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Author Topic: TV tires - Michelin 275/65R18 load rating E - pressure when towing  (Read 343 times)

603Country

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We are relatively new to the TT dragging biz, but learning fast. I was about due for new tires on my Tundra, so I upgraded to E rated 10 ply Michelins. I called Michelin to see what they had to say about operating pressures while towing and not towing. The lady danced around the question and finally said the max for towing and overall max tire pressure was 45 pounds. Well, the side wall says max is 80 pounds, so I ended the call with her. Seems smarter to ask you folks, so here I am. What pressure do you suggest for towing our 2150RB? And what pressure for non-towing?

These are not OEM tires, so the door jamb plate isn't going to give me the answer I need. Thanks.

Kirk

8Muddypaws

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #1 on: August 05, 2017, 10:12:19 AM »
Back when I was towing I always ran the truck tires at the max stamped on the side of the tire.  TV too.
Retired computer professional
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2006 Bounder 34H, 2008 CR-V Toad

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #2 on: August 05, 2017, 11:15:50 AM »
I called Michelin again, hoping to find another techie to answer my tire pressure question. This woman was quite helpful and quite knowledgeable. She said the data wasn't easily available on their charts, so she'd have to do the math with her calculator. She took truck weight and type of cab, and went to work on the calculator. She came back and said that my normal everyday driving tire pressure should be 55 pounds (80 psi is tire max pressure) and to raise that to 65 pounds for the TT and tongue weight that I have.

I feel comfortable with that information, and that's what I'll use. I thought I'd share the data with ya'll. And I'm glad that Michelin has some folks like her. The previous techie was not knowledgable at all.

Kirk

WILDEBILL308

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #3 on: August 05, 2017, 12:20:50 PM »
Kirk, The best way is to weigh your rig set up and loaded for travel. Take the weight on the rear wheels/axle of your truck. Michelin has inflation tables base on weight. I would run that preshure +10 pounds for a safety margin. :))
Any questions let me know.
Bill
2003 Bounder 38N
300 HP 5.9 Cummins
Allison 3000MH Trans.
Towing 2014 Honda CRV
Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

ducnut

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #4 on: August 05, 2017, 03:11:05 PM »
That 2nd "tech" needs to stay away from the phone.

I have 285/65-18 BFG (a Michelin company), mounted on a 9" rim, on my 1/2T Silverado. Likewise, they could be inflated to 80psi.

If your tire shop did not install the correct valve stems rated for high pressures, don't even think about it. Low pressure stems can blow out of the rim, especially as pressures climb during use. I made sure to specify them to the tire tech.

With the stiff construction of these tires, you can run a few psi under what your doorjamb decal shows. I'm 2psi under at the front and 5psi under at the rear. Even that low at the rear and I barely have contact on the outer edges of the tread, empty or unhitched. The heavier the tire construction, the less sidewall flex, and the less pressure gain (an indicator of how hard the tire is being worked).

Even hitched up, I wouldn't run more than 35psi-38psi, or so, in the rear of your truck, unless you encountered sway/instability at the tires.  The specs for your TT show 500lbs of hitch weight. I towed every bit of that tongue weight, everyday for 40K miles, in my truck. I have an Andersen WD hitch (absolutely stellar product) on that setup, as well. The only times I added extra air were when I knew I was going to do something beyond normal, like load 2K pounds in the bed or go to the quarry with a dump trailer and overload the whole rig (21,200lbs is the most I've scaled out :o).

You already have LT tires of heavier than normal construction, your hitch weight isn't crazy, your TT isn't excessively long or high. There's no need to get crazy with pressures or overthink it.

BTW, You've picked up a really nice travel trailer.

603Country

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #5 on: August 05, 2017, 03:55:27 PM »
High pressure stems....I never thought of that. I'll call Discount Tire and ask what they used. They recommended running at 45 psi, by the way.

Not in any way suggesting that you are wrong, but you have to admit that it is interesting that I have gotten so many different opinions on the best or most correct operating pressure when towing or not towing.

If Discount Tire did use the high pressure stems, I'll probably try running at 55 psi and see how the tire sits. If the stems aren't for high pressure, I'll run at 45 pounds and see how that works.

