Tires Designed for EVs

[jackmott]

Yeah, but if "Sticking to the road" wasn't part of the equation, we'd use steel tires with no air at all. We'd still prefer ZERO compression over just gas compression. By definition, compressing the gas obeys PV=nRT, which means temperature increases, which means we will lose some of that energy to the universe. No proof here that the gas compression loss is less than occurs in rubber.

So actually a very hard and stiff pneumatic structure makes this closer to a steel wheel, which is known to basically be the lowest rolling resistance thing we can reasonably make, yet you are continually claiming it would be better if we could just let it all deform more as it rolled.

If rubber didn't lose more energy than air, why would we bother with the hassle of penumatic tires? We could just use rubber and not get flat tires. The whole magic of the pnuematic tire and why we put up with flats is that it is so efficient.

I am *not* claiming we should let it deform more. I am claiming you want materials that deform with the least energy loss. You tire has to deform a certain amount to work, whether it is a Hoosier race tire or an MXM4. Whatever amount of deformation you need, you use the most supple material you can get away with given other constraints, and use air pressure to get there.

 

[gearchruncher]

You see this readily when comparing known low CRR car tires and bike tires. They are using thinner, more supple materials.

Meanwhile, when Michelin advertises low rolling resistance tires, they don't highlight thinner tires at all, and specifically talk about how the TREAD compound matters and their goal is less tread block squirm, which requires stiffer materials:

Michelin details its lowest rolling resistance tire yet

The X One Line Energy D2 drive tire, unveiled at TMC 2022, is for line-haul, dry van truckload, and refrigerated truckload applications. Michelin says its design offers fuel savings...

www.fleetowner.com

And then this talks all about tread compound being the primary driver, not the carcass:

Michelin launches ultra-low rolling resistance line-haul tire

GREENVILLE, S.C. — Michelin North America has launched the Michelin X Line Energy D+ tire — an ultra-low rolling resistance, dual-drive line-haul tire — to the North American replacement market.

www.tirebusiness.com

 

[gearchruncher]

If rubber didn't lose more energy than air, why would we bother with the hassle of penumatic tires?

We use air specifically because it allows deformation, creating a stable contact patch with the ground as part of the vehicle suspension, and because it's cheap and light. It makes a tire do all the things a tire needs to do. Not because it's "efficient".

Non-pneumatic tires are listed as having less rolling resistance than gas filled tires:

https://smartech.gatech.edu/bitstream/handle/1853/37202/cobert_austin_m_200912_mast.pdf

 

[jackmott]

Understanding Rolling Resistance in Car Tires

The resistance of automotive tires to rolling eats up anywhere from 20% to 50% of the energy used by the car.

www.machinedesign.com

Key bit:
"But what contributes to rolling resistance? Experts say that 1% to 5% of it stems from aerodynamic drag. Another 9% to 10% comes from road friction. And the remaining 85% to 95% is due to internal friction or hysteresis of materials"

https://www.sciencedirect.com/topics/engineering/rolling-resistance

Key bits:
"For a rolling tire, deformation of the tire material occurs while entering the contact patch. The original (undeformed) conditions are restored when the deformed area leaves the contact patch again. This process involves energy losses, mainly due to hysteresis of the rubber material. These losses arise in the tread area, the belt, the carcass, and the sidewalls." (there is a chart showing relative contribution of each area)

"
As a result, the rolling resistance is reduced for:
less hysteresis in the tire material
less deformation of the tire.
"

If you add material to reduce deformation, you also increase the hysteresis of the tire material.
If you instead add air pressure to reach the desired level of deformation, you do not.
In the case of tread blocks, yes, tire pressure doesn't help there, and grip and rolling resistance can be at odds, I imagine especially so for knobbier truck tires.

So I think we are all partially correct here, in that there are areas of the tire that may be made stiffer to improve rolling resistance (tread blocks) and areas where you seek to make it as supple as possible (carcass, sidewall, belt)

 

[jackmott]

We use air specifically because it allows deformation, creating a stable contact patch with the ground as part of the vehicle suspension, and because it's cheap and light. It makes a tire do all the things a tire needs to do. Not because it's "efficient".

Non-pneumatic tires are listed as having less rolling resistance than gas filled tires:

https://smartech.gatech.edu/bitstream/handle/1853/37202/cobert_austin_m_200912_mast.pdf

The numbers in that article for the tweel are research targets, they are not real:

"The research targets for these thre e Tweel™ models are to have rolling resistance
coefficients of 5.5, 4, and 3 kg/ton respectivel y"

 

[Pricedm]

FYI - Discount Tire is having a sale thru 5/26 on Michelin (frequent $110 off sales occur) as well as Pirelli ($70 off - first time I've seen in at least six months). Other tire brands (Continental, $70 off) are on sale as well.

 

[vickh]

Please note that all of these tires are Ultra High Performance tires, no performance loss.
Yes, they do have better range - the P Zero Elect is designed to have 15% less rolling resistance than the regular P Zero.
Also the P Zero Elect is running $30 cheaper per tire than the OEM Michelin Primacy MXM4.

My gas sedan has Michelin "Energy Savers" which I believe are just lighter. Any in right size that can make a difference with EVs too? Shop Michelin Energy Saver Tires | Michelin

 

[vickh]

FYI - Discount Tire is having a sale thru 5/26 on Michelin (frequent $110 off sales occur) as well as Pirelli ($70 off - first time I've seen in at least six months). Other tire brands (Continental, $70 off) are on sale as well.

any deals on 2?

