What psi should i run?

I really can't tell you. What feels good to me (and gives me better gas mileage) is actually too high for getting the best tread wear. I like the feel of my 265-70-16 at 35/36, but that's too much for these light trucks in a P rated tire (especially in the empty back end). This pressure will make the rear tires ride high (you can see about an inch of tread on the rear tire edges that doesn't touch the road). I can get away with being that high in the front, but I don't do it anymore.

There are a lot of variables to consider. If millage is a concern, then go a little higher but realize you might wear the center of the tires faster than the edges. If comfort is most important, then air down a little. The factory specs always seem a little soft to me. I've settled in at 34 front, 32 rear. Even 32 has the rears running a little tall. But I don't want to go lower due to gas mileage.

I was running my old 245-65's at factory specs (like 29/30 or something). I actually gained 2-3 mpg when i aired up to 36. Sometimes people don't realize how much pressure affects mileage.

I guess I just like to find that sweet spot where I'm getting good/even tread wear (not running up on the center of the tires). But I'm not down so low that they feel soft.

 

To be honest, those numbers sound a little high- only because I think you'll be riding tall in the back end. Check the side edges of the tread and see if you're getting any wear. Front is probably ok. I'd probably try 34/35 front and 31/32 rear if I were you for starters. See how she feels.

 

Right now I'm running 34 all the way around and im getting about the same gas mileage as I've always got, but some times they just look like there sagging to me like they don't have enough air but I check them and there 34 so that's why I was wondering about going up to 36

 

Another thing I know a lot of people don't like the Tps but I do but my light has never came on i don't know if someone pulled the plug before I got it or what, in my corolla the thing goes on every day, but in the Tacoma I never have the light come on, so I guess there just holding air good. I've reset the Tps to the light comes on and blinks like when your resetting it but then it never comes on so I guess sense I run above what the door calls for it just never comes on.

 

Truck: 2013 AC 2.7L 4x4 M/T
Tires: Dunlop AT20 Grandtrek 245/75r16 (stock)
Average day time temp.: 110F

I did a chalk test (truck unloaded - drove 2-3 miles), results below:

• Front - 30 psi
• Rear - 28 psi
• Approximately 0.5" of chalk left on all tires' edges

Questions:

• Does it matter if the tires are hot or cold when performing the chalk test?
• Will results (chalk wear/fade) vary when test is done during hot/cold tires?
• With the above results, it looks like I could go down more by the looks of the chalk marks. But I'm hesitant to do so with the low numbers I have now.

Note: As mentioned by fellow members how incompetent techs at the dealership could be, they had all my tires at 37 psi.

 

The chalk test isn't really an end-all be-all. But It's a really good starting point. I think the general rule of thumb is you should never have the tires increase in pressure more than 3-4 lbs when hot. When the initial pressure is too low, the tires will run hotter, thus increasing pressure. So, if after running on the highway for an hour, if you're up around 34+ lbs, then your 28/30 is too low of a starting point-- even if that's where the chalk test told you to be. In that case, I'd add a couple of pounds (but I don't think that will happen).

For what it's worth, At an initial cold 34lbs, you won't see much pressure increase at all when hot. At 28/30 you probably will see a little increase. Obviously, ambient temps play a role, as well.

I like to run my tires a little harder than what the chalk test tells me is correct-- simply because I get a little better gas mileage. I also like the slightly stuffer ride, as it doesn't feel quite so mushy. It'll feel more responsive, too. Cornering is so mushy at the recommended pressures. The way I figure, if I get slightly fewer miles on the tires over the life of the tires, I'll make up for it in gas savings.

To be honest, on those Dunlaps, you'll be fine anywhere in the 30-34 range all around, although it'll feel stiff on the back end over 33.

Don't go any lower than where you are at-- your mileage will be crap (and you'll heat up anyway at speed). When I had the Dunlaps, I settled in at 32R/34F, even though my chalk test put me exactly where you ended up. At those pressures, there was very little increase when hot.

Just my .02.

 

Thanks for the insight. I woke up earlier (6 am) today to check on the tires.

Front: 28 psi
Rear: 26 psi

I drove 7 miles going 55 mph and the readings increased by 1-1.5 psi.

• Are these readings too low for cold tire pressure?
• Am I risking a tire blowing up while driving 30 miles on the freeway?
• Is 7 miles too little of a distance to rule out the 5+ psi increase from cold to hot pressure?

