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

PS: I have no opinion/insight/experience on CHANGING the size or width of the tires themselves. I personally wouldn't do it unless I had a good reason/need and even then only after consulting with a few RV and tire experts.

pnichols wrote:


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

Does "2,680 lbs Single / 2,470 lbs Dual - LT-Metric at 80 psi" AS COMPARED TO "3,085 lbs Single / 2,975 lbs Dual - C-Metric at 80 psi"
mean -> 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?

To me, yes...it means the Commercial rated tire is stronger and thus less likely to have a blowout. I think it is very important to consider that most RVers are probably not religious about checking their tire psi all the time. Many people are driving at 75psi or 70psi or 65psi and thus stressing the dually tires. Since the Commercial rated tires have much more buffer (~500lbs per tire carrying capacity), they are less susceptible to issues when the tires are not all the way up to 80psi.

Also, if you do get a flat on ONE of the tires in the rear, the other tire on that side is now carrying DOUBLE the load that it should. 4500lbs?? In that scenario, I'd rather have a stronger tire (the commercial rated one) to give me a better chance of not blowing BOTH tires and then driving on and destroying the rims as well.

Would anyone like to share the downside of getting Commercial rated tires at least on the rear? The cost (in my experience) is minimal. Personally, I haven't noticed a difference in noise or ride comfort. I see very little downside. I place a huge value on safety. Another way of looking at it...blowout vs non-blowout sure makes for a big difference on the day it happens (or doesn't happen).

Safe travels!
Chris

BigToe wrote:
The Ford E-350 DRW and E-450 DRW E-Series Cutaway Chassis OEM 16" x 6" wheels that were manufactured in Canada by Accuride, identified by eight circular hand holes, are rated to 80 psi.

I haven't personally verified the wheel psi rating of the current 4 hand hole 16"x6" OEM wheels made by Maxion in Mexico, but have every indication to believe that they match the original wheel specification of 80 psi Max cold inflation pressure. I have personally verified the OEM wheels made by Accuride in Canada.

The interesting, informational, and arguably irrelevant aspect of the higher rating of the European Tyre & Rim Technical Organisation commercial tire standard developed for Euro Vans such as the Sprinter, Transit, Fiat, ProMaster, and VW equivalents marketed under various names depending on country... tires which we in the United States can identify as "C-Metric" tires (as very distinct from "LT-Metric Load Range C" tires... is that the "500 lbs." higher rating per tire in the 225/75R16C size is at 83 psi.

The stock wheels are only rated to 80 psi.

So the "margin" of weight capacity per tire must be reduced by the C-Metric tires rated capacity at a reduced pressure, which in this case is no higher than 80 psi.

Nexen doesn't offer any Load Inflation Tables. I even called Nexen tech support for this information, and spent 30 minutes on the phone with an Andrew at Nexen, who was not able to locate a Load Inflation Table for any of the five offerings that Nexen produces in the LT225/75R16 or 225/75R16C sizes.

However, most other tire manufacturers do provide load inflation tables, which let the tire user know the weight capacity of a given tire when inflated to less than the maximum psi that the tire is capable of withstanding.

Due to tire industry standards organizations, there is generally consistency from brand to brand in load inflation indices for any given specific tire size.

In this case, to determine how much additional weight carrying "margin" a 225/75R16C C-Metric tire has over an LT225/75R16E LT-Metric tire when both types of tires are inflated to the maximum pressure that the OEM steel wheel is rated for when cold (80 psi), I reviewed the Load Inflation Tables of several different brands of C-Metric tires in this size, and all tables from every brand checked were consistent with each other.

When inflated to 80 psi, a 225/75R16C tire is rated to support 3,085 lbs in single wheel configuration, as opposed to 3,195 lbs when inflated to 83 psi.

In dual rear wheel configuration, the C-Metric 225/75R16C is rated to support 2,975 lbs at 80 psi, as opposed to 3,085 lbs when inflated to 83 psi.

By contrast, the LT225/75R16E tire, when inflated to 80 psi, is rated at 2,680 single, 2,470 dual (per each individual tire).

So to stack the weight carrying capacity differences up neatly in a row:

3,195 lbs Single / 3,085 lbs Dual - C-Metric at 83 psi

3,085 lbs Single / 2,975 lbs Dual - C-Metric at 80 psi (OEM wheel psi rating)

2,680 lbs Single / 2,470 lbs Dual - LT-Metric at 80 psi


On the steer axle, there is a 405 lbs difference between C-Metric and LT-Metric at 80 psi, and on the drive axle, the difference grows to 505 lbs. at 80 psi.


Where the point in REDUCING the mental margin afforded to the C-Metric tire by ignoring the tire's maximum weight capacity at any pressure beyond the pressure rating of the wheel is arguably irrelevant, as all of these ratings exceed the weight capacity of the rear axles of all Ford E-350/450 cutaways, which range from 7,800 lbs to 9,600 lbs, depending on model and year.

