XRAY - Model racing cars

Thanks.

I've only tried a gear diff in the front for a couple of runs with 500,000 running 13.5t boosted, I might try it again this weekend with different oils.

What is the recommended oil weight/part number for using the gear diff in the rear on asphalt please?

Most racers use 700 (359270) or 1000 CSt (359301).

Thank you David. Out of interest why is the weight seemingly so different between using the diff in the rear or the front, ie 1,000 vs 200,000?

It's because you always want a stable car on power.
The basic principle is that the outside tires can carry more torque than the inside tires, that is the reason why we use oil in the front and rear as without oil the inside and outside wheel will carry exaclty the same torque (limited by the inside wheel).

Now, if the outside wheels carry more torque than the inside wheels on power, the car rotates more, and you have to apply the throttle very smooth. If you apply to much throttle, you will spin. That is the reason why it is a good idea to use a thin oil in the rear: the outside tire will always have some grip potential left to keep the car stable.
In the front the situation is different: a spinning front wheel will not make the car instable, you will only feel more understeer. So it is possible to use harder oil, increasing forward traction out of corners.

That is also the reason why a spool in the front works, while it is no good idea to use it in the rear.


Edit: If you are on a track where you don't use the brakes very much in stock, you can use softer oils like 50000 in the front on asphalt. But it's really a lot about driving style and personal preferance.

Not tried 700cst oil in the rear only 1000cst, so thinner would make the car easier to drive though the corner ?

Thank you David, excellent explanation

Good instructions

http://demonpowerproducts.co.uk/images/ ... Manual.pdf

Is it just me or does the xray diff look just like a spec-R? I guess if it doesn't leak then that's good enough, personally I was hoping for something a bit more

Another advantage is that the inner composite bevel gears 304930 fits also into the diffs of NT1.

so have i and the ones i saw leaked, the nt1 does not have bearings on the outdrives and its world champion.......... enough said!

for indoor carpet in the UK (prima felt) what would be a good starting point with the oil?