Increased efficiency with 255/45 20 Hankook Ion on my GT (updated OP)

[tuminatr]

I did lower the pressure to 34 psi, and that trip still had better efficiency than four of the five OEM trips. I totally agree that lowering the pressure reduces efficiency, and it was the worst of the five Ion trips.

On a side note, I don't think the only reason for the bigger size is so I can reduce tire pressure for more comfort. They do look better. And while I have no way to prove it, I think less rotational air resistance at 80 mph is another reason they are more efficient.

If I changed tires frequently like you do, maybe I would get some 245 Ions and see if they are just as efficient as the 255s. That would prove it either way. But alas, I am not up for that.

I am very happy with the results, regardless of the reason.

Next up: Eibach lowering springs efficiency test. Will lowering the car by 1" improve efficiency? In theory it should, but it might not be measurable.

That should be interesting

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[markboris]

Next up: Eibach lowering springs efficiency test. Will lowering the car by 1" improve efficiency? In theory it should, but it might not be measurable.

When we installed the Eibach 1 inch lift springs on Eric’s car, he saw an immediate reduction in range and had that reduction until we replaced them with the lowering springs. I don’t know how much of an increase in efficiency you will see by lowering it but it’s certainly not going to be less range.

Edit: I’ve had my car lowered for over a year and never really noticed an increase in efficiency but then 1. I never really look at my efficiency and 2. I am constantly changing tires sizes and types. All I see is my range estimate when I’m 100% charged and it never varies more than 10-15 miles while the temp is the same.

 

[silverelan]

I updated the OP with the efficiency data. The bottom line: these tires with the larger size are 7.62% more efficient than the OEM setup. Go back to the OP for the full write up and all the data.

7% improvement over the stock Continental CrossContact RX tires is huge.

 

[load97]

I put 255/45/20 Continental Cross Contact Sports XL on with aftermarket Klassen ID wheels. Wheels I doubt are very aerodynamic. But are like 8 lbs. lighter IIRC. I have not noticed any difference in range whatsoever. The wife even took the car on a 2.5-3 hour trip up north and didn't think range was any different than when we went with the stock GTP tire/wheels combo.

 

[mkhuffman]

I put 255/45/20 Continental Cross Contact Sports XL on with aftermarket Klassen ID wheels. Wheels I doubt are very aerodynamic. But are like 8 lbs. lighter IIRC. I have not noticed any difference in range whatsoever. The wife even took the car on a 2.5-3 hour trip up north and didn't think range was any different than when we went with the stock GTP tire/wheels combo.

I don't believe the car trip efficiency is accurate based on comparison to actual OBD data. And it is hard to believe rims that are not as aerodynamic and tires that have higher rolling resistance would give you a similar efficiency.

 

[load97]

I don't believe the car trip efficiency is accurate based on comparison to actual OBD data. And it is hard to believe rims that are not as aerodynamic and tires that have higher rolling resistance would give you a similar efficiency.

I’ve just been looking at percent of battery used to go the same distance. Whether accurate or not, I have not seen much of a variance. Not that I personally care if there was a small hit, which seems negligible ATM. Also, the tires rolling resistance as far as online reviews go, was one of the better ones for non specific EV tires. These weren’t my first pick for tires, but the price was very good so I went with them.

If range is more important, and tire price isn't that important sounds like you found what you were looking for. I wasn’t trying to rain on your parade.

 

[mkhuffman]

I’ve just been looking at percent of battery used to go the same distance. Whether accurate or not, I have not seen much of a variance. Not that I personally care if there was a small hit, which seems negligible ATM. Also, the tires rolling resistance as far as online reviews go, was one of the better ones for non specific EV tires. These weren’t my first pick for tires, but the price was very good so I went with them.

If range is more important, and tire price isn't that important sounds like you found what you were looking for. I wasn’t trying to rain on your parade.

Don't worry, I didn't take anything you posted personally. I was just sharing my opinion based on my experience.

My guess is you don't see a difference because your driving style isn't impacted by the wheel changes you made. So that is good news. However, I am pretty sure your wheel setup on my car would negativity impact range based on how I drive.

 

[Fluid Dynamics]

I went 265 wide and added 20mm spacers...

I also have Eibach sway bars front and back and it handles so much better...

Didn't really notice a drop in range...

 

[Mach1E]

Not at steady highway speeds. At steady highway speeds, rolling resistance and aerodynamics are all that matters. And I only care about highway efficiency, which is why I did the test on the highway.

Yup, even at steady speeds.

Rotational mass still matters. Maybe not as much, but that extra weight makes a difference.

Easy place to see this would be with pickup trucks and huge heavy tires-
Their highway fuel economy suffers as well.

What you could be seeing with your new tires is at highway speeds the added mass and wind resistance is offset by better rolling resistance. But the mass is still a negative factor.

 

[mkhuffman]

Yup, even at steady speeds.

Rotational mass still matters. Maybe not as much, but that extra weight makes a difference.

Easy place to see this would be with pickup trucks and huge heavy tires-
Their highway fuel economy suffers as well.

What you could be seeing with your new tires is at highway speeds the added mass and wind resistance is offset by better rolling resistance. But the mass is still a negative factor.

Einstein wasn't wrong. An object in motion will stay in motion until a force acts to stop it. Rotational mass only matters when you are spinning it up. Once it is at speed, it will want to stay at that speed unless something tries to slow it down. Like friction from rolling resistance. Or regen from the electric motors.

I think what you are seeing with those huge tires is a big increase in rolling resistance, and also worse aerodynamics. At least at steady state speeds anyway. Certainly the big increase in weight impacts acceleration resistance.