However, it seemed to be an interesting observation to make... keeping the pressure limits of the wheel in mind.

Great info. I would summarize it (using your numbers) as:

225/75R16C rated duallies in the rear have a 80psi carrying capacity of 4 x 2975 = 11,900lbs

whereas 225/75R16E rated duallies in the rear have a 80psi carrying capacity of 4 x 2470 = 9,880lbs

Let's assume your rear axle was at a maximum weight of 9,600lbs. Would you rather have the E-rated tires that have only a 280lb margin, or the C-rated tires that have a 2,300lb margin? I would rather have the C-rated tires.

Next question: Does the typical RVer check your tire pressure EVERY DAY before they drive? I'm guessing 99% of people do not. (I have a TPMS so I can see always). What happens to these margins when the tires are actually at 75psi instead of 80psi? Or 70psi? Or 65psi? Answer: It spells trouble for E-rated tires.

What about when driving with your 75-80psi tires and you hit a pothole on the freeway? How much stress does that put on the tires? Seems like the C-rated tires would be able to handle it better.

Side note: Nobody should ever overload their rear axle, even with tires that can handle a heavier load.

Question: What % of RVers have ever weighed their RV fully loaded? We can probably agree that the answer must be "a very low % of RVers".

All of these reasons are why I choose Commercial rated tires with heavier carrying capacity on my 30' Class C RVs. (on my 23' Class C RV I have the E-rated tires, but might even upgrade those to C-rated tires next time they are needed "just because").

Safe travels all!
Chris

BigToe wrote:
The Ford E-350 DRW and E-450 DRW E-Series Cutaway Chassis OEM 16" x 6" wheels that were manufactured in Canada by Accuride, identified by eight circular hand holes, are rated to 80 psi.

I haven't personally verified the wheel psi rating of the current 4 hand hole 16"x6" OEM wheels made by Maxion in Mexico, but have every indication to believe that they match the original wheel specification of 80 psi Max cold inflation pressure. I have personally verified the OEM wheels made by Accuride in Canada.

The interesting, informational, and arguably irrelevant aspect of the higher rating of the European Tyre & Rim Technical Organisation commercial tire standard developed for Euro Vans such as the Sprinter, Transit, Fiat, ProMaster, and VW equivalents marketed under various names depending on country... tires which we in the United States can identify as "C-Metric" tires (as very distinct from "LT-Metric Load Range C" tires... is that the "500 lbs." higher rating per tire in the 225/75R16C size is at 83 psi.

The stock wheels are only rated to 80 psi.

So the "margin" of weight capacity per tire must be reduced by the C-Metric tires rated capacity at a reduced pressure, which in this case is no higher than 80 psi.

Nexen doesn't offer any Load Inflation Tables. I even called Nexen tech support for this information, and spent 30 minutes on the phone with an Andrew at Nexen, who was not able to locate a Load Inflation Table for any of the five offerings that Nexen produces in the LT225/75R16 or 225/75R16C sizes.

However, most other tire manufacturers do provide load inflation tables, which let the tire user know the weight capacity of a given tire when inflated to less than the maximum psi that the tire is capable of withstanding.

Due to tire industry standards organizations, there is generally consistency from brand to brand in load inflation indices for any given specific tire size.

In this case, to determine how much additional weight carrying "margin" a 225/75R16C C-Metric tire has over an LT225/75R16E LT-Metric tire when both types of tires are inflated to the maximum pressure that the OEM steel wheel is rated for when cold (80 psi), I reviewed the Load Inflation Tables of several different brands of C-Metric tires in this size, and all tables from every brand checked were consistent with each other.

When inflated to 80 psi, a 225/75R16C tire is rated to support 3,085 lbs in single wheel configuration, as opposed to 3,195 lbs when inflated to 83 psi.

In dual rear wheel configuration, the C-Metric 225/75R16C is rated to support 2,975 lbs at 80 psi, as opposed to 3,085 lbs when inflated to 83 psi.

By contrast, the LT225/75R16E tire, when inflated to 80 psi, is rated at 2,680 single, 2,470 dual (per each individual tire).

So to stack the weight carrying capacity differences up neatly in a row:

3,195 lbs Single / 3,085 lbs Dual - C-Metric at 83 psi

3,085 lbs Single / 2,975 lbs Dual - C-Metric at 80 psi (OEM wheel psi rating)

2,680 lbs Single / 2,470 lbs Dual - LT-Metric at 80 psi


On the steer axle, there is a 405 lbs difference between C-Metric and LT-Metric at 80 psi, and on the drive axle, the difference grows to 505 lbs. at 80 psi.


