Servicing Giant MTB with Suntour SR forks

[ncutler]

A friend & neighbour has presented me with a Giant Sedona GX that has been lying fallow for a few dusty years. I am coming to regret my over-confidence regarding bicycle maintenance and need help please.

This is not my type of bicycle ( heavy, clunky, over complicated !) but I more or less understand most of it except for:

Suntour SR forks Serial: SF8-M2025-P-26-63. They appear to work, but do I need to do anything ? What happens if I unscrew the plastic caps at the top of the legs ? How can I check their operation ?

The seatpost has this bouncy-springy thing. Does the large silver nut do anything ? Should I fidget with it ?

[rjb]

The seatpost has this bouncy-springy thing. Does the large silver nut do anything ? Should I fidget with it ?

That knurled nut enables one to reduce the excess play as the suspension bush wears. You may need to lower the reflector to give you some room and a few drops of oil helps to keep it from all seizing up.

Not sure about the front forks but the nuts on top may allow the spring in the forks to be tightened up. Pulling the concertina cover up may enable one to ad a few drops of oil to the stanchions to keep them moving freely.

My neighbour asked me to look at her posh brass 13 amp socket which was intermittently working. I suspected that the terminal inside had spread and could just be squeezed back up. I turned the mains off, removed the socket and carefully opened it up. She watched my every move but when I lifted the back plate off springs, covers, links and terminals flew in every direction. I retrieved all the parts whilst still being watched but had the presence of mind to say to her. "I hear you're very good at jigsaws" and watched the look of horror that spread across her face. I eventually got it assembled and working but next time I'll just fit a new cheap plastic version.

[slowster]

I would just leave the suspension parts well alone. I doubt that whether they function or not makes much difference to the ride/comfort of the bike, i.e. they look like relatively low quality suspension parts. It does not look like a bike for serious technical off road terrain, and I suspect it would only be ridden on roads and gentle tracks where there is no need for suspension. If you serviced the suspension parts, I doubt your neighbour would notice much, if any, benefit.

There is no shame in telling your neighbour that you have not touched the suspension, because it is not something you are sufficiently familiar with to tackle.

[Eyebrox]

Suntour forks from that era were very basic. One stanchion had nothing in it - totally empty - and the other had a long hard rubber rod which kept the upper and lower sections apart. The springiness came from the pressure on the rubber rod which was stiff enough to restore the top half of the fork back into position. No remedial work could be done, although there were three interchangeable types of rubber rod, each with its own level of rigidity.

[DevonDamo]

Suntour SR forks Serial: SF8-M2025-P-26-63. They appear to work, but do I need to do anything ? What happens if I unscrew the plastic caps at the top of the legs ? How can I check their operation ?

Those old jobs aren't true suspension forks as would be understood today. Today's forks are typically configured with a spring in the left leg and some damping gubbins in the right to adjust the speed that the spring compresses and extends so that it actually absorbs shocks rather than buck you around like a pogo stick. Those old forks have just got a spring in each leg, with no damping. The only thing you can do is turn those plastic knobs at the top of each fork to adjust the pre-load, i.e. set how firm the spring will be. As it's a separate spring and adjuster for each leg, you might want to open them both out fully (anticlockwise) and then count the same number of clicks on each so you've got the same preload left and right. You have to rotate each cap by about 180 degrees before it clicks onto the next setting. How stiff you want to set them is a matter of personal preference, but they're only fit for cushioning your hands from being hammered by road bumps, so you'll probably just want to set them as firm as you can get them, to minimise the amount the bike wallows and wastes all your pedalling effort. Definitely not worth putting any more work in than that.

Can't help with the suspension seatpost. I've got a similar one in pieces in my spares box, which came off a Dahon folding bike. After taking it apart without the aid of a manual, I decided it wasn't worth the hassle of reassembling. It was a Biologic seat post, in case you want to try hunting down a manual for it but I didn't find anything via a quick Google search.

Edit: Eyebrox above may be right. I thought they were of the same vintage as the ones in the following video, but on closer inspection of your photos, yours don't seem to have the rotating knobs on top of both caps:

[rjb]

I've got a suspension seat pin on the tandem as standard. Realising the misses was bouncing up and down on it and finding the adjustment was at the max firmest, I managed to tighten it right up by adding a polymer wine cork. Now it only compresses under a severe jolt. Mrs RJB is none the wiser.

[Eyebrox]

Mrs RJB is none the wiser.

Unlike the men, they know when it pays to keep mum.

[ncutler]

Thank you all, that's very helpful. The bike's owner is not remotely discriminating, so I think I'll leave the forks alone; they are probably just as heavy and useless as when they were new!

The thing needed a huge amount of cleaning, but doesn't appear to ahve been used much. The transmission is hardly worn and works fine. The gear cables are rusty so will get changed, the brakes didn't work because the cable outers were badly kinked so new brake cables, the chain is much better than it looks and just needs degreasing and lubricating properly. So the deterioration is all to do with neglect and under-use and easily fixed I think.

The owner would be far better suited by simple hybrid with a basket on the front ............

[ncutler]

I doubt that whether they function or not makes much difference to the ride/comfort of the bike, i.e. they look like relatively low quality suspension parts. It does not look like a bike for serious technical off road terrain, and I suspect it would only be ridden on roads and gentle tracks where there is no need for suspension. If you serviced the suspension parts, I doubt your neighbour would notice much, if any, benefit.

The fork has this sticker attached:

I'd suggest that a more honest caution would be along the lines of: "These forks are an essentially useless sales aid: for enhanced rider comfort and safety please replace with a simple steel fork"

[SimonCelsa]

"A man who makes no mistakes makes nothing" is a very apt statement.

I would say don't be fearful and try and give them a good overhaul for peace of mind. They're only a cheap set of suspension forks and probably are held together by an allen socket nut on one of the lower stanchions.

Internally they may require some light lubrication of a coiled spring or something similar. I doubt it would be too complicated.

I removed a similar set of cheap suspension forks from my Specialized hybrid and changed them out with a rigid pair of Surly Ogre forks. Can't say the bikes performance noticeably improved, in fact I did actually miss the dampening effect of the SUS forks over certain terrain.The Suntour forks were fairly simple and the adjustment 'dials' on the top of the stanchions weren't actually connected to anything, something I would never have known hadn't I disassembled them!!

Go on, rip them apart and report back on your findings!!

[ncutler]

Go on, rip them apart and report back on your findings!!

I think I'll leave it alone, The last time I took a coil spring shock absorber apart it took three of us to wrestle it together again! Admittedly this was a light aircraft rather than a bicycle, but the principle remains the same and I am not going to repeat the experience.

As it happens I rode the splendid contraption round t'village after lunch. It isn't quite the clunkiest bicycle I have ever ridden, everything now more or less works and lines up. So I'm going to give it back to the owner with instructions to bring it back for a check after a few miles. I rather suspect that after an initial burst of enthusiasm, moderated by aching knees and scratched ankles, it will spend the next few years languishing back in its barn. I might oganise a picnic; someplace within easy walking distance.

[Philip Benstead]

Have you seen this? https://www.youtube.com/watch?v=BIJPeh-D8D4



Look very straightforward.

[ncutler]

Thanks Philip, that's interesting.

As I suspected; the owner says she won't be able to ride it for a while, but it will have friendly company with the others in my garage.