 

That sounds really low to me for cold starting pressure. I can't say for certain, but I'm guessing that 7mi at 55mph is not enough to determine what your hot running pressure is gonna be. If you drove for an hour at 55mph with the same starting pressures, I bet you'd increase more than 1-1.5lbs.

If you started at 30/32lbs cold tomorrow and drive the same 7mi at 55, I bet you won't see that same increase in pressure. Just a guess.

I don't think you'd blow up a tire at those starting pressures you mentioned, but that just seems really low to me.

 

I drove from home to work yesterday and today, but did not check tire pressure prior to driving.

Total distance (per trip): 29 miles (80% freeway)
Front tire pressure after driving: 30 psi (coming from 28 psi on post #167)
Rear tire pressure after driving: 27.5 psi (coming from 26 psi on post #167)

I didn't notice anything unusual while driving. I may not have enough experience to accurately feel any differences compared to running on 37 psi, but handling seems to be the same. Since the fuel tank was full prior to these tests, I'll find out in a few days whether or not the change in psi affects my mileage significantly.

 

If you fill all 4 tires to 36lbs and drive around, you WILL feel a difference compared to where you're at now. I'm almost certain you'll notice a difference immediately (like within a couple of city blocks). Give it a try- it won't hurt anything and it going back and forth quickly will provide you with some perspective. You may not have noticed the change before if you weren't paying close attention.

After airing up to 36 It'll be harsh but responsive. Once you feel it and compare you'll have a better idea of what you like and help you decide on a good running pressure for you.

I ran at the door specs for years with all my Tacomas. Finally a couple years ago I tried 36lbs all around just for fun and I was immediately amazed at how much I liked it. So much less rolling resistance (think back to riding a BMX bike vs a 10 speed). But the back end is really hard at those pressures in little trucks like ours- especially with an empty bed.

I bet the gas mileage difference between 28lbs all around and 36 all around would be 4 mpg.

The way to do it is to fill up to 36, then drive around a bit. Then drop to 28 and drive around. When I did that I finally settled in at 35f/32r.

 

I definitely like the idea of finding the numbers that would give me the type of responsiveness that would benefit me the most.

I'll report back in a week (after a tank of gas). I just want to see for myself how drastic the mileage would be affected with running numbers this low. The next test would then be on the handling.

 

36 front and 31 rear with c load duratracs gives me even wear. After a 2 hour rip down the freeway they pump up to 39/34 which is about perfect I think.

 

That sounds about right to me. My P rated Michelins don't heat up that much. But I suppose that could be a weight/rubber compound difference.

 

Previous tire pressure:
37 psi (hot) all around - 21.426 mpg

After 16+ gallons of gas:
Running 28 psi front, 26 back (cold) - 21.788 mpg


I was expecting worse mileage after lowering tire pressure, but I got the opposite. Driving habits and routes dis not change.

Am I missing something?

 

28/26 cold might have pumped themselves up to nearly 37 after they heated up. An under inflated tire flexes and works much harder and generates a lot of heat. I found if I put in 30 cold they ended up 39 hot after a long highway run and the tire felt physically hot to the touch. When I put in 36 they ended up 39 as well but felt cool to the touch after a highway run.

 

I run 30 psi cold all the way around as recommended by Toyota. According to my TPMS which I have checked to be accurate the pressure indicates 33-34 psi when warmed up after driving for a while. I consider a 3-4 psi increase to be expected. The outside/pavement temperature has some affect on this but IME this is no more than 2 psi on the hottest days.

In Moab after airing down on the trail to 26 psi and driving back on the hot pavement to a station to air up the gain was still only 5 psi.

 

First this:

Then this:

Finally this:

I gave it 10 days (about 16+ gallons of gas, 85-90% of freeway driving) and observed closely. I've seen a lot of members claim that the mileage drops when one decreases tire pressure. From what I've experienced, it wasn't the case (well, I may have not decrease low enough). I'm guessing that the results from a variety of tires will never be the same.

 

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I run 35 PSI all the way around ... and 35 PSI gives me the best combination of tire wear, mileage, handling and rain driving.
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I surely am not the best nor the most aggressive driver on the road, so let me put this out there:

1. Doing the chalk test, and running the tires according to the "good result".
   1. Am I losing something in the "handling" department?
   2. Would handling only pertain to more aggressive drivers?
   3. Am I sacrificing anything by running with "good chalk test results"?

 

It amazes me that so many people think they are just supposed to air their tires up to the "Max PSI" number listed on the sidewall! Hello!!! 80 psi is way too fucking high people!! Good Lord!! LOL