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No, you really don’t have to get giant ol’ tires to be cool.

I don’t really know what to call this piece, but there’s a lot of information flying around in my head right now, and I thought I’d try to get it written down in case it might help someone else. We just got new tires for our EKKO after about 40,000 miles, so this is all very much on my mind (and wallet) lately. Also, winter is coming up, and though we’ve bought snow tires for our vans in the past, we’re trying something different this time – so again,  more tires on the brain. And finally, when it comes to tire sizes, we decided to stick with the stock size, which is contrary to what almost every other EKKO owner who writes about it does. So I thought I might write this so that you know – it’s OK to stick with the tire size your vehicle came with. There’s a lot to unpack here, so let’s get started.

Problems with the Stock Tires

The tires that come standard on the Transit-based EKKO are the Hankook Dynapro HT, in the 205/75R16 size – singles in the front and dual tires in the back. I didn’t have much of an opinion on Hankook tires before getting the EKKO, and after having them, I can say I’ll never ever buy Hankooks again.  The nicest thing I can say about the Hankooks is that ours never actually exploded.

They were well on their way to exploding though, after about 30,000 miles. The steel innards of the tires on the front wheels were broken, and poking through to the exterior of the tire. We started noticing a vibration in the steering wheel, and when we finally got it in to a tire shop, they found the issue and showed us how lucky we had been.

See the steel cables poking through? And the tears deep in the tread? That’s not supposed to happen.

Several other EKKO owners have reported “rapid unscheduled tire disassembly” events with the Hankooks between 20,000 and 30,000 miles, so I’ve begun calling them the “Dynaplodes”. When we had our issue, we decided to get two new tires for the front wheels. Unfortunately, the only tire available on short notice in the stock size was… you guessed it… the Dynaplodes.

This DOT code on the Dynaplodes let me know they were made in the 29th week of 2020. And then they sat in a warehouse for three years before being sold to me as “new”.

It gets even better – the “new” Dynaplodes they put on our EKKO were, as revealed by the DOT code on the tire, already three years old! Thanks, Hankook! So after paying top dollar for three-year-old emergency replacement tires (which were likely just as defective as the tires they replaced because they were made in the same batch), I had a bit of a bad taste in my mouth about the Hankooks, and I just wanted to be rid of them forever.

Just in case I haven’t been clear – It’s my opinion that the Hankook Dynaplodes are terrible tires, and nobody should buy them, ever, for any reason.

Choosing new tires: The size

This is where you’ll find I run contrary to the prevailing opinions on social media. If you looked at nothing other than the Facebook groups dedicated to the EKKO, you might think that it was mandatory to increase the tire size on your EKKO if you wanted to be in the cool kids club. I think nearly everyone who has posted about tires has either bought or expressed a preference for larger tires. Yet I chose to stick with the stock tire size. Why is that?

Well, first, let me just say that I think everyone should be free to modify their RV in ways that best match with their own personal RVing style, and that includes selecting tires and other suspension components. There’s not one right answer here – it all depends on what’s important to you. To some people, the increased ground clearance of larger tires might be more important than all the negatives I’m about to rattle off. And that’s completely fine: we’re all adults and we can make our own decisions. But here are some of the considerations that led us to stick with the stock size.

Errors in speed and mileage

This one’s pretty straight forward. Your vehicle knows how fast it’s going and how far it’s gone by counting the number of times your tires turn around. In the case of the stock tires on the EKKO, that’s about 750 times per mile, give or take. So once your wheels have rolled over 750 times, the vehicle’s computer knows it’s gone a mile. If it did that in an hour, it knows it’s going one mile per hour. Pretty simple stuff.

So now, let’s say you want to put a larger size tire on your EKKO. Nothing too crazy, let’s just say you wanted to put on 225/75R16 tires (a very common tire size). Since they’re larger, those tires only roll over about 709 times per mile. But your vehicle still thinks 750 rotations is one mile. So when it clocks over 750 rotations, you will have actually gone an extra 41 rotations further than a mile. If you do the math, what the computer thinks is a mile is actually about a mile plus 305 feet. Your speed will also be off by about that same 6%.

In some vehicles, it is possible to reprogram the vehicle’s computer with a new tire size. But that’s not the case with the EKKO/Transit. So running larger tires means that:

  • Your mileage is off
  • Your speed is off
  • Distance to empty is off. (Well, either the dash computer “miles to empty” is off, or the actual miles left to travel in real life are off – one or the other. They can’t both be right.)
  • Any other calculations your vehicle’s computer is making based on speed or distance are off.

