Bought new LT tires for towing and off road
09-14-2015, 04:57 PM
#11
Senior Member
Thread Starter
Was that with the truck fully loaded?
You will get different results depending upon load.
The 48psi the Michelin told me was to match the truck's original tire's MAX weight rating with a fully loaded truck. If you're not running the truck with that much load you can reduce it. But I do so much towing off and on that I never drop the pressure.
You will get different results depending upon load.
The 48psi the Michelin told me was to match the truck's original tire's MAX weight rating with a fully loaded truck. If you're not running the truck with that much load you can reduce it. But I do so much towing off and on that I never drop the pressure.
Well 55 psi was definitely to high. I aired the tires to 45 psi and the front tire wore the chalk evenly across the tread, and the rear tire wore it evenly across except to 3/8" from the edge of the tire tread. At that 3/8" edge you had darker chalk.
Since Ford on my model, states to use the same pressures for front and rear axle, I'm going to keep them the same.
After doing the chalk test, I did get a more thorough reply back from BFGoodrich.
My OEM P series tires has a load rating of 2601 lbs, BUT that's a rating for a passenger car. Truck and SUVs have a lower rating, the mandated lower rating is 91% of that Passenger rating to accommodate a truck/SUVs higher center of gravity and the possibility there is slight overloading. So the industry uses 91%.
When I emailed BFGoodrich I asked why the previous rep didn't take that into account. BFGoodrich did state the 55 psi was incorrect and that I was correct at 47 psi. For that OEM tire load rating on a truck, it should be aired to 47 psi. BFGoodrich definitely said that the Discount Tire rating was to low. I did ask Discount tire why they stated that PSI, and I was told that it was a general psi and the actual needed pressure may be different than their generalized pressure rating.
I did the chalk test at 45 psi. Don't think that 47 psi is going to be much different. I'm going to leave it at 47 psi now that I have a confirmation.
The tire behaves pretty much the same as it did at 55 psi, but slightly more vibration (most likely due to more tread being on the ground) and a less stiff ride.
BTW, did my first tow on the new tires and what a difference. Can't believe how more stable the ride is.
With the P series, a gust of wind would hit the rig and push me a bit. Then the rig would wobble a bit left to right until it stabilized. With constant wind gusts, this made driving a definite 2 handed job and sometimes with white knuckling it.
With the new tires, we had a lot of wind from previous rain storms. While the wind pushed me like before, it was a none issue, and the rig maintained it's stability with absolutely no wobbling left to right! This is why I bought these tires. It's like a night and day difference. One handed driving was easy but I still use 2 handed driving with the rig for safety.
The LT tires offer a more stable, confident ride empty. I actually prefer it to the empty ride of the P series that had poorer handling and more bouncy ride from the softer tires.
After having both, I really don't know why makers put P series tires on trucks. I can see it on Full Size SUVs that are essentially grocery getters, but trucks are meant to do work.
Last edited by Mike Up; 09-14-2015 at 05:36 PM.
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12-13-2015, 06:57 PM
#12
Senior Member
I recently bought new tires, BFGoodrich All Terrain T/A KO2 in LT275/65R18. Original tires are Goodyear Wrangler SR-A tires at P275/65R18.
Discount Tire said for my truck configuration, I should air the E1 Tires at 41 psi in the front and 41 psi in the rear. The original Goodyear tires are rated at 2640 lbs at 35 psi. The Tire placard is to set these OEM tires at 35 psi.
Now with a load E, to equal the same 2640 lbs load rating, I need at least 50 psi in the LT Tires. BUT Discount tire says 41 psi. I wasn't aware of this until I found some LT tire air pressure charts.
Did they screw up, where I should be putting 50 psi in the tires? All the charts say 2535 lbs at 50 psi which is equivalent to a load C tire. I think that's adequate as I know when using P tires for work, you need to take 91% of the P series rating (which is only passengers) to get the light work rating. That would equal the 50psi.
Don't understand why Discount tire feels that 41 psi in adequate in these tires, which 50 psi is needed to meet the OEM tire load rating.
Please enlighten me on this. I'll be calling BFGoodrich tomorrow if I have time.
