mboro1876

Hi all,

I've just snapped up this Suntour VX S for about £15 GBP. Happy with that!

vintage Suntour VX rear derailleur | eBay

medium cage, seems to be the exact same model that came on my bike originally. It looks in pretty good shape and I'm certainly not confident enough to strip down the whole thing for cleaning, but is there any basic greasing/lubing I can do before installing?

Actually putting it on should be a cinch, since I know how to adjust them already and it has an open cage design

The Golden Boy 

You can sand and polish the aluminum.

You can soak the rusty screw in vinegar or something like that.

Pretty much anything in the VX series is a great derailleur.

ramzilla

Really? That ebay ad indicates NOS. All you need to do is bolt it on & go for a ride. If you really want to make sure it works perfectly then, maybe put one or two drops of sewing machine oil on it first.

seedsbelize 

Open cage rds are wonderful machines. I have more of them than I have bikes to put them on. The same goes for top normal fds.

Murray Missile 

I'd remove anything that will come off easily like the hanger bolt and jockey wheels then clean it with dish soap and a soft bristle brush, rinse well and dry. You can soak the rusty steel parts in white vinegar for a few hours but don't put anything aluminum in it for very long. Oil the jockey wheels and pivots with a light machine oil and re-assemble. I use an oil called Tri-Flow but I doubt it's available where you are.

The Golden Boy 

No it doesn't.

It clearly says "used in good condition". The pictures clearly show wear, scratches and rust.

mboro1876

thanks will look at the condition more when it's here. The open cage is really a great design.

mboro1876

I actually have another similar one on the bike this is for already (not great condition), though it has enough subtle design differences to make me think it isn't the same actually, and I know a VX S was original spec. Will be interested to compare them side by side since I can't figure out what the heck the current one is..

jimmuller 

I haven't checked velobase or disraeligears for a while but memory tells me they did make minor changes. I think they didn't all come with a quick-cage at least.

Bobtoo

As far as I know the S (medium cage) and GT (long cage) always came with a quick cage, but the standard short cage VX didn't. That one seems to have a B year code, which I think is 1985. By coincidence Suntour's year letters are close to the UK's car registration year letters

I've bought a few of these and generally just give them a bit of a clean and some oil. They shift really nicely, especially in conjunction with the Power Shifters. In the UK they are normally used with a Compe-V up front.

mboro1876

Yeah looks to be quick cage for sure on here. Once it's here I'll have a look-see what needs doing, RJ the bike guy happens to show a complete disassembly on his youtube but doubt it'll be necessary.

Since I'm here, I don't suppose anyone knows about shifting a 7 speed with these? I remember hearing that all 7 speeds are the same width as a standard 6 just more crammed in, so I'd guess it might be fine.

mboro1876

Hi Bobtoo, just thought I'd update on this since in the event I ended up snagging a lovely pair of NOS Power Shifters too . Went to my co-op and installed it all, but (I think my fault) suffered a snap of the main coil spring in the VX S. So I wonder if the coil spring assembly is the same between VX and VX S, since I'm trying to find one somewhere and don't know how specific I need to be -- any idea?

In any case, the power shifters are absolutely great as you suggest .

Best
John

romperrr 

Another cheer for open cage rds!

jimmuller 

You mean the spring which rotates the cage to keep the chain taut? Most likely it was nothing you did unless you tried to rotate the cage an extra revolution, which is pretty hard to do. They do sometimes break from age or rust.

Since the rest of the Vx RD is the same, I'd be extremely surprised if the springs are different. The 1st gen Cyclone RD looked similar but was different in length and diameter. But I'd guess all Vx and VGT series are the same.

Removing the spring isn't too hard but it does require taking the cage off the inside end of the shaft. You can even do it without unhooking the shift cable. So if you have another RD to provide the spring, take it apart and see how it works. You will see that you can select how much torque the spring exerts by where you set the outer end of the spring into the shaft.

mboro1876

Hi Jim,

That is what I hoped -- that just the cages differ between VX and VX S. Yes it was that spring, I was pushing it forward a little to get an idea of chain length, and I think I went too hard. Maybe you're right and at least I was glad it didn't break in use, but I think I was ham-fisted all the same .