 

I don’t even know what all of those last ones are, or how important they are.  The only people who can answer that question with any authority are Ford engineers. But I do know I didn’t want to have to do the mental math every time I saw a speed limit sign, or a highway mile marker. So sticking with the stock size made sense to me.

Ride height and handling

Time and time again, I see people posting that they “added a lift kit to their EKKO, and it handles so much better now!” I’m sorry, but unless they’re driving someplace where the laws of physics don’t apply, that simply cannot be true. More likely, what’s going on is some post-mod-rationalization, where they’re trying to convince themselves that the money they spent is worth it – physics be damned.

You already instinctively know what I just said about ride height to be true.  I’ll prove it to you. Look at the two pictures below, and tell me: which one handles better? Which one exhibits less body roll?

One of these vehicles can turn a corner without rolling over.

Here’s the thing. Raising a vehicle’s suspension or running larger tires raises the vehicle’s center of gravity. All other things being equal, a vehicle with a higher center of gravity will exhibit more body roll, and less precise handling. End of story.

All other things being equal” is a very critical part of that last point. People rarely seem to raise the suspension or buy larger tires in isolation. They may add a lift kit and also add helper springs to the leaf springs in the back. Or maybe they put on larger tires, but also swapped out for new tunable shock absorbers. Or maybe they did all of this AND added a beefed up sway bar as well.

In those cases, what happened is that the handling improvements resulted from the increased spring capacity, or the new shocks, or the sway bar. The handling improved in spite of raising the center of gravity. Had they done those other things and left the ride height the same, the ride would have been improved even more.

None of this is to say that there aren’t valid reasons for wanting the increased ride height that would result from larger tires. There are plenty of reasons to want more ride height – but better handling isn’t one of them. Since I didn’t want a handling penalty from larger tires, staying with the stock size made sense to me.

Minimum dual spacing

The EKKO has dual tires in the rear. When tires are installed in pairs, tire manufacturers list a minimum dual spacing that they want to have between the centers of the two tires. They do this for safety reasons.

Tires tend to squat as they are loaded – they mush out a bit at the bottom, we’ve all seen this. Well, in a dual setup, if the tires are so close together that they rub when they “mush”, that will cause friction and heat, and will lead to tire failure. This is why the tire manufacturers specify a minimum distance they want the tires separated – the minimum dual spacing. Again, this is a safety thing.

Getting back around to the EKKO, this diagram shows the wheel geometry for the Ford and Winnebago wheels installed on the EKKO rears. From wheel centerline to wheel centerline, we can add up 238.7mm between the wheels.

What I found is that for larger tires, the minimum dual spacing was always larger than 238.7mm. For example, for Michelin Agilis C-Metric tires (a serious consideration) in a 225/75 r16 size, Michelin publishes a minimum dual spacing of 256mm. So that’s Michelin saying that, in order to be safe, you should have at least 256mm between your wheel centers.

That minimum spacing is just over 17mm greater than the spacing on the stock wheels. So, in order to meet the Michelin safety criteria for LT 225/75 R16 tires (which is a size I would have liked), you would need to add a spacer of 17.3mm, or slightly less than three quarters of an inch, between the two wheels. Now sure, adding a spacer is easy enough, and it would meet the tire’s safety requirements. But the design for all the wheel spacers I’ve seen necessitates a change in the mounting orientation of your tires. Basically, when you add a spacer, you have to rotate the wheels differently when you mount them – and that means your tires will be mounted so you no longer have clear access to the inflation valve on the inner tire! So then you have to install valve extenders or crawl on your belly under the van, or come up with some other solution in order to even air up your tires.  No thanks.

But How Do You RV?

This last reason really is (and should be) the main driver behind any RV modification you make… does it make sense for the way you RV? For some people, the increased ground clearance of larger tires makes sense. But for us, larger tires really didn’t make much sense. Here’s why.

Yeah. We rode out to the Biosphere. What can I say? We’re weird.

We’re primarily road cyclists. Road bikes need… roads. So we’re never usually too far from paved roads in our travels. In fact, I’d say our RV mileage is over 99% on paved roads. So for us, prioritizing paved road performance makes sense.

