Correct tire pressure

[AUSMHLY]

For all you tire guys, how do you determine what the correct tire pressure is for the type of tire your running on your car.

Example, my 1964 3000 Mk III drivers handbook mentions Radial-ply tyres (Dunlop SP41) on page 30.

On page 4, Tyres:
Size, 5.90 - 15 tubed.
Front, 20 lb. /sq. in
Rear, 25 lb. /sq. in
Maximum performance speeds:
increase all pressure by 5 lb./sq.in

I'm running Michelin ZX, 175 R 15.
Sidewall says:
Max Load 650 Kg 1433 lbs
Max Press 340 Kp 50 psi

How do I determine the psi for front and back.

Yesterday, someone told me he runs what the tire says on the sidewall. He told me he would run both the front and back at 50 psi.

Also note that the Michelin ZX says tubeless. I'm running tubes. So, does running a tube affect the psi decision.

Your thoughts?

 

[Healeysince59]

I run 32 psi all around. The 50 psi is required to achieve the 1435 lbs max load and is way too high IMHO. The 20 psi/25 psi were for the old bias ply tires and even then they recommended another 5 psi for "Maximum performance speeds".

Marv J

 

[Keoke]

Good combination: Can beused even on "B" roads

Front, 25 lb. /sq. in
Rear, 30 lb. /sq. in

Yesterday, someone told me he runs what the tire says on the sidewall. He told me he would run both the front and back at 50 psi
Irish Whispers.---Keoke

 

[Cottontop]

I've got tubes in mine and run about 30# all around.
30# seems to give the best combination of ride and grip.

Tim

 

[Randy Harris]

185/70 tires. Been running 32 lbs on all corners for years.
Randy

 

[HEALEYJAG]

32 on all fours for 30 years...I can tell when the pressure drops in the tires..doesn't have the same feel

Pete

 

[HealeyRick]

Yesterday, someone told me he runs what the tire says on the sidewall. He told me he would run both the front and back at 50 psi.


Your thoughts?

My thought would be not to take any of this guy's mechanical advice!

 

[TimK]

If your car and cargo weigh 5700 lbs., use the max pressure, otherwise use 30 lbs in rear and 25 lbs. in front like Keoke says. The higher pressure in the rear will help offset the inherent understeer with the nose heavy Healey and give a more neutral performance when cornering.

 

[Johnny]

I've been running 30 in the rear and 28 in front, seems to be about right, as others have said. I've been told if you autocross the car you should inflate the tires to 40 all around.