P Metric vs. LT Metric- which one for a pickup truck?

Maintenance/Repairs
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1

I have a 2004 Chevy Silverado Ext. Cab with 4WD. I still have the original tires on it- they are Firestone Steeltex LT245 75 R16’s. The sticker in the cab (in the door frame) states that I should use LT245 75 R16s inflated to 50 PSI cold. I have 60,000 plus miles on these tires and will need a new set for winter. I have been pricing out some new tires and noticed that their P Metric counterparts are less expensive. I do not tow anything (even though I have a towing package), and I rarely haul heavy loads. I understand the differences between P Metric and LT, however I am not sure if a truck set up for a LT tire could use a P Metric. I have been told that the factory setup for my truck is made for an LT tire and it would handle differenly with P Metric tires. Any suggestions as to what type of tire I should purchase?

P.S.- I do not care about the ride quality of the truck- its a truck! BUT I do care about safety and I will not put P Metric tires on if they will compromise safety! Thanks for any suggestions.

2

Actually, the handling’s not the big issue, it’s probably the load capacity. Go to tirerack.com and see which tires work for your truck. I bet P metrics have insufficient load capacity and lower than specified inflation pressures.

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P= Passenger Car tire.

LT=Light Truck tire.

Tester

4

I like the tirerack site… its great for getting customer feedback on tires. I will have to check on the load capacity and get back to you on that one. This may be a moot point if P metrics will not safely work for my pickup. However, I guess that the only reason I am even REMOTELY thinking about this question is that all major tire companies make a P metric size for my truck, as well as many other pickups. Now if they were only made for passenger cars, then why do I even have the option to buy a P metric tire? My father’s Ford F 150 calls for P255 70 R16s as well. His pickup is set up for towing too. Also, I have talked to others that run P metric on tires on their pickup trucks- regardless of what the OEM sticker tells them to do. I have researched this online and have found that load issues can arise when mounting a tire with insufficient load capacity. But they cited F-350s and heavy duty 1 ton pickups. I have a 1/2 ton that doesn’t tow or haul heavy loads. If I can buy a P metric tire that will sufficient load capacity, what else should sway me from doing this? Any thoughts? Thanks for all of your suggestions.

5

Glad you mentioned the half ton pickup part. You can safely use P rated tires. I have a 2002 4WD extended cab GMC Sierra with automatic transmission and the door sticker says P 245 75 R16. If you have the Z71 or whatever the number is, The truck is set up for off-road use too. It may have a LT rated tire specified and there may be a reason, but I don’t see a reason.

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sjd81,

Don’t worry about the load capacity on your truck. If it came with LT metric tires, you should stay with LT metric tires. P metric tires will not have enough load carrying capacity.

Yes, there is some confusion about tire sizing - and officially, the size includes the letters before and after the numbers. Lt metric tires are built different than P metric tires. Yes, I know you may have some friends who used P metric tires without problems, but I can show you tons of folks who have had problems.

Remember, you said safety is most important! Stick with the LT metrics.

7

With the mileage you have gotten from your tires (60K) you might consider sticking to the same tire. That is awesomely good for a truck tire. Most folks are replacing truck tires every 30K miles. The rubber in the LT tire could be harder and the sidewall stiffer than an equivalent size of P metric. I’m not sure about running a P metric tire at 50 psi; sounds high for a passanger car tire.

You might save a few bucks on the P tires and give it back if they wear out in 30K miles.

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@CapriRacer - I’m confused by your ‘don’t worry about load capacity’ comment. Why not? Are you saying it’s OK to get tires that don’t meet the load capacity spec?

9

Thanks for all the advice. I think that I will stay with LT tires for a few of the reasons stated above. Now if I can find some good deals before winter gets here…

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texases,

No, my comment was that a neophite can get easily confused about load carrying capacity as there are a couple of quirks in there - one of them being that P metric tires have to be derated 10% when used on light trucks, vans, and trailers. For someone who hasn’t figured out how tires work, it’s best that they ignore the business of load carrying capacity and follow the vehicle tire placard.

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OK, as a former shop head technician and service manager who has endured corporate product sales training of several large brand tire manufacturers, let me chime in on the subject for the OP. I have a '97 Ford F-250 loaded with an engine driven welder and other large paperweights… recently outfitted with D load range 285/75R16 rubber.

