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

[HuntingPudel]

The main reason I did not go to 255/40 is because I wanted the extra sidewall for potential comfort improvement. I didnt think a 40 would be able to be as comfortable.

A secondary reason is the load rating. The 40 Hankooks have a load rating that is 100 lbs less than the OEM tires. It might be fine, but definitely I would not have been able to safely lower tire pressure for more comfort. Refer to Lee's post. I can lower the tire pressure safely on the 255/45 tires because they have a higher load rating than the OEM tires.

Not to mention that the 255/40R20 is almost 2/3" less in OD than the stock tire. This would create speedometer and odometer errors that I would not recommend. ?‍?

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[mkhuffman]

Not to mention that the 255/40R20 is almost 2/3" less in OD than the stock tire. This would create speedometer and odometer errors that I would not recommend. ?‍?

Yes! I meant to include this as a reason!

So far, there is no measurable difference in speed VS speedometer using Google GPS from the OEM size - the speedometer is still showing me going 1 mph faster than actual. But that is at slower speeds around town.

Per calculation, it should be 1 mph off at 80 mph. With the OEMs, I was going 79 when the speedometer said 80. Now when the speedometer says 80, I should be going 80. I will be testing that this week.

 

[markboris]

Not to mention that the 255/40R20 is almost 2/3" less in OD than the stock tire. This would create speedometer and odometer errors that I would not recommend. ?‍?

The last couple of years, all the tire sizes I have tested have been the same or larger in diameter than OEM. A couple of weeks ago, I decided to go the other way and run slightly smaller diameter because I wanted a slightly shorter sidewall than OEM. I started out with the 255/40/20's up front and while they match the diameter of the 295/35/20's in the rear, they didn't match the handling capabilities of them. Those two staggered sizes are what Porsche uses on the Tycan GTS so wanted to try them out but after a few days, those 255's just did not cut it in hard cornering. I upped the fronts to 265/40/20's and now the front and rear feel very matched in cornering. Note: this staggered size (265/40, 295/35) is what Mercedes uses on the AMG GT 53. All of these tires are Michelin Pilot Sport 4s's with acoustic foam.

After installing the Eibach GT lowering springs that have given me a smoother ride, and being able to run these tires at a slightly lower pressure than 39 psi, I am very very pleased with the ride of this car and above all, the handling.

On another note, I was talking to Steve a week or so ago about proper tire pressure and he mentioned to use my FLIR to take an image of the tire right after I ran on the freeway. I adjusted my tire pressure to get a more even temp across them. The reason for the bright area on the inside of my left rear tire below is because I have the camber set to -1.8 in the rear which is where I like it.

 

[azerik]

You go FLIR, I use a $5 harbor freight laser thermometer lol

I will admit the sidewall of the Hankooks are the only thing that puts me off about that tire. Are you going to give them 25 days of a trial and hop over to the DSW’s if there isn’t enough to keep you on them?
(They come with a 30 day trial, the Conti’s do as well. They they are supposedly EV tires. According to Conti they only make EV tires.)

 

[mkhuffman]

You go FLIR, I use a $5 harbor freight laser thermometer lol

I will admit the sidewall of the Hankooks are the only thing that puts me off about that tire. Are you going to give them 25 days of a trial and hop over to the DSW’s if there isn’t enough to keep you on them?
(They come with a 30 day trial, the Conti’s do as well. They they are supposedly EV tires. According to Conti they only make EV tires.)

I really like the DWS tires. I have put them on several cars over the years. But no matter what Conti says, they are NOT an EV tire. Sure, you can put them on a EV and they will do great. Except for rolling resistance and consequently range.

I picked the Hankooks because they are designed to improve efficiency, and when I drive outside my local area, I want the best efficiency possible. I guess if I see efficiency has decreased and the handling is worse than OEM, I may return them as you suggested. But I think they are likely good at what they are designed to do, which is a quiet tire that is really efficient. If handling is impacted I can probably live with it due to the other benefits. I am still evaluating...

 

[azerik]

Have you noticed a significant reduction in the hallow tire sound going over cracks/expansion joints? Since switching springs MY RX's tone is higher and dare I say more hallow sounding. I put my pressures back up over 41psi and it's better but still probably the single most annoying noise I get (Because I have hundreds of these cracks on my 8 mile round trip to pick up drop off my daughter at school, daily)

 

[mkhuffman]

Have you noticed a significant reduction in the hallow tire sound going over cracks/expansion joints? Since switching springs MY RX's tone is higher and dare I say more hallow sounding. I put my pressures back up over 41psi and it's better but still probably the single most annoying noise I get (Because I have hundreds of these cracks on my 8 mile round trip to pick up drop off my daughter at school, daily)

Yes, it does seem quieter when hitting rough spots in the road.

 

[mkhuffman]

The larger size tires has a bigger impact on speed accuracy than I thought it would. With the OEM 245/45 tires, my actual speed would settle in around 79 mph when the display showed 80. Sometimes it would drop to 78 briefly.

