E rated tires and air pressure?

[Squatch]

I adjusted pressure yesterday to 45/55 with the camper loaded. Closer to what Cooper suggested and seems good. It drives nice and both front and rear tires seem to match as far as the slight bulge at the bottom.

One thing I've noticed. Before with the camper we had sort of a quick jerk motion in the rear on some highway bumps occasionally that wasn't comfortable. I liken it to the way you sometimes see dump trucks kind of hammer on the suspension for lack of a better description. I had attributed this to the air bags. It has disappeared since the new tires!

 

[Squatch]

Just did a trip of 400 miles or so over the last few days. My tire pressure of 45/55 seems right on. I stopped for fuel after a couple of hours driving and felt the tires. I felt all 4 and they all felt exactly the same temperature. just a little warm as they should be. The tires performed well. I didn't try them on anything worse than a gravel road though. On the highway you can hear them but it's far from obnoxious on my rig. I don't think they help my fuel economy though.

 

[PackRat]

Last time around I put Michelin LT235/85R16E tires on my F-250 4x4 extended cab truck because, well, that is what the door VIN tag called for. Since tire specs are a reflection of the GVWR and conversely, the Front GAWR and the Rear GAWR independant loads, the air pressure in the tires is different.

With a GVWR of 8800 lbs.
Front GAWR of 3920 lbs. = 51 psi cold
Rear GAWR of 6084 lbs. = 80 psi cold
Those numbers reflect what you should have when you are loading that kind of cargo. Now I need to rotate the tires this week and I will see what the TP is before and after the shop does that for me but as noted above, underinflating shortens the life of tires.

1) Check the VIN tag for the tire ratings your truck SHOULD have then check the tires to see if they are within spec.
2) Check GVWR of your rig fully loaded with fuel/water/supplies/gear/etc. and see if you are even within spec.
3) Over loading a 1/2 ton pickup is not a good idea, but running tires not even rated for its original specs is a really bad idea.
4) At the very least, if you are overloading your 1/2 ton truck on purpose, maybe consider getting tires on it for a 3/4 ton truck and using the air pressure they are rated for which is what a 3/4 ton would use to carry the same load you are running.

While you are at it, see if the rear axle is severely over loaded and the front riding high as that gives you a very light steering up front which is dangerous and you might want to consider all the stuff you are hanging on the rear of the truck/camper being moved FORWARD to get weight off the rear axle and shared more with the front.

I've had 1/2 ton trucks....but the 3/4 is more versatile and with just about any camper on it (1200-1700 lbs) the difference is big time. Yes...it is like driving the Queen Mary or something in parking lots or downtown but once away from traffic, etc. that big land barge of mine gets 'er done!

 

[flinchlock]

I emailed Michelin this morning...

I have tried to use Google to help me calculate tire pressure, but no luck, please help.

2007 Tundra: 4.7L V8, 2 door reg cab, 8' bed, 4x4, factory tow package
271HP/313 Lb-Ft 4.7L DOHC 32V V8 w/VVT-i 5-Spd Automatic
Tow Equip: Hitch Receiver, Supplemental Automatic Limited Slip Diff (Auto LSD)
Payload = 1780 lbs.
Tow Capacity = 8100 lbs.

Door Post Sticker
GVWR: 7000 lb
GAWR Frnt: 4000 LB @ 30# with P275/65R18
GAWR Rear: 4150 LB @ 33# with P275/65R18

I have Michelin, LTX A/T2, LT275/65R18 123/120R

CAT Scale with slip-in/popup camper...
Frnt Axle: 3520 lb
Rear Axle: 3740 lb
Gross: 7260 lb

THANKS,
Mike

I received this response...

We understand your need for this information, Mike. When going up to a new tire size, all manufacturer specifications must be maintained. One of the most important of which is the load carrying capacity of your vehicle.