 

[android04]

any deals on 2?

No, deals are always on sets of 4. Which it why I like to rotate my tires so they all wear evenly and get replaced at the same time. And also why I would never use staggered tires.

 

[3sr+buyer]

My gas sedan has Michelin "Energy Savers" which I believe are just lighter. Any in right size that can make a difference with EVs too? Shop Michelin Energy Saver Tires | Michelin

The Michelin Energy Saver was the OEM tire for the Chevrolet Volt and Bolt. The ones on the Bolt had the self-sealing feature which made them heavier.

https://www.tirerack.com/tires/Spec.jsp?tireMake=Michelin&tireModel=Energy+Saver+A/S indicates that at least the following companies have cars (not necessarily EV) using some version of the Michelin Energy Saver as the OEM tire:

• Mini 175/65R15
• GM 215/50R17 and 265/65R18
• Ford 235/45/R18
• Toyota, Lexus 235/45R18
• Honda 235/45R18

However, the 235/45R18 size does not have the 98 load rating specified for the Model 3 (it has a load rating of 94).

 

[gearchruncher]

However, the 235/45R18 size does not have the 98 load rating specified for the Model 3 (it has a load rating of 94).

Not all Model 3's have the same load rating requirements. AWD vs RWD and battery size and chemistry impacts this.

 

[3sr+buyer]

Not all Model 3's have the same load rating requirements. AWD vs RWD and battery size and chemistry impacts this.

Which Model 3 came with tires with a load rating lower than 98?

(2022 RWD (SR+) comes with tires with load rating 98.)

 

[gearchruncher]

Tesla 2022 Model 3 Tires

I have just taken delivery of a 2022 Model 3 Long Range. It came equipped with Hankook Gt 436 235/45/18 tires. When I went to Discount Tires to purchase their certificate that warranties against tire failure, punctures, etc., they said that these tires were not the right tires for the car...

teslamotorsclub.com

The tires on the car doesn't matter, you can always use higher rated tires than required. The door sticker is what matters. What does your door sticker say?

(2022 RWD (SR+) comes with tires with load rating 98.)

Like I say in that thread, Tesla changes things so much, so fast, that there is no such thing as a 2022 SR+ car that you can assume is the same as another car.

 

[3sr+buyer]

The tires on the car doesn't matter, you can always use higher rated tires than required. The door sticker is what matters. What does your door sticker say?

The door sticker lists "235/45R18". There is no P in from the the size, indicating that it is a "Euro-metric" size, rather than a "P-metric" size. Unlike on some other cars, load and speed rating are not explicitly on the label. Another car (not a Tesla) whose label I looked at has a door sticker that lists the tire size with a P in front of it with a matching P-metric load index (and a speed rating).

Charts of P-metric load index indicate that a P235/45R18 tire will have a load index of 94. However, corresponding charts for Euro-metric load index are hard to find (although web sites about the different between P-metric and Euro-metric indicate that, where they are different, the Euro-metric has a higher load index). Just to add to the confusion, tire company and retailer web sites (and the tire sidewall markings) often leave out the P for P-metric sizes, so you can find "235/45R18" tires with both 94 (the P-metric load index) and 98 (the likely Euro-metric load index) load index.

 

[3sr+buyer]

Like I say in that thread, Tesla changes things so much, so fast, that there is no such thing as a 2022 SR+ car that you can assume is the same as another car.

Legally, there is, since the VIN includes a character indicating the model year. For example, an N in the 10th character of the VIN means 2022 (or 1992) model year.

Running changes within the same model year are not unique to Tesla.

 

[vickh]

Which Model 3 came with tires with a load rating lower than 98?

(2022 RWD (SR+) comes with tires with load rating 98.)

How do I find My '19 SR RWD rating?

 

[3sr+buyer]

How do I find My '19 SR RWD rating?

On the tire itself, the load index is after the size. For example: 235/45R18 98W (98 is the load index)

However, if your tires are different from the ones that the car came with, the ones the car came with may have different load ratings. The sticker on the door jamb will tell the tire size (and whether or not there is a P in front of the tire size is important) and may or may not explicitly list the load and speed ratings.

 

[vickh]

On the tire itself, the load index is after the size. For example: 235/45R18 98W (98 is the load index)

However, if your tires are different from the ones that the car came with, the ones the car came with may have different load ratings. The sticker on the door jamb will tell the tire size (and whether or not there is a P in front of the tire size is important) and may or may not explicitly list the load and speed ratings.

Will check. I was trying to see if the SR is lighter ( i believe it's the same as SR+) and be the exception and get the Energy savers

 

[android04]

Which Model 3 came with tires with a load rating lower than 98?

(2022 RWD (SR+) comes with tires with load rating 98.)

Model 3 Performance with 20" wheels came (probably still do?) with tires of a 92 load rating, which meets the minimum specs for axle weight rating. See posts #1 and #2 here 20” Uberturbines on LR RWD Model 3

 

[vickh]

Model 3 Performance with 20" wheels came (probably still do?) with tires of a 92 load rating, which meets the minimum specs for axle weight rating. See posts #1 and #2 here 20” Uberturbines on LR RWD Model 3

so only the larger sizes have lower load ratings.. hmm