Everything You Need To Know About Electric Car Tires

hello everyone and welcome in this video sponsored by Hankook we are talking about one of my absolute favorite subjects tires specifically we're covering electric car tires now you might think it's a tire put it on a gas car put it on an electric car what does it matter well there's some challenges when you slap regular tires on an electric car why because EVS are pretty heavy they are super efficient they're remarkably quiet and they have boatloads of torque so let's talk about how you create a tire to address each of these four challenges let's start with weight these cars are heavy and it's pretty easy to understand why say you want 300 miles of range well that's about 70 pounds of fuel for a gas car but it could easily be a thousand pounds for the battery of an electric car so even if you can save some weight with electric motors versus combustion engines the overall car weight tends to be higher by about 20 to 30 percent so you've got a lot of weight on the tire and at the same time you want to keep keep it as narrow as possible for aerodynamic reasons since efficiency is critical with EBS so that means you've got a bunch of pressure on a fairly narrow contact patch Hancock says based on their own testing if you compare the tread wear of the same tire put on a lighter combustion car versus a heavier EV on the electric car the tire will wear about 20 percent faster so what do you do well you have to increase the stiffness of the tire for example Hancock says this tire has 25 percent higher lateral stiffness and 20 percent higher quartering stiffness versus their standard SUV touring tire so think about what happens when you turn in you're asking this tire to change direction and you have the heavy weight of the vehicle resisting that motion so it wants to laterally stretch the tire so you change the profile and rigidity of the sidewall increasing the lateral stiffness and in doing so you improve your steering response because you don't have that slop when you turn in now you might wonder does this mean you'll lose comfort Comfort well if you were to throw this on a lightweight combustion car sure the tire's stiff so it doesn't match the application you could say the same about taking a heavy truck's suspension Springs and putting it on a car the lighter car would ride way too stiff but that doesn't mean when those Springs are used on a heavy truck that that truck has poor ride quality so think of this as matching the application can you use regular tires on a heavy EV sure but you could be sacrificing steering response and handling now as mentioned more weight generally means more wear so EV tires also use a stiffer compound to reduce the wear impact from higher weight in addition and this is something I'd actually already noticed from my own experience dedicated electric tires tend to have a flatter contact patch for a given Tire width resulting in more rubber in contact with the road helping to spread out the load and improve wear okay so stiff tires obviously important but what's critically important for an EB is efficiency electric cars are crazy efficient and because of this seemingly small changes can make a big impact on range and that's especially true for wheels and tires for tires this is all about rolling resistance in other words the energy lost as heat as the tire deforms moving along the road to rate how well a tire performs here we measure something called the coefficient of rolling resistance some simple math illustrates why this is such a big deal on EVS say for example we have a four thousand pound car that's going to travel 200 miles and we have two Tire options for that car one with a coefficient of rolling resistance of 0.01 a fairly normal car tire coefficient of rolling resistance and one with 0.005 which would be a really really good car tire with some quick math you can determine the tire with more rolling resistance causes you to use an additional eight kilowatt hours of energy over the course of those 200 miles now what if that car was gas versus Electric well taking efficiency into account the gas car would need about 0.8 gallons of extra fuel to compensate for the tire selection and the electric car would need about nine kilowatt hours of extra battery to compensate for the tire selection now think about this from a design standpoint if you're designing a car to run on a high coefficient of rolling resistance Tire adding a gallon to the fuel tank to maintain an equivalent range is no big deal but adding nine kilowatt hours of battery to an EV is a huge deal that's easily a 10 addition to a modern car battery so you need the space for it the price increases significantly and you're adding another 100 plus pounds of weight to the car versus just six for a gallon of gas with this example a simple Tire Choice could easily drop or improve your range by a good 30 miles so for electric cars tires make a huge impact on Range while for gas cars with big fuel tanks you probably won't even notice so how does Hankook improve the coefficient of rolling resistance on their tires well a lot of it comes down to the magic of Tire compounds which is information that basically no tire company has ever been willing to share with me part of this is the process of Vulcanizing the Rubber and curing the tire the more evenly you can cure the tire the better the rolling resistance properties Hancock says you can have up to a 10 difference in Rolling resistance simply based on how you cure the tire also in regards to the flatter contact patch that I mentioned Hancock says their research shows there's not a significant correlation between the contact area and the rolling resistance but if you can create a very even pressure distribution for the area that is in contact with the ground you can improve the rolling resistance moving on to noise noise is a really interesting subject because it's basically a battle that you can never win if you make one part of the car quiet now you notice the other parts more even if