Tires E-350/450: Stock 225/75? Tall 215/85? Wide 235/85?

SJ-Chris wrote:

LT225/75R16C 121/120R: The reason I use them is because they have 2000lbs of extra carrying capacity at 80psi. Gives me peace of mind. I believe they are safer. Safety is important to me.


Personally, I see no downside in having extra weight carrying capacity. In my opinion, they are less likely to blow. If one does go flat, the remaining one that is temporarily carrying the full load will be less likely to also blow.

Note: You should never intentionally overload your rear axle.

Safe travels!
Chris

No downside other than availability and price. Sure, if one needs the added capacity, great. But based on your last statement, that's not likely unless one is actually overloading the "real" axle capacities (aka the 10-11klb range) of the vehicle.
And if the extra capacity is needed, barring some obscure tire clearance issue on the RV, there are other options that are of similar or same capacity and not an obscure Euro tire size (albeit not as obscure as years past with the amount of Sprinter type vans running around.

Overkill is fine, it's one person's own money vs peace of mind I suppose. Just pointing out the (not obvious to everyone) differences and costs/challenges for little to no real world gain.

Grit dog wrote:
And to dispell another myth posted by BigToe, there is no harm in using directional tires backwards other than less than “optimal” traction that is provided by the design of the tread.

Here is the Product Bulletin Issued by Michelin on April 29, 2019:

The C-metric sizes of the MICHELIN Agilis® CrossClimate® tire line utilize a directional tread pattern. These tires have arrows molded into the sidewall of the tire to indicate the intended direction of rotation. To maximize tire performance, it is important that directional tires be mounted correctly on wheels to ensure that the directionality is respected when mounted on the vehicle.

Pairs of steer tires and pairs of drive tires should be mounted such that one tire has the arrows pointing clockwise, and one tire has the arrows pointing counter-clockwise. For vehicles equipped with dual rear wheels, two rear tires should have the arrows pointing clockwise and two rear tires should have the arrows
pointing counter-clockwise.

To optimize wear performance, it is recommended to operate directional tires exclusively in their indicated direction, at least during the first 50% of treadlife. However, once directional tires are worn to greater than 50% of their initial tread depth, there is no negative effect of running them in a direction opposite to the indicated direction of rotation.


_________________________________


Not a myth. Simply the straightforward (haha) directions (haha) from the tire manufacturer.

1. Optimizing wear performance sounds like a good idea, because tires to be too expensive to waste by not following the instructions, thus increasing the likelihood of the tires wearing out prematurely.

2. Optimizing tire performance sounds like a good idea, because lives are too important to put at risk by not taking advantage of all the tire wet traction engineering one paid for with the price of the tire from installing them the wrong way.

3. In my RV usage case, the tires will never reach 50% tread wear before the tires age out. Therefore, if I were to buy directional tires, I would be stuck using them directionally for their entire service life, as they will never wear down to the point where directionality no longer matters.

4. The tire manufacturer knows more about the tires that they engineered and built than I do, so I'll follow their instructions.


Edited to add URL Link to Michelin's Agilis Cross Climate C-Metric Product Bulletin:

Agilis C-Metric Rotation Bulletin pdf

I appreciate the kind words BigToe!

We are all here to learn. Because of the expert information from many many people on this and other RV forums, I have learned quite a bit and have been able to do many projects/fixes on my RVs that I otherwise would not have been able to do. Saves a lot of $$$ not having to go to the local RV shop. And helps me be safer. I enjoy sharing what I have learned so that others can benefit and avoid problems/issues.

One last thing about tires... It may be putting too much faith in a government entity, but I also naively think that the Department of Transportation (DOT) must test/verify all tires that they are putting their stamp on prior to them going on the market/road. Or at least have some sort of monitoring system in place for reports/complaints. The DOT must have as part of it's general mission something to the effect of "We don't want tires on fast moving heavy vehicles falling off all over the place causing tons of accidents and deaths". This makes me (again, possibly naively) a little less worried about brands.

Safe travels!
Chris

And your recommendation was greatly appreciated, Chris!

I was unfamiliar with Nexen tire's offerings in this size until you identified it.

The CT8 HL that you use is the OEM tire that Stellantis fits to the Ram Pro Master, in the 121/120R load index that you are highlighting. When a tire is produced as original equipment for an OEM vehicle manufacturer, it stands to reason that the CT8 HL has been put through an extra layer of engineering and vetting by the vehicle manufacturer, for the sake of their own liability. That says that while Nexen may not be as well known of a brand as Michelin or Goodyear, that particular CT8 HL Nexen tire has been approved by VW and Stellantis for their new vehicle brands to ride on it.

