quote:

ORIGINAL: AAN2705

Wow.

Thank you very much. If you lived close by, I would have invited you over for a BBQ mate. I really appreciate your time to write all of this info. I have summarised up the info and now I am shopping for my oil.
Just one question. You don't have to reply if you not up for writing. I am not sure if my car has a middle diff. what will I be looking for? What does it look like.

Thanks

Once again thanks to all for the info. really appreciate it.
Foxy, I am South African so you would not have got english sausages but boerwors(south african farmstyle sausages) lol.

Thank you for the info.

quote:

ORIGINAL: Foxy

First, the difference between the units...

Here in Europe (and in Japan) we use CST mainly as a measurement for the viscosity of silicone shock and diff oil. It is a fixed unit and so allows standardising. In the US and some other countries, they use wt or 'weight', which is a totally arbitrary unit and can differ (though usually very little) between manufacturers. Since shock oil is so cheap as to not be worth ordering from another country, you should get it at your nearest local hobby store, and use the CST unit, it should be very consistent. The very good oils (Mugen oils for example) are always in CST.

So, how does CST compare to 'weight'? As a general rule of thumb, you add 10% to the CST, then knock the zero off (divide by 10), so 300CST+10%=330/10=33 weight. This is very approximate and as mentioned, due to the arbitrary nature of the weight measurement, it can have a reasonable margin of error.

For off road trucks, you should be looking at CSTs ranging from 200 to 400, 200 will be very soft and 400 will be quite hard. I would recommend 250 or 300 as a starting point with 2 hole shock pistons and go from there (don't forget, the damping characteristics will be affected by the number of holes in the shosk pistons much more dramatically than changes in oil viscosity. 2 holes is the norm, but you could see anything from 1 to 5!)

For on-road cars you should be looking at shocks weights between 350 and 600.

Diff oils are always measuredin CST across the world and you will see numbers from 1000 to 500,000, 1000 being little more viscous than water, and 500,000 being like putty. It is normal in a 3 differential 4wd car (front center rear) to see the oil decreasing in viscosity from front to back (smooth driving style), or the same numbers being used front and center (mid-aggressive style), and also harder in the center than the front for more 'full time 4wd' effect (aggressive driving style).

Increasing the viscosity of the oil in the front differential increases your pull out of a corner under acceleration (allowing the lighter inside wheel to spin less, maintaining more power to the wheel with grip) decreasing has the opposite effect. Increasing viscosity in the center differential will give you much better 4wd traction but reduce turning response. Viscosity of the rear differential will affect how squirelly the rear end is in a very dramatic way. As a general rule never go over 5000cst or the truck will spin with the lightest application of throttle on a loose surface.

As for what settings you should use, that depends on your driving style. If you use an agressive off road driving style attacking and drifting through the corners, you will want a medium viscosity up front, say 5-10k, a medium to heavy middle 7-15k, and as said, always a light rear (1-3k). For 1/10th trucks that only have front and rear, use 5k up front and 1k in the rear. These low values somewhat counter the fact that there is no middle diff at all.

For a smooth technical on-road driving style (this is how I drive, even on off road, as I am primarily an on-road driver and I can't get out of the habit, I also happen to believe this is the fastest way to drive, no matter what the surface), you want heavy up front, 10-20k, medium in the middle, 7-10k, and light in the rear, 1-5k. This requires a style of slowing down to turn then powering smoothly out in order to work best.

On road cars never have center differentials (at least not dedicated racing ones), and for the best results on a high grip track you want a proper one way front diff or a locked front diff if there is no one-way for your car. At least you want very very heavy oil in it if you can't get a spool (tech term for a solid diff), put 50-100k in the front. Same as off road applies to the rear, but to a lesser degree, go for 10-30k.

Hope that helps, you got me on a day I felt like writing.

quote:

ORIGINAL: Foxy
If I were still around I'd take you up on the BBQ offer. God I miss english sausages.

Attachments

Click for fullsize