Tire pressure and ride quality

Status
Not open for further replies.
Personally, I use the recommended tire pressure from the manufacturer as the lowest I'd consider using. On both of our vehicles I inflate about 3-4 psi higher to get better gas mileage without sacrificing ride quality very much.
 
Problem with some cars is that hihger inflation pressure tends to throw the steering out of balance and your vehicle travels all over the road, this is particularly a problem in heavy SUVs, at least for front tire, keep the recommended pressure.
 
To add to the history of the Firestone/Explorer debacle... I believe the main reason Ford went to 26 psi was to lower the center of gravity for their Explorer, to gain points on NHTSA's rollover ratings and reduce pressure from the public over SUV rollovers. The rollover test was static in nature.

Knowing this, I have no reservations with second-guessing the manufacturer's tire inflation recommendations. Sometimes the engineering behind the numbers is political and not technical.
 
I rented an 06 Camry in Atlanta last Christmas and drove it to central Florida. I noticed a *slightly* choppy ride and steering was kinda vague, even for a Camry. I didn't get too concerned, and figured it had already hurdled some curbs and train tracks during its career as a rental car.

I got to my destination and checked air pressure. Enterprise apparently thought 43 lbs was prudent for this car. I drained them to 40 and called it good. If they want their tires to wear on the centers, I guess thats their business...I cashed in on the gas mileage savings.
 
The recommended inflation on the factory placard is just the engineers trying to address the needs of the masses. Alternative tire pressures are okay, but diligent pressure monitoring is required. Always, always, always verify the maximum tire pressure on the sidewall of the tire to ensure that it exceeds the vehicle placard inflation. For example, I see too many people put P-Metric tires on a 3/4 or 1 ton truck. Most of these call for 80 psi in the rear tires on the placard, but the tire's maximum may be as low as 44 psi. I'm sure you can all see the potential dangers here. If you run under the recommendation pressure, be sure that you manually check tire pressures with a quality gauge at least once per week. I would also not run under 30 psi in any automobile/truck tire regardless of what the placard states. Also, if you cart any kind of load (including passegers), get the pressures back up to the spec on the vehicle placard. This is why placards are there . . . there are entirely too many "what-ifs", and the recommendation is a good compromise for a vast majority of end users.

1sttruck, I have always had to run 40 psi (as long as it does not exceed the tires' maximum pressure) for Tauri to wear their tires evenly. I have not really noticed any negative effects so long as the alignment is in spec.
 
Oddball,

First, I want to thank you for bringing up the issue of P metric vs. LT metric tires. You are absolutely on point. LT metric tires carry a much larger load than the same "size" in a P metric. If you use a P metric in place on an LT metric, then the risk of tire failure is exponentially increased.

To make sure that this type of mixing doesn't take place, I ALWAYS use the letters in front of the size. I suggest everyone who reads this adopt that as well.

Unfortunately Tire Rack does not adopt this practice and if you only enter the tire size in their serach engine, it will return both P metric and LT metric tires. One of these days they will get their pants sued off of them, and they'll have to do some reprograming. Why they don't fix it now is beyond me!

(OK, end of rant!!)

On a different subject: It's permissble to inflate all P metric (and Euro metric tires as well) up to 44 psi, even if the sidewall says something below that figure. This is due to a different interpretation of the regulation concerning what must be printed on the sidewall. However, I would not exceed what's on the sidewall if the vaue is 44 psi or higher (for P metric and Euro metric tires.)
 
i could see where you could theoretically overload and kill a tyre as you said "the risk of tire failure is exponentially increased"

if you had a p metric inplace of a lt and then ran it around overloaded.

however my step dads truck had 80,000 miles and something like a 8 years on a set of p metric tyres and that includes towing a 21 foot sailboat + people + extras. he finally replaced the 2 rears because the tread was low.

so i dont think its quite as critical as you make it out to be.
 
As long as you know that the tires are P-Metric instead of the factory specified LT rated tires, and adjust the payload accordingly everything should be fine. My point was that I see two different things happening with this type of situation. First is a tire salesperson sells a P-Metric tire instead of a LT tire because the lower cost of the P-Metric made the sale (or due to ignorance/laziness/insert whatever reason here), and the customer is not aware of the lower performance rating of the P-Metric tires. The second is the kids at Wally World (or other tire shop) going by the vehicle placard and never looking at the tire, and taking a 35 or 44 psi P-Metric tire up to 80+ psi.

