Tire pressures

[Michael Oritt]

A while back a friend gave me an almost-new set of Hoosier Vintage TD's that fit my Courier (5.00 x 15) and recently I mounted them up for the first time and ran them at the VARAC Vintage Festival at Mosport last weekend.

I was impressed with their performance versus the Dunlops: They warmed up quickly and stuck through a full session, plus they did not slip near as much nor require as much correction to get the car to track. I am sold on them, though I will still need to go back to Dunlops for VSCCA events.

In any case I wonder what pressure I should run them at. I have always run Dunlops at 17/19 psi front/rear but was told by someone to judge whether a pressure is correct by looking for an increase during the event of about 2-3 psi, with a higher growth indicating the the pressure was too much and a lower growth indicating too little. This turned out to be 21/23.

I'd appreciate input from other listers who use TD's both as to what pressures they use and what their thoughts are regarding this method of determining what psi to use.

 

[aeronca65t]

I'd like to know this too.

Right now, I'm running the DOT radials (Toyo 888s) which like about 40 psi (hot). Obviously, the bias tires require much less pressure.

I've been thinking about the TDs for the new car. They're a little cheaper and the wear doesn't look too bad.

 

[John Turney]

My thoughts:

Do you have a tire temperature meter or an infrared temperature meter? If, after running some laps, you compare the temperature at the center of the tread with the temperature at the edges, you can get an idea if the pressure is right. If the temperature is higher at the center, the pressure's too high and if it's lower the pressure is too low.

 

[red57]

Probably no help at all but....

I run the 5.50x15 TDs on my Healey and I have found that starting with 26 cold they come off the track around 30-31. The wear has always been very even.

Obviously your Courier is lots lighter than the Healey (mine is near stock weight at 2375#) so logically you want less air than I. I remember Hoosier Tire West suggesting I run them a little harder (cold ~28) but I find they grip better where I am at. I have tried them as low as 24 cold but they didn't feel as stable to me so I went back to 26.

In my case I have found no gains by staggering them so I run the same front and rear.

I love these tires but they make the car so easy to control, they sort of suck me into going a bit to fast for them and tend to do a little too much sliding around which eats them up fast - I get 2 to maybe 3 weekends out of a set depending on how much fun I'm having.

With a lighter car like yours, I bet they last a lot better.

Dave

 

[Michael Oritt]

Thanks for the suggestions, guys.

I'm now at Mid-Ohio and asked one of the tech's at Bob Woodward Tire for his input and he said that as a rule the tires should be about 1.3 psi per 100 lbs. of actual weight including driver which for my car is probably 1600-1700 lbs. That works out to around 21-22 psi and since my car does have a bit of rear weight bias I guess the 21/23 figure is pretty close to this recommendation.

 

[dougie]

Michael -

I agree with Dave, I love the TD's for the grip and their price vs. Dunlop's. I have been experimenting with a lower starting pressure of late and found 24 psi for my 2250 lbs big Healey which leave me at 29 psi at the finish which feels great.
They're only good for 2 full weekends with these heavier cars though.

 

[BoyRacer]

I have been running the Hoosier Vintage TDs (5.50x 15) for many years now. They will last me an entire season. I like them. I start around 21 to 23 pounds depending upon the ambient temperature. They grow about 5 pounds during a race. However, my car is a D modified and only weighs around 2000 pounds. I am not as front end heavy as the D production Healeys. That really saves the front tires from serious wear. I usually start with the front tire pressures about 2 pounds greater than the rear.
I have discovered over the years that the tire guys always seem to recommend higher tire pressures. I think there might be a question of liability if they were to recommend lower pressures (which seem to work better in many cases) and something bad should happen.

 

[DrEntropy]

In the dim recesses ISTR that 2~3 pound increase as a bellweather. That would suggest you increase your initial pressures by one PSI each end. John's pyrometer suggestion would be a good confirmation of the "theory". The Elan always "felt" best at 18/21 on most tires I'd fit (Michelins, mostly). Lighter cars like the Courier and Elan get really squirrely REALLY quickly with pressure changes of just a couple pounds. I'd be for keeping 'em 18/20~19/21 to test with. Just seems to me anything higher and you're gonna be on a contact patch th' size of a golf ball. :shocked:

Been led to believe Harbor Freight has a fairly priced pyrometric gizmo, haven't looked tho.

Interested to learn of any results, too.