Falcon LS

Thought this would make an interesting topic. What's your opinion?

videcormeum

Always the tire's recommended pressure.

Car manufacturers often list a lower-than-optimal pressure to increase ride comfort (as in my Nissan).

M.

Falcon LS

Same with my truck...manufacturer recommends 32 PSI, tire manufactuer recommends 35...and that's what I keep them at.

mmarshall

There are rare exceptions like the Ford-Firestone fiasco a couple of years ago, but in most cases the vehicle manufacturer's PSI recommendation is best. It is not just a case of wanting car owners to have the smoothest possible ride. This figure...sometimes separate PSI's for front ant and rear, sometimes the same....appears on the driver's door jamb, in the glovebox, or in the owners' manual. There are MANY different factors that go into this recommended PSI......things such as the tire speed rating, type and firmness of suspension, optimal braking distances, amount of load the vehicle is designed to carry, traction on slippery surfaces, quickness of steering response, tracking stability, ability of the tire to resist heat, resistance to pothole damage, type of wheel the tire is mounted on, RIDE COMFORT...yes, that is one of them.......projected tread life, front-seat vs. back seat rated loads, etc....and many other factors. As you can see, it is NOT a simple figure to come up with. Auto Engineers not only do a lot of math figuring out the best possible PSI but also even use computers to come up with a figure.
Tire PSI should be checked when the tires are cold ( having sat at least 3 hours or driven less than one mile). They heat up fast after that...and heat increases pressure. Every 10 degrees of air temperature means 1 PSI of tire pressure....gotta check them especially when temperatures cool off quickly in the fall.

If, for any reason, you choose not to use the manufacturer's PSI and run higher pressure, DO NOT exceed the figure that is stamped into the tire sidewall. That is the highest ALLOWABLE pressure, not the highest
recommended pressure. That is the highest COLD pressure that the tire can safely handle without a significant risk of failure. Exceeding this PSI will not only give an extremely harsh ride but risk a blowout or tread and belt separation as well.

MikeP

Just wondering where you would find the tire manufacturers' inflation recommendations? My '04 LS430 with 17" wheels has Dunlop tires, so I looked on Dunlop's website for information. Their suggestion was to follow the car manufacturers' recommended tire inflation. I find 32psi as per Lexus, a little too soft for my tastes so I have been using 35psi. That;s not a major difference, but I find cornering response better and I'm hoping for a little better tire wear and fuel ecconomy.

Mike

mmarshall

I think you at least partially answered your own question...even the tire companies themselves now often admit that for overall use, the auto manufacturer's PSI rating is best.

However, that is not ALWAYS the case.....as the notorous Ford Explore-Firestone fiasco a couple of years ago proved. Ford deserved at least part of the blame for that by recommending, in response to owner complaints about the Explorer's ride, PSI's that were clearly too low for those Wrangler SUV tires when the tires were under heavy loads, at higher speeds, and at high temperatures. Firestone, even though it recommended higher PSI's than Ford, gets part of the blame for not designing enough of a safety margin into those tires....other competing tires did not fail at such a high rate under the same conditions. And, last, even though the media did not hit much on this, the PUBLIC deserves part of the blame, too, for not regularly checking their tire pressure and than driving their Explorers too heavily loaded at too high speeds at road temperatures that were too high...most of the Exporer tire failures happened in summer on very hot road temperatures in the Sun Belt states from FL to CA.

NeverSatisfied

I follow the PSI # on the tire, but fill it 2 PSI less.

Vladi

I do have one question that I always wanted to ask.

If you have custom wheels (let's say 20s) will the tire pressure monitor in a car work properly or not?

TopSCecreT

me too

Gojirra99

Yes it should work with the tire pressure sensors transferred to the custom wheels. Tire pressure sensors are usually placed in the valve stems(if those on the aftermarket wheels can accomodate them), or they can be banded by straps around the circumference of the wheels. I have the former set-up for my SC430 & the latter for my G35c.

Falcon LS

That's a lot of interesting and nice info! Thanks a lot!

chuckb

I run 32-33 cold for comfort

Ice350

iTrader: (1)

32 psi is definitely not for performance tires. That is way too low and you'll have excessive tire wear. I learned of this before the tire shops. I remember arguing with wheel/tire shop guys 15 years ago on the issue. They were treating high performance tires the same way they do for regular titres. Now they seem to understand. I wasn't a tire tech but they weren't experienced with the product like I was. Now for what I run. On my ES300 with H-rated 235-45-17 tires, I run 34 psi in the summer and 36 when it's cool. On the other car with z-rated lower profile tires, I run 38 when it's hot outside and 40 when it's cool.

mmarshall

38-40 PSI might give you the handling you want but there are trade-offs. You'll have a pretty harsh ride, bumps will pound the suspension and the car's structure resulting in squeaks and rattles, and it can make the car skittish in a bumpy turn. I'm not necessarily saying this WILL happen to your car, but this is often what happens with overly hard tires. Also, if they have TOO much PSI, the center of the tread will bulge out and you will only have the center of the tire's contact patch....the sides will not touch the road at all......and that will actually degrade braking, handling, and hydroplaning resistance.
But......if you're happy with the car at this PSI, fine.

Ice350

iTrader: (1)

The manufacturers specs listed on the side of the tire says max is 45 psi. I'm well below that. Plus, the fat set up gives enough cushion to compensate for the stiffness. Yes, I'm happy with this setting...I've used it for many years.