square or staggered?

[Kim Schwartz]

Is there any concensus as to what is better on a track for a 128i with stock sport suspension? Square or staggered setup?

[SkinnyVT]

Square, you don't have near enough power to require more rubber in the rear, going staggered would just increase the understeer that is built into the car. Plus you can rotate tires with a square setup.

[Joe@ApexRaceParts]

A square set up on your 128i would be preferred. This will create a much more neutral driving car on the track that is prone to much less understeer. Considering that you do not have the power to warrant a staggered wheel set up the wider rear tire would not be necessary. A square fitment of 18x8.5" ET45 with 235/40/18 tires would work great and not need any spacers or fender rolling.

[Kim Schwartz]

I have been using a square setup on the street and now on track and really do prefer it. I was starting to shred the tires on the square set up and went back the the stock staggered set up for the street and just wondering what people were running on the track.

[love67]

square set up always works better, it helps turn in better!

[flinchy]

Originally Posted by Joe@ApexRaceParts

A square set up on your 128i would be preferred. This will create a much more neutral driving car on the track that is prone to much less understeer. Considering that you do not have the power to warrant a staggered wheel set up the wider rear tire would not be necessary. A square fitment of 18x8.5" ET45 with 235/40/18 tires would work great and not need any spacers or fender rolling.

235 would be borderline. 245 on my stock 130i isn't enough.

[HP Autowerks]

Originally Posted by Kim Schwartz

Is there any concensus as to what is better on a track for a 128i with stock sport suspension? Square or staggered setup?

Since you will not likely to over power the rear tires like the 135i, square set-up will be fine. Otherwise, as much tire as you can get under the fenders will be a better choice.

Using a square set-up to mask understeer is fine, but it is better to get to the root of the problem.

[bmw1racer]

When I wear out these OEM runflats, I'm going to switch to a square setup with non-run flats... Right now, I've got 225/45-17s in the rear and 205/50-17s in the front.

What would be a good choice for a square setup and not screw up the odometer? 225/45-17s all around?

[Rukuss]

Originally Posted by HP Autowerks

Since you will not likely to over power the rear tires like the 135i, square set-up will be fine. Otherwise, as much tire as you can get under the fenders will be a better choice.

Using a square set-up to mask understeer is fine, but it is better to get to the root of the problem.

And what is the root of the problem???

[Kim Schwartz]

Originally Posted by bmw1racer

When I wear out these OEM runflats, I'm going to switch to a square setup with non-run flats... Right now, I've got 225/45-17s in the rear and 205/50-17s in the front.

What would be a good choice for a square setup and not screw up the odometer? 225/45-17s all around?

I'm using 225/40/18 in each corner and they are the same rolling diameter as the stock set up so there should be no problem.

[Kim Schwartz]

Originally Posted by Rukuss

And what is the root of the problem???

As a side effect of a staggered set up the car is understeer prone but I don't know if that is a problem as such, just a response to the tire set up. So yes, what is the problem that needs to find a root?

[bmw1racer]

Originally Posted by Kim Schwartz

I'm using 225/40/18 in each corner and they are the same rolling diameter as the stock set up so there should be no problem.

That's what I figured... My only concern is that the front wheels are narrower (7") than the rears (7.5") and whether the fronts can handle the wider tire (225/45s)...

[HP Autowerks]

Originally Posted by Rukuss

And what is the root of the problem???

Lack of static and dynamic camber, soft bushings with excessive deflection(dynamic camber change) and body roll(more dynamic camber change) just to name a few.

[Rukuss]

Originally Posted by HP Autowerks

Lack of static and dynamic camber, soft bushings with excessive deflection(dynamic camber change) and body roll(more dynamic camber change) just to name a few.

HP how do we solve this problem? what parts are needed? and what is the cost?

Thank you

[HP Autowerks]

Originally Posted by Rukuss

HP how do we solve this problem? what parts are needed? and what is the cost?

Thank you

For better static and dynamic camber, a set of M3 front wishbones or the complete control arm set will help. Static camber will gain about -.5 to -.75. Adding a larger front anti roll bar will further reduce body roll induced camber changes. The above will greatly reduce understeer and may be all you need.

[Rukuss]

Originally Posted by HP Autowerks

For better static and dynamic camber, a set of M3 front wishbones or the complete control arm set will help. Static camber will gain about -.5 to -.75. Adding a larger front anti roll bar will further reduce body roll induced camber changes. The above will greatly reduce understeer and may be all you need.

Can you PM me the price for this set up?

[Kim Schwartz]

Originally Posted by bmw1racer

That's what I figured... My only concern is that the front wheels are narrower (7") than the rears (7.5") and whether the fronts can handle the wider tire (225/45s)...

With a 45-47mm offset on 7.5" wheels there is no problem whatsoever.18" wheels have even more clearance as the damper is at an angle.
For my purposes, it is enough of a change. Rebuilding the suspension might be more appreciated if it were more of a track car than a road car. My point is there are only problems if you percieve there to be a problem. There may be no suspension problem, there are just personal preferences.

[evilstib]

Originally Posted by HP Autowerks

Since you will not likely to over power the rear tires like the 135i, square set-up will be fine. Otherwise, as much tire as you can get under the fenders will be a better choice.

Using a square set-up to mask understeer is fine, but it is better to get to the root of the problem.

Well said. More tire in the rear doesn't increase under steer. It just lessens oversteer.

[Evice]

I currently have 245/40R17 on my 128i, wrapped with Hankook RS3s. It is PERFECT! On track or on street. No rubbing, no spacers, no fender rolling.

A bit info: You technically "can" increase understeer with asymmetric ramped race differential, on deceleration, with more meat in rear tires. It might not apply here but I thought I mention it

[Kim Schwartz]

I get to research my own question now as I have worn out the tires on my 18" wheels and have put on the original BMW staggered set back on with the Pirellis. These will be my track set for now.

[omar14711]

I have 2 sets of stock offset wheels for my 135, one with street tires and one with slicks. After a day at the track mistakenly I put one of the rears in the front and to my surprise they cleared. I have camber plates -2 degrees and 15 mm spacers in the front And 255/18 tires. Plan on trying to square up with 255 all the way around. On stock oem wheels

[e82n54]

Originally Posted by omar14711

I have 2 sets of stock offset wheels for my 135, one with street tires and one with slicks. After a day at the track mistakenly I put one of the rears in the front and to my surprise they cleared. I have camber plates -2 degrees and 15 mm spacers in the front And 255/18 tires. Plan on trying to square up with 255 all the way around. On stock oem wheels

Others have successfully run 4 OE rear wheels for a square setup too. I considered this, but the cost of replacing 18" tires gets expensive fast. I went with 17" wheels because the tires are much cheaper. I bought 17" wheels and tires for close to the same price as 18" tires only.

The wheels are TireRack brand: TRMotorsports 17x8.5 ET40 - $150 each wheel