I'm not a tire expert either, so the questions that PNichols asked above are questions that I was curious about as well. Where a given brand of tire produced in two iterations for the same application and usage has the same material weight, why would one tire have a higher weight capacity than the other? What makes the higher rated tire stronger, even while having less material weight?

Michelin claims to use over 200 different raw materials to produce a tire. while another tire manufacturer claims to use only 17 different materials. While it can be assumed that Michelin, being the oldest tire company, and having introduced significant innovations to the industry such as radial tires, is more advanced... some of the ingredients introduced into tires today are to make them more environmentally friendly at end of life, and that sophisticated soup of materials may not necessarily translate into tire longevity.

RV tire purchases are not routine for the long term RV owner who does not regularly trade in their RV, but rather are a once every 7 to 10 year expense now exceeding $2,000.00 to replace tires that have plenty of tread left but simply aged out. Blow outs are a much bigger deal on an RV than in a car, for reasons which SJ-Chris already mentioned. These factors inspire more questions on the selection of RV tires versus daily driver tires that may see more frequent replacement.

Earlier, I failed to mention that Firestone, the manufacture of the Steeltex R4S that used to be Ford's OEM tire on the cutaways 20 years ago, now offers the Transforce CV tire in the 121/120R load rating.

Unlike the F-53 Class A motorhome chassis, or any given modern day 1 ton and higher pickup or chassis cab, the Ford E-Series cutaway chassis challenges the limits of the Ford recommended LT225/75R16E tire size. I began this thread asking if any Class C owners have changed tire sizes, whether it be for increased tire capacity margin, increased ride height/ground clearance, increased approach/departure angle, increased tire contact patch, or decreased contact patch to penetrate through light snow to the ground.

The relatively recent emergence of the C-Metric tire being offered in the US, with higher load index ratings, have broadened the weight capacity margin... but a tire still has to do other things besides carry weight.

Wet traction comes to mind. Not skidding out in the rain. Not spinning wheels and burrowing in on grassy slimy surfaces at unimproved campground. That sort of thing. A tire must still be a tire in all other respects besides carrying weight.

It appears that the ETRTO standard calls for Curb Guards (anti abrasion buttresses on tire side walls where they might repeatedly grind against a sidewalk curb in urban parcel delivery applications) in all C-Metric tires, and this is another benefit that is useful when navigating Class C RV's through destination cities.

Asking about what tires people use and reciprocating the favor by posting what tire explorations I have made, is part of the process of learning, and I appreciated the opportunities to learn from you.

Grit dog wrote:

And why would one intentionally use tires (225-75-16C) that are far less popular and less available than all the applicable comparable tires that are commonplace and can be found at any tire shop virtually anywhere in North America?

LT225/75R16C 121/120R: The reason I use them is because they have 2000lbs of extra carrying capacity at 80psi. Gives me peace of mind. I believe they are safer. Safety is important to me.

I carry a spare LT225/75R16C 121/120R. I've yet to have a flat with these, but if I do I have a replacement in my spare. If for some strange reason I got 2-3 flat tires at the same time, well I'll deal with it if it happens. If I got two flat tires and was somewhere that only had the E-load rated tires for sale, I would have them put those on the front axle and move the Commercial rated tires to the rear.

Personally, I see no downside in having extra weight carrying capacity. In my opinion, they are less likely to blow. If one does go flat, the remaining one that is temporarily carrying the full load will be less likely to also blow.

Note: You should never intentionally overload your rear axle.

Safe travels!
Chris

And to dispell another myth posted by BigToe, there is no harm in using directional tires backwards other than less than “optimal” traction that is provided by the design of the tread.
There are about 5 other reasons to maybe carry 2 spare tires. This is absolutely not one of them….

I'm not a tire expert.

The simple way I look at it is....

LT225/75R16 115/112R <---- E-Rated load tires that come stock on most 30' Class C RVs. Very little load carrying buffer, especially if not cold inflated to 80psi.

vs

LT225/75R16C 121/120R <---- What I am calling "Commercial tires". (the 121/120 load rating is what you are looking for if you want more weight carrying capacity). These give you ~2000lbs of extra load carrying capacity on the rear axle. I put them on the front also.

You should never overload your rear axle per the amount on the sticker on the driver side door jam. The "extra" buffer, in my mind, especially comes in handy due to the fact that people (myself included) sometimes drive on tires that are less than cold 80psi inflated.

Just what I do and what I would recommend to family/friends.

Safe travels!
Chris

Grit dog wrote:
Just buy some new tires.
No advantage going larger or wider unless you need greater weight capacity.

