Just got my "made in china" American Racing wheels and Firestone Indy 500 tires.  FYI; the 3.79" (or -18mm) backspacing seems perfect bolt-on; good clearance with the suspension; maybe 3/4" and a hair over the caliper from the outside perspective.

Now; about tire pressure; my 74 sticker says 20psi front and rear.  The manuals I have (Chilton, Haynes, Service Manual) says "look at the sticker or refer to the tire manufacturer".  Well, the tire manufacturer says "refer to the car sticker...".

Is it just me or 20 is too low?  I have set them at 26 right now and  it looks a little soft.

I can't tell from a driving perspective because ... Surprise!  my battery was dead.  Currently charging; so first ride around the block in 2 years is scheduled for tomorrow morning (can you tell I won't sleep tonight?).

Steph.

I keep mine at close to the max pressure on the tire sidewall. I have my Firehawks set at 38 PSI of Nitrogen. At 20 PSI my car ( a 79 ) would be too bouncy and not handle as well.

Hi Steph, 
     My Indy 500s are about 5 months old.  The Firestone tech that put them on said 32-34psi however 44 psi max is the fine print on the tires.  It gets very hot here in the desert. Road temps have to be above 120+ degrees when the air temp is 108.  I tried 38 psi but that did not feel right.  I dropped to 32 and have been happy with performance. I may increase it to 38 psi for the winter months.
  kwoody2010-09-24 18:40:27

The tire pressures listed on the placard are what the car was designed for. My '74 also says 20 psi, and that's what I run them at, unless I'm on the road, with a load. I will then pump them up to 28psi...no more. More air makes the car twitchy in the twisties, and it rides much rougher.....I don't like that.
Putting too much more air in them than the factory recommends will alter the handling, and may make the vehicle unstable at certain speeds, if you're running thru the mountains, or on a track.
The listings on the tire sidewalls are normally for the maximum pressure recommended at maximum rated load of the vehicle.

I don't think 26psi is too low, Stephane, especially on a big block car.

I have Firestone GT II on my 81 vette.  Placard on door says 30 psi.  Thats what I use!! dskopp2010-09-24 20:02:26

Thanks all.  I had the feeling there was no one size fits all!  I'll go around the block at 26 (low speed) and most likely take some out (maybe 22 or even the recommended 20) after.  Looking at it again; it doesn't seems so bad.

btw Dan (and no big deal; happens 9 times out of 10); it's Stephane (with no "i").  You could say it's french for "Steven" or "Stephen" or even "Stephan".  I even had a Walmart "associate" refusing my credit card once; saying that I was not allowed to use my girlfriend's card!  Upon showing my driver's licence w/picture; she realized I was not a "Stephanie".



Steph.

I've put a a lot of miles on mine @ 20-26 psi...both fully loaded, and just criuzin. I have not seen any issues with tire wear, or any handling problems. Some folks just don't like the 20 psi stuff, since most of us have have been raised to believe that the "proper"inflation for (car)tires should be 32 psi...
It just ain't so, in a lot of cases. Even the Cad SLS Mama drives has the pressures listed at 28psi...
Use what is listed on the sticker, and don't venture too far from it, and all will be fine.

I put mine at 30 psi..my thought was that this car came with bias ply tires and a lot smaller than what I have on it now. I think my owners manual shows 17 psi..I look for bad tire wear and also how it handles..plus a car that sits a lot like years or even months should have max tire pressure in them so they don't get flat spots..
Rich

Anything over 30 is probably way to much.