With your original tire size P275/65R18, calling for 30 PSI in the front and 33 PSI in the rear, it gave your vehicle a load carrying capacity of 2,421 lbs (per tire) in the front and 2,535 lbs (per tire) in the rear. For safety reasons, Michelin's recommendation is to always meet or exceed these thresholds with a new tire size.

With your new tire size of LT275/65R18, the inflation pressure you would need to use to be in compliance with this is 50 PSI in the front and rear, granting your vehicle a load carrying capacity of 2,535 lbs (per tire) on both front and rear, thereby exceeding the threshold requirements.

 

[klahanie]

^ flinchlock, like others I like to use the Toyo Inflation Table.

Looking at the Table I'm not sure that the load capacity of the P metrics given in Michelin's reply has been reduced by 1.1 for light truck use (see Table, page 5). If not the application capacity would be 2200 FR / 2304 RR (that makes more sense to me with GAWRs of 4000/4150). This is important because that would reduce the equivalent LT pressure down to ~ 42/45 according to the Table.

Furthermore, I would use my actual weights rather than the "load carrying capacity of your vehicle", reducing the min pressure for your quoted weights to ~ 35psi. This would give a more comfortable ride off highway compared to 50 psi.

Note, the table lists "minimum" pressure for a given weight - nothing saying one can't go higher. *

ON EDIT: S/B * The table lists maximum weight for a given pressure - nothing saying one can't go with a higher pressure for the same weight (I do for highway driving)

 

[flinchlock]

I just sent this to Michelin...

Some friends of mine wonder if you took into account this...

*"When a P-metric or metric tire is installed on a light truck (SUV,
pickup, minivan), the load capacity of*
*the tire is reduced by a factor of 1.101*
*as prescribed by the Federal Motor Vehicle Safety Standards*
*(FMVSS)."*

Their response...

We understand your concern for this issue, Mike. However, the load inflation chart is not a recommendation, it simply provides the weights an individual tire can hold at a specific inflation rating.

This particular inflation chart is more meant to support larger Commercial trucks, but does still have some light truck tire sizes listed on it.

Mike

 

[CamperCamper]

Quote

I have tried to use Google to help me calculate tire pressure, but no luck, please help.

2007 Tundra: 4.7L V8, 2 door reg cab, 8' bed, 4x4, factory tow package
271HP/313 Lb-Ft 4.7L DOHC 32V V8 w/VVT-i 5-Spd Automatic
Tow Equip: Hitch Receiver, Supplemental Automatic Limited Slip Diff (Auto LSD)
Payload = 1780 lbs.
Tow Capacity = 8100 lbs.

Door Post Sticker
GVWR: 7000 lb
GAWR Frnt: 4000 LB @ 30# with P275/65R18
GAWR Rear: 4150 LB @ 33# with P275/65R18

I have Michelin, LTX A/T2, LT275/65R18 123/120R

CAT Scale with slip-in/popup camper...
Frnt Axle: 3520 lb
Rear Axle: 3740 lb
Gross: 7260 lb

THANKS,
Mike

I am running the exact same E rated tires on my 2015 Tundra. After much effort, I was able to get Michelin to supply me with the following pressure/load chart for these tires. Hope it helps.

Inflation Guide per tire loads:

35 psi 1940 lbs 3880 axel load
40 psi 2130 lbs 4260 axel load
45 psi 2310 lbs 4620 axel load
50 psi 2535 lbs 5070 axel load
55 psi 2660 lbs 5320 axel load
60 psi 2825 lbs 5650 axel load
65 psi 3000 lbs 6000 axel load
70 psi 3150 lbs 6300 axel load
75 psi 3305 lbs 6610 axel load
80 psi 3415 lbs 6830 axel load

 

[iowahiker]

My Ford half ton truck has factory LT load range E tires for 8200 GVWR and a door tire pressure of 60 psi rear and 55 psi front. Someone posted the new Ford half ton with LT load range E tires for 8000 GVWR was 50 psi front and rear. Both are above "charts" but that was Ford's choice, works for me.

