The recommended cold tire pressure for my truck using LT E rated tires is 42psi. E rated tires at this pressure makes for a hard ride. Which is okay but I'm not sure it's really ideal for driving around w/o a load.

My understanding is that the cold tire pressure recommendation is influenced by several factors, including: 1) max load, 2) improved gas mileage. It's not necessarily considering comfort and handling (dry, wet, snow) at perhaps the expense of gas mileage, especially w/o load.

Is it okay with modern LT E load tires to under inflate assuming no load? Would handling and ride quality improve w/o introducing any safety issues?

Mostly checking on safety - I can test the handling and ride quality if it's safe to do so.

I'm thinking maybe something like 35-38psi (from the recommended 42psi).

I like 50 psi. Yes it is a firmer ride. But big rigs (3/4 and 1 ton) are heavy and I like to run mine with a little more pressure. I do haul and tow items pretty frequently and do not like to adjust pressure up and down a lot. Ymmv

Yup, understand if you're towing and hauling. And I'd use recommended pressure when I'm loaded up for a trip.

But as just daily driver around town when not on a trip, not sure I need the recommended pressure. And was wondering if it may handle better, be safer and more comfortable w/ reduced pressure.

I'm wondering because at the recommended pressure, there is very little road feel and steering response could be better. The tires are feeling a little different as the tread is wearing.

quote:

Originally posted by konata88:
But as just daily driver around town when not on a trip, not sure I need the recommended pressure. And was wondering if it may handle better, be safer and more comfortable w/ reduced pressure.

I'm wondering because at the recommended pressure, there is very little road feel and steering response could be better. The tires are feeling a little different as the tread is wearing.

Assuming you're asking about your SUV...or did you get an actual truck with an open bed.

At the recommended tire pressure you should have the optimal handling and safety margin. Lowering the tire pressure will give you a softer ride, but also reduce handling and braking as there would be less contact between your tread and the road.

If your steering is vague or feels "off", I'd have your alignment checked

Are you rotating your tires regularly?

When you say "recommended pressure" are you talking about on the sidewall or on your door?

Did your vehicle come with Load Range E tires to begin with?

If not, the door jamb sticker will be wrong and you’ll have to look up the load inflation table for your size tire to find the minimum pressure required to carry your vehicle’s front and rear axles’ weight rating. If your vehicle came with P-metric tires and you put LT load range E tires on it, then it will ride stiffer even with the minimum required pressure. Most P-metric tires have a max cold PSI of 36 or 44 while a load range E tire is 80. The load range E tire is built stronger to contain air at that pressure.

I'm not sure you could get anywhere near max load for an E-rated tire in a SUV. Maybe a truck-frame based SUV with a lot of tongue weight, but you'll be taxing suspension before tires. You're not creating a hazard running the tire with a little less PSI.

Your TPMS will complain about low tire pressure for anything under door sticker minus ~10%, but I doubt it came with E-rated tires. I would test 38-40 and see if it feels different. Some places around here fill to the max on the tires rather than the door sticker, I let some air out when I get home and don't go back. Wife's car feels like a pogo stick at 42psi.

As a former tire salesman, you should choose tires for your application, not what you think you want. You will not get an E-rated tire to ride as nice as a comparable P-rated tire.

quote:

The recommended cold tire pressure for my truck using LT E rated tires is 42psi.

The elephant in the room: what kind of truck is this? Load range E tires are usually found on "one-ton" (350/3500) trucks, and they don't run that low of a pressure. If you use these on a half-ton, no wonder it rides rough.

https://ricksfreeautorepairadv...k-tires-1536x649.jpg

Load Range E typical sidewall max is 80 psi.

Your 42 psi is half the max.

I am not sure that your application warrants E.

quote:

Originally posted by egregore:

quote:

The recommended cold tire pressure for my truck using LT E rated tires is 42psi.

The elephant in the room: what kind of truck is this? Load range E tires are usually found on "one-ton" (350/3500) trucks, and they don't run that low of a pressure. If you use these on a half-ton, no wonder it rides rough.

IIRC, he has either a Sequoia or a Land Cruiser.

quote:

Originally posted by 9mmepiphany:

At the recommended tire pressure you should have the optimal handling and safety margin. Lowering the tire pressure will give you a softer ride,

but also reduce handling and braking as there would be less contact between your tread and the road.

