Suntour XCM fork maintenance

larkim

First things first. I am not going to buy new forks for this bike as finances mean that that is not feasible at the moment.

My 14 year old son has a 2011 Hardrock Sport Disc with Suntour XCM forks (XCM-V3-26-DS-MLO apparently). They've become very stiff, so I've removed the lowers for a good old clean out, lube etc as a basic / easy to achieve job.

I've got his bike suspended from the rafters in my garage at the moment, so had a quick press on the lower rods of the stanchions. The lock out side moves freely, but the preload side is very stiff, and when I squeezed it in about 10cm last night (about as much as I could manage given the way it was suspended and due to stiffness) some water dribbled out of the bottom where the lower rod enters the main stanchion.

I don't believe that these forks have any sort of oil damping in there, so I presume this is just water ingress from use (pointing to either a failed / compromised seal somewhere, or just a design flaw in this entry level fork).

My plan is to remove the spring from the top of the fork and have a good look inside, re-grease everything, empty out any water trapped in there etc.

Any suggestions for how best to proceed? Most of the maintenance videos I've seen online seem to involve physically removing the whole fork assembly from the bike, but to be honest I'd like to avoid that as I can see me losing part of the assembly / headset. I've got a bike maintenance stand (Lidl) so I can manipulate the position quite well.

Any hints or tips for me to make the best out of this bad job of maintenance?

(As at the top, I'm not going to pump any money into a new fork as he is saving for a bigger frame / more competent bike througout this year, so I'm just looking to try to get back some fork movement where it has all but disappeared currently).

Thanks in advance for any help!

Matt

The Rookie

The seals are well known for leaking, so yes water gets in the top and fills the lowers, the MLO has no damping (the HLO does) remove the lowers by undoing the two bolts on the bottom and pulling, clean it all up, grease it well, I would use red rubber (waterproof) grease, plenty of it above the bushing and below the seal, then refit, can be done in 20 minutes easily. No need, or benefit, in stripping the top half at all, just pull the lowers off.

larkim

Cheers for the quick reply. Just to be clear though, I've already removed the lowers and its not there that the water was present. (I'm sure there was water in there, but that had probably drained away)

The water is in the top section of the shiny stanchions - where the lower rod (the thin section with a screwed thread at the end) enters the top shiny section - which is why I am considering removing the preload screw to access the coil on that side.

Matt

The Rookie

OK, in that case you will need to strip the uppers.

maringirl

You will need a special serrated tool to remove the tops caps - available from Greyville Enterprises. Strip down clean inside with isopropyl alcohol, re-grease spring with suspension fork grease and refit. If you do this regularly then it will prolong their life - bit if they haven't been done since 2011 then they are already going to be a bit manky inside.

larkim

Cheers - I soon realised that on Friday night when I made a failed attempt with a plumbers basin wrench to try to get it off. I could see immediately that it wasn't going to work and that I'd destroy the cap on top of the forks, so I've got the tool on order.

The forks are just 2 years old (bought December 2011), but you're right, they've not seen much love in that time. The whole bike needs a few hours of TLC with LBS, but I thought I'd try to free the forks first of all. It took long enough to get the forks dropped from the frame on Friday too as the conical ring was very firmly wedged into the headset, but a few solid taps via a hammer / block of wood shifted things. Of course, now I've got the headset to clean / de-grease / re-grease etc as well - we're not terribly good at putting aside time for these things in our household!!

Thanks for the advice / steer.

Matt

larkim

Tool to release the spring arrived tonight, so despite not having any grease nor time to do things properly, I couldn't resist taking out the spring to have a look.

My problem seems to be on the "preload" side - the LO side springs nice and easily (too easily?), but for the life of me I can't depress the rod on the preload side. So I assumed there was some jam in there which was causing the problem.

Cap removed fine with the tool, and I could see that the pre-load knob was set to fully compressed. But that was only about 20mm anyway.

Extracted the coil, and removed the rod from the end. Couldn't see anything obviously "stuck". The large rubberised stopper through the middle of the coil seemed fine, plenty of grease all over the coil. Nothing seemingly "stuck".

I did try to compress the spring slightly outside of the forks, and that didn't seem to give very much. Re-assembled, and I'm still in the same place - the preload side really doesn't want to play.

With no obvious sign of damage to the spring, is it possible that the coil has lost its mojo? Next step is to completely degrease it (when I have a tub of grease to hand) and see if the coil has actually snapped / failed somewhere. Other than that, can anyone think of any other potential scenarios? Am I being misled as to how "springy" it should be based on the springy-ness of the LO side? Is it simply that I'm not able to put enough force into it to get it to give even 10mm of the 80mm travel which I should be seeing on this fork?

Any help gratefully accepted!!

Matt

maringirl

It will be hard to compress it just by hand - clean it off, liberally grease and refit and see if it feels better. Springs are very durable so unlikely to have lots in boing!!!

The Rookie

You have the full body weight on the spring when riding, something you can't do with your hand on top of a 25mm diameter coil. Maybe the actuation rod through the bottom of the upper to the lower is seized, did that move OK?

larkim

Too often these threads die without the full resolution!

I secured a couple of hours of time from SWMBO (as well as the use of the kitchen!) to get this sort this weekend.

In summary, things I had never done before:-
- removed the lower stanchions
- removed the fork from the bike (needed some persuasion with a hammer and a block of wood)
- cleaned out the internals of the lower stanchions and re-greased with Stendec fork grease (looked very similar to the stuff that this guy used on the video - http://www.youtube.com/watch?v=vvaPjoIA_tI )
- used the Suntour tool to remove the spring from the silver stanchions (straightforward) to confirm there was nothing seized or blocking the lower pushrod)
- cleaned and lubriacated the externals of the silver stanchions as recommended in the video
- re-assembled lowers and uppers and confirmed that we now had forks which actually moved
- re-assembled fork onto the bike

Pitfalls that I came up against
- the nut (not a bolt with these forks) which screwed onto one of the lower pushrods was tough to get on - I think I must have cross-threaded or squashed a few of the threads, so that when I was trying to re-attach the nut and the pushrod were both rotating together. Very difficult to get any purchase on the lower pushrod to resist against the forces required to screw back together, so I ended up disassembling again and winding the screw on and off past the sticky section about 50 or 60 times whilst disassembled, to a point where it felt to me that there was much less resistance. After the third re-assembly, I was able to get the nut on and tightened without apparently doing any damage to the thread or the nut
- re-assembling headset / attaching stem. Being a complete novice I presumed that the top cap into the star fangled nut needed to be tight once re-assembled, so as soon as I thought I had finished the steering was very notchy. Read up on what this was supposed to do, realised my mistake and second time re-assembled seems fine. (I did take the opportunity to clean the bearings / races and re-grease with the TF2 red stuff)
- didn't allow enough time overall, so I've still got brake pads / cables to sort out.

Overall, job done and I seem to have some springy forks back again!

Thanks for all the help / steers along the way.

Matt

The Rookie

Well done, and the right result (back to no worse than they were when new).....