 

[idahoron]

I have the LTX M/S2 tires on my 05 tundra. My front axle is 2900 my back axle is 4420 Total load is 7300 pounds.
There is no way I would run air pressure as low as the info above.

 

[CamperCamper]

I have the LTX M/S2 tires on my 05 tundra. My front axle is 2900 my back axle is 4420 Total load is 7300 pounds.
There is no way I would run air pressure as low as the info above.

Help me to understand. Do you know something you would like to share? I am under the impression that the manufacturer is providing reliable information for the tire I am running. The ride is comfortable and not too stiff or bouncy. My tires have 30,000 miles on them and 95% tread left on the tires. What pressure would you run, why would you deviate from the recommended pressure and what could I expect to achieve by following that recommendation?

Thank you in advance for your insight!

 

[Advmoto18]

For the most part...most tire manufacturer psi recommendations are approved by the legal office after the engineering sign off. Recall the Firestone tire fiasco a few years ago?

The last thing nearly all tire manufacturers are going to do today is publish a litany of psi recommendations based on axle weight because 99.9% of the buying public is completely unaware of this spec let alone know how to determine such. Under inflation has resulted in many accidents and not just with the problematic Firestone tire. As a retired airline Captain, we checked the tire psi before every flight, either at the tire or on the display in the cockpit (I'm old so its still a cockpit). I used to check the tire psi on my vehicles regularly (several times a week) before TPMs. Now I rely on TPMs. Sadly, I can't call up the current tire psi on my show me everything display (except tire psi) in my '16 Super Duty.

Most of use on WTW are aware of our weights because we are pushing the GVWR envelope and have likely weighed our rigs at a Black Cat or similar scale. If you have the scale numbers for your loaded rig, it is very easy to enter the TOYO tables and determine your optimum inflation psi. TOYO offers the info because they sell hard core tires for hard core use and off-roaders who find the information is valuable And yes, you use the information at your own risk and peril. Sadly, the legal department for most other manufacturers has pulled this type of info from the public domain.

 

[idahoron]

I run 50 on my front and 55 on the rear. By the table above I would be running under 35 pounds of pressure on my front. No WAY am I going to run that low. The tires would heat up like crazy. Gas millage would tank, and every time I went around a corner the truck would lean. No thanks.

 

[BillTheHiker]

I just had a fascinating phone call with a customer service rep at Cooper Tire headquarters regarding the correct psi for my tires: Cooper AT3 245 75 R16 load range E. Truck is a 2008 Tacoma TRD off road 6' bed 4x4 V6. total weight with loaded camper is about 5530, which is only 200 pounds above GVWR. I bought them last month from Discount Tire and they put 40 psi in all four tires. Ride and handling is good, both highway and some moderately washboard roads, but the tire pressure warning is always on. I tried going as low as 35 psi per tire and still have the warning light and at that psi the tires visually bulge out a bit and look under-inflated. Discount Tire does not have an answer other than trying out different psi to see what happens.

After doing a little research, the Cooper rep said he thinks I have too much tire for the truck and he recommended going back to the 4 ply AT3. He said there is no difference in the side wall thickness and that while the E range tire is stronger internally, that strength is designed for much heavier load than what I have and he thinks that I should be fine with the 4 ply even off road. He said if I stick with the E tires 29 psi on all four is the correct number, but he does not recommend it as the tire would be too flattened out and might not handle well.

He said Cooper will work with my dealer to refund the cost differential if I get the 4 ply.

So what do you guys think, should I switch to the 4 ply?

 

[klahanie]

.

He said Cooper will work with my dealer to refund the cost differential if I get the 4 ply.

So what do you guys think, should I switch to the 4 ply?

Wow, you don't hear that too often. I'd find out why the TPMS light is on first. Mine comes on when a tire pressure measures less than the Ford spec. Seems yours is because it is higher but I'd want to make sure of the cause first. As for a 4 ply, no I wouldn't switch. Not being smart but for 6 ply rating "C" - prob what they mean - I might. According to the Toyo supplied table the psi would be the same for C and E versions up to the C max of 50psi, 2205# max load then E version continues to a higher max psi and load. So if 29 psi is the correct number for the E it will be the same for the C version of that size. Would the light still come on ?

