Hilly just did my Street Glide a week ago. The 15w made the front way to hard and due to our lovely MX tracks the ride was terrible. Swapped it out to 10w and still is nice and firm but allows the fork to soak up the bumps a lot better. My pick is the 10w.

Hilly , what is misleading on the bottle ?? I've used Belray 15w fork oil and I found it better, (firmer) than stock which is 10w . Some even mix , (same brand), 10w and 15w together and end up with 12.5w. By the way I ride a tourer !!

I used Motul, told that s/eagle oil was "not the best" Can tell you that the std crap that came out was stinky black gunge. Had to flush both forks several times to get something remotlely clear out.

Pauly, you posted just before me. So you weren't happy with the 15w !! At least you an expert at fork oil changes !!!

Hilly, I think if you are serious about sorting your suspension, what you need to do is pick a good quality oil, and stick with that brand.
Unfortunately it's trial and error, and you need to start somewhere.
As you have found out, fork oil rating appears to be hit and miss, and the primary function of fork oil is to work as a hydraulic fluid,
but the containers are marked in SAE grade which is not totally relevant.
You could possibly use Race tech oil, as I would expect it to be correctly labelled.

I've used a fair bit of Shell advance in both synthetic and mineral , and currently using 15w in the FXDX adjustable cartridge forks.

Well this embarrising.................i actually put 20w in first up and then swapped it for 15w!!! So its got 15w in it...................Corona must have increased the alchol content as i dont feel drunk.

Even cSt is a bit hard to fathom, as it is temperature dependant .

http://transmoto.com.au/comparative-oil-weights-table/

Here's a good one:

http://www.qemsc.com.au/documents/suspensionoils.pdf

Another rating that is important is the viscosity index, higher the better, but not as important for forks, as the temperature isn't as high as shocks.

34cSt @ 40 is closer to a 10w than a 15w

 

So the train had standard HD in it and the front was like spungebob square pants, I replaced with HD heavy duty oil. flushed once and filled to correct lever ia mmeasuring height of oil column. No talk of weight on the bottle though. I was going to start heavy and then try thinner oils until I found what I liked. Well I never got past the HD heavy as it stopped the nose dive and made a heap in handling improvement in the front. I may try thinner next time, but only as I trial.

Im in the Ville too Hilly so I am happy on our roads.

20w belray for me

Had mine swapped from the std HD oil to the SE/heavy duty HD stuff at last service. Firms up the front end a bit more and not as much dive. It is definitely an improvement over stock but cant compare to anything else. This is with std forks and springs on a softy custom.

On another note, I also had a lowering kit fitted in the rear and the preload set to rider weight etc which also made a big difference over the stock settings as well.