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[D_o_S]

Hi,

I'm calling all users that are running this tire (mainly) but anyone with experience is welcome to help...

Before, I had:

Bridgestone Potenza RFT 225/45 R17 standard load front
Bridgestone Potenza RFT 255/40 R17 standard load rear

Now, I'm running

Goodyear Eagle F1 Asymmetric 2 225/40 R18 92Y NON RFT front
Goodyear Eagle F1 Asymmetric 2 255/35 R18 94Y NON RFT rear

I'm having a very, very hard time finding optimal tire pressures for this "new" setup. I have had the car on these tires for a year now, and basically, I set the pressured on day 1 - weather changes - on day 2, car acts "horrible"

For instance:
Yesterday, the ambient temperatures were around 4 C. Car handled superb
Today, the ambient temperatures were around 16 C. I started the car and immediately noticed something was wrong. I could turn the steering wheel with my finger at a standstill, usually, it takes quite a solid grip. During my drive to work, the car felt like it was on "roller skates" or "marbles" compared to what the car feels like usually. Also, the car was out in the sun before I got on my journey, so the tires were likely warmer than 16 C.

When I got to work, I parked the car in an underground garage. When I came back to drive it later, the wheel became harder to turn, about half way between "normal" and "on marbles". On my way home, the tires behaved much better than in the morning, yet outside temps were still the same.

Now, to the pressures - I had them set at 2.65 BAR front HOT, and 2.85 BAR rear HOT. I set the warm pressures on a 8 C day, the tires were around 30C HOT (normal driving).

If I set the pressures to 2.2 Bar front COLD and 2.6 Bar rear COLD, the car behaves normal. However, I have doubts - first, this is a little less than what the sticker says. However, I have been as low as 2.0 BAR on the fronts, without any issues (unintentionally).

My question is: what do I do to avoid this "marble" feeling? Can I run the fronts at say 2.2 and the rears at like 2.6 without issues? How about 2.1/2.5?

In brief: if I set the lower of the two sticker values (2.3/2.7) the car feels like its on marbles some days. If I set the pressures lower, the car feels much better.

I also checked the Alpina B3S the local dealer has at the showroom. That recommends like 2.7/3.0 bar !!! on Michelin PS2 non RFT, which seems strange...

What bothers me is that I'm chasing tenths of bars (I do have accurate measuring equipment, so I wouldn't doubt that), and this seemingly insignificant difference in pressure makes a night/day diff in road feel, and most importantly, safety - when the car is "on marbles" I can physically tell I can lock up the wheels like 20% easier than with good grip.

I don't care about fuel economy.

Any help very welcome...

EDIT: Basically, everyone seems to recommend: Higher pressure = better handling. For some reason, I am not experiencing this, rather the very opposite.

If you read here: http://e89.zpost.com/forums/showthread.php?t=606411, jannisa recommends LOWER pressures than RFT, and says "you'll hate them if you go up more" - which is what I'm experiencing...

Another thing that comes to mind is a friend of mine with his GTI - stock pressures were like 2.2, when he changed to PZero Corsa, he ran them at 1.8.... sooooo

[emre]

After a lot of trial, I find 35psi front and 42psi rear (cold) work best for me. That is 2.41 and 2.90 bar, 0.1 less than what sticker says both for front and rear.

I agree that even a small change in pressure makes a difference in road feel.

I am using nitrogen and am very happy with it, not affected by the temperature changes and once you set the tire pressure it stays the same for a very long period of time.

I'm running 235/35/19 and 265/30/19 Asymmetric 2

[D_o_S]

Thanks,

do you ever get the "marble" feel? Also, when braking, do you hear a "woosh" sound? When normal, I hear the "woosh" sound (like an airplane slowing down after landing), when "on marbles" I don't hear it...

As I said:
2.2 bar or so - car handles great, BUT psychologically I'm scared of (a) tire wear and (b) ripping the tire off the rim during an evasive manouvre...

Right now, I set the pressure to 2.1 bar front (0.2 less than sticker) and 2.5 rear (-0.2). I'll test tomorrow or friday and will report back

[Bartman619]

..what emre said..probably try using nitrogen fill for the tires.

[D_o_S]

It's been a while, my saga continues...

2.1/2.5 didn't work, I could feel the front's were MADLY underinflated, massive sidewall roll, rears were OK after like 15 minutes of driving...

I resorted to the stock specs for a while...

Everything seemed ok, until today. I tried some stops from 160km/h to ~80 km/h while bedding in the brakes today. When the speed dropped to like ~100 km/h, I triggered ABS (on a dry road!). Surely, this is not normal? The tires would squeal before ABS kicked in.

I'm thinking, the fronts felt OK, perhaps the rears are overinflated? Right now I'm running 2.3 front and 2.7 rear, haven't had the "marble" effect for quite some time.

The only thing that bugs me is the fact that the front tires look like they're flat? On the rears, you can see like 5 mm of the tread when looking from the side, on the fronts it looks like they're sitting on their sidewalls...

[Doctor///M]

Originally Posted by D_o_S

It's been a while, my saga continues...

2.1/2.5 didn't work, I could feel the front's were MADLY underinflated, massive sidewall roll, rears were OK after like 15 minutes of driving...

I resorted to the stock specs for a while...

Everything seemed ok, until today. I tried some stops from 160km/h to ~80 km/h while bedding in the brakes today. When the speed dropped to like ~100 km/h, I triggered ABS (on a dry road!). Surely, this is not normal? The tires would squeal before ABS kicked in.

I'm thinking, the fronts felt OK, perhaps the rears are overinflated? Right now I'm running 2.3 front and 2.7 rear, haven't had the "marble" effect for quite some time.

The only thing that bugs me is the fact that the front tires look like they're flat? On the rears, you can see like 5 mm of the tread when looking from the side, on the fronts it looks like they're sitting on their sidewalls...

...go back to RFT's. I believe that the soft sidewalls of the non-RFT's reduce the car's handling and steering feedback.... dramatically. They also bug me to this day and I only made the switch about a month ago.

[D_o_S]

Originally Posted by S3RI35

...go back to RFT's. I believe that the soft sidewalls of the non-RFT's reduce the car's handling and steering feedback.... dramatically. They also bug me to this day and I only made the switch about a month ago.

You'll get used to it, I wouldn't switch back to RFT anyday...

Regarding pressures, I'm now running 2.3 front, 2.5 rear, all seems good.

Front tires are wearing even. Rears are more worn at the center (1mm difference), I always ran 2.7 BAR or above before, so this is definitely too much pressure.

[Dmitry83]

Hi,
I've got the same tyres and size on e81.
For now I feel the optimal combo is 2.2/2.6 bar- comfortable at the railway crossing and steering enough sharp.
Regarding the temperature- the 10 degrees drop causes around 0.2 bar pressure decrease, but also keep in mind the summer tire rubber becomes harder at a temperature below 10 degrees, and gets a marble effect with any pressure.