Tyre pressure

[Charles]

Hi Guys

I've recently had Set of Image Halibrand replica wheels fitted to my Dax. I run Rover 4.0 litre with a rover box. Wheels are 8"x15" front with 215/60/15 tyres and 10"x15" back with 275/60/15 tyres. Chaps who fitted tyres said pressure should be 30lb all round. Car feels very unstable after 40mph. Can anyone tell me what tyre pressure I should be running with please as my technical knowledge only expand to changing a spark plug!!!!!!!

Thanks in advance

Charles
Dax owner

[robert]

That would be fine for a 5 series BMW but not for a light Cobra. Go for 22 in the front and 23 in the rear.

Robert
Forum Admin

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[wilf]

I bet your car felt as if it was on tippy toes with those kind of pressures - way too high.
A reasonable starting point is 25psi front and rear, then reduce the fronts until you like the way it feels. I used to run 19psi in the fronts of my old Sumo, 21 rear. I run the Crendon at 23 rear, 20 front.
You won't go far wrong a couple of psi either side of these or Robs suggestion. It does seem to me that Cobs like a slightly higher pressure in the rear than the front. Every car will be different, there is no "ideal" pressure - find some that make you feel happy with the way it rides and handles.

Wilf

[Charles]

Thanks Guys. I'll try that. Will keep you posted.

Charles

[nbracken]

Charles, if your car still feels twitchy after you have dropped the tyre pressures, you may want to check the castor angle on the front uprights. If you have too little castor this will also make the car feel unstable.

[Charles]

Thanks Nigel. I'll hopefully be ok with tyre perssure alone, but failing that i shall try your suggestion.

best wishes
Charles

Charles,
here is a thread from Club Cobra - one run by our American Cousins.
Some interesting stuff regarding contact patches, temperatures and other tyre pressure related stuff.


http://65.200.22.105/forums/showthre...=tire+pressure

Cheers

Jack