It’s not that we never go off road. We sometimes do. But cycling is such a strong part of our RV adventures, that when we do go off-road somewhere, we often find ourselves saying

“Uhhhh… OK. We’re remote.  Now what?”

There’s no right or wrong to that – it’s just the way we roll. We can stay someplace remote a day or two, but after that, we start getting antsy. So off-roading just hasn’t been a big part of our RV plan, and I don’t see that changing any time soon.

Sure, we go off-road sometimes, but we never stay there long.

AND… here’s the thing for us. Since we installed VB Air Suspension in our EKKO, we always have the option to inflate the airbag system to its maximum. That will gain us about 2 inches of lift in the back. Now granted, we can’t drive very fast that way, but we can at least drive over obstacles or get ourselves out of a jam. So, in a way, we can have the increased ride height when – and only when – we really want it.

Back around to picking tires

Remember, all this started when I wanted to replace the Dynaplodes, right? Well, it turns out, there are very few (like maybe 5, max) tires made in the stock size and weight capacity. If I were willing to select a larger tire size, I’d have a lot more options. But when I put everything down on paper in a chart, it came out looking something like this:

So with all that going against larger tires, it just made sense for us to stick with the stock size. Perhaps if I were a rock climber instead of a road cyclist, and I lived and breathed far from paved roads, then the improved clearance would really have made it worth it to get larger tires. But for us, it just didn’t make sense.

Choosing the Toyos

OK, first a bit about the numbers on the tires. Let’s take the first set. 205/75R16C. Those are the tread width (205mm) the aspect ratio (the tire sidewall is 75% of tread width) and the wheel radius (16 inches). And yes, I realize that’s an awful abomination of metric and standard measurements all jumbled together, but that’s what makes our country great, right?

That first set of numbers describes the tire’s geometry. The second set gets to performance. On the outgoing Dynaplodes, those were 113/111R. The numbers here refer to weight ratings – and there are two of them, 113 and 111. The first number, 113, is the weight rating when the tire is used as a single. In this case, that’s 2535 lbs per tire. The second number is the weight rating when used in a dual configuration 111 – in this case 2403 pounds.

(Interesting side note – I’ve found at least three different explanations for why the dual rating is less than the tire used as a single! Depending on where you look, it’s either because of a. unequal load sharing between tires when used as a pair, b. a safety factor so the surviving tire might be able to carry the load if one tire failed, or c. lower weight so the tire deforms less and maintains an adequate spacing from its neighbor.)

It’s very important to choose a replacement tire with the same or better weight ratings as the original equipment. So as an example, although the Continental Vanco are available in the stock size, they would NOT be an acceptable replacement, because their load rating (110/108) is a good bit less than the Hankook Dynaplodes (113/111).

And the final letter, “R”, is a speed rating. A speed rating of R is good for 106 mph. I don’t know how fast you drive your RV, but I’m probably good with that. Again, it’s wise to replace your tires with something with an equal or better speed rating.

So when filtering out the tires available in the right size with the right ratings (and not considering the Dynaplodes because they suck), the field narrows very quickly. In fact, I wound up looking at only two tires. The Michelin Agilis CrossClimate, and the Toyo Celsius Cargo. Besides brand and appearance, the one area where they had a notable difference is in the winter service rating and the “3 peak Mountain Snowflake” symbol (3PMSF).

But before I get into exactly what that symbol is, some interesting back story on the Michelin tires. They had been available before, and then they were recalled and off the market. Now, they’re available again. It turns out that the reason they were recalled is because they had a 3PMSF designation before, but they technically didn’t qualify for it. So Michelin recalled the tires, and basically just scratched the 3PMSF symbol out of the mold. That’s how they fixed the recall!

So apparently, there’s really something to that rating – if it was enough to make Michelin go through the expense of a recall. The Toyo Celsius Cargo tires have the 3PMSF symbol, and always have had it. SO what is it?

Well, the 3PMSF symbol indicates the tires meet certain U.S. Tire Manufacturer Association (USTMA) requirements for severe snow conditions. It’s a performance based rating – as opposed to the “Mud and Snow (M+S)” designation, which is strictly based on the tire tread design. A 3PMSF rated tire will have actually been tested to provide some level of traction during acceleration on medium packed snow. They’re not tested on ice, or for cornering, or a host of other things, so it’s not a perfect standard.  Nor is a 3PMSF tire a true winter tire.  But they should, under most conditions, provide superior winter traction to standard all-season tires.