Thanks for the comments.

Kirk

603Country

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #6 on: August 05, 2017, 04:28:04 PM »
Yup! High pressure stems. I went to 50 psi and tire contact looks about right. I'll go with that for a while.

Kirk

scottydl

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #7 on: August 05, 2017, 05:25:19 PM »
Kirk, The best way is to weigh your rig set up and loaded for travel. Take the weight on the rear wheels/axle of your truck. Michelin has inflation tables base on weight. I would run that preshure +10 pounds for a safety margin. :))
Any questions let me know.

As Bill said above, weighing your complete (loaded) trailer and comparing that to the tire manufacturer inflation tables is the answer to your question.  See this forum library article for instructions on how to weigh your entire rig to get the numbers you need.  I personally wouldn't add the 10# as that could harden the ride quite a bit, but that's personal preference.  ;)

All 'E' truck tires should have a max psi of 80#.  But you only need to run what is required to carry the weight you have, which will also be different for front and rear axles.  On my Suburban, factory tire pressure (for just cruising around) is 35# front and 50# rear per the doorjamb sticker.  Another doorjamb sticker discusses tire pressure for towing heavy loads and recommends 45# front and 80# rear.  I used that for awhile (when towing) and it worked fine but was a pretty rough ride.  After getting weights of everything and doing the axle math, I now run 43# front and 73# rear when towing.  Best of both worlds, the right support for my trailer load + maximum shock absorption for a smoother ride.
Scott, wife, 3 boys... and the dog
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WILDEBILL308

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #8 on: August 05, 2017, 07:41:23 PM »
As Bill said above, weighing your complete (loaded) trailer and comparing that to the tire manufacturer inflation tables is the answer to your question.  See this forum library article for instructions on how to weigh your entire rig to get the numbers you need.  I personally wouldn't add the 10# as that could harden the ride quite a bit, but that's personal preference.  ;)
All 'E' truck tires should have a max psi of 80#.  But you only need to run what is required to carry the weight you have, which will also be different for front and rear axles.  On my Suburban, factory tire pressure (for just cruising around) is 35# front and 50# rear per the doorjamb sticker.  Another doorjamb sticker discusses tire pressure for towing heavy loads and recommends 45# front and 80# rear.  I used that for awhile (when towing) and it worked fine but was a pretty rough ride.  After getting weights of everything and doing the axle math, I now run 43# front and 73# rear when towing.  Best of both worlds, the right support for my trailer load + maximum shock absorption for a smoother ride.
I am not use to dealing with little truck tires. ;) I would still have some cushion for safety. The tire preshure in the tables is the "minimum" for that weight. If you are in a area that is hot and set your preshure and you go someplace cooler or a cold front comes through you are now underinflated for the load. :P
Bill
2003 Bounder 38N
300 HP 5.9 Cummins
Allison 3000MH Trans.
Towing 2014 Honda CRV
Home base Fort Worth, Texas
A man who carries a cat by the tail learns something he can learn in no other way.
-Mark Twain-

ducnut

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #9 on: August 05, 2017, 10:19:59 PM »
Not in any way suggesting that you are wrong, but you have to admit that it is interesting that I have gotten so many different opinions on the best or most correct operating pressure when towing or not towing.

Not at all surprising. Your Michelin "techs" are most likely customer service reps looking at a matrix graph, trying to come up with something for an answer. As for a lot of answers I read in many threads, its keyboard cowboys who know everything, about everything. In reality, they know very little and throw out something they hope will stick or regurgitate something they've seen elsewhere. If someone isn't intimately knowledgeable of the subject, I wish they'd just refrain from posting, as it only adds confusion and further misinformation.

First off, the doorjamb sticker is an average suggestion, trying to cover many scenarios. It's not perfect and not set in stone. Case in point is my truck, which shows 35F/35R. My frontend is substantially heavier than the rear. Therefore, I wouldn't need as much pressure in the rear to support its weight, since it's lighter. Likewise, if I follow the sticker and go load 1000lbs of material in the bed, now, I'm underinflated for the load. But, wait!!! The sticker tells me blah, blah, blah. We need to be inflated for the actual load and not what a sticker or sidewall says.

