Filebase article using motor oil in forks...

The article says to use 10w30 to prevent foaming and maintain viscosity in all temperatures so damping is unaffected. something to that effect. Has anyone ever done this? DO the additives in motor oil present any deterioration problems for the fork seals? And finally, can a heavy guy use 20 w 50 to replace 20w fork oil? This is an interesting concept to me, because I ride in temperatures that really get cold (below 20 f) and really hot (above 100f). Thanks for any replies.

I'm also curious about this since I just can't seem to find a heavy enough fork oil... Any opinions?

If you have any brass or bronze parts in the forks it might be a good idea to use a sulphur free oil. I read that this is necessary in transmissions with bronze bushings because the sulphur attacks the bronze. Was not keen to verify what I had read so no first hand knowledge as to whether this is factual info.

My FT500 calls for ATF. I'm putting new seals in sometime in the next couple of months and will be resizing the damping ports. I read that the stock damping is very light and my ride confirms this. I also read that the fix is to weld up the damping ports and drill them out a bit smaller than OEM spec.

Don't know if light damping is why you want thicker oil, but if it is, modding the ports may be an option.

-Duck

Since I'm planning on tearing down my forks again this weekend I was wondering if there's any articles anywhere about modifying the damping rods or closing up the damping ports so these forks work more effectively. Mine tend to dive almost to the point of bottoming out when braking hard.

I always ran straight 30w in all of my conventional-fork motocycles. ATF was always too thin.

20w-50 might be a bit much though...
The trick with for oil, is to use a little more than the recomended ammount to stiffen them up.

I think I'll stick with the 20w fork oil until next year, at least. It's worked well in the summer..we'll see how it is in sub 30 temps.

When I rebuilt my forks this spring with new seals I used the recommended weight and qty in cc's of fork oil. But I did not measure the oil height from the top of the fork.

When I hit a bump my forks feel like they rebound too fast, extending all the way out and making a clunking sound. Is that an indication of too thin oil?

ive allways run good 20/50 in forks,when i was younger i used to like to see how far i could carry the frontend so i used heavier oil to help stiffen the landing a little.i never had any problems with the frontends,it was the occasional backflip that i really hated!my dad allways told me it was the excessive horsepower to brain cell ratio thatl get ya in trouble! happy wrenching

20w50...that's what I wanted to hear. I guess as it heats up a little it will get a little thicker, right? If you used it for wheelies, I guess it should be good for bumpy roads..that's what's out here...big old heaved up areas that really can bottom you out at the speed you need to keep from being run over.

No, that's backwards. As the oil heats up it becomes thinner, not thicker.

Multi viscosity oils work like this: Polymers are added to a light base(5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

www.micapeak.com/info/oiled.html

guitargeek wrote:

No, that's backwards. As the oil heats up it becomes thinner, not thicker.

???????????? Not the way I learned.

I do not question that if you heat single weight oil it will get thinner. However, the discussion was about multi weight oil. It is designed to be at the lower viscosity when cold and higher viscosity when hot.

Post edited by: hwms, at: 2005/11/24 22:09

Post edited by: hwms, at: 2005/11/24 22:19