Michelin LTX 235/75R15 XL Upgrade?

[gmw photos]

Originally Posted by Dean E

Hello all,
I would like to get a set of the Michelin LTX M/S2 P235/75R15s to replace the old set of ST205/75R15s. The 1984 vintage steel rims are 5.5 inches wide (measured with a set of calipers), but the Michelins are specified with 6.5 inch width, and suitable for a range of 6-8 inches.
I assume that because my old 5.5 inch width rims are outside the 6-8 inch range for the new Michelins, the handling would not be right, and that there would be too much wear at the center of the tread.
I am disappointed because I don't want to go back to the ST design.
Thanks for all of the detailed and reasoned info!

Dean,
How much load capacity do you need ? Good Year G26 Cargo in a 195/70-15 load range D has 1985 lbs capacity at 65psi, and fits a 5 to 6 inch rim. It is a LT tire.
Another choice is a Continental Vanco 2. In a 215/70-15 LR D, 2271 @65psi. Specs a 5.5" to 7" rim. That's a couple of ways to avoid a ST tire replacement.

[CapriRacer]

Originally Posted by switz

Are there any Canadian regulations that require the 10% derating of a passenger rated tire used on a trailer like in the states? .....

Just to clear up a point.

The derating of P type tires when used in trucks, vans, and trailers is part of the tire standard as published by the Tire and Rim Association (TRA)- the US tire standardizing organization. The fact that the US Federal Government has such words in their regulation is more a reflection of TRA than a regulation per se.

The Canadians follow the US tire standards. If the Canadian government has put this derating in their regulations, - again - it is a reflection of TRA.

In the big scheme of things, it doesn't matter. The tire manufacturers subscribe to TRA and their standards (with a few isolated exceptions) and that should settle the issue.

[Andrew T]

Hi Dean

I am not sure what your trailer is but you can use a Yokohama Geolander 215/75R x 15 LT Load Range "C". I have used this tire quite often in place of the 205 ST tires. My only concern is I am not sure how much longer they will be available.

Switz: The trailers are just not that heavy, I have weighed a lot of 30 & 31' classics loaded for travel and I have not seen one over 8000 on the axles. Even 34's are only 8600-9200. Before the switch to Dexter 30's came with 4000 pound axles.

LT vs XL: The unofficial answer is from Michelin is that they are the same tire. They used to make 3 different 235/15', P standard load 35 PSI, P extra load 41 PSI and LT 50 PSI. When they rationalized these to one tire they labeled the LT as an P XL to get the extra load capacity for applications where it was necessary. Just make sure when you get them that they are 50 PSI capacity but I am sure all the 41 PSI tires are out of the system by now.

Andrew T

[Ridgerunner3]

I gave serious consideration to the Vanco2 tires before I purchased the Michelin 15 XL's. Tire Rack said they were closing out the Vanco2 tires. I contacted Continental by email and asked about the continued availability of the 225 70 15 Vanco2. Continental said that they were discontinuing the Vanco2. I am not sure if this means that they are discontinuing the whole line of Vanco2 or just that one size. No information on what will replace the Vanco2 in my size.

[SteveSueMac]

Can I assume the 15X7JJ rim number on my tire placard is telling me the rim is 7" wide? And what does the JJ mean? Thanks

[Dean E]

Thanks Top. I ordered a set from tire rack.
Dean E

[gmw photos]

Originally Posted by Ridgerunner3

I gave serious consideration to the Vanco2 tires before I purchased the Michelin 15 XL's. Tire Rack said they were closing out the Vanco2 tires. I contacted Continental by email and asked about the continued availability of the 225 70 15 Vanco2. Continental said that they were discontinuing the Vanco2. I am not sure if this means that they are discontinuing the whole line of Vanco2 or just that one size. No information on what will replace the Vanco2 in my size.

Certainly, the idea of a tire being discontinued might be one factor to consider. However, it's been my experience over my 40 plus years of driving, that all tires eventually get "discontinued". We have one vehicle in the family right now that seldom gets driven that has a set of Good Year aquatreads on it, that are now discontinued. Technology, and marketing moves on. If I can get a product that is being discontinued at a deep enough discount, I am often willing to roll the dice that it will last out it's useful life without failing.
But it's true that if a guy bought a set of four tires, and fails one in a year only to find it discontinued, then he could be stuck buying a pair or maybe even a whole set to replace ?
Hey....there's an advantage of using ST tires....dealers keep plenty of "matching" tires in stock, 'cuz they know they will be seeing you again soon !

