When to change your fork oil

Some interesting observations in a compelling discussion.

https://davemosstuning.com/travel-chat-when-to-change-fork-oil/

Man, was that an eye-opener, thanks, John. Now to get out there and change my oil.

Wow, for once I am doing something right. Who knew?

Shit, I just changed it in february and I'm already 2000 miles past due again.

Interesting comments and a good explanation of how fork oil is contaminated, but I dont agree with his comments on fork oil temperatures, at least under normal street riding conditions. The front forks do not get hot for a couple of reasons (volume of oil and the externals being air cooled when moving) and there isnt any reason to think the oil inside is hot either. Shock oil can get very hot since it has a very low volume of oil, much greater pressures, and only gets minimum air flow. Dont believe me....ride hard for an hour and grab the front fork legs or tubes with your bare hands. They will be warmer than the air but not by much. I dont recommend doing this test with the rear shock.

I also take issue with his comment on fork travel, at least on most street bikes. There isnt any way that street bikes are constantly using 5 inches of travel, its probably in the 1-2 inch range except under heavy braking.

What was his actual recommendation? If it is 6,000 miles I think he needs to do some actual street riding and look at the condition of the oil and then assess whether fresh oil made any actual difference in the forks performance. The last time I changed the fork oil on my C14, after 18,000 miles, the oil was clear and I could not detect any improvements with the new oil...but that is an inverted fork.

Dave Moss is a recognized suspension tuner but he makes his living working on track bikes and what may be necessary for optimum track performance isnt necessarily required for normal street use.

We'd all go broke if we changed fluids as much as some folks want us to. I like the 20k interval for street riding /touring.

I need to get to the garage and change my fork oil four times really quick....

I agree- suspension purist vs real world riders. For his regular customers? Sure, maybe. But for me, not so much.

My mechanic told me to wait until the seals started leaking to change the fork oil, but then what does he know?

I use to ride 12000 a year and changed oil every year and changed seals, bushings every 2years. Now ride 8000 year and just do it all once every 2years including shock.

MCRIDER007 said:

Interesting comments and a good explanation of how fork oil is contaminated, but I dont agree with his comments on fork oil temperatures, at least under normal street riding conditions. The front forks do not get hot for a couple of reasons (volume of oil and the externals being air cooled when moving) and there isnt any reason to think the oil inside is hot either. Shock oil can get very hot since it has a very low volume of oil, much greater pressures, and only gets minimum air flow. Dont believe me....ride hard for an hour and grab the front fork legs or tubes with your bare hands. They will be warmer than the air but not by much. I dont recommend doing this test with the rear shock.

I also take issue with his comment on fork travel, at least on most street bikes. There isnt any way that street bikes are constantly using 5 inches of travel, its probably in the 1-2 inch range except under heavy braking.

What was his actual recommendation? If it is 6,000 miles I think he needs to do some actual street riding and look at the condition of the oil and then assess whether fresh oil made any actual difference in the forks performance. The last time I changed the fork oil on my C14, after 18,000 miles, the oil was clear and I could not detect any improvements with the new oil...but that is an inverted fork.

Dave Moss is a recognized suspension tuner but he makes his living working on track bikes and what may be necessary for optimum track performance isnt necessarily required for normal street use.

Click to expand...

Yeah, he's like the suspension guru around the SF Bay area, so I made an appointment, and had him add new springs, change the fork oil, and "tune" the front end. I told him I ride lotza shity roads 'n goat trails, to keep it soft.

Even though I made the appointment a month in advance, he struggled to find my springs when I got down there. Then he struggles to install them, and after "set up" the bike was almost un-rideable the front was so stiff. Rode a few miles, pulled over, 'n softened everything up. The front springs were still too stiff on their softest setting, and next oil change I replaced them. Maybe he's a "track guru" but sucks at setting up street stuff. (Though this was about 6 yrs ago, maybe he's gotten better?) Personally, I think he's more of a snake oil salesman.

I used to go to the late, great Jim Lindemann for suspension needs, and he was much better at tuning track and street. (RIP Jim.) He did recommend 8 to 10 K mi. and I shoot for 10K but seldom make that, and my oil is always stinky, nasty when it comes out.

I change the fork oil about every 2 years. In my mind, I can tell the difference new oil makes, but my mind is a dangerous thing...

I wish the manufacturers would put a drain plug on the lower fork legs, which would make the job tons easier. Yeah, I know that some of the splooge in the bottom of the fork lower wouldn't get removed, but by changing the oil more often, you'd flush that stuff out anyway.

hppants said:

I wish the manufacturers would put a drain plug on the lower fork legs, which would make the job tons easier. Yeah, I know that some of the splooge in the bottom of the fork lower wouldn't get removed, but by changing the oil more often, you'd flush that stuff out anyway.

Click to expand...

I used to think that a drain plug would be sufficient to drain fork oil but now I think that is only true for the old damper rod forks where the limited damping is at the top of the damper rod. Most modern cartridge systms use tiny passages at the bottom of the fork to achieve low speed compression damping and a simple drain plug at the bottom of the fork may be insufficient to clear the crud from those passages...and a simple oil flush and drain with the forks removed may also be insufficient. I started using a cleaner solvent to flush the forks and was surprised how much crud was still in the forks after the old oil was drained.

I flush with kerosene until it comes out clean and then hang the tubes up to drain . after 130k my 03 still had original seals and bushings.with no leaks. did this every couple years along with all the other fluids.

Decided to change my fork oil after reading this thread. Went down to the local dealer and about passed out when I paid $65 for two quarts of 10w Yamaha fork oil. Must be pretty good stuff.

For a second I thought I had walked into the beemer dealer by mistake.

There are lots of fork oils and most are way cheaper. Depending on the application I use a lot of ATF in forks.

Hi Ray, Yeah, I thought about buying the cheap stuff but I somehow got the attitude that nothing's too good for my FJR. Best damn bike there is, imo. Going to flush the forks with kerosene as well. Good suggestion you had.