Discount Tire said for my truck configuration, I should air the E1 Tires at 41 psi in the front and 41 psi in the rear. The original Goodyear tires are rated at 2640 lbs at 35 psi. The Tire placard is to set these OEM tires at 35 psi.
Now with a load E, to equal the same 2640 lbs load rating, I need at least 50 psi in the LT Tires. BUT Discount tire says 41 psi. I wasn't aware of this until I found some LT tire air pressure charts.
Did they screw up, where I should be putting 50 psi in the tires? All the charts say 2535 lbs at 50 psi which is equivalent to a load C tire. I think that's adequate as I know when using P tires for work, you need to take 91% of the P series rating (which is only passengers) to get the light work rating. That would equal the 50psi.
Don't understand why Discount tire feels that 41 psi in adequate in these tires, which 50 psi is needed to meet the OEM tire load rating.
Please enlighten me on this. I'll be calling BFGoodrich tomorrow if I have time.
Just an older fart putting in my 2 cents...I have ALWAYS run max pressure on P rated tires ...I have 4 Ford P/U"s....I have updated 3 with LT tires (2 in 17'' 1 in18'') I run about 300 plus lbs + for load & go with consistant high mileage trips & have found using 55lbs air pressure I get not only normal wear but also exceptional long life!! The only time I play with air pressure is when I rented a trailer & was pulling a heavy load !!!! GOOD DAY!!
12-13-2015, 07:35 PM
#13
built ford tough
my pop has the michelin ltx ms2 on his truck, he runs 50psi on the regular and 60 when towing, has been doing it for years with no problem, hes running factory 17" alloys
12-18-2015, 02:00 PM
#14
Senior Member
The rating for the tire is at max load. so unless you are at max load there isn't a need for the max air pressure. Tire pressures are about the surface area of the tire contacting the ground. Pounds Per Square inch is what supports the load. A wider tire would need less PSI to support the same load as a more narrow tire. A E rated tire can hold more PSI to increase the load.
Add in different tire manufactures and constructions combined with vehicle weights and usage there is no exact right pressure. You must take in consideration a lot variables to find the "right" pressure.
Ask ford and firestone.......
Add in different tire manufactures and constructions combined with vehicle weights and usage there is no exact right pressure. You must take in consideration a lot variables to find the "right" pressure.
Ask ford and firestone.......
12-18-2015, 05:44 PM
#15
If it's a E1 load tire, the load rating is too low at that air pressure.
Our tires are rated at 2640 lbs which load charts show 2601 lbs for our P275/65R18 tire size. My KO2s are 3472 lbs at 80 psi which the chart shows 3415 lbs at 80psi for that load rating.
With only 41 psi in the tire, the tire is rated for only 2166 lbs which is way to low when OEM tires are rated for 2601 lbs chart/2640 lbs actual.
I aired all my tires up to 55 psi and WHAT A DIFFERENCE. The ride is so much better and tires track so much better. Truck acelerates better as the rolling restistance is now lower. I don't have any vibration when driving now. It's just as the OEM tires were now. Noise is way down now as well. Tires were much louder. Now they are as quiet as the OEM tires were.
BFGoodrich rep told me that keeping them at 55 psi will also offer better tread wear. I have a hard believing that 41 psi is correct.
The reason I researched this is because of the harsher vibration, when driving at 41 psi. The tires felt low with the vibration and the truck didn't accelerate as well, as if the rolling resistance was much higher as you have with a deflated tire. Airing up to 55 psi took all that away.
I'm convinced. I may do the chalk test but driving offers a lot of info as well.
Our tires are rated at 2640 lbs which load charts show 2601 lbs for our P275/65R18 tire size. My KO2s are 3472 lbs at 80 psi which the chart shows 3415 lbs at 80psi for that load rating.
With only 41 psi in the tire, the tire is rated for only 2166 lbs which is way to low when OEM tires are rated for 2601 lbs chart/2640 lbs actual.
I aired all my tires up to 55 psi and WHAT A DIFFERENCE. The ride is so much better and tires track so much better. Truck acelerates better as the rolling restistance is now lower. I don't have any vibration when driving now. It's just as the OEM tires were now. Noise is way down now as well. Tires were much louder. Now they are as quiet as the OEM tires were.
