Tire pressure

Don't leave it there. Raise it to 50. Imagine the possibilities of posting amazing mpg's!

 

I think it's typical for new cars to be shipped with significantly higher pressure than the design pressure. I assume it's to prevent flat-spotting the tires during the delivery process, but I don't really know. There was a bunch of people encountering the same issue (higher than door placard pressure) with 3rd gen Miata's so I suspect it's an industry thing.

2 psi makes a noticeable difference in my Miata. Higher pressure gives noticeably lower grip but the break-away tends to be less abrupt and turn-in is sharper. Most of us probably won't be running that close to the edge in our trucks. I've read that over-inflated tires are more susceptible to road damage, but I'm not sure by what mechanism. Higher inflation pressure will increase the speed at which hydroplaning occurs (that's a good thing).

When Toyota is adding road squeegees, gap seals, tailgate spoilers, and vortex generators to gain every bit of mileage they can, it seems reasonable that if increasing tire pressure had a useful benefit in that department they would go for it. It's certainly cheaper to change the number printed on the door frame than it is to add dual mode fuel injection and extra gears to the transmission. So there must be something to the tire pressure they chose.

My guess is vehicle stability, ride comfort, and maybe braking distance, but I'm not Mike Sweers.

 

This.....^^^^^^

 

Think of tires as a reinforced balloon. You have an optimum volume for the tire and over inflation can stretch the tire beyond said volume. A higher starting pressure increases the likelihood of having enough energy to push the tire to that breaking point. Hitting something as simple as a pot hole will lead to a spike in pressure that can cause a blow out. Hitting a sharp object is more likely to slice the tire because the tire cannot deform as much to prevent a puncture.

As for inflation, there's way too many variables at play to say only 30 psi should be run. Type of tire used, how loaded down is the vehicle, what's the ambient temperature, so on and so forth. Lower pressure increase tire temps due to increased contact patch with the ground. They also increase likelihood of a blowout in a corner due to less sidewall support. It also has increased wear due to improper ride.

Higher pressure increases susceptibility to damage from road hazards. It also tends to cause uneven wear down the middle of the tire which if unchecked causes handling issues and ride quality problems.

 

Yes, there is science behind picking a psi..... do you think they just say" OK, pick any number between 1 and 100"? Seriously....

 

I will check with my dealer today to see what they say. Personally, I Just want to know WHY they over inflate beyond spec. It is more of me being curious than anything else.

 

Way to change what I said. Sure it's science, soft science that includes subjective aspects like comfort vs harsh ride.

Seriously..... pick a number between 1 and 100? Seriously?

 

Here's some fun reading...if you're REALLY board. I think over inflating tires is equivalent to the fat guy munching on his cheese burger & fries, concerned about dying from a lightening strike instead of a heart attack.

Most of us are not hyper milers and I'd guess for most of us changing our driving habits would net the largest gains in MPG vs. worrying about max PSIG. If that's a concern...

https://www.fueleconomy.gov/feg/maintain.jsp

I can't vouch for how well controlled PMs study is/was but, it's real world.

http://www.popularmechanics.com/cars/a940/4199963/

 

Is everyone here in this discussion running stock tires? If not, please educate me on how the door sticker is still valid for different tires. Most of us are running some type of larger, LT, AT equipment.

I'm running BFG KO2's in 265/70/17. As a relative novice, I need the information for that tire.

Thanks,

G.

 

On my second set of stock/OEM tires here...

 

Then, the door sticker says it all for you.

G.

 

Yes, the tires are over-inflated for the carrier ride to their destination. Yes, dealers and tire shops over-inflate and usually run 35 psi because thats all they can remember. Yes, Worthywads is a complete idiot!

The placard in the door sill represents what pressure to run on the given recommended tires according to that vehicles GVWR. Tires will heat up and pressure will raise 2-4 psi average. This is part of the GVWR figure.

If you are always going to run a full load in the bed then you will need to increase the tire pressure a couple of PSI otherwise run whats in the door. If you get drastically different tires then do some homework to run the correct pressure.

 

Like Tom Brady's football

 

Hey G,
Regardless of size, a tire's handling and durability is directly tied to using the appropriate inflation pressure for the vehicle. With a variety of wheel and tire choices for new vehicles, it's essential to rely on the vehicle manufacturer to specify the appropriate inflation pressure for the tires. Using the vehicle's weight capacity for each axle and other considerations, the manufacturer can best calculate the psi needed to ensure the tire handles and performs well.

All too often, many drivers and mechanics assume the maximum tire pressure listed on the tire's sidewall is what is recommended for proper inflation. However, that number represents the maximum pressure that's safely allowed, but is likely higher than what is recommended by the vehicle manufacturer.

Tire pressure can vary on several things, including:

• Changes in temperature
• Changes in altitude
• Time

For best results, look for a placard on the inside of the driver's door or a similar chart in the owner's manual to determine the recommended psi for your application. - See more at: http://blog.tirerack.com/blog/docs-...ressure-for-my-new-tires#sthash.bgAu68rP.dpuf

 

Sam, are my BFG KO2's "Drastically" different from the OEM's. This stuff is pretty confusing to me. I was probably running my Wrangler's way too high on my 06, but got great mileage and wear on them. I just want to educate myself to "get it right".

Thanks,

G.

 

No, they are not drastically different than OEM's. Funny as the wife has a Wrangler and I had one a couple years ago. I had Cooper 33's on it and ran door sill pressure. The Sahara's come with 18" rims and 32's.
I would run 30 which when heated will be 32-35 hot.

 

What is your placard recommended psi?
Size and load rating of your stock tire? (Example: P/265/70/16/112T; 112 is the load rating)

 

I'm assuming your truck came with Firestone Destination LE2 P/245/75/16/109...
Your stock tires have a load rating of 109 and I assume your placard recommended tire pressure is 29 psi.
This gives you a load requirement of 2,072 lbs. This is an inflated figure mandated for P tires on light truck/suv application; by a factor of 1.1(110%)
You have an adjusted load requirement of 1,884 lbs.



So now you have LT/265/70/17 and a load requirement of 1,884 lbs. It doesn't matter if it's a Load C, D, or E.
35 psi would give you 1,890 lbs.

If it happened to fall in between or off the chart, you can extrapolate; 1psi=so many lbs.