the overall volume level is lower this is what happens with electric cars because electric motors are much much quieter than combustion engines according to Hankook about 50 percent of the noise you hear in a gas car is the powertrain in an electric car that number is 15 this is really interesting because I've had people ride in my car and say wow there's a lot of wind noise even though you can just open your glove box pull out your sound meter and naturally integrate into the conversation that by decibels it's actually a very quiet interior I'm fun at parties so you eliminate a lot of noise with an electric powertrain and quiet Interiors are great but now you also need to reduce wind noise and tire noise so that it doesn't stand out so much so for tires what can you do well if you look on the sidewall here you can see it says sound absorber and there are both internal as well as external features on the tire to help reduce noise one of the most prominent of course is this polyurethane foam insert within the tire so as you're driving you have a resonant noise generated from the tire contacting the ground this resonance passes from the tire to the Wheel from the wheel to the suspension from the suspension to the chassis and then you perceive it within the cabin what this foam does is essentially acts like a damper so it dampens that resonant vibration generated helping to prevent the noise from reaching the Cabin Hancock says depending on the tire size and road condition this insert can have as much as a nine decibel impact and remember a 10 decibel difference means you perceive the noise to be twice as loud there are other features to reduce noise as well within the water channels you can see this zigzag pattern or knurling this helps break up and suppress the resonance generated within the groove and Hancock says this alone is good for a 0.3 decibel noise reduction and a pass by noise test another feature you can see on the summer tires are expanding lateral grooves so each of these lateral grooves are a way for noise to break out from these Center channels so you'll notice on tires that have big tread blocks with large gaps in between them tend to be pretty loud tires so here they're using expanding grooves which start off small to minimize how much noise breaks out while still allowing for water to escape finally in this one I find the most fascinating is multi-pitch sequencing so at first glance if you look at these tread blocks or pitches it actually looks pretty consistent as you go around the tire but if you actually measure them you can see okay we've got 28 millimeters there 22 millimeters there 19 millimeters there so there's actually a lot of variants in these tread block widths this is intentionally randomized so you don't have a consistent rhythmic nature to the tire pattern hitting the road surface and generating noise pretty wild you can optimize the randomized nature of the pitch sequence to reduce overall noise now I don't have a perfect example of an all-season Tire with and without all of this technology tested back to back but just for fun I did measure the noise level at 60 miles per hour on the highway on a set of off-the-shelf summer Tires with no internal foam versus these ion all seasons and after multiple runs at 60 miles per hour these tires average just over three decibels quieter and keep in mind there are multiple sources of noise powertrain wind tires and eye measuring total overall noise not just tire noise so just by switching tires the overall cabin noise is three decibels quieter going back to our decibel scale that means riding with the summer Tires was about 25 percent louder that's significant finally and perhaps the greatest advantage that EVS have they've got torque and that torque delivery is nearly immediate for accelerating overall grip is obviously important to minimize wheel spin since you're putting down so much initial torque and the tires construction needs to be able to handle all of this torque but when you really think about it this ties in with the vehicle's weight as well all cars need to be able to perform an emergency stop so the tires need to handle maximum longitudinal grip whether accelerating or decelerating EVS tend to be heavier so the overall force exerted on the tire is greater again this means we need to improve the rigidity of the tire in both the construction and the compound especially when we're talking about performance tires for performance EV applications like summer Tires much of this rigidity comes from the internal construction of the tire with jointless belts and in the case of this summer Tire an aramid belt aramid has very little elongation so as you're reaching higher and higher vehicle speeds you have massive centrifugal forces on this tire so aramid helps maintain the shape of that tire minimizing the increase in diameter this is important for tires with high speed ratings such as a y-grade so if you look at this tire specifically the ion All Season it has a utqg rating of 600 for the wear rating and a for the wet rating and an a for the temperature rating there's a 50 000 mile warranty so it lasts a long time has great wet grip and solid durability and hankooks ion summer tire has Europe's AAA rating meaning the highest rating for Rolling resistance wet grip and noise and the ion lineup covers the full range of conditions with the summer and all season variants as well as an ion winter tire I am a big fan of Summer tires so I hope to try those out once we get out of these colder months all of this simply shows that if you design for it from the beginning you can account for the challenges that EBS put on tires thank you all so much for watching if you have any questions or comments feel free to leave them below

Channel: Engineering Explained

Views: 1,169,728

Keywords: electric car, ev, ev tires, electric tires, hankook, hankook ion, engineering explained, all season tire, winter tire, summer tire, tire engineering

Id: 8pM9o2Ifcro

Length: 11min 45sec (705 seconds)

Published: Fri Dec 23 2022