Whether you benefit from the higher ply rating idk. From purely a load perspective you don't need an E. I have read though that you should have a 50% over capacity in the tires for durability [EDIT for off highway use] which the C might accomplish. Overall I think cornering stiffness and general road compliance is where difference between the ply ratings will show.

I'm sure someone with experience will reply soon ...

 

[Idahostat]

Hello Group

So on a 10ply E rated tire when air down for traction, does the tire get a little wider, lot wider or just some what softer ( that may be a reach ) for traction on a given surface/materials?

This relates to mud flap width, durflap whom I have contacted about width and length of flaps suggested the "normal" length ( 9" ) as I do not intend on lifting my truck ( nor towing anything at this time ) and as I expect to run/use the default Michelin 275/70/18R ( 10.8" width for many of us who do not calculate in metric that easily ) base model is 12" in width so as to reduce flung materials. However a wider 14" mudflap would tend to contain aforementioned "flung" objects with wider ( not necessarily taller tires ) when the front wheels are turning. Not sure how much of this flap would hang outside the wheel wells ( images on the durflap web site are suggestive on an inch or two ).

Any experience?

Terence

 

[Advmoto18]

Hello Group

So on a 10ply E rated tire when air down for traction, does the tire get a little wider, lot wider or just some what softer ( that may be a reach ) for traction on a given surface/materials?

Regardless of tire rating, airing down...
1. Allows the tire to conform to the terrain
2. Increases traction, which reduces wheel spin (less rut digging and adverse impact on land)
3. No, the tire carcass does not widen but rather lengthens, thereby increasing the footprint which allows you to have better performance, especially in sand due to enhanced floatation. Your tread pattern is only as wide as manufactured, why it doesn't and can't widen. But airing down allows lengthening of the tread in contact with the terrain.

 

[Idahostat]

Thanks Advmoto18

The lengthening makes sense, for some reason my thought was the tire sidewalls allowed widening which is not what happens.

So as this related to my choice of mud flaps width I can stick with the 12" or not.

Thank you for you patience.

T.

 

[TGK]

I recently purchased a 2017 F150 4x4 SuperCrew with the 3.5L EcoBoost. Plan on doing some towing with it and also use as daily driver. It came with 275/65R18 Goodyear All Terrain P-metric tires. I switched to Michelin LTX AT/2 E rated tires. After installation, the tire dealer inflated to the 35psi spec as posted on the door jam. Given that max psi for these tires is 80, I was skeptical. So, I contacted Michelin directly via their chat talk. I explained to the rep details regarding the truck, original equipment tires, factory suggested psi and also about the new Michelins I put on. I asked for a recommendation for psi for these new tires. They said they would check and put me on hold for quite a while. They eventually came back and told me to run them at 60 psi minimum. They said they used a chart to calculate that based on the type of vehicle etc.

I stepped up to LTX AT/2's because I have them on an old F250 that carries my Grandby and they have stood up extremely well on the rocky/gravel roads I drive on in eastern Oregon. They supposedly are know for durability on gravel. I also wanted the stiffer sidewall when I tow my older Airstream trailer. I rented one of these F150's from the local Airstream dealer last fall and hooked up my trailer and drove it up around mount hood. It had the factory P-metic tires on it. Power going up the grade was impressive. However, I noticed some sway on the way back on 84. Some folks believe the stiffer sidewalls on the E rated tires give a better towing experience and get help reduce sway. I guess I'll find out next week when I hook the trailer up for a longer trip. I've got close to 2,000 miles on the tires now and the truck rides and handle fine. It may be a touch harsher than with the factory tires, but very acceptable to me at this point. With the trailer hooked up and loaded for a trip, as well as additional gear, passengers, dog, canoe, etc., in the truck I will have a respectable load on the truck.

