Miles between suspension refreshes

bmart

Control Rider
You're right, but there are formal specs for things. I've made fun of the 'every weekend oil change guys' for years as the science doesn't support it. I send my engine (cars and bikes) oil off periodically for testing and even at my intervals, I change it too early. It shows as well in spec for the duty it has to perform.

The shearing and pressure forces of engine/transmission/clutch oil can't really be compared to fork oil, probably why Ohlins recommends 30k intervals and Honda recommends 7.5k for engine oil. I'm not suggesting those intervals for track/race use, but for under normal circumstances. Still, I know many who change their suspension fluid every season and engine oil every 1k miles or so...on their non-track use bikes. There's nothing wrong with it, but they're mostly just throwing their $ away and adding to recycling or worse.

Maintenance cycles/consumables are always an interesting conversation and have, I'm sure, been the source of many family brawls. lol (The newest Mobil 1 Extended Performance runs easily 20k miles in a car within spec. Crazy good tech.)

For me, a slow track guy, every 7.5k or so for suspension seems fine. I'm at that now on the "A" bike. I wish that Thermosman was closer so that I could visit and see what comes out when he drains both ends!

To add to the topic of engine oil that you touched on, I go 1500 miles on the track bikes (much of it coaching rolling around looking backward, not at speed) and the 'used up oil' tests have always come back as well in spec (aside from the one posted below). I tow a lot with the cars. Their interval is 7500 miles, so I change it then. Again, the oil test guys say I'm changing it way too early. Unlike my old cars, oil technology has come a LONG way. So like you, but at a later cycle, I still don't want to run it until it doesn't work well and create any damage.

Have any of you also tested engine, or perhaps more interestingly, suspension fluid? I'd be very interested in seeing the results at any mileage, car or bike. I've attached a few of mine. A 2004 Subaru that has nearly 100% towing duty; Mobil 1 since I bought it. The R6 was one of my track bikes. The aluminum turned out to be the clutch boss. Definitely worth the cost of the test to avoid a failure while in use (and easy to pay for with all of that extra oil money!).
 

Attachments

tad158

Astronomer not Astrologer
By the end of my season I usually notice a change in tire wear, and the setup becomes more finicky to tire pressure.
 

bmart

Control Rider
That's an interesting comment, Tad, one that I've heard from others over the years. I may not be sensitive (or fast enough) to notice that.
 

tad158

Astronomer not Astrologer
Not that I can "feel" the difference (as I am head A group slow poke ) just that the tire shows it. I try and get the most out of my tires, so I notice it trying to dial in the wear with pressure adjustments.

Also it isn't that the oil viscosity is changing due to age, but that it is becoming contaminated with brake dust and such in the front and other dust and rubber cap in the rear. Think about how the damper works, it controls forces by forcing the oil though tiny orifices. So if you have junk in the oil it changes how the oil moves through the valving, changing the damping.

That said I do my forks every year because it is easy and for the cost of a jug of oil and two seals it is worth it. The rear, I get 2 seasons, 24 days, before I get annoyed with the tire wear and send it to MRP for a refresh.
 

Motofun352

Control Rider
Most of the "junk" in the fork oil is babbitt from the slider bushings. This stuff is an alloy usually of tin, copper and antimony. That's why when you inspect one of the bushings it often looks copper colored. The copper is the hard(er) metal in the alloy and the tin is meant to wear away. This is what is contaminating the fork oil. Does tin in the 5wt oil affect it's viscosity? Don't know but it certainly doesn't help it. I know that babbitt in typical oil lubricated pillow block bushings lasts for years but in these cases the oil is constantly refreshed.
 

tad158

Astronomer not Astrologer
That is a good point. There is also the springs scraping the inside of the fork body.
 

bmart

Control Rider
Dug out some more notes. The last time the track forks were done was after 5600+ miles. Clean inside and no wear. I got new fluid anyway. :)

I'll report back after this time (7400 miles).
 

Motofun352

Control Rider
I don't worry too much about my steering damper. I've done 1 rebuild in 7 years on my Pit bull damper. While you may be able to feel some damage or deterioration, I'd be hard pressed to tell myself. The steering damper is a third order level device. First tires, second suspension then damper.....
 

bmart

Control Rider
Both of mine were done at their last suspension interval, so I won't send those off this time. Also going to try a WP shock for a bit next season. Any of you guys use those?
 
Top