Shock oil for 1997 YZ 250

The Showa ABS pistons are a much better/effective deal then playing with oil wt. Still, it is something you can do, and I typically use a 15wt in outer chamber and 5 wt in cartridge on my set ups for those that don't opt for the ABS pistons.

Shocknut said:

The Showa ABS pistons are a much better/effective deal then playing with oil wt. Still, it is something you can do, and I typically use a 15wt in outer chamber and 5 wt in cartridge on my set ups for those that don't opt for the ABS pistons.

Click to expand...

Is this ABS piston another version of the botom out aluminum ring at the bottom of the inner chamber? Or is it the plastic insert to mimic a higher oil volume?

terry hay said:

Given that the inner chamber affects damping and the outer chamber affects airspring effect and bottom out cone, it is feasable to run different oil weights. You can actually tune the effectiveness of your bottom out system by varying your oil weight in the outer chamber without affecting the air spring. Pretty cool huh!
Terry

Click to expand...

so let me get this straight- on the outside chamber of the TC fork, the type of oil can also have an effect on bottoming as well as the airgap????

ie. if you run a heavier oil at the same height as a thinner oil, it would be less likely to bottom?????

Because the bottom out cone has a close tolerance with the bottom out piston and the fact that oil wont compress, we see a rapid reduction in fork velocity when the piston enters the B/O cone. The oil in the cone is displaced by the piston and has to escape under pressure. The thicker the oil, the greater the pressure, the greater the bottoming resistance. If you maintain the same volume you won't affect the air spring no matter what weight you use. Mind you the thicker the oil, the more abrupt the transition from on the bottom out, to off it. Don't get carried away.
Shocknut, is the ABS piston the same as an extended bottom out cone?
Terry

Terry,
the ABS piston is probably what you know as oil lock piston located on the end of the Showa cartridge. I have cones in my YZ and I've tried tuning with different diamter oil locks and they seem to have a far greater impact then simple oil viscosity changes.

Mind you I'm not refuting the hydrualic principle, my opinion is based solely on personal experience.