I'm open to additional thoughts on this topic.

 

[Advmoto18]

I recently purchased a 2017 F150 4x4 SuperCrew with the 3.5L EcoBoost. Plan on doing some towing with it and also use as daily driver. It came with 275/65R18 Goodyear All Terrain P-metric tires. I switched to Michelin LTX AT/2 E rated tires. After installation, the tire dealer inflated to the 35psi spec as posted on the door jam. Given that max psi for these tires is 80, I was skeptical. So, I contacted Michelin directly via their chat talk. I explained to the rep details regarding the truck, original equipment tires, factory suggested psi and also about the new Michelins I put on. I asked for a recommendation for psi for these new tires. They said they would check and put me on hold for quite a while. They eventually came back and told me to run them at 60 psi minimum. They said they used a chart to calculate that based on the type of vehicle etc.

I stepped up to LTX AT/2's because I have them on an old F250 that carries my Grandby and they have stood up extremely well on the rocky/gravel roads I drive on in eastern Oregon. They supposedly are know for durability on gravel. I also wanted the stiffer sidewall when I tow my older Airstream trailer. I rented one of these F150's from the local Airstream dealer last fall and hooked up my trailer and drove it up around mount hood. It had the factory P-metic tires on it. Power going up the grade was impressive. However, I noticed some sway on the way back on 84. Some folks believe the stiffer sidewalls on the E rated tires give a better towing experience and get help reduce sway. I guess I'll find out next week when I hook the trailer up for a longer trip. I've got close to 2,000 miles on the tires now and the truck rides and handle fine. It may be a touch harsher than with the factory tires, but very acceptable to me at this point. With the trailer hooked up and loaded for a trip, as well as additional gear, passengers, dog, canoe, etc., in the truck I will have a respectable load on the truck.

I'm open to additional thoughts on this topic.

I don't think load rating has much to do with preventing adverse sway. A sway bar is the most effective method to control or minimize sway.

Sidewall rating is merely the ability to carry a given load. As your load increases, so should your tire rating in order to carry the axle weighted load.

In so far as tire inflation is concerned...
There is a sweet spot psi for your individual axle weight. Sadly, most tire companies no longer publish the information to determine the "sweet spot psi". Likely due to Firestone tire failures (due to poor design and under inflation for loading) a few years ago. Now manufacturers/installers recommend airing tires up to the cold psi rating on the sidewall and go ride. Further, TPMs seem to be calibrated for this sidewall placarded cold psi number as well. Well, that's not a very comfortable ride, especially if you are light loaded and have E rated tires. As a matter of fact, the ride can be quite harsh, even on decent tarmac.

Toyo still publishes information to help you find the sweet spot. I don't run Toyo tires, but the Toyo numbers have worked for me on BF Goodrich, General and now Michelin E rated tires. But, to use the chart and determine your psi, you must get weighed. You need the front and rear axle weights. I weighed my truck unladen and again laden with the camper and all my camping stuff. I run the laden psi all the time since my camper stays in the truck full time.

99.9% of the motoring public is poorly or not informed on tire psi management. Such being the case, manufacturers/installers simply state to air up to a high psi regards of the vehicles weight.

 

[TGK]

In the past, I towed my trailer with the '99 F20 SuperDuty with load distribution bars but no sway control. I never experienced sway with the load bars on or without. I did experience a bit when towing with the rented F150 last fall. There appears to be a lot of users on the Airstream Forums website that attribute some benefit to load range E tires for reducing sway, but one always has to take what they read on forums cautiously. The trailer is medium size tandem axle with a gross weight rating of 5,200 lbs.

For the heck of it, I contacted Michelin again to see what they'd say regarding psi on their LTX AT/2 E tires vs the P-metric C OEM tires. This time they told me to run 55 psi front and rear vs 60 psi a few weeks ago. They suggested I increase the pressure when towing and loaded up.

Thanks for the input.