Tire Pressure

3756 Views 21 Replies 7 Participants Last post by Jteezer, Mar 3, 2008

Jteezer

Discussion Starter · Feb 25, 2008

This is a first time running into this, door sticker says tire inflation to 26lbs. Tire says 35lbs. I like the more firm ride with more air, but why would Toyota reccommend 26lbs in them. Doesn't that go against everything you hear about tire life, gas mileage etc. having your tires under-inflated? I know the reasoning for off road, but whay the reccomendation for 26lbs? I have inflated them to the full 35 for now... anyone with any thoughts?

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toto

· #2 · Feb 26, 2008 (Edited)

Generally speaking, you don't want to run a tire at whatever the "Maximum Pressure" says on the sidewall. That pressure rating doesn't take any variables into consideration about your vehicle, its weight, or the load you're putting on the tire. Consider the Max Pressure a not-to-exceed number, and not a recommended setting.

That said, a max rating of 35 doesn't sound like much - those can't be very big tires.

I think the rating on the door jamb is a little low on the Tacoma. Toyota's recommended is 29 PSI for the 31x10.5, and the tire has a max of 50 PSI. I run them about 34-36 PSI.

The correct pressure is determined by how well the tire surface meets the road. Overinflated is as bad as underinflated. If the tire is too hard, the center of the tread will wear out faster than the edges, and the sidewall won't have as much flexibility for absorbing pot holes.

Jteezer

Discussion Starter · #3 · Feb 26, 2008

Good insight. The size tire on the truck is stock size, BFG Rugged Trail 265 70 16. Load on the truck is basically the truck itself. I guess I am used to my Ford having 32" BFG Mud Terrains which I ran 50lbs. in and loved the ride along with the life I got from those tires even w/o rotating them often.

TuRDle

· #4 · Feb 26, 2008

I have the same tires on a dub cab as you jteezer and I have been using the door jamb guide. I usually fill to around 28 to compensate for the amount of time that goes by between pressure checks. But its pretty accurate. I still have original tires on an 04 with 47K miles and there will be plenty of tread left after 50K.

hossmaster

· #5 · Feb 26, 2008

running 32psi in my 265/75/16 bfg AT's. got 77k on the set and counting

TuRDle

· #6 · Feb 27, 2008

47,001 47,002, 47,003 47,004 47,005 47,006 47,007.....just wanted to keep ahead of hossmaster in number of posts.

hossmaster

· #7 · Feb 27, 2008

TuRDle said:
47,001 47,002, 47,003 47,004 47,005 47,006 47,007.....just wanted to keep ahead of hossmaster in number of posts.

oh I had 55k on my factory bfg rugged trails and discount tire gave me 8 bucks a tire for them when i got my AT's

chipsndukes

· #8 · Feb 27, 2008

hossmaster said:
running 32psi in my 265/75/16 bfg AT's. got 77k on the set and counting

I just have standard street tires, but either way I go with 32-35PSI cold to ensure long life and fuel efficiency.

My assumption is the factory puts lower tire pressures to ensure better ride quality, most people are probably more sensitive to that, and don't realize or don't care about the penalty they're paying in tire wear and economy.

Chipsndukes

Jteezer

Discussion Starter · #9 · Feb 27, 2008

Well, I am testing the gas mileage theory out now with this last tank and 35lbs in the tires, doesn't really seem like it is making much difference at all... seems like I am still getting about 19 mpg, but will know better in the next day or two.

Hossmaster, you wouldn't happen to have a picture from the rear of your truck with that size tire on it would you?

What size options do I have for this size rim... when you put in factory size not many to choose from, really want BFG Mud Terrains.

TuRDle

· #10 · Feb 27, 2008

chipsndukes said:
I just have standard street tires, but either way I go with 32-35PSI cold to ensure long life and fuel efficiency.

My assumption is the factory puts lower tire pressures to ensure better ride quality, most people are probably more sensitive to that, and don't realize or don't care about the penalty they're paying in tire wear and economy.

That would be true if the tires inflated to the recommended pressure exhibited unusual wear but that doesn't seem to be the case.

chipsndukes

· #11 · Feb 27, 2008

TuRDle said:
chipsndukes said:

I just have standard street tires, but either way I go with 32-35PSI cold to ensure long life and fuel efficiency.

My assumption is the factory puts lower tire pressures to ensure better ride quality, most people are probably more sensitive to that, and don't realize or don't care about the penalty they're paying in tire wear and economy.

That would be true if the tires inflated to the recommended pressure exhibited unusual wear but that doesn't seem to be the case.

Click to expand...

I think there's just a tolerance zone that you need to stay in between.

Vastly underinflated will result in immediate and visible MPG drop and tire wear issues you would notice after maybe 5K miles, same with vastly overinflated.

Keeping within the 26-35PSI I think is more psychological, but as they say, every bit helps, I can feel the difference when my tires have 35 PSI as opposed to 26 PSI, I get good gas mileage too, and because my tires (or anyone's for that matter) lose air with time, I start high (32-35PSI), then after 3 months they are down to 26-28 PSI and I fill them back up. Works for me.

Chipsndukes

hossmaster

· #12 · Feb 28, 2008

Jteezer said:
Well, I am testing the gas mileage theory out now with this last tank and 35lbs in the tires, doesn't really seem like it is making much difference at all... seems like I am still getting about 19 mpg, but will know better in the next day or two.

