Alternative to lowering
 

If you wish to maintain stock ground clearance but get most of the advantages of lowering springs fit a set of these:

https://mcasuspension.com/traction-mod

Then crash bolts front and rear to get the static camber settings you want.

Cheaper and as effective.

Lowering the CG by an inch really doesn't affect handling much.

What about combining these with some moderate lowering springs (TRD, Eibach Pro-Kit, RCE Yellow) on stock shocks? Best of both worlds?

And I didn't know we could use crash bolts in the rear. Part number? I would like to reduce the negative camber in the rear.

Whiteline offer a camber bolt kit to adjust the rear camber.

OR go with RCE yellow, it only 20mm and I have never ever scrape on anything so far.

then camber bolt in the front.

and LCA arm in the rear.

This. RCE yellows, camber bolts up front and SPC rear lower control arms.

That mod doesn't increase spring rate, which is the goal of lowering springs for some people...

Not knocking it, but it definitely isn't a replacement for most people.

You could increase the spring rate while maintaining stock ride height and using the MCA brackets. The BRZ has a pretty effective spring rate from the factory. The lowering springs have to increase the spring rate.

Why do you want to reduce rear camber? Factory camber is pretty good, just not always equal right to left, which is the main reason my mechanic fit crash bolts, to equalize rear camber. I asked him to also max it out so it's about 1.8 degrees each side now.

Doesn't the rear gain negative camber upon compression? So to optimize the contact patch in a corner you would want to have little static negative camber to keep as much tire width on the ground as possible. Correct me if I'm wrong! I thought it'd be best to get a lot of front negative camber and close to zero rear negative camber.

I never knew people got lowering springs for anything other than lowering before this.

The chassis is Impreza which is awd. Removing the drive from the front axle means the engineers needed to dial in more understeer.

You want around 1.5 degrees rear camber and about zero front camber for normal street driving. Rear axle camber gain helps stabilize the chassis as you feed in more power. The front axle is limited somewhat by the strut design, although the Porsche Boxster/Cayman initially used four wheel struts and was a superb handler.

Lowering changes the static alignment. The reduction in roll moment from lowering the CG is pretty modest. You need higher rate springs when you lower the car to prevent bottoming out.

The MCA traction aids reduce anti squat almost exactly as lowering would do, though MCA recommends their brackets regardless of suspension height.

What the heck is anti squat?

I can see how the MCA suspension mod can maybe lower the rear end a little, but what do you do about lowering the front end?

I wouldn't go with lowering springs because 1) this car doesn't need higher spring rates 2) shorter springs means less suspension travel which negates anything good about a lower CG 3) blown dampers. But I could see moving the pickup down to lower the car and maintaining the stock suspension travel being a good thing if you can lower the front too.

It is the force applied to the chassis by the alignment of the suspension arms in a longitudinal direction. It is essentially the same as roll resistance provided by the roll centres but that is across the car.

A quick google will get you a diagram.

Weight transfer is carried into the body by springs acting on the suspension arms. Those suspension arms generate leverage. If the leverage is angled up into the body (as the rear trailing arms on the BRZ are) then weight transfer under acceleration is resisted by the springs but that resistance is partly direct by the spring acting on the spring perch and partly apportioned to the body by the angle of the trailing arm.

Fitting MCA traction aids reduces this leverage effect.

The benefit is gained in transitions, such as accelerating harder out of the corner. More of the weight transfer goes directly through spring compression and less through the trailing arm. The ride is softened, the contact patch is stressed at a slower rate and, if the geometry change is correct, more grip is available to accelerate and corner the car.

MCA did a lot of work testing their brackets to ensure the desired effects actually occur. They do. These brackets make the BRZ easier to accelerate out of the corner. You get more power down to the road earlier. Lowering the suspension has a similar effect.

The drawback is more suspension movement for a given weight transfer. Fitting higher rate dampers to the rear reduces this negative. Lowering springs are stiffer so achieving this effect by lowering springs automatically reduces spring compression effects.

I use my BRZ year round for daily driving. I like the softer ride to the point that I also fitted rear springs from the 2017 model year. That helps traction also. The Edelbrock Supercharger can develop enough torque that reducing anti squat can deliver more grip allowing more throttle to be used earlier.

Another benefit of the MCA brackets whether lowered or not is the transitions effects on the springs are slowed down a bit which, depending on how you like to drive, can make you faster. Some may find this makes the chassis less responsive for the same reason.

There is no perfect setup, just a perfect setup for a particular driver.