The result is that when you change one component, you usually have to change everything to get it to work.

I've found a lot of Suntour NOS stuff on Ebay.

Your bike has the Suntour disease. Like a cancer, it spreads through the whole bike.

Suntour cog spacing and indexing is just a tad different from Shimano and replacement parts are unavailable through normal channels. The result is that when you change one component, you usually have to change everything to get it to work.

Can I replace the 6 speed Suntour with a 7 speed Suntour freewheel - even if I switch to friction shifting?

If you can defeat the indexing, just operate your shifters in friction mode.

You may also be able to use a 7- (or 8-) speed Shimano index shifter and a Shimano 7-speed freewheel with your SunTour derailleur. When my friend's daughter pretzled her Shimano derailleur, I gave my 1970 SunTour V-GT, which worked fine with her Shimano shifter and freewheel.

Can I replace the 6 speed Suntour with a 7 speed Suntour freewheel - even if I switch to friction shifting?

If you switch to friction shifting you can do anything you want to do. That is, so long as the freewheel fits your rear dropouts. Even then, assuming this is a steel frame, you can get the rear spread slightly to accomodate a little wider freewheel.

I am running an old Raleigh with a Suntour 6 speed rear with an SRAM derailer and Rivendell friction shifters (Suntour design). It works perfectly and shifts like a dream.

I have an old road bike with ALL Suntour drivetrain. It has indexed downtube shifters with 6speed freewheel. I want to replace the freewheel because the gearing is too low.

1. Can I replace the freewheel with other brands like shimano or sram?
2. Can I replace the 6speed freewheel with a 7-speed? Would other brands work?
3. If I replace the freewheel with a 7 speed and I want to keep the index shifting, do I need to replace the shifters?

Thanks

I worked on a lot of Suntour equipped bikes when I was a shop owner. I would make the following suggestions:

Keep the bike a 6-speed. If you change to 7-speed, may as well go Shimano since you'll have to change shifters as well.

If you keep the bike a 6-speed, assuming you can find a new 6-speed freewheel, you'll probably need to buy a new chain as well, since the new freewheel won't shift as well (or acceptably, for that matter) with the old chain, whose links are profiled to fit your present freewheel cogs. Do not buy a used 6-speed freewheel since there is no reliable way of determining whether anychain will work on it.

There is a reason Suntour is extinct. This company had good market share before the invention of index shifting. After index shifting, their market share went downhill when they repeatedly demonstrated that their indexed drivetrains did not work as well as Shimano. Much of this had to do with patents (e.g. centron mechanism on rear derailleur & Hyperglide cassette teeth profile) that Shimano had that SunTour would have had to trespass on in order to make a comparable product. There were also issues of durability. Personally, while I would have liked to have seen SunTour succeed in order to keep a more competitive market among bicycle component manufacturers, the truth was that SunTour never was able to deliver a drivetrain that worked as well as Shimano.

check your shifters as some of them had a position for 6speed and 7speed.

as far as durability, my 14 year old Superbe Pro is still going strong.

I have an old road bike with ALL Suntour drivetrain. It has indexed downtube shifters with 6speed freewheel. I want to replace the freewheel because the gearing is too low.

1. Can I replace the freewheel with other brands like shimano or sram?
2. Can I replace the 6speed freewheel with a 7-speed? Would other brands work?
3. If I replace the freewheel with a 7 speed and I want to keep the index shifting, do I need to replace the shifters?

Thanks

1) Yes. I've used SunTour freewheels in my bike with Shimano 6-speed drivetrain without problems. I think I also once ran a Shimano 6-spd fw in my bike with SunTour drivetrain. The freewheel spacing is slightly different between SunTour and Shimano but it is close enough that it will probably work OK.

2. Yes.

3. Maybe. Some of the SunTour indexed levers have 3 positions on the lever housing: 6-speed indexed, 7-speed indexed, and friction. If you've got one of those, you won't need new levers - simply switch it to 7-speed indexed.

I have the 1984 Suntour Superbe group (friction) on my Trek 660 and after over 140,000 miles still going strong; the Superbe was the best EVER made...in my opinion! About 3 years ago the Suntour 6 speed Winner freewheel wore out so my bike shop replaced it with a 7 speed Shimano freewheel with no problems. The only thing they had to do was to redish the rear wheel drive side just slightly to make it fit. I also understand that Sach (owned by Sram now?) still makes a 7 speed freewheel as well. If though you want a superb freewheel and don't mind paying more, then try to find a 7 speed Winner freewheel on E-Bay. They made 2 types (that I'm aware of), one was called a corncob which is for racing (11-18), and the other was a sport/touring (13-28) which is what I now use since that's all Shimano and Sach make; but I don't race anymore so it's not an issue.

If your downtube shifters are Indexed Superbe PRO, the right will have settings for Ultra and regular spacing. If you can find an ultra 7 freewheel you can simply replace the freewheel and chain. If you can only find a used one, I believe you could re-use 3 or 4 of the COGs in your current 6-speed with the spacers from the Ultra-7.

If your Suntour parts are Superbe PRO, think hard before you abandon them. Back in the day when Suntour became extinct, I was averaging about 0.75 mph faster on my Suntour bike than my Dura Ace Bike, all else equal. Although the Dura Ace bike shifted better under extreme conditions, the hyperglide stuff used angled teeth in the cogs and bulged outer plates on the chain. Although this would change cogs eaiser, it was noisier and created more drag than the Suntour bike.

I ride my Superbe PRO / Ultra 7 bike to this day with straight cogs and a Sedis chain with bulged inner plates. It is very quiet and smooth even if it does require precise adjustment.