[switz]

If the trailer axles alone are carrying much more than 7,200 pounds when fully loaded, then the 10% reserve becomes a smaller and smaller reserve capacity as the weight approaches your hypothetical 8,000 pounds load which exceeds the derated maximum 7,940 load rating and at that point are actually overloaded.

Also, unless one acquires, or has access to, independent wheel scales, the user does NOT know if the four wheels are each carrying identical weights. Unless the trailer is dead level when fully loaded and attached to the tow vehicle, the axles can be carrying different loads. If the user has not exactly balanced the load left to right then one side of the trailer would be heavier.

Thus loading the tires to maximum capacity could allow some tires to be actually overloaded while others might still have a small reserve.

What happens if a tire acquires a nail and goes flat? The other tire on that side would have suddenly have twice the load. How long can it carry that before failure?

It has been mentioned in the these tire threads that if a tire goes down, both tires on that side should be replaced due to the stress of twice the normal load.

Thus, I personally opt for the higher rated Michelin LT 225/75R16E tire for the new 2,700 pound heavier trailer. I am perfectly happy with the Michelin LTX (P) 235/75R15 XL tires on our 25FB International and, in my opinion, they are sized to the load and have a more than adequate safety margin of actual load to rated capacity.

My guesstimate of the reserves on the 27FB are about 22% and that is about the same number I calculated as the reserve on the 25FB.

YMMV

[Tireman9]

Originally Posted by Andrew T

Airstream always recomends the maximum pressure for any tire they install. That is because lawyers study so much about tires in law school.

If you run 80 PSI in those 16" tires you are going to really shake the Airstream badly and if you have to make a panic stop in the wet they will have almost no bite.

Your foot print on the road in square inches is roughly the tire load divided by its PSI. So you if you have 1600 pounds on a tire with 80 PSI in it you only get about a 20 square inch contact patch.

The best way to determine tire pressure is to get your actual axle weights. Many truck stops have scales that are divided into sections. Park on the scale so your tow vehicle front axle is on one section, the back axle on another section and the trailer axle on a third section. Once you know your weight per tire you can check load inflation tables for the correct pressure to carry. A tire will be more reliable, ride smoother and have more traction at the correct loaded pressure. Goodyear's RV section has most of the tires used on tow vehicles and trailers listed. Toyo has one with almost all the other sizes.


Andrew T

Don't knkow about the lawyers but as a tire engineer I can tell you there is sound scientific evidence and a reason for all owners tandem axle trailers to run whatever tires they have at the pressure on the tire that is associated with the max load capacity.
Using Finite Element analysis it has been shown that during any cornering (even curves on an Interstate) the side loading that is working to tear the tread and belts apart is about 24% higher on the trailer tires than tires on a car, TV or motorhome even if running identical size & type tires at identical loading.
This force comes about because some of the trailer tires are being dragged around the corner rather than turned and steer around.
Anyone who has parked a tandem axle trailer and watched the tires has seen this sliding force in action.

I have post that addresses this feature as well as the logic behind individual tire weighing as the axles are not loaded 50/50 nor are the loads 50/50 side to side.

[dkottum]

Always good to have the experience and advice of a tire engineer and a retailer who are both very good at what they do to help us decide about tire pressures.

Except we never know which is better advice, design or actual experience.

doug k

[Krazyjohnny]

I just put these on my trailer today. They are stamped on the sidewall rated at 2183 lbs per tire at the max cold air pressure of 50 PSI. Out the door with the no hassle bring it back for replacement deal for right at $800.

Here is where things get funny....I have been dealing with this particular Discount tire Store for at least 15 years and bought at least 7 or 8 complete sets of tires from these guys. They have most always been this very tire. I know the owner and he has always taken good care of me. Anyway.... He comes out and asks why I went with the P metric instead of the ST? I said have you not seen how poorly ST tires are made and had one come apart on you? He said he hadn't because he replaces his on his trailers every couple of years. I said, of course you do because you own the place.

I asked him to sell me on something else if these were supposedly substandard. I told him the GVWR of the trailer is 7600 lbs. Each of these tires is rated for 2183 at 50 psi. I then went in to the whole math thing on how much weight the tongue had on it vs. the actual axle load and then his head started spinning.

I then asked, They are also speed rated for the actual highway speed too are they not?

He agreed they were and that they were a better built tire than the ST type tires. His also stated that they were made with a better chemical compounds than the ST tires and that is why ST tires should be replaced every couple of years.

