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[sle39lvr]

I have OEM 162's that are 8" and 8.5" wide.

Currently I got factory sizes 225/40/18 and 255/35/18.

As I got PSS's recently, since they are very grippy, I feel like my car lost 'balance'. Lots of initial understeer.

Some told me to get more chamber (within recommended range) in the back since there would be less tire surface on the ground initially, but I am thinking about tweaking the tire sizes.

- Should I go skinnier tire in the back? 245 series? Would that be too stretched on a 8.5" rim or would it look odd?

- Should I go wider tire up front? 235 series? Would that be awkward looking on a 8" rim?

Thanks in advance.

[Red_Bean_Bun]

Maybe your tire pressure is not right ?

[driverman]

Originally Posted by Red_Bean_Bun

Maybe your tire pressure is not right ?

+1

I'd start out with BMW's recommended pressures and then adjust them a bit.

[sle39lvr]

I am way passed all that. After a lot of experimentation, I'm running 34/42 psi.

Either way, I would love to go for a square setup, but don't want to leave 162's. So, want to tweak the tire size and see..

[gtaccord]

You can do 225/40s all the way around even with the 8.5s in the back. I think you can also do 245/35s as well.

[sle39lvr]

Originally Posted by gtaccord

You can do 225/40s all the way around even with the 8.5s in the back. I think you can also do 245/35s as well.

Yea, I guess I can just changed the rear two to 8" and run 225 all around.

So far, I am leaning towards 245 in the rear.

[flip4335]

Originally Posted by sle39lvr

I have OEM 162's that are 8" and 8.5" wide.

Currently I got factory sizes 225/40/18 and 255/35/18.

As I got PSS's recently, since they are very grippy, I feel like my car lost 'balance'. Lots of initial understeer.

Some told me to get more camber (within recommended range) in the back since there would be less tire surface on the ground initially, but I am thinking about tweaking the tire sizes.

- Should I go skinnier tire in the back? 245 series? Would that be too stretched on a 8.5" rim or would it look odd?

- Should I go wider tire up front? 235 series? Would that be awkward looking on a 8" rim?

Thanks in advance.

Don't change the rears. Understeer is not due to the rears being grippier.

How many miles have you put on the tires? It takes anywhere from 500-1000 miles to wear off the protective coating on the rubber of new tires. Until then, you will have some pretty slick tires, and it may seem like they are unbalanced.

And, if you go down one tire size in the rear, you will have speedo issues, because the wheel diameter of a 245/35 rear will be 24.75 inches, smaller than the 225/40 fronts at 25.09 inches by way over .335 inches or over a quarter inch shorter. Thus, when you are traveling at 60 mph, the speedo will read 59 mph. In other words, when you think you are traveling at 60 mph, you will really be traveling faster, at 61-62 mph. Plus, your vehicle will be looking up at the sky, so the headlights won't be aligned...LOL

Understeer occurs when you apply too much power into the turn so the front tires lose their grip. My driving instructor advises to go into a turn slow by letting up on the pedal, and accelerate at the apex so you end up going fast out of the turn.

[sle39lvr]

Originally Posted by flip4335

Don't change the rears. Understeer is not due to the rears being grippier.

How many miles have you put on the tires? It takes anywhere from 500-1000 miles to wear off the protective coating on the rubber of new tires. Until then, you will have some pretty slick tires, and it may seem like they are unbalanced.

And, if you go down one tire size in the rear, you will have speedo issues, because the wheel diameter of a 245/35 rear will be 24.75 inches, smaller than the 225/40 fronts at 25.09 inches by way over .335 inches or over a quarter inch shorter. Thus, when you are traveling at 60 mph, the speedo will read 59 mph. In other words, when you think you are traveling at 60 mph, you will really be traveling faster, at 61-62 mph. Plus, your vehicle will be looking up at the sky, so the headlights won't be aligned...LOL

Understeer occurs when you apply too much power into the turn so the front tires lose their grip. My driving instructor advises to go into a turn slow by letting up on the pedal, and accelerate at the apex so you end up going fast out of the turn.

I had the tires for over 5K miles by now.

I think the diameter difference will be minimal, 1-2mph being off shouldn't be that bad. Plus when I get new tires, will have coilovers, should be able to compensate for the height difference.

Yea, I see that. My car came with a 16" square set up. Other than bad RFT's rolling on corners, car felt very balanced and rotated around the hips. I definitely felt it go away when I upgraded to a staggered set up.