AMG9

Front 255/35R-18, Rear 285/30R-18 Yokohama ADVAN Neova AD08s. This is on a c63 coupe. I have put about 2500 miles on them. I wanted the most grip possible for a dd car without changing wheels. I made the mistake of buying the expensive wheel tire warranty. It covers me if i change my tires, but not my wheels. For the price, i could have bought a set of wheels and maybe tires and sold them after lease return.
I did not want a taller over all diameter because I think this car is already geared too tall in all gears except first. Mich PSS was my first choice, but they dont make a 30 series tire in 18 inch, going wider with a 35 series aspect ratio would have given me a taller overall diameter, so I decided on the ADO8. The tire calculator shows that this setup is .3 inch shorter diameter in the rear (of course my wheel size may effect that somewhat).
The positive side: No clearance issues at all. No rubbing with 3 people in the car. Lateral grip has increased tremendously, the car now leans significantly more in steady state corners (like on a skid pad) as the springs are now overwhelmed by the increased grip. I know I am definitely taking the corners faster.
Braking has improved, but I expected better grip under braking. I can feel the front end does not lock up as easily. I have no measured data.
Acceleration, again, I expected better grip having gone up 3 sizes, but the car still breaks loose out of controll in first. My zero to 60 times are more consistent as I don't spin as easily, my 0-100 times are about the same but more consistent, meaning that I can reproduce my best times more often bec i have better grip in first. Overall times are not much better probably bec these tires are so heavy compared to stock. Tire rack weights showed something like 4-6 lbs heavier per tire than stock.
This leads into the negatives now.....I can surely feel this added weight.....the car feels slightly but noticeably more sluggish on the throttle as if it has lost some throttle response. Especially at higher speeds, It takes longer for it to pick up and go. Whatever rotating mass I saved with the P31 / brakes, I have now gained back with these tires. I wonder if any of you guys who have moved to 19s have had the same experience.
Most negative aspect of this setup:
I absolutely hate what I have done to the steering response and stability of the car at speed. I have completely ruined it. No kidding, with 44 nitrogen filled psi, it feels like I have 10 psi in the tires. I have checked pressure several times as I can't believe how bad the car turns in or changes direction. The faster I go, the more noticeable it is. Steering is also heavier but I'm getting used to that.
I would not blame this lack of response and stability on the tires, I simply have too much tire on these wheels. Although the overall height of the tires are the close to stock, I have added about an inch more tire laterally on each wheel. The tires I have chosen need wider wheels to stretch out and tighten up that extra rubber. On stock wheels, the car is floating on this extra unstretched amount of tire and it sucks. I will either have to get some wheels or, I may sell these tires. If I keep my stock wheels, next time I will sacrifice some grip and go with 245/18, 265/18 PSS.
This combination of tire weight, sluggish ness in acceleration, heavier steering and delayed/dull steering response, at first made the car feel as if it had gained 500 lbs. I have adapted and am somewhat getting used to this but, I would not recommend such a large upgrade in tire size with stock wheels.
By the way my stock tires were contisport 5Ps.

MIG

Hello.
Replacing the front tires with 235 to 245 will not increase understeer?

gthal

Going 255 in the front and the related sidewall flop would be the only reason you notice less steering response and sloppiness as the AD-08 are RAZOR sharp tires when properly matched to the rim. My experience with them is that they are almost TOO responsive and cause the car to feel hypersensitive. They would be the most responsive tire of PSS, RE-11 and Star Specs in my experience.

They are also SUPER grippy... more grip than PSS and similar to RE-11. The downsides of AD-08 are noise and comfort (which make them hard to live with as a daily tire) but the upside is responsiveness (when properly fitted to the rim) and ultimate grip. They are VERY popular in the M3 crowd.

bhamg

Some interesting and useful observations...they all make sense.

AMG9

I Agree. My thread was getting to long so didn't elaborate, but all reviews showed that the advans are super sharp in steering. There is actually a metal insert in the side walls which help stiffen it. Most of the problem is from the front, but the weight gain is greater in the rear tires according to tire rack specs. Having said that, I still do feel a noticeable lag and wobbling in the rear when I make sudden directional changes and when I'm hard on the throttle.

AMG9

If you mean changing the fronts to 235 or 245 and keeping the rears the same 285, then you would increase under steer.
In my case, I don't feel a significant change in the overall balance of under steer to oversteering behavior of the car. Meaning that steady state cornering balance front to rear is about the same as before, just that things happen at higher speeds.

esses

i absolutely love AD08's on my GT3. the grip and steering response is excellent, and they are very consistent as you get more heat into them. they do, however, run wide for any given size.

ced357

So, if fitted correctly these tires should out perform Michelin PSS's in a straight line?

AMG9

That is an interesting point. I have never seen a tire test include an acceleration test, showing how different tires improve acceleration in a straight line. That would be a good test. Car and driver rated the AD08 as having Better LATERAL grip than PSS in the dry. I don't know which one is better in straight line accel. AD08's are heavier than PSS. The extra weight may nullify any extra grip you get from them as the car has to work harder to rotate that weight during acceleration. Also the sizes they are available in (for my wheels) are different, so we are not compareing apples to apples here.