The most important thing to remember is that if you want your vehicle to haul what the factory says it can, make sure the replacement tires meet the factory specification. This includes exact tire size, load range, speed rating, and if applicable the UTQG ratings. Any deviation from the specifications may require adjustments to towing and payload capability, and /or driving style.
 
I run 35psi in my Pathfinder. Recommended pressure is 26psi but it feels too wobbly at that pressure.

I run 28psi in my Mazda3. Recommended pressure is 32psi but the traction and wheel hop are terrible at that pressure. I like the ride quality better at 28psi too, since our roads aren't the greatest.
 
quote:

Originally posted by Master ACiD:
....however my step dads truck had 80,000 miles and something like a 8 years on a set of p metric tyres and that includes towing a 21 foot sailboat + people + extras. he finally replaced the 2 rears because the tread was low.

so i dont think its quite as critical as you make it out to be.


If the truck came with P metric tires, and that is what was used, then there isn't a problem. But if the truck came with LT tires and P metric tires were used, then I would say your step dad was very lucky.
 
Colt, I can understand why the ride would be better, smoother at lower tire pressure. But I'm very much with CapriRacer. Tire pressure play a huge role in vehicle safety. A tire expert I know ell who has been with both Goodyear and Firestone/Bridgestone told me that all the investigation/analysis by the manufacturers showed that 26 PSI was too low and the low pressure compromised the integrity of the tires. When you lower the pressure, the tires will wear faster, be more at risk of sidewall damage, and you're likely to get lower MPG. I can't encourage you strongly enough to keep the tires at 35 PSI or higher. We run at 40 PSI on our Honda Accord, which results in a somewhat stiffer ride but the handling is good, tread life is longer and the MPG is higher. Well worth the stiffer feel.
 
I agree with higher psi on tires. Remember, as tires get hot the psi increases. Winter 40 PSI is different than the Summer 40 PSI. Nitrogen is nice in that regard in that it doesn't get as affected by temps.
 
quote:

Originally posted by Nebraskan:
Nitrogen is nice in that regard in that it doesn't get as affected by temps.

We've been all around the nitrogen mulberry bush a few times. For normal street driving nitrogen has no noticeable advantages over normal air.
 
Has anybody ever heard of using chalk to run a line across the width of the tire to determine how a tire will wear(center wear or outer wear)? You need to make sure you drive in a straight line for 'X' distance to check this out.
Is this still a viable way to check how a tire will wear given the air pressure you use?
 
quote:

Originally posted by Cogito:
We've been all around the nitrogen mulberry bush a few times. For normal street driving nitrogen has no noticeable advantages over normal air.

Careful, we aren't allowed to discuss religion on this board.
 
quote:

Originally posted by Mattchou:
Has anybody ever heard of using chalk to run a line across the width of the tire to determine how a tire will wear(center wear or outer wear)? You need to make sure you drive in a straight line for 'X' distance to check this out.
Is this still a viable way to check how a tire will wear given the air pressure you use?


There are some who freqent BITOG that subscribe to the theory, but since most tire wear occurs in the cornering mode, I'm not a fan. I'm afraid that folks will look at the data using the chalk method and underinflate their tires, forgetting that tire durability is dependent on tire pressure.
 
Quote:

"If the truck came with P metric tires, and that is what was used, then there isn't a problem. But if the truck came with LT tires and P metric tires were used, then I would say your step dad was very lucky."

I've had 6 full size half-ton pickups since the mid-70's and put a cumulative hundreds of thousands of miles on them. I usually ran P (passenger) tires on them and never had a problem with P tires. And I did quite a bit of towing and a lot of hauling, including heavy hauling such as logs I hauled home and cut into wood stove firewood. I ran the tires on all types of gravel roads and in the woods and fields.

Now on a 3/4 ton or 1 ton pickup I'd definitely run LT (light truck) tires.
 
If the recommend pressure is 35, you should probably be running about 40 psi. There are many benefits to running slightly high pressure, but only ride comfort by running slightly low. However, there are many disadvantages to underinflation.
 
quote:

Originally posted by DaveInLA:
How accurate are those $30 gauges at Walmart?

I don't know which gauges Wal-Mart sells, but the digital Accutire gauges the Tire Rack sells are supposed to be accurate to within .5 psi. I have one and I really like it.

[ August 24, 2006, 01:50 PM: Message edited by: Go_Hogs_Go ]
 
Consumer Reports once did a study on tire pressure gauges. They found that most of them - even the cheapie pencil types - were within 1 psi of the actual pressure. This is fine by me, especially since tire pressure can change 3-5 psi just from the weather or sitting in the sun.
 
Status
Not open for further replies.
Back
Top