Then I turned up the economics on him... So if I were to purchase the ST tires that are limited to 65 mph for $500 bucks and come back in here every two years and purchase another set for the same money that is $1500 bucks in 6 years. Where as I can spend $800 for a better tire that is speed rated for highway speeds and get a better ride and performance from it for half over the same period? I told him the trailer doesn't know the difference does it?

He said I guess you are right. I just smiled he smiled and I went home.

Thanks again to everyone here for their input and experience.

[Dean E]

Originally Posted by gmw photos

Dean,
How much load capacity do you need ? Good Year G26 Cargo in a 195/70-15 load range D has 1985 lbs capacity at 65psi, and fits a 5 to 6 inch rim. It is a LT tire.
Another choice is a Continental Vanco 2. In a 215/70-15 LR D, 2271 @65psi. Specs a 5.5" to 7" rim. That's a couple of ways to avoid a ST tire replacement.

Thanks, GMW.

I ordered a set of the Continental Vanco 2, 215/70-15 LR D tires from Tire Rack.

I only need to deal with 5500 lbs GVWR, so I will have a good margin of safety. This setup goes on a trailer I currently have on the east coast, an '84, 24-ft Skyline bunkbed. (My newer project, an '89 32-ft Land Yacht trailer, is presently in storage near Reno, NV.)

[Kosm1o]

LT vs XL: The unofficial answer is from Michelin is that they are the same tire. They used to make 3 different 235/15', P standard load 35 PSI, P extra load 41 PSI and LT 50 PSI. When they rationalized these to one tire they labeled the LT as an P XL to get the extra load capacity for applications where it was necessary. Just make sure when you get them that they are 50 PSI capacity but I am sure all the 41 PSI tires are out of the system by now.

I have 4 of the M/S ones and bought a newer one of the M/S 2's. For my spare. They look identical.

Andrew T[/QUOTE]

[CapriRacer]

Originally Posted by SteveSueMac

Can I assume the 15X7JJ rim number on my tire placard is telling me the rim is 7" wide? And what does the JJ mean? Thanks

The JJ is a code concerning the contour of the flange.

[SteveSueMac]

Thanks, Capri

[jcanavera]

Originally Posted by Krazyjohnny

Then I turned up the economics on him... So if I were to purchase the ST tires that are limited to 65 mph for $500 bucks and come back in here every two years and purchase another set for the same money that is $1500 bucks in 6 years. Where as I can spend $800 for a better tire that is speed rated for highway speeds and get a better ride and performance from it for half over the same period? I told him the trailer doesn't know the difference does it?

He said I guess you are right. I just smiled he smiled and I went home.

Thanks again to everyone here for their input and experience.

This is the exact conclusion I came to. Having ST's fail in late year three and early year four meant more frequent changes. The economics alone justify the swap.

Jack

[gmw photos]

Originally Posted by jcanavera

This is the exact conclusion I came to. Having ST's fail in late year three and early year four meant more frequent changes. The economics alone justify the swap.

Jack

Which brings us full circle to the comment I made earlier in this or another tire thread, "the difference between price and value".
In my mind, the LT tire even though it's price is a little higher, is the better value since it lasts longer and potentially gives more reliable service.
Sadly the RV industry, like many industries that build something for public consumption, often want to simply buy from the low cost provider to at least in theory remain competitive in the marketplace, but to also help their own bottom line profit. In general, we consumers support this kind of activity very often. Witness all the cheap crap we buy at wally world that comes to us at a low price point, but has little value because it breaks or otherwise fails so soon.
There needs to be a median reached of "reasonable" in both price and value.
Ok.....off my early morning soapbox rant !

[jcanavera]

And tires aren't getting any cheaper. When looking at a set of Maxxis E rated ST's, the price in 4 years had gone from $100 each to almost $150. Last summer I was able to get the 16" Michelin's from Discount Tire Direct for $202 each plus another $70 rebate from Michelin. And Discount sent them with free shipping and no local sales tax. The icing on the cake was checking the manufacturing date on the tires which was either 6 or 8 weeks earlier.

If you watch for those summer discounts you can get a great deal on the Michelins. They did the $70 rebate again this summer.

Jack

[Tireman9]

Originally Posted by SteveSueMac

Can I assume the 15X7JJ rim number on my tire placard is telling me the rim is 7" wide? And what does the JJ mean? Thanks

Yes 7 is rim width, which is a design standard not an exact physical measurement as we are dealing with curves and slopes.

JJ is the spec for the curvature of the flange portion of the rim like the "lip" on railroad wheels. There are a number of specs but for general purposes you can consider J and JJ essentially identical as far as being a consumer.


R1, R2, G variations give different "contours"

[SteveSueMac]

Thanks Tireman!