Anyone put small van tires on their car?

[Daschicken]

When I got my current tires, which are 205/60/16s at 25.7" tall, I looked for a 195 option, which doesn't exist in 16" wheels without dropping below my stock tires' 25.5" height. Now, there is actually a 195/70/15 option that is 25.7" tall....I could combine that with the 11 pound 15" wheels from the 1990s mazda millenia. Unfortunately, the only tire types available in these sizes are van tires, which are designed to carry a crap ton of weight. This may actually be not so bad, since I would assume a tire with better load carrying capacity can have lower RR. Plus these van tires are rated with max psi between 65 and 75! My only concern would be the strength of the rim. Would it stand up to those pressures, or would I have to grab van rims as well? This is probably the closest we can come to trailer tires legally.

Speaking of trailer tires, how low RR would they be? They seem to sacrifice grip and wear, so they must have low RR, plus they can carry a ludicrous amount of weight.

[Stubby79]

The pressure won't bother the wheels. They wouldn't be able to put up with the stresses a car puts on them if mere low(ish) air pressure was a hazard.

Are you trying to go down a size in width for reduced rolling resistance or what? If so, you might want to consider the width of the actual grip on the tire. I've had tires in the same size with considerable difference in the contact patch width, one being "sporty" that had grip right to the outer edge of the tire, and a typical all season that curved in as it reached the tread...there was probably 1" total difference in the width of what touched the road.

Besides that, just changing down a tiny bit in tire width probably wouldn't make up for the cost and effort put in, unless you're due for tires anyway.

[Jez77]

The van tyres will be much heavier than car tyres which will cancel out any gains from aero I'd think. They also are unlikely to have any of the high tech low rolling features car tyres have these days

[Daschicken]

Originally Posted by Stubby79

The pressure won't bother the wheels. They wouldn't be able to put up with the stresses a car puts on them if mere low(ish) air pressure was a hazard.

Are you trying to go down a size in width for reduced rolling resistance or what? If so, you might want to consider the width of the actual grip on the tire. I've had tires in the same size with considerable difference in the contact patch width, one being "sporty" that had grip right to the outer edge of the tire, and a typical all season that curved in as it reached the tread...there was probably 1" total difference in the width of what touched the road.

75 PSI is a lot of pressure.

I would be trying to get a thinner and taller(or same height) tire for better aero. I would think the high load capacity and max pressure of the van tires COULD allow for low RR. Already have Ecopia EP422+es, which are pretty serious low RR tires already. I don't know about the relationship between tire size and contact patch width vs rolling resistance, but am doubtful it is as simple as less contact width automagically = less RR. Compare the Michelin defender to the Michelin energy saver. The defender may be the one with less contact patch, yet the energy saver is the lower RR tire. The Kelly edge A/S has a VERY small contact patch, and is EXTREMELY light. Those edges are the lightest tires I have ever felt, but I can't seem to find specs online. I don't think the edge is considered a low RR tire though.

Originally Posted by Jez77

The van tyres will be much heavier than car tyres which will cancel out any gains from aero I'd think. They also are unlikely to have any of the high tech low rolling features car tyres have these days

The van tires I saw in that size were about 26 pounds, my current tires are either 19 or 20 pounds, bridgestone lists multiple weights for some tires... Combine that with the lightweight mazda rims and the new tire combo would be just a pound or two heavier. Yes, I doubt the van tires are built for low RR, but due to their design they may be low RR anyways.

Dunno. That's why i'm asking! Seems like something people here would want to try! I am not due for new tires any time soon, so its not going to be me.

[Stubby79]

Originally Posted by Daschicken

75 PSI is a lot of pressure.

I stick with my above assertion; it's practically nothing to the steel or aluminum of your wheel.

I have a portable air tank for inflating tires. It's maybe 16 gauge, and holds 100psi with no issue.

My propane tanks are not much thicker, and have to be able to withstand 300+ psi, or else they would rupture if they sat out in the sun.

A wheel is made of much thicker steel than either. You're not going to be able to put in enough pressure as to be able to warp or spread the metal and make the tire pop off or any such thing.

Light truck wheels aren't particularly any more stout(based on weight) than an equivalent passenger car's of the same size. Weigh a couple some time.

Even if the tire could handle 75psi, I doubt there's much to gain past a certain point. I wouldn't want to put up with the harsh ride that would give me. To each their own.

If you need reassuring, there are videos on youtube where people get tires to explode by pumping in more and more air...it's always the tire that gives way, never the wheel.

Oh, and, at a guess, the additional mass of the heavier tire will probably end up costing you more fuel than you save from the tiny difference in aero, unless you drive purely highway or have regen braking to absorb the excess power needed to rotate the additional mass. Lighter rims will help, but the farther out the mass is, the harder it is to accelerate...you'd still be losing out, over-all, even if the combination was the same weight.

That's my take on it. Have fun with your quest.

[oldtamiyaphile]

Euro type van tyres are available in LRR. I get up to 50mpg city out of a van the same size as a Ford E-Series -it's certainly not aero or weight on my side.