Just throwing this back out there. Appreciate the dissertation on tires, but why?
And why would one intentionally use tires (225-75-16C) that are far less popular and less available than all the applicable comparable tires that are commonplace and can be found at any tire shop virtually anywhere in North America?

pnichols wrote:

For a given tire size between the two tire types that the C-Metric version is a more rugged/stronger tire?

i.e. That the C-Metric version has more plies? If so, if carrying capacity is not an issue ... should one use the C-Metric type tires if they wish for more puncture-proofness - as in occasional offroad travel with their Class C?

SJ-Chris wrote:

To me, yes...it means the Commercial rated tire is stronger and thus less likely to have a blowout.

Would anyone like to share the downside of getting Commercial rated tires at least on the rear? The cost (in my experience) is minimal.

Downsides of a C-Metric tire are brand specific.

With the Michelin Agilis Cross Climate tire, a tire which has been vetted, approved, and installed by Ford Motor Company on the E-Series Cutaway motorhome chassis in production as fleet orderable upgrade option, there are some differences between the C-Metric version of this tire, versus the LT Metric version that Ford installs on the E-Series Cutaway.

The main downside is that the C-Metric version is DIRECTIONAL. With 6 tires on the ground, and one on the spare tire rack, the spare is only good to replace 3 of the tires without playing musical tires on the side of the road in order to have all tires rolling in the right direction.

And unless one carries two spares, fitted with a directional tire facing each direction, there is still a 50% chance that the tire that blows will be a tire which is in the opposite direction of the spare, leaving one with 4 tires in one direction, and 2 tires in the other direction, when one really needs 3 tires in each direction.

Not having to worry about which tire faces which direction simplifies a lot of factors with tire procurement, maintenance, rotation, and emergency replacement in a pinch. For a dual rear wheel application, the Michelin Agilis Cross Climate in C-Metric designation having a directional design is a significant disadvantage in convenience, that to my mind outweighs the C-Metric versions overcapacity in weight rating.

Now to refer to what Michelin has to say about their two versions of Agilis Cross Climate tire in the 225/75R16 size:

Q: What is the difference between the MICHELIN® AGILIS® C-Metric sizes vs. the LT sizes?

A: The C-metric convention can be thought of as the European equivalent of the LT-metric. Just as LT-metric describes a tire with a higher load rating and higher pressure than the equivalently sized P-metric tire, C-metric describes a tire with a higher load rating and higher pressure than the equivalently sized European Metric tire.


Q: Why is the MICHELIN® AGILIS® CROSSCLIMATE® tire offered in two different tread designs?

A: The MICHELIN® AGILIS® CROSSCLIMATE® C-Metric tire was designed in Europe specifically for the European style vans that are also offered in the North American market. The C-Metric is a directional tread pattern. The LT sizes are non-directional and were designed by the North American Research and Development team to best suit ¾- and 1-ton
pickups and vans. Both treads offer comparable performance.


The PNichols question is whether or not the C-Metric version of the tire is "tougher" traversing unavoidable potholes at speed than the LT Metric version of the same tire.

Well, the C-Metric version weighs 37 lbs, while the LT-Metric version weighs 39.9 lbs, making the LT-Metric version 2.9 lbs heavier than the C-Metric version. If this extra weight is due to there being more ingredients in the LT version of this tire, does that make it tougher?

If so, then the toughest tires in this size range might be the Michelin XPS Rib, the Bridgestone R238, or the Goodyear Endurance RSA ULT... all weighing in at more than 50 lbs per tire, due to the additional steel belting in these tough commercial tires that traverses the carcass from bead to bead. Heck, the Endurance RSA is over $500 per tire in the LT225/75R16E size, and is retreadable, so it had better be tough. Yet the tread on some of these ribbed all position steer tires is designated as "Summer" only.

That's fine for a lot of RV users, but what about those who travel through the rains of the Pacific Northwest, or those whose Chalet branded coaches serve as ad hoc ski chalets in the Sierra? These usage cases need not be blazing through blizzards, but light snow flurries where no 4WD nor chains are required shouldn't send a coach skidding into an embankment for lack of tread traction or sufficient sipes in the tires.

So for all season recreational uses, an all season tire would be preferable over a "summer" tire. And for more adventurous RV'rs, an all terrain tire might even be considered. At the very least, a tire with a Three Peak Mountain Snowflake Rating (3PMSF) should be considered as minimum verified threshold of wet and unexpected light snow performance.

