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[zzimbile]

Finally getting rid of my run-flats and putting a set of PSS on my 135i in the coming weeks and wanted to see the advantages of disadvantages of going square vs 225/255. I thought it was a no-brainer to go 225/255, but I wanted to give both sides a shot before I made my decision. Seems like the only benefit to going square is you can rotate them? Definitely not my area of expertise and I searched to see if this was the case. Seems like most people who went square enjoy it, just wanted to see the pros and cons of each.

[bmw1racer]

Originally Posted by zzimbile

Seems like the only benefit to going square is you can rotate them?

Nope.

It's to take out most of the understeer that you get with a staggered setup.

[VMRWheels]

Rotating your tires to maximize the life of them is one aspect, however most people that go square also enjoy the benefit of reduced understeer, like bmw1racer mentioned.

[bmw1racer]

Originally Posted by VMRWheels

Rotating your tires to maximize the life of them is one aspect, however most people that go square also enjoy the benefit of reduced understeer, like bmw1racer mentioned.

Here's a question: If you have a square tire setup, should you rotate the tires if the wheels are not the same widths?

In my case, the front wheels are 7.0" and the rears are 7.5".

Not that I really plan to rotate them anyways when I go square...

[zzimbile]

Originally Posted by bmw1racer

Here's a question: If you have a square tire setup, should you rotate the tires if the wheels are not the same widths?

In my case, the front wheels are 7.0" and the rears are 7.5".

Not that I really plan to rotate them anyways when I go square...

Now that's a good question. I think i'm going to go staggered, but thanks for the input

[VMRWheels]

Originally Posted by bmw1racer

Here's a question: If you have a square tire setup, should you rotate the tires if the wheels are not the same widths?

In my case, the front wheels are 7.0" and the rears are 7.5".

Not that I really plan to rotate them anyways when I go square...

While you typically wouldn't, if the wheel specs allow for it, and the tire sizing is the same, you could in theory.

[Stohlen]

Keep in mind you aren't reducing understeer by going squared, you're just reducing rear grip to give the car a more balanced feel. The front wheels of a 225/255 setup will lose grip at the same speed in an identical turn as a 225/225 setup. This is why i prefer a staggered setup in which you then dial out understeer with a stiffer front suspension and additional camber. This allows you to max out rear traction by dropping the pressure in your tires a few PSI.

Neither method is really wrong, but a square setup is easier to drive on the limit/the fastest, while a staggered setup will let you keep the power down if setup properly.

[zzimbile]

Thanks for the input. Looks like I'll be getting a staggered setup this weekend!

[PrematureApex]

Originally Posted by Stohlen

Keep in mind you aren't reducing understeer by going squared, you're just reducing rear grip to give the car a more balanced feel.

??? No.

You are certainly reducing understeer. You can do that one of three ways w/tire sizing: 1. up-sizing the front tires (gaining more front end grip), 2. reducing the rear width (reducing rear grip) or 3. a combination of both.

Any way you do it, "giving the car a more balanced feel" is accomplished by reducing understeer (the tendency for the front tires to break away first), period. By definition, neutral means understeer has been reduced. It doesn't matter if you did that by making the rear break away sooner, or the fronts break away later. It's all the same. Which end breaks away ffirst. That is 100% independent of ultimate grip.

[Solo_M_Tech]

If your doing it for looks go staggered. If your doing it to improve performance go squared. If your worried about rear traction go with a 235 square set up. Just my opinion.

[zzimbile]

Can you fit 235s up front on stock suspension without modifying anything?

[Stohlen]

Originally Posted by PrematureApex

??? No.

You are certainly reducing understeer. You can do that one of three ways w/tire sizing: 1. up-sizing the front tires (gaining more front end grip), 2. reducing the rear width (reducing rear grip) or 3. a combination of both.

Any way you do it, "giving the car a more balanced feel" is accomplished by reducing understeer (the tendency for the front tires to break away first), period. By definition, neutral means understeer has been reduced. It doesn't matter if you did that by making the rear break away sooner, or the fronts break away later. It's all the same. Which end breaks away ffirst. That is 100% independent of ultimate grip.