With the 255/45 tires, I have to set the cruise at 78 to go the same speed as before. The actual speed is probably just under 79 when the speedometer shows 78, because it tends to oscillate between 78 and 79 when set for 78, but spending most of the time right at 79. So it appears the difference between the two tires is 1.5-2 mph.

 

[mkhuffman]

Looking forward to your impressions. I have been eyeing these, but out of the handful I am considering they are by far the most expensive.

Have you noticed a significant reduction in the hallow tire sound going over cracks/expansion joints? Since switching springs MY RX's tone is higher and dare I say more hallow sounding. I put my pressures back up over 41psi and it's better but still probably the single most annoying noise I get (Because I have hundreds of these cracks on my 8 mile round trip to pick up drop off my daughter at school, daily)

I think I have enough experience with the tires now to provide a review.

High level: they are awesome, but they are NOT performance oriented tires.

Specifics:
1) Very quiet.
2) No "hollow" sound on road imperfections noticed at any speed.
3) At 34 psi, so smooth, and super comfortable. Low psi impacts efficiency, but holy cow these tires feel so good at 34 psi cold.
4) I can spin the tires when cold on dry pavement. I could not do this with the OEM tires. So, they are not nearly as sticky as the OEM tires. If you want to hit the curves at high speed, you will slide more than with the OEMs. I actually think sliding is fun, but it won't improve your speed in the curves for sure.
5) Because they are more slick, they should be more efficient. That is how it works. But I have not been able to gather enough data to determine if this is true or not. As I drive more, I will be capturing data via CarScanner and I will compare and determine if there is an efficiency improvement. I think there is, but I do not trust the car efficiency reading at all. I will post my efficiency measurements later when I have enough data to do that.

So in summary, I really like these tires. I am glad I went up a size even though it messes up the accuracy of the speedometer, because it means 34 psi is much more safe. And man, after running at 41 psi and then 34 psi? Amazing improvement in comfort.

Let me know if you have any questions.

 

[Chainspell]

Thanks for the follow up! How cold is cold? Does the sliding diminish more when they've warmed up?

 

[azerik]

Good info! I'm really debating getting the summer tire version if they ever come back at a reasonable price. I'm not super worried about getting 50k out of them, the summer tire has a little more square sidewall and only a 30k warranty.

 

[mkhuffman]

Thanks for the follow up! How cold is cold? Does the sliding diminish more when they've warmed up?

I will have to get back to you on that. I just know that when I first come out of my neighborhood in the morning, with temps in the 40s, I can spin them pretty easily. That was not possible with the OEMs. I think they will get more sticky as they warm up, but I have not been able to confirm that yet.

I will do some more WOTs in the near future and let you know.

 

[mkhuffman]

Good info! I'm really debating getting the summer tire version if they ever come back at a reasonable price. I'm not super worried about getting 50k out of them, the summer tire has a little more square sidewall and only a 30k warranty.

Well, I really like them. And I know comfort and quietness are important to you, so I think you will like these as well.

BTW - have you updated the Eibach GT spring thread recently with your impressions? I may have missed it. I am probably going to follow you down that path, but your impressions will make a big difference regarding if I do it or not.

 

[markboris]

I think I have enough experience with the tires now to provide a review.

High level: they are awesome, but they are NOT performance oriented tires.

Specifics:
1) Very quiet.
2) No "hollow" sound on road imperfections noticed at any speed.
3) At 34 psi, so smooth, and super comfortable. Low psi impacts efficiency, but holy cow these tires feel so good at 34 psi cold.
4) I can spin the tires when cold on dry pavement. I could not do this with the OEM tires. So, they are not nearly as sticky as the OEM tires. If you want to hit the curves at high speed, you will slide more than with the OEMs. I actually think sliding is fun, but it won't improve your speed in the curves for sure.
5) Because they are more slick, they should be more efficient. That is how it works. But I have not been able to gather enough data to determine if this is true or not. As I drive more, I will be capturing data via CarScanner and I will compare and determine if there is an efficiency improvement. I think there is, but I do not trust the car efficiency reading at all. I will post my efficiency measurements later when I have enough data to do that.

So in summary, I really like these tires. I am glad I went up a size even though it messes up the accuracy of the speedometer, because it means 34 psi is much more safe. And man, after running at 41 psi and then 34 psi? Amazing improvement in comfort.

Let me know if you have any questions.

Thanks for the review Mike. You are correct in that they are not performance tires. More of a grand touring tire and from the extensive reading and reviews I have seen on them, they concur with your findings of being quiet and not harsh at all. Basically most grand touring tires are like that anyway. I bet that you won't get much loss of range if any and if you do, most likely from going one size up.

 

[markboris]

BTW - have you updated the Eibach GT spring thread recently with your impressions? I may have missed it. I am probably going to follow you down that path, but your impressions will make a big difference regarding if I do it or not.

I know this question was directed to Erik but wanted to say in talking with him he really likes the springs and I'm going to try to meet up with him this weekend as I am in AZ right now.

On another note, Eric (with a C) is coming to my place next week and we are changing out his Eibach lift springs for the GT Pro-Kit lowering springs that Erik (with a K) and I have installed. Now we will have someone that will be able to give us his opinion of both. We are also installing the Koni rear shocks at the same time.

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