And the lack of a 3PMSF symbol introduces another potential downside of some C-Metric tires. While both versions of the Agilis Cross Climate have 3PMSF certificaton, neither version of the Nexen CT8 HL are certified 3PMSF.

Like Michelin, Nexen offers their commercial CT8 HL tire in both C-Metric and LT-Metric versions, neither of which are 3PMSF rated, but both of which are heavier in weight, at 42.76 lbs, than either version of the Michelin Agilis Cross Climate.

Note that both C-Metric and LT-Metric Nexen CT8 HL's weigh exactly the same, at 42.76 lbs. So which tire has more ingredients? Which tire has more belts? Which tire is tougher? And unlike the directional versus non directional tread design difference in the Michelin Agilis Cross Climate, to my understanding, there is no difference in tread between either version of the Nexen CT8 HL.

However, Nexen makes 5 commercial tires in the 225/75R16 range (not including their snow tire that receives studs). Other than the two CT8 HL tire versions, the three remaining Nexen light truck tires are 3PMSF certified. Nexen's latest tire, their new ATX, weighs in at 43.50 lbs, which is about a pound heavier than their C-Metric CT8 HL.
So which is tougher on the day to day, irrespective of weight rating?

I'm not qualified to answer to that question, but will close with one more interesting difference between the two versions of the Michelin Agilis Cross Climate.

As previously discussed, the peak weight carrying capacity of a C-Metric tire is rated at 83 psi, which is also the maximum cold inflation pressure rating of the tire.

Typically, an LT Metric load range E tire has a maximum cold inflation pressure rating of 80 psi. However, the LT Metric Michelin Agilis Cross Climate has a maximum pressure rating of 90 psi, which is higher than the 83 psi max of C-Metric version of the same tire.

Now get this... there is no change in weight carrying capacity rating between 80 psi and 90 psi on the LT Metric version of the Agilis Cross Climate. The tire is simply designed to withstand more internal pressure. One would think that means that the tire is tougher...to be able to hold nearly as much pressure as a steel sidewall load range F tire, at 90 psi. Yet no additional load capacity is stated for when the tire is inflated past 80 psi, and let's not forget that the OEM wheels on this platform are limited to 80 psi cold inflation rating.

An advantage that an LT-Metric version of this brand and model of tire may have over a C-Metric version of the same tire, is that in the summer, while traveling for hundreds of miles on hot Arizona roads, with heat expanding the air within the tire while increasing the tire's internal pressure... having a 10 psi margin of allowable pressure build up all fall within the 90 psi rating of the tire, offers some comfort not unlike the comfort felt with having a larger margin in tire weight carrying capacity.

pnichols wrote:

That's good data above in your post.

However it raises one important question rarely discussed in any of the forums:

For a given tire size between the two tire types that the C-Metric version is a more rugged/stronger tire?

i.e. That the C-Metric version has more plies? If so, if carrying capacity is not an issue ... should one use the C-Metric type tires if they wish for more puncture-proofness - as in occasional offroad travel with their Class C?

SJ-Chris wrote:


To me, yes...it means the Commercial rated tire is stronger and thus less likely to have a blowout.

Would anyone like to share the downside of getting Commercial rated tires at least on the rear? The cost (in my experience) is minimal.

Chris

The potential downsides to getting a C-Metric tire depend on the brand and model of tires being compared.

But first, to clarify, the term "C-Metric" is used instead of "Commercial", because there are a plethora of Commercial tires in the LT-Metric size and Load Range E rating that are not C-Metric.

To suggest that only C-Metric tires are "Commercial", whereas tires in the same size without the appended "C" after the rim diameter are not, does not properly reflect the long standing tire offerings available in North America for decades prior to the importation of Euro Vans, beginning with the Sprinter, and continuing with the Fiat (Ram Pro Master) and Ford Transit.

In Europe, these Euro vans are fitted with tires specified by the European Tyre and Rim Technical Organisation (ETRTO), which developed a Commercial tire standard to distinguish tire characteristics from Passenger car tire standards.

We have the same distinction in North America, where we have P-Metric passenger car tires, and LT-Metric light truck tires. "C" is to Europe what "LT" is to the United States. It isn't as if an LT tire is not a commercial tire. And it certainly isn't as if to get a "true" commercial tire in the United States, one must look for, or insist upon, a tire size appended with "C". That is not the case.

None of the Commercial tires on Peterbilts, Kenworths, Freightliner Medium and Heavy Duty, Navister International light, medium, heavy, or severe duty trucks use tires that are C-Metric. Does that mean that these trucks are not specified with "Commercial" tires? Of course not.