Actually less pressure increases contact area and traction which is why off road vehicles and dirt bikes run low pressure. The main concern with lowering pressure too much is excess heat generated at high speeds. Rule of thumb is after lowering pressure drive the vehicle to bring the tires up to temperature and the psi should increase 10%. If it increases less than 10% they are over inflated so let some out, much over 10% and they are under inflated so increase psi.

I'm not familiar with your specific truck tires but could much of the harsh ride be attributed to the heavy duty nature of the tires themselves? I had a nice car that came with run flat tires and it rode harsh over anything but a perfectly smooth road, it was jarring on a gravel road. I lowered pressure to just above where the TPM would activate but if it made any improvement I couldn't discern it. When they wore I changed to conventional tires and it rode 100% nicer.

Why are you running e rated tires at all?

On my Jeep I ran the E rated at 32 psi, did that for 20 years with no side effects. I have a new Bronco and I'm running the E rated at 35 psi. With the Jeep I could turn off the TPMS, I don't have a tool for the Bronco and 35 doesn't trigger a warning. Both vehicles had 35" tires, 315/70R-17.

One of my vehicles is a diesel F-350 SRW pick up. The truck came with E rated tires and the placard suggests 65/80 psi.

This is all well and good when I’m carrying my truck camper but when empty it’s a very harsh ride. I posted this very question on the ford-truck forum about two weeks ago. The consensus seems to be either 55/50 or 60/55 which is what I’m trying now.

Buddy of mine ran E rated tires on his regular cab short bed Silverado. I thought he was crazy and it'd ride like a tank. It didn't and he got great life out of two sets of them.

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IIRC, he has either a Sequoia or a Land Cruiser.

I'm glad somebody is telling us something.

Those don't need Load Range E (old 10-ply rating) tires. Load Range C (old 6-ply rating) for a little stiffer sidewall, at most. It must ride like a buckboard wagon full of bricks. Even lowering pressure from an already low (for that kind of tire) 42 psi will do little or nothing.

My dad ran E-range on his 1/2 ton Silverado, 2x 4Runners & Denali Yukon XL, but also towed frequently with them all.
On a Duramax 3/4 ton Chevrolet as well, but more appropriate on there.

Thanks for the input guys.

I'm not really wondering what the RCTIP is - I looked it up in the tables and it's 42psi.

I'm wondering why that's the RCTIP. I'm guessing it's influenced by factors I'm not too concerned about like load assumptions and gas mileage. I'd like it to be influenced more by things I do care about like steering response and traction.

These are A/T tires - KO2's - and meant for off-road / off-pavement trips. In the size I needed, they are only offered in E load. That being said, I'm not sure I really need RCTIP just to drive around town and not sure it's really optimal w/o any load. So, just wondering if I can get better results by lowing the inflation below RCTIP.

Yep, your ride is going to suck until you get tired of it and replace them. With something appropriate to the application.

Now, if only those trying to help knew what you drove....

quote:

I'm not really wondering what the RCTIP is ...

I did, but after a few minutes was able to deduce it: Recommended Cold Tire Inflation Pressure. It's right on the doorjamb label; I don't know where this "table" business comes from. But it was with the OEM tires. And it's a recommendation, not engraved in a stone tablet or anything. You can play with it, but IMO maybe one driver in 500 can tell any difference.

When I was in the business, I inflated tires to the "Rick-tip." If somebody wanted something different and it was reasonable, I complied.

I’m sorry, I got interrupted while posting and the No below was directed at konata88’s post three posts up:

No. The numbers from the load inflation tables are not recommended numbers. They are the minimum pressure required to carry the load listed for each PSI.

42 is not an answer on the load inflation tables for LT tires. I suspect you are looking at a P-Metric table.

Without weighing your vehicle, you are guessing what the pressures should be. An educated guess would be to use the front and rear axle weight ratings divided by 2 as the load the front and rear tires would carry individually and look up the PSI required in the tank for your tire size.

If you have the actual weights, look those up and don’t go below the PSI for those weights. For example, the rear tires on my truck call for 80psi at which the are rated to carry 3,750 pounds each. According to the CAT scale, the rear axle my truck unloaded weighs 3,300 pounds. That’s 1,650 pounds per tire. The lowest pressure on the chart for my tire, 35 PSI, says it will carry 2,080 pounds. I don’t like the ride and handling under 50PSI, so that’s what I use when not towing or loaded. I carry a compressor if I need more air.

Load inflation table, my truck’s tires are 275/65r20 single because it’s not a dually:

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