Okay, nit-pick if you must... My point is that going from a staggered 225/255 setup to a square 225/225 setup, you're not increasing front end grip. You're decreasing rear end grip and thus making the car more neutral, and easier to drive on the edge. This is ideal for a less experienced driver as a neutral car is easier to keep from scrubbing speed in the corners. However a staggered car (refering to RWD here) allows the vehicle to be setup for more rear end grip and thus put the power down better, decreasing lap times if it driver is experienced enough to keep it from pushing excessively into the corners and scrubbing speed.

I get that understeer and oversteer is a condition, not a definition of traction. I just used the terms improperly.

[PrematureApex]

Originally Posted by Stohlen

Okay, nit-pick if you must... My point is that going from a staggered 225/255 setup to a square 225/225 setup, you're not increasing front end grip. You're decreasing rear end grip and thus making the car more neutral, and easier to drive on the edge. This is ideal for a less experienced driver as a neutral car is easier to keep from scrubbing speed in the corners. However a staggered car (refering to RWD here) allows the vehicle to be setup for more rear end grip and thus put the power down better, decreasing lap times if it driver is experienced enough to keep it from pushing excessively into the corners and scrubbing speed.

I get that understeer and oversteer is a condition, not a definition of traction. I just used the terms improperly.

It's not nit-picking, your statement was plainly and simply wrong.

Regarding your latest...

A neutral car requires much more skill to drive vs. an understeering car. That's the whole damn reasons the car is set up for understeer from the factory; to be safer, to be easier to drive, so that over driving the car results in relatively safe scrubbing of speed, vs. potentially swapping ends. It's why BMW gives a stagger to a car with 50/50 weight distribution. Safety and liability. In reality, it would be a better handling car form the factory on a square setup

It would be ridiculous to argue that an experienced driver prefers understeer vs. a novice. Just about all track guys are striving to achieve a neutral setup. And most go right to a non-nstaggered setup (generally 255 all around) to achieve that.

Now, if you're competing, where 10ths matter, are you going to deal with a bit of understeer in order to add more rear tire? Probably, sure.

But for most of us, we're talking about DEs and trackdays, where there are no trophies and a balanced chassis is much more enjoyable and involving to drive than one that understeers.

Considering the OP is buying PSSs (which aren't track worthy), I think it's safe to assume he'll enjoy a neutral car that isn't plowing around everywhere the occasional times he is driving at 10/10ths.

[Stohlen]

Originally Posted by PrematureApex

A neutral car requires much more skill to drive vs. an understeering car. That's the whole damn reasons the car is set up for understeer from the factory; to be safer, to be easier to drive, so that over driving the car results in relatively safe scrubbing of speed, vs. potentially swapping ends. It's why BMW gives a stagger to a car with 50/50 weight distribution. Safety and liability. In reality, it would be a better handling car form the factory on a square setup

It would be ridiculous to argue that an experienced driver prefers understeer vs. a novice.

An understeering car is safer than a neutral car on the street because losing traction in the front tires is easier to recover from than losing traction in the rear. That is why cars are setup to understeer from the factory. That does not mean its easier to drive quickly at the race track. Its harder to drive at the race track quickly and requires more skill to reach the cars potential. I'm talking about lap times, not crashing.

And I never said an experienced driver would prefer understeer. I just said with a 225/255 setup (staggered and thus understeer) he would go faster than a square 225/225 setup. This is my whole point. Obviously a 255/255 setup would be better than a 225/255 setup, but that wasn't what we were discussing.

The whole point i'm trying to make is that going square doesn't improve vehicle performance if you can fit a bigger tire in the rear.

[zzimbile]

Thanks for the input and opinions

[jmcphillips1]

I'll take pictures when i'm done, but I changed my order and ended up going with 215 for the front and 225 for the rear on stock M-Sport 128i rims in the Michelin Pilot Super Sports. All tires should be here on Wednesday, so hopefully I'll have them mounted on Thursday morning and I can report back with photos and driving impressions.