Fork oil change - 5 year protocol

[Guest]

It's been five years since the fork oil has been changed on my bike. Five years ago, I changed out all the O-rings, main fork seals, stainless hex etc. because it was the first time the fork oil had been replaced in probably 20 years. At that time the fork springs were also changed to Progressive brand fork springs (I'm happy with them, but I know Sonics are popular too). It was a major job to do this project.

Now it's time to replace the fork oil again, at least that's what I've been told, and I think it's a good idea. So should I break down the fork tubes into bits and start over? The O-rings etc have got to be fine after only five years, so I'm not going to change those, but what about the main fork seals (OEM seals cost about $11 each)? Should those be changed just because it's so much trouble to change the oil anyway? The main seals haven't leaked, just a smudge on the outside every once in a while.

[bluewool]

I change my fork oil every two years and do not disassemble until I need seals. I empty them, rinse them with mineral spirits and let them dry, and refill them.

[Brendan W]

I wouldn't take them apart without a very good reason like leaking seals, suspect broken bits inside or completely blocked up with sludge. Usually I leave it two years to replace the oil. Five might be a bit too long as metal parts are abrading in there all the time.
The 850 is on a six month interval since I got it 18 months ago because there is sludge coming out still albeit reducing every time and I made a call not to dismantle forks that weren't leaking. Secondary transmission is on six months as well for the moment for the same reason.
I don't understand how changing out the fork oils is so much trouble. Are you removing them from the bike or something?

[gustovh]

To check is to know.

V

[Gorminrider]

I change the forkfluid every season but apart from being nasty-looking every time, but I wonder if it truly makes a difference to the seal-life....I wonder because who changes the fluid in the rear shocks? It's not possible with stock ones. not easily without mcgyvering them anyways.

I see that there are differences in construction (forks vs shocks)
--The seals in rear shocks are so much longer and the rod so much smaller in surface area so less dirt getting driven onto seals
--the shocks are in the rear and protected from dirt
--the (many) shocks are steel construction versus aluminum

I am guessing that is how they are expected to get away with not having fluid changed out. What do you think?

[DPage]

Thanks for the help, I did some searches and realized that I was making this out to be a lot more difficult that it actually is. I'm going to remove the fork tubes, drain the old oil with the top caps removed, rinse the tubes with mineral spirits and let them dry, then put in new oil to the right level. It will probably take a few hours, but is not nearly as time-consuming as rebuilding the forks. And it also looks like this should be done every year or two, not every five years.

[Brendan W]

Your making me feel like I take short cuts. I open the drain screws, pump out the old and add the new from the top. Less than an hour including measuring the springs.

[jona]

I just drain old, refill with correct amt. every spring, I avg. 10k a year.

[dennisht]

What weight fork oil?

[RichDesmond]

Logical time to do it is when you change the front tire. At that point it's 5 more minutes to have the tubes off. All together it should add about 30 minutes to the job.

I like ATF as the rinsing agent.

10w fork oil for most people, if you have better springs and ride on the sporty side then 15w.

[bluewool]

Hmm. That's a good thought. Fork oil is cheap. So is ATF.