Suntour 6speed indexed road drivetrain woes
 

I am backwards engineering a drivetrain for my Masi Gran Criterium. Basically I'm trying to build up the drivetrain around a really sweet set of Superbe Pro index 6/7 speed downtube levers that I got from ebay. I would be delighted if I could get an Ultra 6 14-24 tooth freewheel that I also got from ebay to index with these levers. Initially I was using an XC-Expert rear derailleur but I now believe that these were designed for Shimano freewheels. So today I put on a Suntour Radius rear derailleur that I had. I was playing around with it in my driveway but it got dark before I could get very far. It didn't want to index properly either. My levers have notches for 7 speed, and 6 speed and friction I believe. I was trying it on the 6 speed notch without much success. The friction setting unfortunately was not strong enough to hold and would autoshift into the next higher gear. I don't want to overtorque my braze on bosses. If anybody who has sucessfully indexed a Suntour 6 speed I'd love it if you can help me out.

Try the shifters in 7 speed mode as the ultra 6 is a narrow spacing. kinda close to 7 speed spacing it may work abit better.

From the info I have, an ultra 6 is not going to work. Suntour index are designed to work with either a 5, 6, or 7 speed Winner or Winner Pro freewheel. The rule of thumb in the info I have is that if the freewheel uses a four-prong removing tool, it should work. But again, an ultra 6 will not. They do say a Winner or Winner Pro ultra 7 will work if it uses a four prong remover.

Usually the derailleur needs to have a cable adjuster inline to work properly. From the list I have, the two derailleurs you mention do not make the cut. From what I understand, Superbe Pro and others with four digit numbers in their names (with one exception) are the compatible derailleurs.

Quality of the cable and the cable housing is also going to impact how the system works. The cable has to be flexible, but stretch is a problem. The higher quality the cable, the more precise the shift. Cable housing also has to be flexible, but it cannot compress.

CV-6 is correct. Ultra 6 freewheels were not designed for indexing and are not compatible with the 6sp lever (for standard spacing).

I'll try this today and post back the result. I see no reason why it shouldn't work since "Ultra 6" as far as I know is the same as the spacing for Winner Pro 6 or 7.
The 6 speed setting on the shift lever wanted to pull too much cable, this supports your suggestion to use the 7 speed setting.
The XC-Expert is an 8 speed compatible indexing mountain bike derailleur. It DOES have a barrel adjuster.
Same with the Radius. It looks like and economy version of a Accushift Sprint derailleur. It also has a barrel adjuster. Its actually kind of compact and looks like it would handle an Ultra 6 just fine.
I got the Ultra 6 off ebay new old stock for $20, and thought it might fill a void and index in Accushift acceptibly for a while while I get the funds together to build up a 7 speed Suntour freehub that I have collected a few compatible cassettes for. I really like those shift levers and hate to have to swap them out for Mavic Retrofrictions but I suppose I could do that.

Ultra 6 does not have consistent spacing between cogs. The Ultra 6 cog spacing is (on average) much the same as 7sp but individual cogs will not be indexed correctly. The chances are that your set-up won't work very well and it will be because of your freewheel.

I have a Suntour Blaze NOS RD, it looks like the cage capacity should wrap 28t with a 28t largest rear cog, that I believe will index with your shifters, either six or seven speeds. PM me if this would be useful.

I would guess, however, that your Superbe shifters and XCE RD (even if set up to work with Shimano) should index a Suntour seven speed fine, based on spacing info here...http://sheldonbrown.com/k7.html .

I can report that Suntour Accushift 7 speed shifters index a Deore LX RD and Shimano hyperglide cassette very well. One of the keys to using the XCE RD I think, based on the spacing, is seven speed--its just about identical between Shimano and Suntour.

Too, your derailleur cable housing must be compressionless. It should make a sufficiently big loop coming off the chain stay so that it enters the RD barrel adjuster in a straight path--as opposed to entering at an angle. If you have bottom bracket braze ons passing the RD cable thru to the chainstay, you also might want to consider a three or four inch section of teflon housing to minimize friction--a great enemy of indexing.

Good luck.

I've got the compressionless housing covered (Shimano 5mm). I cut a nice gentle curve and the ferule fits the little eye on the chainstay perfect. The inner cable is new and came with the shift levers.I might put a little locktite on the screw that goes into the shifter boss on the frame since it seems to not want to stay tight. The set up is very crisp. I actually just bought a NOS Superbe Pro rear derailleur yesterday. A little embarassed to mention it, partly because I payed quite a bit, partly because I'm still undecided on its use. I haven't gotten the derailleur yet.
There's an ebayer named "pacebicycleheaven" I believe that sells a lot of Suntour stuff and he has documented how XC-Expert rear derailleurs (ironically) are not Suntour Accushift compatible but instead Shimano compatible. I'm inclined to believe him. I have 2 XC-Expert rear derailleurs that will have to be sidelined for other projects.

LWaB: I'm sure you are right about the non compatibility of ultra 6 due to spacing variation. I get my bike smarts through books and forums like these, but mostly I have to try something myself and see HOW it is compatible or non-compatible. This is why I'll be tinkering again today (its my day off).

It looks like my 120mm spaced campy high flange tubular wheel will best serve me with the longer axle I recently purchased. I plan to swap axles, then have the wheel relaced and dished at my LBS. Then I'll use a used Winner Pro 12-24 7 speed that I got for 15 bucks off ebay - I know that'll index crisply with the Superbe Pro levers.

mrmw: I appreciate your optimism on cross compatibility, I have run close but not perfect index systems before but the imperfections are a hassle. This is why I appreciate Shimano so much. A lot of their stuff is practically plug-n-play, the way it should be. I know for a fact that Suntour 7 speed clusters both freewheel and cassette are proprietary and not cross compatible to Shimano. This observation is based on the smallest 2 cogs being slightly wider spaced than the remaining 5.

Update: Said Suntour "Ultra 6" freewheel has just been indexed. Here's the details. I used the 7 index setting. I set the high stop correctly (its no longer dark out), I tensioned the cable with the adjuster barrel out several full turns. I clicked through the cluster once, had to turn the adjuster barrel in about one full turn and VIOLA, in like one minute, my 6 speed cluster is indexed. Next up: mount a new training tubular and test ride. I will post the result here. Actually this rear cluster with the 2 prong body looks a lot like the Winner Pro 6 speed spacing if not identical. I guess I'll have to ride and also take some measurements with my metric dial calipers to validate this. My Masi frame is originally intended as 120mm rear triangle.

Glad it worked for you. The info I used was an old troubleshooting doc that was from the mid-80s, so some of the info is probably obsolete.

Congratulations with getting it working in the stand. Good luck with getting it on the road.

Thanks for your help and encouraging words. Now to get that Vittoria tubular mounted and get out there with it. This bike was just begging for a Suntour drivetrain. Don't ask me why.