Do you follow the vehicle manufacturers recommended specs for air pressure?
- Thread starter SilverGs
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JB.
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The former. The latter is mostly irrelevant, except, obviously, you don't want to exceed it. Changing tires makes no difference as long as they're P-metric (like the stock tire) and the size doesn't change.
The equation gets thrown off when switching to an LT tire, which many do. To match the equivalent load carrying capacity in the stock tire, about 12 extra psi is needed in the LT, but as a result, the tire spring rate is not matched to the suspension the same way as before.
JB.
New member
I was reading the question as "are you supposed to".
With a stock or equivalent tire, I'd do similarly to MikeInNH.
scottm
New member
I would think manufacturers would spec a little on the high side for mileage. The tires are stamped with max pressure, not recommended, as they have no idea what rim width or vehicle weight they will end up on.
I go a little higher than what the door sticker says, for better mileage and higher hydroplaning speed and more awesome cornering performance.
I go a little higher than what the door sticker says, for better mileage and higher hydroplaning speed and more awesome cornering performance.
This is exactly what I do for the same reasons. The max rated pressure on the Dunlops I have is 51 psi. I inflated them to 45 psi.
KB084RUNNER
New member
I always go 2 psi over what is on the door sticker.
JB.
New member
Tire manufacturer has no idea what vehicle it's going on (usually). The vehicle engineers spec the tire to match the vehicle.
BlackWorksInc
New member
I run pretty much 36PSI in all my SUV/Truck tires at work, unless its an LT rated vehicle. Its usually the best footprint, comprimise of gas mileage and wear.
By the way... on the LT285/75R17 Nitto TerraGrapplers I have, are you saying I should be running them at 48psi instead of 36? I am just wondering.
By the way... on the LT285/75R17 Nitto TerraGrapplers I have, are you saying I should be running them at 48psi instead of 36? I am just wondering.
bergs
New member
I think you'd be surprised as to how exactly how an OEM chooses a tire and how that tire gets produced.
The short and skinny is that there is usually a contract between the OEM and a given tire mfg of the OEM's choosing. A run of tires are specially made for the OEM by that tire mfg (which are in fact different than the "same" tire you can buy off the shelf) and it all comes together on that one little door jamb sticker along with the suggested tire pressure.
To further my point, consider that my life more or less depends on tire pressures when I'm racing my motorcycle. If I were to blindly use Honda's recommended tire pressures on the swingarm sticker, I'd be off the track and into the weeds in no time.
As I stated already, personally I choose to put my faith in what a tire mfg recommends for pressure since they are the ones who connect my vehicle to the tarmac but to each their own and I respect that.
JB.
New member
No, that's a substantially bigger tire than the stock P265/65/17 so 32psi in the LT285/75/17 is about equivalent to the load capacity of the stock tire at 32psi.
36psi sounds good.
JB.
New member
Not surprised at all and I agree that the OEM tire is not the same as the after market tire of the same name. It can suck for the reputation of the tire maker, but they are the junior partner in that deal.
The only thing I disagree with is what the tire maker recommends. Every one I've ever contacted deferred to the vehicle manufacturers recommendation.
Now if you ask them about racing that's a different application and I wouldn't presume to try to tell you anything about that. :bigok:
Tire pressure has everything to do with weight of vehicle and foot-print of tire. Change either one and you need to change the tire pressure. It has NOTHING to do with how the tire was made.
Running at max tire pressure is sure fire way to reduce tire tread life..and also drastically reduces handling. Running a little over what's recommended will NOT hurt anything.
Running at max tire pressure is sure fire way to reduce tire tread life..and also drastically reduces handling. Running a little over what's recommended will NOT hurt anything.
scottm
New member
When my brother was a product planner for Toyota, they did a lot of performance and mileage tests. One cool thing was running over a glass plate at various speeds wet and dry, and taking high-speed video from underneath. Every manufacturer is different, the Explorer debacle revealed some ugly details about how Ford was deciding on tires and pressures back then.
bergs
New member
The only reason the vehicle mfg spec is used is for solely out of liability. It saves a tire distributor lots of headache in potential lawsuits.
Very easy to have someone say "I crashed my car because he/ she told be to put 42 psi even though <insert vehicle mfg> says 35..."
I respectfully disagree that it has *nothing* to do with how the tire is made. Carcass flex and sidewall strength are part of the equation and not directly related to a vehicle's weight.
I'll agree with that...INDIRECTLY though. A tire manufacturer designs the tire to have a specific contact patch. The contact patch is the amount of tire that the manufacturer determines the optimum size for tire performance. That contact patch along with weight of vehicle is the ONLY determining factor to determine what the tire pressure is. What happens when you under-inflate a tire the sidewall will flex...and this will cause a larger foot print.
HowStuffWorks "How do 30 pounds of air in your tires hold up 2 tons of car?"
Fact or Fiction? Tire contact patch and air pressure.
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