russell_gasper

Hi

I have just finished building my Impulse, and have taken it to the local track. All of the other guys there were taiking about diff oil & tyres etc & completely confused me! I have some questions I am hoping can be answered!

1. What is a 'one way diff' and why and where would you use one?

2. How stiff should the diffs be to turn? Which (front or back) should be stiffer and why?

3. Which tyres are softer 27's or 37's. Should the softer ones go on the back or front?

4. Which shocks should be harder, front or back?

5. My car seems to loose traction at the rear end going into and coming out or corners. What could be the cause?

Sorry for all the questions!

Regards
Russell

Boomer

A one-way lets the front wheels free-wheel when they are not being fed power (coasting). My advice, leave it be for a while until you can handle the car perfectly without one. You lose ALL your brakes with a one-way and the car gains a ton of front steering and usually becomes quite a bit more unforgiving.

This depends on your car. They probably should be fairly stiff. Front should be stiffer than the rear - this makes the car a bit more stable and gives it a touch of understeer which, in turn, makes it easier to drive and less unstable. If your diffs are sealed units (I think they are) try 100,000 wt in the front and 50,000wt in the rear. (only a suggestion)

The tire ratings are a hardness rating, so the lower the number, the softer the tire. As a rule of thumb, always put harder tires on the front than on the rear. It seems to be usual to go about 45 on the front and 40 on the rear - ish. I'm running 45/42 or 40 depending on the track.

Again, harder in the front.

All of the above.

Advice (you can take it or leave it. . . ) go to www.mytsn.com and get a standard setup for the Impulse and stick to it. One can be found here: Serpent Site, Foam Setup - Use this for a while and get a feel for the car.

No problems

InitialD

Russ, you can post your questions on the Impulse at the Serpent Impulse we have at the non hpi forum. It's very active there;

http://www.hpiracing.com/rcforum/sho...&goto=lastpost

To answer your questions, refer below;

1. Please refer here;

http://www.rccaraction.com/articles/oneways.asp

2. If you need lots of steering, front should be less stiff than the rear. Conversely true for an understeer car. Remember, it's all relative. Your driving style will dictate if you like an oversteer or an understeer car. Track style and car setup also dictates this.

3. 27 is softer. Lower the number, the softer the tire. Softer tires usually go at the rear.

4. Like the tires, softer setup for the shocks (i.e. more holes, softer spring and even lower shock oil weights) are used in the rear.

5. The answer would lie in the car setup.

You could post your car setup in the forum above and the guys over there can scrutinise your car setup and give suggestions to improve your car handling.

Is your car the normal Streetspec or the PRO kit?