One of the ways the Toyo Celsius Cargo tires get their 3PMSF designation is the tread design. The inner two tread blocks, as you can see, have more sipes and a winter tread pattern. The outer two tread blocks are a more typical all-season design. Interesting, huh?

Stef and I like to RV all winter, and to take our RV to ski areas and other snowy destinations. We had never had a winter traction issue with the Dynaplode M+S tires and all-wheel-drive, but having the 3PMSF tires seemed like a smart way for us to go.  So, even though we’ve had good luck with Michelins in the past, we decided to go for the Toyo Celsius Cargo tires.

Toyo Celsius Cargo Installed – What do I think?

We ordered a set of 6 tires from the local Discount Tire. They arrived inside of a week, and we had them installed a few days before we headed off on a 1500 mile trip. We went into Colorado, and up over Monarch Pass (11,000+ feet). Over the course of the week, we drove the tires on dirt roads, city streets, and plenty of highway and interstate miles. In one sentence: We Love These Tires!

This was sort of the most snow we saw though, so a full winter evaluation is still on the to-do list.

There are two main things I’ll point out about our tires. The first is this. I’ve found the tires to be considerably quieter, and much less harsh than the Dynaplodes they replaced. The whole RV rides much smoother and quieter now.  (And I’m kicking myself for not doing a proper before/after decibel test, but perhaps I can do something to compare to my numbers from last summer. Something for another day, and a different post. Anyway…)

This is purely conjecture on my part, but I’m guessing that the Toyo Celsius Cargo tires have softer sidewalls than the Dynaplodes. Besides being smoother and quieter, the steering response of the Toyos feels somewhat… softer??? than the Dynaplodes did. I’m probably not describing it correctly, but say like in hard cornering, I can detect a delay or a “shift” in the steering. For the most part, this doesn’t bother us, because we don’t drive the RV like a race car, so we don’t need twitchy super-excitable steering.  All of those observations line up with what one would expect from tires with a softer sidewall. I couldn’t find any sidewall stiffness ratings to compare the two tires, so this really is just conjecture on my part.

The other thing I like about the Toyo tires is that I was able to get proper load and inflation tables for these tires from Toyo. A couple years ago, when we first got Number One, I had tried to get load and inflation tables for the Dynaplodes, but Hankook just ghosted me and never responded.  Toyo customer service, on the other hand, was responsive, and sent me the data I asked for.  (They probably have more time than the Hankook people, because they’re not swamped dealing with people pissed off about their exploding tires.)

If you don’t know what load and inflation tables are, you should. They are what tell you – for your particular tire – what you need to inflate it to in order to carry how much load. I once wrote a post on how to use these tables and the actual weight of your rig in order to set your tire pressures properly. That post is here. I was happy to be able to set my tire pressures using actual data now that we had the Toyos.  I’ve excerpted the data from Toyo for our tire size in this PDF.

Toyo Load and Inflation Table

Really quickly, the heaviest I’ve ever gotten our rig was straight up 11,000 lbs. Right at GVWR – on the nose. Don’t believe me? Here’s the weight slip.

Well, that’s as heavy as I’ll ever get the RV, so how do I use that to set the tire pressure? Well, on the front axle, it weighs 4300 pounds – so that’s roughly 2150 pounds per tire. From there, I increase that weight by 10% to account for uneven loading and a general safety factor, and you get 2365 pounds.

Well, according to the load and inflation tables, to safely carry 2365 pounds, the Toyos need to be inflated to…. 70 psi. That’s exactly what’s listed on the door!

Same thing for the rear axle – instead there are four tires instead of just two to share the load. Also, you need to use the “Dual” line in the table instead of “Single”. And when you do that, the recommended psi is… 55 lbs! Again, exactly what’s printed on the door sticker. So – good news – the tire inflation pressures listed on your door sticker (at least in an EKKO) are accurate for the Toyo tires at a maximum load.

Conclusion?

Whew! That was a lot. (Like 3,500 words worth about tires.) I hope this was helpful to you. At the end of the day, as long as you’re safe, and you’re happy with the tires you have, that’s really all that matters. And I feel like I nailed both of those by switching from the Dynaplodes to the Toyo Celsius Cargo.