cudak888 

A local friend wound up with one of these oddball (ok, semi-oddball - just not popular due to the Rise of Shimano) Suntour XC cassette freehubs. Last week it wasn't freewheeling at all, so we dribbled some WD40 in the bearing dustcap area in hopes of breaking up the gunk. It did, briefly, and then started freewheeling in both directions due to stuck pawls.

We decided to tear it apart - first, to do something better than rely on WD40 to break up old lubricant, and second, to document how the Suntour cassette body comes apart, as it's really difficult to find info about this online.

First, the victim:



Two chain whips were required to get it off, given that it was still freewheeling. Removal is the same as a Shimano UG - spin the small cog off in the opposite direction of chain wrap.



Axle out. Note that while we took the drive side off first, I really recommend undoing the non-drive-side cone and nut instead. The freehub dustcap doesn't sit fixed on the drive-side cone and not only gets in the way of the wrench flats, trying to access it can push the dustcap down on the raceway. This will cause it to rub the freehub body upon reinstallation (requiring you to take it all apart and tap it with a socket back into place).



Nothing new here, pretty much like Shimano:



But this isn't like Shimano. The hub has a captive bolt in it accessible from the left side by a 10mm Allen key. Think of it as being the reverse of a Shimano freehub: While Shimano has the threads on the freehub to hold it to the shell, Suntour fit them to the hub shell to thread into the freehub.



You can't undo this with a socket-type Allen key, it won't fit. Only a long 10mm key will fit. We used the wheel for leverage with the Allen key in the vise.



Out it comes. You'd think the wheel would fall when it loosens up, but since you're loosening a captive bolt in the hub, the freehub body simply loosens from the top.



And it's off. This is when we discovered the freehub body is not serviceable at all, except for outright replacement. However, it did give us access to a gap between the freehub inner and outer bodies with a direct line to the bearings and pawls. We shot it full of WD40, spun it a bajillion times, and all seems to work fine.

In an ideal world, after washing the lubricant out with something as non-lubricating as WD40 (I don't care how they market it, this stuff is not a lubricant; if anything, it was used here as a degreaser), I'd dunk this thing in 30 weight oil and give it an hour to soak into the raceways and pawls.



And that's about it. We reassembled it afterwards to good success. Same process as disassembly, just in reverse.

-Kurt

Lug Life

Glad you were able to get the hub functioning again. And thanks for documenting the process to share it here. It's good info that should undoubtedly help others who might need to open one up of these XC hubs sometime. It does make me wonder however if we might expect any variations between different models of Suntour freehubs. Suntour's catalog of freehubs is pretty short, but are there any that are fully serviceable?

mpetry912 

I was amazed at the ratcheting mechanism. "Liked"

Glad you got it back together

/markp

cudak888 

Based on this thread and the following picture from mechBgon, there are at least three variants of Suntour freehub body which are theoretically compatible with Suntour freehub bodies: AP and AP 8-speed - both of which have no indexing groove, differing only in width for the extra cog - and MD / Microlite / PowerFlo, which all share a third design of the same freehub body with an indexing groove like Shimano HG:



I doubt any are fully serviceable, but I wouldn't be surprised if these hubs were produced in larger quantities than they were needed; they've just been lost to time.

I wouldn't discount the dunk-for-lubrication method either. This could have been achieved with a dunk in mineral spirits followed by a dry and subsequent soak in 30 weight oil. I wouldn't do this if a freehub body is working outright, but it might be the best way to save one that is stuck.

-Kurt

bikemig 

Very useful thread. My plan for servicing a suntour cassette is a little different: I just won't buy a bike with one even though I'm a suntour fan. When I bought my first mountain bike--a 1991 Team Stumpjumper--I loved all the suntour/WTB greaseguard stuff and I really liked that it had a freewheel, not a cassette. Yeah I know it's a weaker wheel and all that but I wanted something that would be serviceable down the road. Recently I passed on a good looking early 90s Trek 750 as I didn't want to mess with one of these so I'm still sticking to my plan for servicing them which is to just say no, .

ThermionicScott 

I could be mistaken, but this looks almost like a flat for a tool. If there's another one on the opposite side, maybe a socket could be ground to make the tool.

cudak888 

Ooh. You might be right.

Anyone else here have one of these hubs and willing to investigate? The one in these pics has already been reassembled and went back home.

-Kurt

mgopack42 

If it is only on one side, It might be a circlip that is camouflaged by the residual gunk. pastorbobnlnh might have some knowledge here.

pastorbobnlnh 

Absolutely no clue, mgopack42 but thanks for thinking of me.

trainman999

I have an XC Comp hub it is either an MD or an 8 speed it had slots to unscrew the race like a Shimano my guess would be the race on yours unscrews too

cudak888 

Interesting. Very different from the 7-speed XC we were working on. I'd need to put one in some soft jaws and give it a few taps with a punch to see if it opens up.

FYI, I've been told the WD40-soaked freehub is still working as intended as of yesterday.

-Kurt