Badly rusted suspension fork

Question

I have a $300 MTB used for commuting. It has been three years now, and the rain and snow have said their word. Two weeks ago I disassembled the fork and spent a good one hour with the sandpaper, removing rust. Still some was left. It has been two rainshowers from then. Yesterday I had another look and ... it is not promising.

I have move aggressive means of removing material (so that there will remain no rust) - a grinding wheel. However, I am afraid to use it, as I guess it will be weakening the tubes too much. I do not seek top performance - it is a no-steal bike (for example the handlebar is visibly bent).

Below are the two pictures. Should I clean the rust? How? How reliable is the fork currently? How long does it have left?

enter image description here

I'm more worried about the bent handlebars. A stuck suspension fork will only become a rigid fork while a fatigued handlebar can fail unexpectedly (as aluminum has a tendency to do.) They're a replaceable part that could cause a nasty accident. — WTHarper, Jan 20 '13 at 01:22
So long as that's not a sliding surface it's not what I'd consider "serious". Removing the rust will remove any protective plating and make matters worse. — Daniel R Hicks, Dec 07 '13 at 13:34

score 8 · Answer 1 · answered Sep 26 '12 at 13:11

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This is obviously (from the images) a suspension fork, and a very low-end one. Suspension forks are heavier than their rigid counterparts, but the trade-off is that they absorb shocks. These rust spots MUST MEAN the fork has long ago COMPLETELY LOST its ability to work properly as a suspension. As a result, you are carrying useless extra-weight, are not getting a suspension effect, are risking some worse failure along the way, and are risking some crash/injury.

The surface presenting the rust is the surface where sliding occurs (the "telescopes"). This surface must be perfectly smooth and shiny, and the rust shown necessarily means it is not, and never will be, as new again. Grinding will remove dust, but will not make the surface smooth nor prevent more rust to build-up afterwards.

My suggestion: sell the fork for metal recycling, and buy either a new suspension fork, or a rigid fork.

Hope this helps.

answered Sep 26 '12 at 13:11

heltonbiker

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The fork tended to work worse the last year, but after I disassembled it and oiled it with teflon oil, it is working very very perfectly! My worry is exactly that it will fail when I least expect it. – Vorac Sep 26 '12 at 13:34
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That it goes up and down does not mean it serves any purpose besides going up and down. Below-low-end suspension (I mean rust, common, even low end forks don't rust) only eats up energy that you otherwise could have put into forward motion, destroys your back and look cool. I'd go for a rigid fork, too. – Baarn Sep 26 '12 at 13:49
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The fork probably won't break, but most probably will have some play and be uncomfortable. 2) TEFLON OIL is absolutely not intended for use inside a suspension. Silicon-based grease (or, considering the low-endness, ANY grease) is best, just in case you prefer to keep this fork.

heltonbiker

Sep 26 '12 at 14:48

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The surface does not have to be perfectly shiny if it is a non-hydraulic, spring-loaded fork. The shine is esthetic only. If you push down on it and it returns, it's working. In any case, it is possible to make the surface completely shiny! Just sand it with finer and finer papers and then give it a polish with a polishing compound. But, I would not waste my time, though. – Kaz Sep 27 '12 at 21:36

@Kaz I partially agree. Shiny and smooth are two different things and you can get one without the other. By "shiny" I mean a surface that most likely will work fine against bushings, providing low friction, sealing of lubrication / against water and preservation of the bushings themselves. By smooth I mean cylindrical, not dented, bent, grooved or otherwise irregular. In any case, the OP suspension is wasted by both criteria. – heltonbiker Sep 27 '12 at 21:47

@Kaz, if you post this as an answer, I will accept it. Ant the a discussion could form under it as to how adequate it is. Also note that the rust is only at the lower end - when the fork is assembled, no rust is visible. – Vorac Sep 29 '12 at 07:03

score 8 · Answer 2 · answered Sep 26 '12 at 14:38

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Throw that thing out and get a rigid fork. You don't need suspension unless you're riding off-road, or jumping over cars, or whatever it is the kids do these days. And bad suspension is worse than no suspension.

Rigid forks are pretty durable, so you may be able to find up a used one. Make sure that the crown-to-axle distance is similar to what you have now, otherwise it may change the handling characteristics.

answered Sep 26 '12 at 14:38

Mike Baranczak

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I partially agree, because I had to put a suspension in my commuter, due to severe discomfort caused by bad-quality asphalt in my way to work and back day after day. But I fully agree that a good tire with a rigid fork can be WAY better than a poor suspension fork - with any tire. – heltonbiker Sep 26 '12 at 14:50
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Rigid forks are antideluvial. Why don't you trade in your car for a horse and wagon? And I don't mean coach: those had, like, suspensions. – Kaz Sep 27 '12 at 21:19
You benefit from a suspension on roads because roads are not perfectly even. They have potholes, cracks, sloppily repaired excavation work, transitions from concrete to asphalt and vice versa, manhole covers, curbs, ... – Kaz Sep 27 '12 at 21:39
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@Kaz Suspension can be good, yes. But cheap suspension is worse than a rigid fork. By the way rigid for being antediluvial, ever seen suspension in road bikes? – Baarn Sep 29 '12 at 10:38
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Even a spring with no damping is better than no suspension, but of course, only if it's reliable: the spring does not break, and the sprung and unsprung parts do not detach, etc. Anything could be crap. A solid fork could crack. I severely bent one once. Road bikes themselves are antideluvial. They are for sport, where you want to shave off fractions of a Newton of drag to beat the other guys to the finish line. For regular mortal use, they are ridiculous. – Kaz Sep 30 '12 at 05:46

score 4 · Accepted Answer · answered Sep 26 '12 at 18:53

In addition to the visible rust on the stanchion tube (that's what those are called), the rust has most likely damaged the gaskets sealing off the lower tubes - the portion of the fork that the stanchion tubes slide into. Even if you got the rust off and got the stanchion tubes in a good-as-new condition (which is probably impossible) you'd still have to replace the innards of the fork. It's probably more economical to just replace the whole thing. If you insist on trying, a buffing wheel and buffing compound will get you closer than a grinding wheel. But personally, I'd just replace it with a rigid fork, especially since you ride in the rain and snow.

Accepting the answer. The fork still works - more comfort when jumping sidewalks and road holes and the occasional dirt road one day trip. Good point on that there is more rust than I see. — Vorac, Oct 22 '12 at 11:09

score -1 · Answer 4 · answered Feb 09 '14 at 01:13

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oh guys, get creative. rust is a chemical reaction. reverse the chemistry.

answered Feb 09 '14 at 01:13

Jump4Joy

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There is some merit to this answer, but you should explain in words what it's saying. – Daniel R Hicks Feb 09 '14 at 13:52
Welcome to Bicycles! This answer really needs some more details, not just a link to a video. Maybe just describe the technique that's used in the video? – freiheit Feb 09 '14 at 19:49

Badly rusted suspension fork

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