Change that fork oil!
Road Warrior
Joined: Nov 2008
Posts: 1,636
Likes: 7
From: Jackson, Michigan
Psst - for this job it's not worth the hassle. Just read the info and follow my lead as I'm bullheaded and had to learn the hard way on a couple of points.
Thread Starter
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Road Warrior
Joined: Feb 2007
Posts: 1,785
Likes: 4
From: Oklahoma
Beware of the cynic! As true as all these factors may appear from the outside, if you choose to specialise in this field a whole new world opens up to you!
I am not fully conversant with the exact design of the forks in the HD touring range but traditionally...
Forks (and all suspension for that matter) needs to dissipate energy based on 2 variables, namely displacememt (crudely simplified as "how deep is that pothole") and velocity, (namely "how steep are the sides of that pothole"). If you have the benefit of studying fluid dymamic theory you will begin to understand the dashpot principle which essentisally boils down to a frictional resistance based on the resistance between 2 closely spaced mechanical components seperated by a viscous fluid. In the case of a fork, the inner and outer sleeve are seperated by the fork oil, and the rate at which they move relative to each other is damped by the fluid. This takes care or the "velocity" component, the old fashioned forked used to have a spring inside which took care of the "displacement" component. Look at a typical car shock absorber which has the outer coil spring and the inner damper. Take out the spring and the car would sag down, take out the damper and the car would bounce up and down like a yoyo each time it hit a bump - 2 different but complimentry functions
So, why use fork oil vs engine oil vs cooking oil for that matter. Each lubricant carries additives which facilitate performance in a specific environment. In the case of fork oil, shear strength (tearing resistance) is really important.
In summary, do not be cynical about working fluids. They are not "the same thing in a different bottle" - use the right stuff. The additives in the fluid are very different and designed specifically for each application
I am not fully conversant with the exact design of the forks in the HD touring range but traditionally...
Forks (and all suspension for that matter) needs to dissipate energy based on 2 variables, namely displacememt (crudely simplified as "how deep is that pothole") and velocity, (namely "how steep are the sides of that pothole"). If you have the benefit of studying fluid dymamic theory you will begin to understand the dashpot principle which essentisally boils down to a frictional resistance based on the resistance between 2 closely spaced mechanical components seperated by a viscous fluid. In the case of a fork, the inner and outer sleeve are seperated by the fork oil, and the rate at which they move relative to each other is damped by the fluid. This takes care or the "velocity" component, the old fashioned forked used to have a spring inside which took care of the "displacement" component. Look at a typical car shock absorber which has the outer coil spring and the inner damper. Take out the spring and the car would sag down, take out the damper and the car would bounce up and down like a yoyo each time it hit a bump - 2 different but complimentry functions
So, why use fork oil vs engine oil vs cooking oil for that matter. Each lubricant carries additives which facilitate performance in a specific environment. In the case of fork oil, shear strength (tearing resistance) is really important.
In summary, do not be cynical about working fluids. They are not "the same thing in a different bottle" - use the right stuff. The additives in the fluid are very different and designed specifically for each application
Road Warrior
Joined: Nov 2008
Posts: 1,296
Likes: 3
From: Cheltenham, UK
Shear strength enhanced
Possibly a Viscosity Index builder
Anti foaming
Does ATF have the same additives in the same proportions, I really don't know but I doubt it. On that basis I would argue that there is no point deviating from what is specified by HD for the sake of saving pennies.
I find it amazing that people will spend hours and lots of money discussing front end instability, wobbles, methods of stabilising etc and then be complete relaxed about putting non specified oil in something which absolutely could have an impact!
Stellar HDF Member
Joined: Jan 2008
Posts: 3,036
Likes: 65
From: Earth
I just changed mine per IClick's write up. Except I already had the radio out as I sent it in to iron Cross Audio for some work. Went pretty smooth and I refilled it with SE Heavy. my oil that came out looked similar to the 1st post. All in all a very easy change. If I read it right somewhere here that HD was charging close to $300.00 for this service??? That is absolutely absurd as far as I am concerned. If you can change your other fluids this is a walk in the park with IClick's write up. Great job again to IClick for the post!!!!
Novice
Joined: Sep 2008
Posts: 21
Likes: 0
My brother has an 09 ultra classic. He did not like the dive he felt in the front end on braking and had the fork oil changed to SE 15wt. He loves it. Any other recommendations out there? My 09 RK rides great but I want to change the oil out. I am considering Racetech fork oil. Experiences would be appreciated.
Tourer
Joined: Nov 2005
Posts: 361
Likes: 4
From:
I'm going to change my fork oil and if anyone has done an 08 Ultra that can share any do's and don't, that would be cool. I have the book, so it should not be a big deal, but sometimes those harley books don't tell all, if you know what I mean 
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The workshop manual for my 09 RK states I have to remove the fork legs for an oil change, that and the need to remove all the headlight shroud etc means this will have to wait till winter. I am guessing it will take me a good few hours.
Road Warrior
Joined: Nov 2008
Posts: 1,636
Likes: 7
From: Jackson, Michigan
I ran 225 miles today and really enjoyed the handling and ride compared to the stock oil. It just seamed more connected to the road. I hit a curve a little hotter than I wanted to, I just leaned hard and she hung in there great.