Where the point in REDUCING the mental margin afforded to the C-Metric tire by ignoring the tire's maximum weight capacity at any pressure beyond the pressure rating of the wheel is arguably irrelevant, as all of these ratings exceed the weight capacity of the rear axles of all Ford E-350/450 cutaways, which range from 7,800 lbs to 9,600 lbs, depending on model and year.

However, it seemed to be an interesting observation to make... keeping the pressure limits of the wheel in mind.

That's good data above in your post.

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

Does "2,680 lbs Single / 2,470 lbs Dual - LT-Metric at 80 psi" AS COMPARED TO "3,085 lbs Single / 2,975 lbs Dual - C-Metric at 80 psi"
mean -> 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?

The Ford E-350 DRW and E-450 DRW E-Series Cutaway Chassis OEM 16" x 6" wheels that were manufactured in Canada by Accuride, identified by eight circular hand holes, are rated to 80 psi.

I haven't personally verified the wheel psi rating of the current 4 hand hole 16"x6" OEM wheels made by Maxion in Mexico, but have every indication to believe that they match the original wheel specification of 80 psi Max cold inflation pressure. I have personally verified the OEM wheels made by Accuride in Canada.

The interesting, informational, and arguably irrelevant aspect of the higher rating of the European Tyre & Rim Technical Organisation commercial tire standard developed for Euro Vans such as the Sprinter, Transit, Fiat, ProMaster, and VW equivalents marketed under various names depending on country... tires which we in the United States can identify as "C-Metric" tires (as very distinct from "LT-Metric Load Range C" tires... is that the "500 lbs." higher rating per tire in the 225/75R16C size is at 83 psi.

The stock wheels are only rated to 80 psi.

So the "margin" of weight capacity per tire must be reduced by the C-Metric tires rated capacity at a reduced pressure, which in this case is no higher than 80 psi.

Nexen doesn't offer any Load Inflation Tables. I even called Nexen tech support for this information, and spent 30 minutes on the phone with an Andrew at Nexen, who was not able to locate a Load Inflation Table for any of the five offerings that Nexen produces in the LT225/75R16 or 225/75R16C sizes.

However, most other tire manufacturers do provide load inflation tables, which let the tire user know the weight capacity of a given tire when inflated to less than the maximum psi that the tire is capable of withstanding.

Due to tire industry standards organizations, there is generally consistency from brand to brand in load inflation indices for any given specific tire size.

In this case, to determine how much additional weight carrying "margin" a 225/75R16C C-Metric tire has over an LT225/75R16E LT-Metric tire when both types of tires are inflated to the maximum pressure that the OEM steel wheel is rated for when cold (80 psi), I reviewed the Load Inflation Tables of several different brands of C-Metric tires in this size, and all tables from every brand checked were consistent with each other.

When inflated to 80 psi, a 225/75R16C tire is rated to support 3,085 lbs in single wheel configuration, as opposed to 3,195 lbs when inflated to 83 psi.

In dual rear wheel configuration, the C-Metric 225/75R16C is rated to support 2,975 lbs at 80 psi, as opposed to 3,085 lbs when inflated to 83 psi.

By contrast, the LT225/75R16E tire, when inflated to 80 psi, is rated at 2,680 single, 2,470 dual (per each individual tire).

So to stack the weight carrying capacity differences up neatly in a row:

3,195 lbs Single / 3,085 lbs Dual - C-Metric at 83 psi

3,085 lbs Single / 2,975 lbs Dual - C-Metric at 80 psi (OEM wheel psi rating)

2,680 lbs Single / 2,470 lbs Dual - LT-Metric at 80 psi


On the steer axle, there is a 405 lbs difference between C-Metric and LT-Metric at 80 psi, and on the drive axle, the difference grows to 505 lbs. at 80 psi.


Where the point in REDUCING the mental margin afforded to the C-Metric tire by ignoring the tire's maximum weight capacity at any pressure beyond the pressure rating of the wheel is arguably irrelevant, as all of these ratings exceed the weight capacity of the rear axles of all Ford E-350/450 cutaways, which range from 7,800 lbs to 9,600 lbs, depending on model and year.

However, it seemed to be an interesting observation to make... keeping the pressure limits of the wheel in mind.

Thank you SJ-Chris for your detailed response!

pnichols wrote:

BigToe wrote:
Tire Choices for Ford E-Series Cutaway Class C Motorhomes


What replacement tires did you put on your Class C motorhome built on a Ford E-350 or E-450 (aka E-Superduty in older rigs) cutaway chassis, and what were your reasons for your tire selection?

Did you stick with the stock tire size of LT225/75r16 ?

Did you go taller and skinnier, changing to LT215/85r16 ?

Did you go taller and wider, changing to LT235/85r16?

Did you upgrade to 10 ply rating Load Range "E"? (If you have an older E-350 originally specified with 8 ply rated Load Range "D")

Did you switch to European style 225/75r16C, such as what is specified for Euro van cutaways like the Transit and Sprinter?