Hossmaster, you wouldn't happen to have a picture from the rear of your truck with that size tire on it would you?

What size options do I have for this size rim... when you put in factory size not many to choose from, really want BFG Mud Terrains.

will this work for what your looking for???

need more info to help you, there are a couple of choices

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TuRDle

· #13 · Feb 28, 2008

I'm gonna see what kind of mileage I get at 50 psi

TuRDle

· #14 · Feb 28, 2008

Nice truck hoss. Is that a factory installed luggage rack? Is it limited edition?

filthypoor

· #15 · Feb 28, 2008

This is a very interesting thread....... I've always inflated my tires to whatever the max. pressure on the tire recommended. I thought that the max. pressure indicated on the tire WAS the pressure they should be inflated to in order to get the most tread life AND mpg. I havent had my taco that long so I just looked at my tires. They say 44 psi. max. and they also say "uderinflation will cause tire failure." (the 44 psi kinda tripped me out because I assumed the max. pressure would be at least 50 psi because they are 31's.) Anyway, I just thought that if the tires were inflated BELOW max. pressure they would start to wear prematurely and my gas mileage would start to suck even worse than it does now. I'm a little leery about letting air out and running them under max. pressure.

02TAC

· #16 · Feb 28, 2008

Are you going to get better MPG if you run your 265/70-16 tires at 35 instead of teh Toyota Recommended 26 PSI. Probably, but you will also get increased wear in the center of the tread and therefore shorter tire life than you would if you used the recommended pressure. The vehicle manufacturer, not the tire builder, has done the research to determine what tire pressure works best with a given vehicle. This is not only for ride comfort, but for tire wear. I find that on my TOy, teh factory tire pressure is just about right on for contact patch, but like was mentioned above I usually inflate them to 28 instead of 26 just so they do not get to low if I do not check them as often as I should.

Size of the tire does not determine max pressure. The carcass design does. For example, I use General Grabber AT2s in a 265/70-16 load range SL whichj has a max inflatiuon pressure of 44psi. The same tire in a 245/75-16 load rage E has a maxx pressure of 80PSI.

filthypoor

· #17 · Feb 29, 2008 (Edited)

02TAC said:
Are you going to get better MPG if you run your 265/70-16 tires at 35 instead of teh Toyota Recommended 26 PSI. Probably, but you will also get increased wear in the center of the tread and therefore shorter tire life than you would if you used the recommended pressure. The vehicle manufacturer, not the tire builder, has done the research to determine what tire pressure works best with a given vehicle. This is not only for ride comfort, but for tire wear. I find that on my TOy, teh factory tire pressure is just about right on for contact patch, but like was mentioned above I usually inflate them to 28 instead of 26 just so they do not get to low if I do not check them as often as I should.

Size of the tire does not determine max pressure. The carcass design does. For example, I use General Grabber AT2s in a 265/70-16 load range SL whichj has a max inflatiuon pressure of 44psi. The same tire in a 245/75-16 load rage E has a maxx pressure of 80PSI.

This is interesting stuff. I was thinking that the toyota recommended pressure was for the tires that were on the truck from the factory. I've never gone by the vehicle manufacturer recommendation for psi on any car or truck I've ever owned. Maybe I'll try it and see what happens. Just seems like 26 psi is way to low but I'll give it a try and see how the truck rides.

chipsndukes

· #18 · Feb 29, 2008

I don't buy the mfg recommendation for all tires either, but can't really back it up.

I still think there's quite a range, and that a lot of the mfg. recommendation has to do with ride quality and the "one-size-fits-all" theory.

If the tire can take the pressure, is spec'ed for it under all loads, don't see the harm, there's definitely a reduction in rolling resistance, but here this thread is gonna turn into a pi**ing patch, and we don't want that.

...just think of the bike tires when I was a kid, more air, easier pedalling, just keep it within the limits.

Any tire design, vehicle dynamics experts out there?

02TAC

· #19 · Feb 29, 2008

The problem you run into with high tire pressure is it does exactly th opposite of what happens when you air down your tire for off roading. You air down to increase contact patch ( I drop mine to 15 PSI for beach running at low speeds)and allow the tire to deform over obsticales easier. When you over inflate the tire (from manufacturers specs) you actually reduce contact patch and make the tire less flexible. Your tires require a certian PSI to support your vehicle with the correct contact patch. Is the factory setting correct for all situations? Nope, but it the best compromise the factory can offer. For example, even at 26 PSI the rear tires on my Taco are overinflated if the truck is unloaded. Do the chalk on the tread test and you will see this, I have. However, Toyota is not going to tell you to run 22 PSI when empty and expect you to pump them up to 26 or 28 every time you want to haul something. Some vehicle maunfactures have a different pressure setting if the vehicle is to running high speeds alot. This is primarily to help reduce tire flex which induces heat into the tire and can cause failure. SO... Is the factory setting the best for evey manner you use your truck? No, but it is a good all around compromise setting.

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Jteezer

Discussion Starter · #20 · Mar 3, 2008

Well, I have tested the theory on the gas mileage inflated to 35 psi all the way around. I really did not see a significant amout of additional mileage, MAYBE 3 to 4 miles total on the tank so a fraction of a mile per gallon. I do run a higher pressure when running in soft sugar sand as opposed to lower for a bigger "footprint" though, seems to compact the sand better and help you stay above it.

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