BFGoodrich rep told me that keeping them at 55 psi will also offer better tread wear. I have a hard believing that 41 psi is correct.
The reason I researched this is because of the harsher vibration, when driving at 41 psi. The tires felt low with the vibration and the truck didn't accelerate as well, as if the rolling resistance was much higher as you have with a deflated tire. Airing up to 55 psi took all that away.
I'm convinced. I may do the chalk test but driving offers a lot of info as well.
01-09-2016, 07:05 PM
#16
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It really doesnt matter if the rating at 41 psi is 2166 lbs. That would mean each pair of tires(per axle) could support like 4333 lbs which is well beyond what your trucks GAWR or your GVWR are at. Leave it where its comfortable, and when you go to tow or haul air them up to a higher pressure so that they are more stable. The tires are far from your limiting factor. Its not an F250/350
Is the equation using axle weight/2 divided by max load of tire times max psi the place to start?
Last edited by matman72703; 01-09-2016 at 07:25 PM.
01-10-2016, 12:33 PM
#17
Senior Member
Just purchased a set of KO2s 275/70/18 to replace OEM GY SR-A 275/65/18. Having seen this thread, I asked the tech (at Sam's Club) what pressure he put in the tires. He said "I put in the pressure shown on the placard." I wasn't about to try to explain to him E vs P and weight loading ratio to max pressure. But, I am curious what psi people are getting along with for a LT tire. Am I correct in saying 35 psi is WAY Too low?
Is the equation using axle weight/2 divided by max load of tire times max psi the place to start?
Is the equation using axle weight/2 divided by max load of tire times max psi the place to start?
I asked Michelin and they said about 50psi is right for my LT-Es. I've upped that to 60psi
01-10-2016, 12:43 PM
#18
I run P rated tires and tow 5000# and go off road...without incident or problems.
You do not need LT tires to tow or drive off road.
I'm not willing to sacrifice ride quality by putting on 10 ply tires.
Fuel usage also goes up with LT tires.
If I was to tow 9-10.000#...regularly, I'd buy an F250...and probably get LT tires.
You do not need LT tires to tow or drive off road.
I'm not willing to sacrifice ride quality by putting on 10 ply tires.
Fuel usage also goes up with LT tires.
If I was to tow 9-10.000#...regularly, I'd buy an F250...and probably get LT tires.
01-10-2016, 12:55 PM
#19
Senior Member
Discount tire rotated my tires and put 35 psi in them. The placard says 55 front 60 rear. Always check your tires before you drive away. BTW may rear axle rating is 4,800lb. So I need tires with AT LEAST 2,400 lb capacity.
Based on my placard and the tires the OP bought, I think 41 psi is way too low. 50 sounds a lot closer.
Based on my placard and the tires the OP bought, I think 41 psi is way too low. 50 sounds a lot closer.
01-10-2016, 01:46 PM
#20
This is something of a re-post but here goes.
I have LT LR C tires. I run 40 unloaded and 50 when towing. I've got 70K on these tires now and they have at least 5K more in them. They wear nice and evenly; no rounded outer edge either. I've pulled a 5,500 lb RV trailer over 15K miles on these tires.
My out-takes:
You only need maximum pressure when heavily loaded or towing
Load Range E is overkill on a 1/2 ton
Load Range C rides better than E (worse than P) and provides sufficient load capacity and lateral stiffness for towing control
Goodyear Wrangler AT LT Load Range C
Just my observations and opinions. Not looking for a war of words.
I have LT LR C tires. I run 40 unloaded and 50 when towing. I've got 70K on these tires now and they have at least 5K more in them. They wear nice and evenly; no rounded outer edge either. I've pulled a 5,500 lb RV trailer over 15K miles on these tires.
My out-takes:
You only need maximum pressure when heavily loaded or towing
Load Range E is overkill on a 1/2 ton
Load Range C rides better than E (worse than P) and provides sufficient load capacity and lateral stiffness for towing control
Goodyear Wrangler AT LT Load Range C
Just my observations and opinions. Not looking for a war of words.