Tire inflation for 20 inch tires versus 16 inch?

[SyberTiger]

I noticed the large 20 inch tires have a higher "max pressure" rating than the standard factory tires. Last time I took the X into an alignment specialist he said my tire pressure was way too low. I had 30 in the front and 35 in the back as recommended on the sticker inside the gas cap cover. After I changed out the rims and tires for the 20 inch ones I just kept using the original recommendation. The specialist said the 20 inch tires should easily be inflated to within 10% of their max rating. He recommended 46 to 48. I went with 46 but he said if I wanted a quieter ride I could go as low as 42 but that would affect gas mileage and the 46 to 48 was optimal. Anyone else out there with 20 inch tires? If so what is your tire pressure?

My new tires are rated at 51 max psi thus 46 is within 10% of the max.

 

[Tbars4]

that is a good rule of thumb and you forgot to say what your max pressure is for your 20" tires...
a lot of people i see are running their tires as it says in their truck except, that is for the tire that came on the truck originally, oem...when you get new tires, the manufacturer info of those tires on your truck superceed the original equipment...

 

[CDW6212R]

Ditto, always adjust the air pressures based on the tire "MAX" ratings. Don't waste the time it takes to read OEM recommendations, those are part of why Explorers were rolling years ago. They are always too low, for a smooth ride, at the expense of handling, mileage, and safety.

Any vehicle which weighs more in the front should have more air pressure in the front tires. Each tire is different, and for each vehicle. So you the driver have to watch your own tire wear, and adjust the pressures to obtain the best wear, ride, handling, etc.

Start with something like 80-90% of the "MAX" rating in the front tires, and a few psi less than that in the rear tires. With new tires(never been used on that vehicle before), you should carefully monitor pressures, tire wear, and especially the way the vehicle feels driving. Add and subtract from the tires to make the vehicle as safe as possible, etc. More pressure will get you better fuel mileage, watch them carefully. Good luck,

 

[JDraper]

The Chalk Test:

Finding the Perfect Tire Pressure - the Chalk Test
There is a trick you can do to determine precisely how much pressure to keep in your tires for your particular vehicle. It will give you the best tradeoff possible between mileage, tire life, and comfort. Make sure you use an accurate tire guage so that once you learn this pressure you know it is correct.

With a cold vehicle and cold tires, air them up a little over pressure . Take a chalk and mark a chalk line sideways across the tread of a front and rear tire. Drive your vehicle several yards in a straight line (30-40 or so should do it). Now look at the chalk marks.

You should see the inside of the chalk marks worn off but the outsides should still be showing. In other words, the bowed out overinflated tire was wearing the middle of the tread and not touching the outside of the tread.

Release a couple of pounds of pressure from the tires and repeat the experiment. Continue until the complete chalk marks wear evenly. (Once there, you might want to then release another pound of pressure to make sure the entire tire is bearing down across the tread with weight). You have now determined the tire pressure at which you are keeping the entire tread on the road.

Under this pressure you are wasting available fuel economy, generating excess heat, and prematurely wearing the tread. Over this pressure you will get better fuel mileage but it will come at the cost of comfort from the rougher ride and decreased tread life from wearing the middle of the tread out prematurely. Keeping at this pressure will wear the tire evenly and thus extend its life to its greatest extent and offer the best compromise possible between gas mileage, comfort, and safety (you'll have your whole tread on the road). The pressures may be a couple of pounds different between front and back for your particular vehicle application.

 

[CDW6212R]

Wow, but that I think that that is very wrong, and I know it from very simple logic. Tires do not operate at those cold temperatures. Plus far more important than that, tires grow and expand as speed increases.

The contact patch is radically different at normal or average speeds traveled, compared to the shape at no speed and cold.

I think that the chalk idea might get you similar psi numbers to what is posted on the door jambs.

That concept/idea may be applied to normal operating temperature tires, if you could make a test at normal average speeds. But that isn't likely to be possible with chalk on normal roads.

Honestly you might use that "cold" test to get some baseline to start with. But that's the exact same thing you can get without the effort, by simply reading the "MAX" psi rating, and setting the psi at 80-90% of it.

Take a 44psi tire(read the sidewall), set your pressures at about 40psi front and 36psi rear. Drive the vehicle for a while and decide over time if more or less air is needed. It takes many hundreds of miles to begin to see any tire wear patterns, so you must watch them carefully, and often. Regards,

 

[JDraper]

Try it sometime..you might be surprised at how effective and accurate it really is.....This is not something new, it's been around for quite a while. The big caveat is that it only works for new tires. If you've already worn the tire, it's no good because you already have a wear pattern on the tire that alters the contact patch.

 

[Kellav]

I noticed the large 20 inch tires have a higher "max pressure" rating than the standard factory tires. Last time I took the X into an alignment specialist he said my tire pressure was way too low. I had 30 in the front and 35 in the back as recommended on the sticker inside the gas cap cover. After I changed out the rims and tires for the 20 inch ones I just kept using the original recommendation. The specialist said the 20 inch tires should easily be inflated to within 10% of their max rating. He recommended 46 to 48. I went with 46 but he said if I wanted a quieter ride I could go as low as 42 but that would affect gas mileage and the 46 to 48 was optimal. Anyone else out there with 20 inch tires? If so what is your tire pressure?

My new tires are rated at 51 max psi thus 46 is within 10% of the max.

Please help me? I have 20 inch tires on my Tahoe, can anyone please tell me how much psi should I put in my tires?

 

[TechGuru]

Personally I'd go with 5-7 psi under the max listed on the side of the tire.

 

[CDW6212R]

Personally I'd go with 5-7 psi under the max listed on the side of the tire.

Ditto, and with the fronts about 3psi higher than the rear tires. My latest tires with 51psi MAX ratings, I began with 42psi in the front, and 38psi in the back. So far the wear is fairly even, though my left front for work has always worn the inside edge a little extra. That for me is the work usage(tons and tons of tight turns), and the camber likely has a little too much camber on the left. I just rotate the tires enough to balance the wear, which has worked well for many years now.