I think Tirerack has a great writeup and explanation of load ratings and inflation pressures. Check it out… you can learn a lot from their writeups.

First thing to think of is the load capacity of the tire, as opposed to its inflation pressure. A tour de France cyclist has over 100 PSI in his rail-thin bike tires, whilst my buddy who has a street-legal monster truck resting upon HUGE 5-foot high tires has only 6 PSI in his tires. 150 lb cyclist vs 6000 lb diesel truck.

Can you put passenger tires on your what I assume to be a 2500 Silverado (I don’t recall 1500 Silverados coming with the Steeltex). If you go with a P tire, your max inflation pressure will drop from the 80 PSI that Chevy chose to use 50 of, to 44 PSI on a Passenger tire (I don’t know of any P tires that have higher max pressures). Can you get down the road safely doing this? Probably, but don’t plan on carrying anything heavier than a paperclip in the bed, half a tank of fuel, and no passengers.

The Steeltex was an AWESOME product. Some bean-counters at Bridgestone are probably to blame as to why Firestone discontinued this product. I serviced a lot of vans and trucks with the newer Transforce AT product… and I have to say they wear quite well. Currently I’m running Cooper Discoverer ATRs that are wearing QUITE well after 12K miles. Now, you might be wondering why I dropped from an E load range tire which came on the truck originally to a D load range tire. My truck is a turd without 4x4 engaged, and isn’t that great with it. I hated getting stuck on flat muddy ground because the sheer heft of the vehicle (almost 7000 lbs empty), so I decided to go with something wider and a bit taller both for off-road handling and looks. The 285/75R16 D load range Coopers have nearly three hundred pounds MORE load carrying capability at its max pressure of 65 PSI than the E load range 235/85R16 tires did at 80 PSI.

Also, a lot of trucks list a higher pressure on the placard for the rear tires. This is because they assume the rear is loaded. A good trick to do is to inflate all-around to whatever you like, but then draw a few lines of chalk across your tread. Go drive around for a few miles, and see if the chalk is wearing evenly. If the chalk disappears on the outside, you’re underinflated for that SPECIFIC load configuration (you, the angry girlfriend, the dog, and a full tank of fuel etc), or overinflated if the chalk is rubbing off in the middle of the mark. Adjust accordingly for your everyday configuration to find that sweet spot (both front and rear pressures) that allows the load to be distributed evenly across the entire tread footprint.

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I am not a fan of the chalk method for determining inflation pressure as it assumes that if a tire tread is wearing evenly, the tire is properly inflated - and that is just plain not true.

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W123 Benz,

Thanks for the insight on this subject. I am now “steering” (no pun intended!) away from a P Metric tire for the more appropriate LT. Believe it or not, my truck is a extended cab 1500 4x4 Silverado that came with the Steeltex (C load range). I am not sure if they were on thier because the truck is set up with the towing package or not.

With that being said, I am going to stay with the LT tire for many reasons stated earlier. I had narrowed it down to the Cooper Discoverer ATRs and the Firestone Destination ATs. After calling around and reading many a testiment on the Tirerack site- I am going to go with the Firestones. I used Tirerack before to research the Destination LE’s for my wifes SUV, and they lived up to their ratings as they are a great tire. I am hoping to get the same performance out of the Destination ATs for my truck.

My last question concerns the size- should I stay with the 245s or should I go up to the 265s? I have read a lot of posts and the majority state that the 265s look better on the silverado, but you get less MPGs and the speedo is affected slightly. This and the fact that a wider footprint during the winter months will cause more sliding has me leaning towards the stock size of 245 75 R16. Any thoughts? THanks!

14

The reason the speedo is affected is because of the change in outer diameter of the tire. the first number, 245, is the width of the tread. The second number, 75, is the ratio between the tread width and sidewall height. The last number, R16, is the rim diameter. So going from a 245/75R16 to a 265/75R16 adds a 1 inch diameter difference for a 3.9% change in the speedometer. If to go with a 265/70R16, if you can find them, the overall diameter is close to the same, and the speedo difference is only 0.5%, nearly identical.

I used my favorite tire size site, http://www.miata.net/garage/tirecalc.html, to determine this.

