Chassis set up etc.

[Sam McDowell]

I just had my first track day in my GTD. Great fun. I learned a lot and have several questions.
My instructor said the rear end felt loose, which brings up questions about shocks etc,
What kind of coilover shocks are on there? I cannot find a name. The car was factory built in 1990. How do I service/adjust them? They have air valves at the base.
The sway bar appears small for the weight in the rear. What should the diameter of the bar be & how do you adjust it?
How do you adjust the toe in at the rear?
That's enough for now.
The NASA people are a great bunch. I will do many more events with them.
Sam

 

[Jon Briggs]

Is that NASA as in Apollo 11? Didn't know they branched out into track days.

And you might find a lot more answers to you questions here: GTD 40 Car Club Forum - GT40s.com

 

[Ian Anderson]

Sam

First questionis what tyres and pressures were you running?

Ian

 

[DARREN]

Shocks with air valves in will be Gas Mono type, it's critical that the gas pressure is correct and it needs to be around 14 bar. The shocks won't function at all well if the gas pressure is low. You'll need a special charging head to re-gas them as a normal tyres type will not work properly. The gas volume is so low that any loss of air when you remove the lance will significantly reduce the gas pressure. Penske shocks in the US sell a charging head that allows you to maintain gas pressure while you close the valve in the shock.

If the rear is loose (over steer) it's likely to be the shocks not working well, the springs/tyres or sway bar (or combination) being too stiff, or perhaps more likely toe out on the rear wheels and or toe out bump steer at the rear.

Hope that helps.
D.

 

[Sam McDowell]

D, Thanks. I have the build manual from 1990 (when all else fails, read the instructions; man law # 4). It specs front toe in at 1.6-3.2 mm and the rear at 0-1.6 overall. It says the rear is done by shims on either side of the inner mountings of top links & bottom reverse A arms....
14 bar, hmm, I think I can convert that. Does it need to be nitrogen or will compressed air do?
The tires are Dunlop 205/60R15 & 255/60R15 G/T Qualifiers at 32 psi.
By the way my weekend ended early due a blown head gasket. They are Motorsports heads. Any suggestions on a better gasket for the repair?
Sam

 

[DARREN]

Hi Sam,

Nitrogen is best but dry compressed air will be OK too. 14.5 psi = 1 bar.

D.