Have you had an experience with any particular brand and model of tire for your E-350/450 RV that caused you to swear "never again"?

Do you have a particular brand and model of tire that is your trusted "go to"?
Thank you!

We have a smaller (24 ft.) Class C for just the DW & myself. We wanted a Class C which provided all the comforts of home for two in varied weather conditions, while at the same time providing enough travel/camping flexibility and chassis ruggedness so as to amost match what a 2WD TC could provide. We do take our Class C carefully offroad at times.

As such, we searched for and bought it new built on the optional-for-it's-weight heavier duty E450 chassis instead of the common E350 chassis usually used for small Class C rigs.

At the first tire change opportunity we did not go for the stock LT225/75R16 Load Range E tires that came on it. We instead chose LT215/85R16 size Load Range E tires. These tires are rated for the same weight carrying capacity - but are taller for more offroad ground clearance. Plus as a bonus they are slightly narrower so as to both provide more space between the dually sidewalls for improved sidewall air cooling when on the highway during high ambient air temperatures and ... they "punch through to the underneath hard road surface" better under slush and snow conditions due to their higher pounds-per-square-inch downwards tread pressure.

As for "guaranteed quality", our Class C came with Michelin LT tires, so we bit the expense bullet and replaced them with Michelin LT215/85R16 tires.

For another vehicle (non-RV) I was recently at the tire shop talking with the sales person. I asked about changing the tire size (taller tire). On my particular vehicle, he mentioned that if I changed the tire size it would make the speedometer off (speed and distance) as the car/computer/etc is calibrated for the manufacturer's recommended tire size. I found that interesting. The same could/might apply on an RV (not sure). Whether that matters to you when selecting tires is purely up to you.

Safe travels!
Chris

BigToe wrote:
SJ Chris

What are "Commercial rated tires which each have ~500 lbs. more carrying capacity compared to the E-load tires?"

Can you please tell us the size, numerical load index, (eg 115/112R), manufacturer brand, and model name/number of the tires that you picked out for your 30' Class C Thors?

The term "Commercial" is used to broadly across too many sizes and types of tires for me to find the type of tires that you recommend.

Thanks.

Sure, no problem. Here are the tires I put on my 30' Class C the last time I needed tires:

LT225/75R16C 121/120R (the 121/120 load rating is what you are looking for if you want more weight carrying capacity). You should never overload your rear axle. These Commercial rated tires give an extra 2000lbs carrying capacity on the rear axle which is big given the E-load rated tires have very little buffer in their max carrying capacity vs the max rear axle load rating. This is ESPECIALLY important if/when your rear tires are not optimally inflated.

Specifically the ones I got were Nexen Roadian CT8 HL (google it if the link doesn't work)
https://www.bigotires.com/tires/sku/nexen/roadian-ct8-hl/lt225-75r16c-121-120r-e/000000000001100191

At this time, they are ~$150-160 per tire (not counting all the other **** they add on when you get tires, which you will pay regardless of what tires you buy).

I have had zero problems with them for 2-3 years now. Personally, I didn't notice a difference in ride comfort or noise (...Class C RVs are pretty noisy when driving to begin with...).

Question: Does a CASUAL RV USER who will only put 2,000-10,000 miles per year on their RV need tires that will "last 80,000 miles"? Nope! Your tires will "age" out before they "wear" out.

Hope that helps.
Chris

Thanks for your responses pnichols.

BigToe wrote:
Thanks PNichols.

If you have an E-450, then you must have 4.56 gearing?

What transmission does your rig have? How many speeds?

Did you notice any difference in shift points on grades with the taller tires?

I "think" that our E450 has a 4.56 rear differential, but am not absolutely sure as some E450's may have been available with a 4.30 rear differential. I tried researching this using the codes on the door sticker but was never able to determine the rear differential gearing for sure.

Our 2005 Itasca Class C's E450 chassis has the 5-speed 5R110W transmission. As I understand it, this transmission actually has 6 distinct internal gear ratios, with the computer invoking one of the two internal ratios for one of the transmission's gears - depending upon (outside air ambient?) temperature.

I have not noticed any difference in shift points with the taller tires, but any effect purely due to tire size may be masked because I mainly travel in Tow/Haul mode.

The speedometer reads a bit on the "too-slow" side with the taller tires, but this is of no concern to us (a dealer could maybe tweak this). We cruise with a speedometer reading in the 58-60 MPH range, with the tach reading around 2200 RPM ... and hopefully our mileage being in the 9-10 MPG range (but I don't keep records on this).

Of course the larger diameter tires somewhat compensate for the high 4.56 rear differential by moving the overall drive train's ratio lower. However we do prefer the E450's overall drive train's ratio - even with our taller tires - being higher than that of a stock E350's because we prefer the improved low speed pulling power during occasional offroad travel.