Now, I presume, you left Discount Tire in the same truck you drove in. The only thing you changed was a bit larger tire, which adds a bit more tire volume, which means you can run a bit less pressure (1-2psi). However, for some reason, you feel the need to run 50psi in them. I don't understand why. You've changed nothing about the weight of your truck, so there wouldn't be any need to drastically increase your pressures beyond factory, because you're not supporting additional weight. If anything, take advantage of the extra volume/flotation of them and drop a few. It's a 10-ply tire and will already ride rougher than what came on it. A 6- or 8-ply tire could've handled what you're going to be towing. But, I understand wanting to be equipped. No worries, there. You would only need to bump up the rears, once you're loaded or hitched. Lastly, an overinflated tire will have less grip than one properly inflated for the weight being carried.

As I stated above, your TT doesn't have a massive tongue weight. If I could suggest anything, it would be a nice, automatic ride-height airbag system and a WD hitch. The airbags will keep the truck at a set height and desired attitude, your TT at a desired attitude, and help to stabilize the rig. A WD hitch will further the stabilization and help mitigate porpoising. I have both and have never had an issue with any trailer configuration or weight.

Do not add 10psi extra to any tire, for peace of mind (I'll save the essay). However, a TPMS would be great to monitor pressure gain. When you see pressure in a tire creeping up beyond what the others are sitting at (assuming all are equally loaded), you'll know you're having an issue at that location. Likewise, if you see more than 10-15% pressure gain across similarly loaded tires, you'll know you need to bump pressures to better support the weight. If you're at max psi on the sidewall, you'll need to investigate heavier tire options. Overspeeding, bad wheel bearings, bent axles, poor alignments, etc do not count.

The Suburban mentioned above has the factory presuming it's going to be carrying passengers in the rear, so they purposely suggest a much higher pressure in the rear to support their weight. I only mention this, so people don't automatically assume they need to be running the same level of pressures, in the same positions, in their empty or dissimilar vehicles. That thing is a heavy beast, ready to haul everyone and pull anything.

Gary RV_Wizard

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #10 on: August 06, 2017, 08:34:00 AM »
I pretty much agree with ducnut. If the tire size (275/65R18) is the same and you merely upgraded from Load range D to E, nothing has really changed and the door sticker is still accurate. You could increase 5 psi if you think the trailer tongue weight is higher than an average truck payload, but the tongue weight on your trailer is probably rather modest.

The best answer is to weigh the truck with and without the trailer hitched up and compare to the Michelin load/inflation tables for that tire. You will notice that the D & E tires use the same psi at all load levels and the only difference is that the E can go higher than the D. Since the LRD tire can comfortably handle even your heaviest load, there is no need to use inflation pressures in the higher range the E can handle.
« Last Edit: August 06, 2017, 08:39:58 AM by Gary RV_Wizard »
Gary
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603Country

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Re: TV tires - Michelin 275/65R18 load rating E - pressure when towing
« Reply #11 on: August 06, 2017, 11:58:09 AM »
Ok, I see your logic. With the old tires, I ran at 35# front and back and bumped up to 40 when towing the TT. I have the Blue Ox 1000 WDH and went to 40 pounds because it felt a touch squirmy at 35. Felt better at 40.

We used to have an old (1966) 26 foot Overlander Airstream. It never felt squirmy. Never knew it was back there, and I never messed with changing tire pressures. And I didn't have a WDH because I didn't know then that I needed one. We didn't travel with it much, so towing was not done often.

My country neighbor is a cattleman and a long distance trucker. He was over this morning, looking for his prize bull, who was munching grass on my back pasture, and I asked him a few towing questions and the tire pressure question. He has an assortment of cattle trailers and horse trailers. He has the same 10 ply tires on his diesel dually, and he suggested 55 pounds. Toyota recommended 45 pounds. Discount tire recommended 45 pounds. First call to Michelin resulted in a suggested 45 pounds, and the second call at 55 pounds.

I'll drop pressure to 40 (5 higher than in the past) front and back and try that out for a while.

Now I'll go see if I can find the fence gap the bull used to visit me today.

 

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