Has anyone used 10w fork oil and if so, did it make any difference?
I picked up 10w by mistake and don't feel like driving all the way into town to change it to 5w.
I am putting some spacers in the forks to see if I can increase the preload a bit. I am in the process of sticking in some .46 springs when I can afford them.
Any thoughts?

 

I think you may not need much oil if you pour the existing oil out and save it. Do you have to drain the oil or just remover the springs drop in a spacer and replace the springs? the spacers are going to displace some oil. So if you you add a little 10w to a lot of 5w you would have something like 5.1w

Thats my thoughts

 

Thanks, I decided to scrap the spacer idea after reading this

http://en.wikipedia.org/wiki/Suspension_(motorcycle)

and just put in the heavier oil, which I think will do what I want for now, till I can order the .46's, or .48's. I am carrying a fair shwack more weight on the front end with the larger fuel tank, and probably a tank bag.

 

You'll hardly notice the difference. If you do, it will be for the better.

Ride on
Brewster

 

Thanks

 

The difference between 5W and 10W in a suspension system is significant. In motor oils not as much, totally different application and criteria when it comes to "oil weight" obviously.

When rebuilding shocks/forks, prior to putting the springs back in, one can feel the difference, easily measure and visually see the difference between 5 and 10W from hand pressure alone or a very modest amount of weight compressing the fork and timing how long it takes for it to fully compress.

Then throw in weight of bike + rider + speed + varied terrain and the difference can range from barely noticeable to WTF! ... a lot of variables, suspension component manufacturer, factory set up, riding conditions, spring rate, oil weight, valving etc.

Thinner oil

• More responsive to sharp edged higher speed impacts
• Decreased damping on longer duration slower speed impacts

Thicker oil

• Less responsive to sharp higher speed impacts
  thick oil can't be forced through damping valves quick enough and the suspension "hydraulic locks" = essentially becomes rigid
• Increased damping on longer duration slower speed impacts

One the biggest misconceptions/mistakes people make is using oil weight + damping adjustments to compensate for suspension bottoming out or other problems that originate from incorrect spring rates.

 

Brewster, I respect your frequent comments and opinions on the forum here, but are you sure about the lack of difference in this case? While I haven't done it on my KLX, I've tried going between 3 levels of viscosity in some other forks in the past, and I thought the difference was huge. In fact I think most folks will notice the jump from 5wt to 7.5wt in most instances. Going to 10wt is a whole other step. Using oil to offset a spring issue isn't usually a good idea, but I realize the final plan is to install stiffer springs. The fork and shock on the KLX already had a noticeable compression spike IMO with 5wt oil. 10wt would seem to aggravate that issue tremendously. The OEM KLX fork main piston won't flow enough 5wt oil in some conditions resulting in a noticeable spike.

Obviously this is just speculation on my part, as I haven't tried 10wt in the KLX fork, but I wonder how the fork will react on really fast bumps or on bigger square-edged hits.

 

I can see what you guys mean. I will give the higher viscosity oil a try. I did notice a difference when when putting them back together. I found that bottoming was the issue so I will see if this helps or hurts. I can see that the valving is probably not going to flow 10wt as easily as 5 and that I may have a problem on sharp fast hits.
Thanks for your help

 

If the KLX300 had some real valving in the stock forks, I'd agree with ya. But, 3 shims and a light spring isn't what I'd call adequate valving. Plus, if the original poster is going to .46 springs, he's carrying some weight.

Ride on
Brewster

 

The stock spring is already preloaded enough for the bike weight, why it's longer than the lighter R bikes spring. Wouldn't try and shim it anymore. Even with the correct spring in them they really need better valving, IMO. Tried many oil viscosity and spring combos in mine and have pretty much concluded it needs more work (or live with it).