Here is some data that proves Einstein was correct:

 

[Mach1E]

Einstein wasn't wrong. An object in motion will stay in motion until a force acts to stop it. Rotational mass only matters when you are spinning it up. Once it is at speed, it will want to stay at that speed unless something tries to slow it down. Like friction from rolling resistance. Or regen from the electric motors.

I think what you are seeing with those huge tires is a big increase in rolling resistance, and also worse aerodynamics. At least at steady state speeds anyway. Certainly the big increase in weight impacts acceleration resistance.

Here is some data that proves Einstein was correct:

He was correct, and so am I.

It takes more energy to keep heavier tires spinning because of those forces you mentioned.

If you want to test this theory it’s pretty easy-

Add some people in your car and test your highway efficiency.

Again- mass is the enemy. And rotational mass has an even larger affect than adding mass to the rest of the car.

If you want to test the theory with your own power that you can FEEL, get on a lightweight road bike, cruise at 20 mph.

Then switch to a mountain bike and try the same.

It isn’t just acceleration that takes a hit.

And yes, again as you have seen, you can OVERCOME these things by lowering rolling resistance. Here is an example with bike tires- when they increase the tire pressure and lower rolling resistance, the wider tires are more efficient. At recommended pressures the narrower ones are-
https://www.bikeradar.com/advice/buyers-guides/are-wider-tyres-faster

 

[tuminatr]

[

He was correct, and so am I.

It takes more energy to keep heavier tires spinning because of those forces you mentioned.

If you want to test this theory it’s pretty easy-

Add some people in your car and test your highway efficiency.

Again- mass is the enemy. And rotational mass has an even larger affect than adding mass to the rest of the car.

If you want to test the theory with your own power that you can FEEL, get on a lightweight road bike, cruise at 20 mph.

Then switch to a mountain bike and try the same.

It isn’t just acceleration that takes a hit.

That is an example of rolling resistance. My road bike the tires are at 100psi my mountain bike they are at 35 PSI

Also knobby tires vs smooth city tires. MTN bike again has more rolling resistance.

 

[Mach1E]

[
That is an example of rolling resistance. My road bike the tires are at 100psi my mountain bike they are at 35 PSI

Because they can be because of the width and the amount of pressure it takes to get the same size contact patch.

I updated my post with a link that proves it.

You also can raise the pressure in your mountain bike tires to lower resistance and it will still take more energy to maintain speed.

Do you honestly think weight/mass doesn’t impact cruising efficiency?

Even if you only want to focus on rolling resistance and ignore everything else- weight increases rolling resistance.

Experiment #2-

Throw some weights in a backpack and try to cruise at 20 mph on your road bike-

Experiment #3- strap those same weights to your legs and do the same.

You will see the weights on your legs (rotational mass) have a much larger effect.

 

[mkhuffman]

Because they can be because of the width and the amount of pressure it takes to get the same size contact patch.

I updated my post with a link that proves it.

You also can raise the pressure in your mountain bike tires to lower resistance and it will still take more energy to maintain speed.

Do you honestly think weight/mass doesn’t impact cruising efficiency?

Even if you only want to focus on rolling resistance and ignore everything else- weight increases rolling resistance.

Experiment #2-

Throw some weights in a backpack and try to cruise at 20 mph on your road bike-

Experiment #3- strap those same weights to your legs and do the same.

You will see the weights on your legs (rotational mass) have a much larger effect.

I admire your tenacity.

Weight only reduces efficiency when you are accelerating. It is physics.

In the real world, I agree weight does matter on the highway because there is no highway that is perfectly flat. So you do have to "accelerate" to maintain the same ground speed when going uphill. But seriously. 5 lbs is hardly a drop in the bucket. Or 10 lbs.

Anyway, I think this horse is dead. Physics is physics, and you can't change it.

I was wrong: it was Newton, not Einstein, who you are arguing with:

An object in motion stays in motion is a phrase that summarizes Newton's First Law of Motion1. This law states that an object will maintain its state of motion unless acted upon by an external force12. This means that an object moving at a constant speed and direction will continue to do so, and an object at rest will remain at rest, unless a force changes its motion. This property of objects is called inertia2.

 

[tuminatr]

Because they can be because of the width and the amount of pressure it takes to get the same size contact patch.

I updated my post with a link that proves it.

You also can raise the pressure in your mountain bike tires to lower resistance and it will still take more energy to maintain speed.

Do you honestly think weight/mass doesn’t impact cruising efficiency?

Even if you only want to focus on rolling resistance and ignore everything else- weight increases rolling resistance.

Experiment #2-

Throw some weights in a backpack and try to cruise at 20 mph on your road bike-

Experiment #3- strap those same weights to your legs and do the same.

You will see the weights on your legs (rotational mass) have a much larger effect.

I do think weight/mass has an effect but not the way you have described. All of these factors are application-specific on an EV lightweight wheels does not necessarily help.

As I stated earlier this is not a theory i tested lightweight wheels (TSW Bathurst 18x8 18.6lbs) on my premium vs CR1. The result was the CR1 (18x7 30+ lbs) was noticeably more efficient in the city and on the highway.

My conclusion was aerodynamics has more of an effect on efficiency. You look at everybody's lightweight aluminum wheels and they have very bad aerodynamics. And I got much more energy back through regenerative braking than I gained in efficiency because of the lightweight wheels.

Now if someone made a very lightweight aerodynamic wheelset for an EV that could be the best but unfortunately they would be expensive and therefore not worth it.

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