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I didn’t bring this up earlier because it would have just confused matters, but it becomes important now:

SJD: Is the vehicle a K1500 or K2500? Tire Guides says that K1500’s didn’t come with LT type tires in 2004 - AND - K2500’s had inflation pressures like 50 psi front, 80 psi rear. Tire Guides has been known to have errors - and they usually don’t fix them, even if they are pointed out - but as a general rule, the information is reliable.

The reason I bring this up is that if Tire Guides is right, then you have a K2500 which came with 6.5" wide rims - and LT265/75R16’s are too wide for those rims.

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Vehicle is a 2004 K1500. I checked the VIN to confirm model year, etc… Not sure why this one came with the Steeltex tires. I attached some pics from when I purchased it many years ago. The door sticker inflation guide says to run them 50 psi cold, both front and rear. Not sure if pics of rims with tire will tell you if its a 6.5’’ wide rim, but I attached just in case. How could I tell what the rim size is? Thanks.

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OK, this is just an example of the type of errors Tire Guides has.

Those are 7" wide wheels per Tire Guides. You can tell by looking on the back of the wheel. It ought to be stamped with something that looks like this: 16X7JJ

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Thanks for the info. I crawled under my truck to look at the wheels but was unable to see the stamp. I am guessing my disk brake setup might be hiding it. I will ask the garage to check for me if I go with the 265s.

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Sorry it took me a while to get back online… been busy trying to rejoin the ranks of the gainfully employed with the $5000 machine resting in my truck that’s not making any money.

Regarding the Destination line of tires, they tend to be really good for short wheelbase lighter SUVs, and so-so for trucks in terms of tread life. They ride great, and in fact are some of Bridgestone/Firestone’s most popular products, but having sold/installed HUNDREDS of sets of that product alone, let me tell you that you probably shouldn’t expect more than about 40K miles out of it. Firestone’s mileage warranty covers DEFECTS and DEFECTS ONLY for that particular warrantee period (50K, 60K, 65K, etc). Basically, they’re warrantee policy says that vehicle configuration, driving habits, vehicle loading, driving conditions, the lunar phase, etc will effect your tread life.

This has the advantage of protecting the company from morons who drive away from the garage and immediately proceed to head to their buddy’s place to drink beer and do donuts and/or burnouts in the vacant parking lot next to his house, and returning a month later to say. “hey, my tires suck bro!” I can remember ONE particular arse in particular where I revelled in telling him to buzz off because of the 20 previous visits where we notated that the front end of his vehicle was shot so badly it was INSANE to even CONSIDER driving down the road. When he read me the riot act and I offered to give him a new set of tires for free if we did the front end work (we’re talking tie rod ends, ball joints, every moving component ready to part ways with the vehicle). Needless to say, he didn’t take me up on the offer and did what most chumps do and called my district. He wanted to smoke another good set of rubber in 25K and come back complainin’… IF the front end miraculously didn’t send him into a guard rail at 55mph before his next visit.

Managers at Retail Operations will put immense pressure on sales personell to NOT give pro-rated discounts on new tires that didn’t last that full 65K, ESPECIALLY if the customer didn’t come in EVERY 3-5K religiously to rotate, balance (with of course the lifetime balance option at $20/tire), check alignment (with of course the lifetime alignment plan for the vehicle), and basically live at the store (your results may vary depending on how much of a doofus the district manager for your retail location is). This puts guys like me, with a military background and not willing to compromise on our values, in the place of pissing people off, or pissing our district off and ending up in the unenjoyment line. Luckily I found myself in the latter, thus giving me the escape velocity required to escape from retail purgatory.

Basically, what I can tell you from my application is that those Destinations will last a good 40K, and probably not any more. In regards to your question of your wheel size, they are probably a 7" wide rim, as the GM/Chevy 16" five-spoke wheels were mostly 7" wide. You could DEFINITELY fit a set of 265’s on those. Since you’re not really after a “lifted” look and are concerned about the speedometer, you could go from a 245/75 like you’ve got now and get 265/70s (you’ll want to stay with the more common and hence cheaper 70 series profile). Your tires now have a height of 184mm off the bead lip, the 265/70’s will have a height of 186… so they should be NEARLY identical in circumference and not effect your speedo.

Hope that helps.

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That helps. I will be getting the tires in October. Thanks again for the advice!