As to pressures, your rims will be 100% fine at 75psi. Bare in mind that there's a bell curve to tyre pressures for tyres used on surfaces other than rail road tracks - there's a point at which RR starts to increase again.

In once you get to 50-60psi, the gains above that are tiny, and probably not worth the increased wear and tear on suspension components and occupants. The extra crashiness could even fatigue an alloy rim in time.

I only run around 60psi in my van (at ~2tons).

[Hersbird]

I think you might be ok with the trailer tires. They won't handle as well or have as much traction but I bet in normal driving you wouldn't even notice. They will also ride stiffer but I bet that stiffness which is in the sidewalls, translates to lower rolling resistance. In a corner that stiffness along with the narrow tire means it doesn't distort to the road and steering angles as well for grip. Add in rain and it might be quite noticeable. That's where you have to think whats right for you. I bet a newer accord with that as a negative still handles better than anything pre 80's and definitely better than anything on old bias ply tires. So bottom line, we used to do just fine on poor suspension designs and inferior tire compounds but you have to not be Too Fast and Too Furious.

[Daschicken]

Originally Posted by Hersbird

I think you might be ok with the trailer tires. They won't handle as well or have as much traction but I bet in normal driving you wouldn't even notice. They will also ride stiffer but I bet that stiffness which is in the sidewalls, translates to lower rolling resistance. In a corner that stiffness along with the narrow tire means it doesn't distort to the road and steering angles as well for grip. Add in rain and it might be quite noticeable. That's where you have to think whats right for you. I bet a newer accord with that as a negative still handles better than anything pre 80's and definitely better than anything on old bias ply tires. So bottom line, we used to do just fine on poor suspension designs and inferior tire compounds but you have to not be Too Fast and Too Furious.

Yeah.....Not gonna happen. I like hauling ass around corners. Also, I would bet that the handling difference between passenger tires and trailer tires is a whole lot more dramatic than you make it sound.

You better believe that if I get the chance I would try it out(in a big parking lot..), but I don't see that happening any time soon. I don't have a set of 15" rims yet, and the trailer tires that exist for 15" rims are a little wide. There are some 205/75/15s, but I bet the majority of 15" trailer tires would be 225/75/15s. The 14" size is the most appealing to me, but I don't think the brake rotors would allow a 14" rim to fit.

12" 145/80/12 Radial available believe it or not! Even at this size there are tires that can hold 1500 lbs! My tires are rated around 1390 IIRC.
13" 175-185/80/13
14" 205-215/75/14
15" 205-225/75/15
16" 235/80-85/16 At this point they are practically tractor trailer tires. It takes just ONE tire to support my car's GVWR.

[CapriRacer]

First, I have a couple of webpages you ought to read:

Barry's Tire Tech - Rolling Resistance and Fuel Economy

Barry's Tire Tech - Followup on Rolling Resistance and Fuel Economy

With that as background, let's start with the van tire thing.

Those are the European equivalent of LT tires. They are built more or less out of the same type materials. So are trailer tires, so what I am about to write applies to them as well.

Because these tires carry a lot of load compared to their size (compared to passenger car tires), the tread rubber is much stiffer and has poorer hysteretic properties (heat generation due to internal friction). Now you may think that a stiffer tread rubber would be better for rolling resistance, but because an inflated tire's casing to sooooo much stiffer than the tread rubber, the tread rubber's stiffness hardly impacts the overall tire's stiffness - so the tread rubber's only influence on RR is the hysteretic properties, and for LT tires (and van, and trailer tires), that's much worse than for a passenger car tire.

Put another way, don't use LT tires, trailer tires, or van tires (European style) on a car.

Increased inflation pressure? Up to a point that improves fuel economy, but not only is there diminishing returns, there's a point where the contact patch becomes so small that there are traction issues in the wet. This point seems to be dependent on the road surfaces in the locale where the tire is operating, so it isn't the same everywhere.

Aerodynamics? If a tire is fully exposed to the oncoming air, like an F1 or Indy car, a tire's width would be important. But 3/4 of the tire is surrounded by the car body, so a tire's width doesn't have much influence on the overall aero drag - and is easily overwhelmed by such simple things as the improved RR due to the increase in width.

Increase in tire size? That seems to be a good thing relative to FE. About 2 steps seems to be what most cars can accommodate - so in the OP's case, going from 205/60R16 to 225/60R16 might be possible. That increase would effectively reduce the overall gearing of the car, and folks here have reported improvements due to that kind of change.

And this should be coupled with a careful selection of make and model of tire - one that meets the wear, traction, and RR needs of the owner.

[elhigh]

I put light truck tires on my Pickup for a couple of years, and it had a significant deleterious effect on the fuel economy, about a 15% drop if I recall. I seriously hated them and even though I was seriously poor at the time, just as soon as I could call them "worn" and had a bit of money saved, I replaced them. My mileage came back immediately.

The truck rode better too.

If you don't need the LT tires for their load capacity, I strongly recommend you avoid them.