best tire pressure for radials

[Gold Bird]

I tried to do a search today about this but could not find it. Just wondering what a good tire pressure is for radials on our birds. Mine are from Diamond back and they said it ranges from 32 to 40 depending on the car. I believe they are 215s on stock 14 inch wheels. Had the car out for the first time this past weekend but now its time to go back in the garage, the joy of Michigan weather!

[Anders]

Very good question,
As I have ordered Coker P215/75R14 tires, I vent into there web and mailed my question to them. As soon as I got an answer, I put it up here.
Try to mail Diamond Back and see what they say.

[Guest]

I'd say at least 32 Ya might want to add after you drive it and see what she feels like.

[Gold Bird]

After sitting all winter, they had only 25 in each tire, put them all at 35 and seems ok, still has a nice ride but a little more responsive. DB tires was pretty iffy on what was best.

[Dakota Boy]

35 psi has been the "standard" for as long as I've been driving cars (1985 or so!)

[DKheld]

Just my opinion - there are a ton of variables. Some of it will depend on whether you want to inflate for tire wear or for a smooth ride, types of road (curvy or straight) etc.

For instance my truck calls for 36 psi on the door guide and apparently the previous owner followed that guide - great ride but when I bought it the tires were completely worn out on the edges @ 23K. Alignment checked perfect so they were obviously under inflated as far as tire wear. The tire calls for 44 psi. Replaced with a new set of the same type. I keep 42 in the rear and 44 in the front and after 25k you can hardly tell them from new - only rotated twice.

On my truck I keep slightly more in the front to compensate for the extra weight on the tires up front. Those pressures were from trial and error, what the tire called for and observations like when puling off the interstate to a gas station I can see whether the dust covers all the tire or if the edges are not touching (over inflated) etc.

I know you can't go by the door guide on the Tbird. It's a heavy car so my opinion would be to inflate on the high side - 35 psi sounds right on. That's what I have in mine and I am running the DB's also. Probably needs a little more in the front for better tire wear because of the weight and I try not to go more than 4-5 psi difference front to back.

You can probably find the pressure recommended for the DB tires on the inside of the tire since the WW covers up the lettering on the outside.

Could be completely wrong but that's how I do it - mostly for tire wear.

Eric
registry 5347

[Jimz Bird]

I have been digging around as of late looking for the same and alignment specs on the older Birds with Radials and found this a couple of days ago. Kinda the opposite of the "dust" technique mentioned by Eric.

"Air the tires up to about 40lbs. put 100lb bag of sand in the passenger seat. Water down a strip on your driveway and then drive the car through the water and note the tread pattern on the drive pavement. Then air down the tires 2-3 lbs and drive through again. Keeping doing this until you see the full contact patch of the tire. That's the ideal air pressure for your vehicle.
At first you'll probably get a little bit of the shoulder, but you want to end up with a full width pattern."

If you haven't read the article posted by Doug in the
"60 Bird needs alignment." thread here is a link to it.

http://www.americanheritage.com/articles/magazine/it/2001/4/2001_4_28.shtml

Thanks for that Doug! WELL worth the read.

[Dakota Boy]

Can a person use thier wife instead of the 100 lb. bag of sand?

[Jimz Bird]

Yea, but I think the standard response is:
"Your mileage may vary" depending on the size of "bag" you use.

[DKheld]

I had not seen that tire article - thanks for the link. When I first went to radials from bias plys I still had the drum brakes, standard suspension and bias tire alignment settings. No other changes were made and the car drove 1000 times better. I had to change the alignment when I went to the Granada spindles and disc's. As good as the car drove before I made the spindle change I would stay with the standard alignment settings? unless the tires wear badly. Of course the front end had all new bushing etc so it was as close to new as you could get.

As for using your wife that would probably work however I would recommend the use of 3 girls (one in each seat position) just so you would be sure to have all 4 tires balanced for even tire wear. ( ya' think the wife would go for that excuse for having 3 girls in the car?)

[Anders]

Very good question,
As I have ordered Coker P215/75R14 tires, I vent into there web and mailed my question to them. As soon as I got an answer, I put it up here.
Try to mail Diamond Back and see what they say.

I actually got the answer from Coker within a few hours, but forgot to put it up here.
"I recommend 35 psi on the p215/75r14 tires"

[Gold Bird]

Thanks to all for the answer on the tires, 35 seems fine. Will post some pictures as soon as the weather gets better here in Michigan of the new paint job on the car, really turned out nice!

[dgs]

The markings on the tire side wall are not recommendations, they are the max pressure for that tire. Newer cars have the manufacturer's recommendations on the driver's door jamb or in the glove box. These are what they felt was best for ride, handling, tire wear and MPG. Some will say that they are just trying to sell you a car, so they'll make all kinds of compromises to make a good first impression. I suppose there's some truth to that, but on the other hand, they are degree'd chassis engineers with years of experience and most of us aren't, so I tend to defer to them.

Of course, with our cars, we're running completely different tires than were available then, so all bets are off. The water test mentioned above sounds like as good a measurement as any.