Originally Posted by tngarren

When you refill and measure fill from the top of the fork tube, do you pump the dampers during the process to fill them with fluid? My shop manual is silent on it. TY.

Originally Posted by hattitude

I fill them, pump the dampers slowly to release all the air pockets, then check that the level is correct... I usually have to add just a tad more after pumping....

Originally Posted by hattitude

If you are satisfied with your front end performance, stick with the same weight fork oil. If you want to change performance, you can change weights, or even mix weights, to get a performance you like. Just remember, the thicker the oil, the less compliant (stiff) and thinner the oil the more compliant (bouncy) your front end will perform.

Another thing to note, fork oils get thinner, when they heat up. Most have a basic spec and then a 100°C spec. Harley Type E is 20W, but drops to 7.95W @ 100°C. If you are a hard rider, who frequently "works" his suspension hard, you may want to start with a heavier weight fork oil..

I believe most HD bikes come OEM with their Type E fork oil (20W).

If you want a more compliant (bouncy) front end you could go with HD Type B fork oil (10W)...

If you are a canyon carver and want a stiffer front end (Ha, I said stiffer front end) you could go with the Screamin' Eagle Type heavy fork oil. It is also 20W, but fades (gets thinner) less at high temp than Type E.

HD also used to make a very heavy SE fork end oil called extra heavy, which is like 60W... I would guess for racing only, probably unsuitable for street use...

I use Bel-Ray High Performance Fork oil... They make it in 5W, 7W, 10W, 15W, 20W, and 30W. So you can pick a weight and give it try, or there are numerous weights for mixing...

The beauty of fork oil is that it's not that hard to change, and if you pick a weight that doesn't suit you, it's not too hard to change it to something more/less compliant....

Good luck with your decision...

PS- Here's a chart by Spectro Oil on fork oils. It shows the "thinning" of the oil at temp..

Originally Posted by y22c

This is not a chart showing the thinning of fork oil at temperture

This is a chart showing the min and max viscosity of a particular grade of fork oil at the test temp of 100c (212F) in centistokes.

It says that a SAE Grade 5 fork oil must have a viscosity between 3.80 and 4.09 centistokes at 100C to be labeled an SAE 5 fork oil.

Anything below 3.08 does not qualify for a 5 weight (too thin) and anything above 4.09 is a 10 weight.

This is why company A's 5 weight fork oil can offer a different feel in the the forks than company B's fork oil, one can be blended to the low end of the range and the other to the high end...they are both 5 weight but could react differently in your application

Originally Posted by hattitude

I knew that, but very good follow-up information...

That's why I put the word thinning in quotations.... but I can see I was clumsy in my wording and use of that chart...


I was unaware that was the test for fork oils to qualify for their various weight ratings, I thought it was just a standard for comparison..... so thanks for the education on that point...

Thank you for clarifying...

Originally Posted by y22c

This is the min and max chart for all straight weight oils, including the oil grade after the "W" in multi-viscosity engine oils.

It is not the min and max chart for "W" rated oils