The same holds true for 3500/4500/5500/6500 and 350/450/550/600 trucks from the Big Three domestic pickup and chassis cab manufacturers. These trucks are specified with commercial tires that do not have "C" appended after their rim size. In otherwords, they do not use C-Metric tires. But they do use Commercial tires all the same.

Some examples of LT-Metric Commercial tires include, but are not limited to,

Americus Commercial LT All Season Tire -
LT225/75R16 115Q LRE 10 PLY


BFGoodrich Commercial T/A All Season 2
LT225/75R16 115/112R LRE 10 PLY


BFGoodrich Commercial T/A Traction
LT225/75R16 112Q LRE 10 PLY


Bridgestone Duravis R238 Commercial Summer Tire (LRE)
LT225/75R16 115R LRE 10 PLY 14/32nds 50.5 lbs. $311 Steel Sidewall Casing


Bridgestone Blizzak LT Commercial Winter Tire (LRE)
LT225/75R16 115R LRE 10 PLY 17/32nds 36.9 lbs. $204


Bridgestone Blizzak W965 Commercial Winter Tire (LRE)
LT225/75R16 115Q LRE 10 PLY 17/32nds 42.5 lbs. $144


Bridgestone Duravix M700 HD


Firestone Transforce HT2 Highway Terrain Commercial Light Truck Tire
LT225/75R16 115R LRE 10 PLY


General Grabber HD Commercial Truck Tire
LT225/75R16 115Q LRE 10 PLY


In creating the list above, I simply worked my way through the alphabet, and grew "tired" of adding tires to this list by the time I reached letter G in the alphabet. And I didn't even cover all of the tires available by brands beginning with A-F (Falken just came to mind as I type this), but it seems certain that if I made it as far as the letter "G" without mentioning Goodyear, the Goodyear Blimp will probably dump their holding tank over my house next time they go floating by, so let me add the following two tires to the list:

Goodyear Endurance RSA ULT 16"
LT225/75R16 115Q LRE 10 PLY 50 lbs

Goodyear Endurance RSD ULT 16"
LT225/75R16 115Q LRE 10 PLY 49 lbs.

These Endurance tire casings are so tough, Goodyear states that they are re-treadable. Not that this means a hill of beans to owners who time out their tires before they wear out, but still, the Endurance RSA ULT is in Michelin XPS Rib and Bridgestone R238 territory.

Lateral scrub-resistant tread compound
Premium enhanced casing
Reinforced shoulders and steel-steel belt package.

All of the foregoing are Commercial tires, listed for last mile delivery, school bus, emergency services ambulance, urban utility, etc.

Hence, to distinguish the Euro Centric designation for the 225/75R16C tire, the "C" shall be referred to as "C-Metric", which is Europe's near equivalent to what in the USA is called LT-Metric.

There are no downsides to getting commercial tires, as there exists enough variety among commercial tires available in North America, whether designated as LT Metric or C Metric, that the plethora of alternative choices effectively cancels out any downsides.

So to focus only on any downsides of getting "C-Metric" tires, one has to consider the question brand by brand, where a given tire brand may make an 225/75R16 in P-Metric (out of the question), LT-Metric (as specified by Ford, the E-350/450 manufacturer), and C-Metric (as recently applied with tires specified for Euro vans).

Some tire brands don't even offer a C-Metric tire in North America. Moving up a letter in the alphabet to "H", consider Hankook. Ford specifies and equips new E-350 and E-450 cutaway motorhome chassis with the Hankook Dynapro HT LT235/75R16E tire as standard equipment.

Every year it seems, Ford works with Hankook to tweak the specs on this tire. The details of the changes are propietary, but the evidence that changes have been made are found in the material product code. Currently, the following product codes for this tire might still be available at any given tire distributor:

2021163 (36 lbs)
2020873 (39 lbs)
2020694 (39 lbs)
2001831 (40 lbs)

If one were to take delivery of a 2023 Model Year Class C motorhome built on a Ford E-350/450 cutaway chassis today, then the standard tire would be the 2001831 material product code of the Hankook Dynapro HT LT225/75R16E LRE tire.

UNLESS... the motorhome manufacturer took advantage of Ford's FIN option to have Michelin Agilis Cross Climate tires fitted instead. Unlike Hankook, Michelin offers the Agilis Cross Climate tire in both LT Metric and C Metric variants.

However, Ford will only supply the LT-Metric variant on the E-350/450 cutaway, if the ordering fleet specifies (and pays for) that option.

This post is getting long in the tooth, and may soon reach the character limit, so I'll stop here and examine the Michelin Agilis Cross Climate comparison between the LT225/75R16 versus the 225/75R16C in my next post.