I have taken the cage off of the spring assembly, and located the spring. (In fact, since it's toast anyway, I even tried bending the spring a little to make a new tab). I see the different holes into which the spring can fit at the top of the shaft, but what I don't see is how to get the spring out of the hole it's currently in. There is a hex bolt at the top of the shaft which, in some pictures, appears to be part of a kinda dust cover, to take off and remove the spring 'upwards'. But I can't lever it off of mine. Any idea?

bp2k8

I use chromax and it works quite well for polishing and removing rust. Congrats. Suntour to me are superior to shimano and sram and up to par with campagnolo

jimmuller 

The critical parts as far as the spring is concerned are the cylinder it fits into and the shaft that goes through it. The inner diameter of the coil spring has to accommodate the diameter of the castellated flange on the end of the shaft. The cylinder has to be the correct length and diameter. Coil springs are a funny lot. As they are twisted (always to tighten them) they get longer by one wire thickness for every complete revolution so the cylinder and the length of the tab at that end have to allow for that. Most are designed to go only a limited rotation, rarely more than 360deg. And that wire is really hard to bend. But even if you could, you'd shorten the spring so that it might not fit properly into the hole at the bottom of the cylinder. I learned about this when I tried to have some Cyclone springs made. I couldn't generate enough interest to amortize the cost so I abandoned the idea.

That hex nut serves two purposes. It keeps the outer tab of the spring from popping out of the slot at the castellated end of the shaft, and it provides the pivoting surface for the entire shaft to rotate in the cylinder. Usually you unscrew it from the shaft with a hex wrench (6mm?) as the first step before you remove the cage at the other end. That way you can hold the cage to keep the shaft from turning when you unscrew the hex nut. Once the hex nut is off, the shaft can pull out from the other end of the cylinder by letting the spring slip out of the castellated end. Then you can remove the cage. If you need to grip the shaft for that purpose, put pliers or similar on the part that fits within the spring so as to avoid marring any bearing surface or threads. Once the cage is removed from the inner end of the shaft the shaft will come out through the outer end unless the spring hasn't come loose yet. The inner end of the spring has a tab that fits into a hole at the bottom of the cylinder. It may be stuck but it should come out without too much trouble.

Wait. Before you do anything, if you haven't done so already remove the stud that prevents the cage from unwinding. Then you can work with a de-torqued spring.
Hope this explanation helps!

mboro1876

thanks -- my first idea was to try bending a new bottom tab, and I actually got a pretty good straight one done, but due to spring length as you say, it was impossible to pretension the spring enough to get it into the correct orientation relative to the stop screw.

that is very clear indeed, but I'm either missing something or super unlucky. The following video shows the process:

and at 2:18 he does your thing of holding the cage and body in place while undoing the 6mm hex bolt. In my case (maybe because the spring is already snapped?), undoing the hex bolt simply pulls up the whole castellated shaft, unscrewing it out of the cage along with the spring. I honestly think I'm doing exactly what is shown there and what you describe.

In any case thank you so much for your time. If I can't make progress perhaps I'll just try and source the whole spring+shaft assembly.

Cheers!

mboro1876

In the end:

1) A really helpful forum member here provided a new spring, including the castellated post and hex-bolt top cap part.
2) It showed up today, shipped via a family member who lives in the UK. Wow.
3) The spring was identical and the shaft looked the same, but... the threaded section that screws into the cage was smaller. Suntour, wtf .
4) So it came back to somehow getting my old spring assembly apart. In the end, I basically soaked the whole thing in WD40 and then degreaser. Grabbing the (non-threaded part of) the castellated post with vice grips was enough to allow the top cap to come off.
5) I assembled it using this helpful video:

going nice and easy when choosing the spring tension so as not to tempt fate this time. Looking forward to put it on the bike. Thanks to all.