20mm Spacers didn't work for me

[churchx]

Originally Posted by rvoll

The alignment is stock as the car is only a month old. I changed the tires as soon as I got the car, so it's not the tires that made the difference. I did notice the heavier feel when I changed the tires, but that is what I wanted. Those tires made the car seem more controlled. Again, spacers should not make this much of a difference, hence the surprise.

So there was not much mileage in tires aswell. Given that they were new, very probable for first hundred of miles they hadn't lubricant from mold worn off yet and might be not at full grip. Also possible that due car being new and still under brake in process, you may have driven less agressive. I still think that it's tires that surfaced eather to notice stock understeer that already was there even with primacies. There is reason, why front camber in OE alignment is by 1dg less then in rear, and why in performance alignment many prefer in front slightly more camber then in rear, opposite to that of OE.
In your place i'd keep using primacies though. They are not THAT bad of tire, too expensive though to be bought as next set, once initial set is worn through.

[fatoni]

27 years of racing and owning porches (not sure what that matters but, hey) and you dont know how to dial out a little understeer?

[mnuttall]

Someone correct me if I'm wrong, but I think adding spacers should slightly reduce the roll stiffness on the axle to which they are applied. Since you put spacers on the rear only that should shift the balance toward understeer; adding front spacers (and/or camber) should help.

[rvoll]

Originally Posted by churchx

In your place i'd keep using primacies though. They are not THAT bad of tire, too expensive though to be bought as next set, once initial set is worn through.

The Primacies were gone on the first day I had the car. Sold them in a couple of hours on Craigslist. I'm an old guy and didn't want to wait until the Primacies were gone to upgrade (who knows, I might be gone tomorrow or killed when my wife finds out about my girlfriend). You're right, they aren't bad tires, but the PS4S are a LOT better.

[rvoll]

Originally Posted by fatoni

27 years of racing and owning porches (not sure what that matters but, hey) and you dont know how to dial out a little understeer?

I know you're taking every opportunity to take a slight, but honestly, I never had to play with the suspension on my Porsches -- only wheels and tires. Track days were for fun with me, and not serious racing. I owned only 928's and my last GTS was stroked. Aside from track wheels/tires, I made no mods. I have a lot of knowledge about wheels and tires and corporate strategy was my avocation, but I'm a novice at suspensions and FI, especially with the BRZ. I do know how the car drives, however. And yes, that's a highly individualized perception and each of our sensitivities are different. I took off the spacers this morning and went for a drive. The difference didn't seem as pronounced as I remembered going the other way, but it was there. The car felt more nimble and controlled. I don't go to the track anymore and don't push my cars as much as when I was young, so how the car feels going about town is of prime importance to me. And no, you won't convince me that wide tires/wheels on this car when NA makes sense from a performance perspective. Looking back, I should not have been so concerned about a more flush look and just stuck to my guns about performance. However, I do read these forums and so many of you run with spacers I thought I'd give it a try.... Done...

[Yoshoobaroo]

Originally Posted by rvoll

And no, you won't convince me that wide tires/wheels on this car when NA makes sense from a performance perspective.

I agree. Wide tires are fine for chasing times, but it doesn't make for a fun car. I've been setting my car up to be fun, not for lap times, and it's not easy to pick mods that complement each other and improve the feel of the car rather than the measurable capability. That's why I run 215/45/17 tires (max performance summers) on a 17x7.5 15lb wheel. The 0.5" wider wheel helps reduce squirm, and they have 10mm extra offset over stock wheels. I run stock springs from a 2017 because most coilovers and lowering springs are too stiff for skinny tires. I use adjustable 19mm/16mm sways to dial in the rotation, and that's it really. The car feels light and nimble and most important of all; predictable and fun!

[NoHaveMSG]

Originally Posted by Yoshoobaroo

I run stock springs from a 2017 because most coilovers and lowering springs are too stiff for skinny tires.

When I went to FLZ's I noticed this. Felt great on track with my 245's, back to the stock wheels and tires the car pushed. Never noticed it before even though I was running spacers on the front to clear my BBK with my street wheels.

[Anthonyc77]

Why did you only put the spacers on the rear? Definitely should have put some up front as well.

[Yoshoobaroo]

Originally Posted by Anthonyc77

Why did you only put the spacers on the rear? Definitely should have put some up front as well.

He had 20mm on the front and 25mm in the rear

[wparsons]

Originally Posted by Yoshoobaroo

He had 20mm on the front and 25mm in the rear

Nope, only put the rear ones in:

Originally Posted by rvoll

So normally, I wouldn't even slightly mod my new 2018 BRZ, but so many of you have added spacers to get a flush look, I thought the very slight increase in understeer wouldn't be a problem. So yesterday, I received a set of 20mm spacers from ft86speedfactory -- their own brand -- and put them on the rear wheels. So many have said that 20 in front and 25 in back would be perfect. Their spacers are really well built, hub centric, and just good looking. The only other functional mod I made on the car was replacing the OEM Primacies with 225 PS4S.

Originally Posted by rvoll

I changed the tires about a month ago, so it's not the tires that make the difference. My use of the word "severe" is probably an overstatement. I really wasn't expecting to feel very much difference and when I could immediately notice the understeer, it was a surprise. Over the years, I've tracked a number of cars, so I am very sensitive to changes in handling. And I could feel the understeer at low speeds, i.e., slightly more effort to turn corners, etc. I don't push my cars anymore and purchased this one as a little fun car.

That's not understeer at all. If you're feeling more effort in the wheel, I'd check tire pressure again. There's simply now way that putting spacers on the rear axle made the steering heavier. IMO, you were expecting it to do something and it was all placebo or something unrelated to the spacers.

[Yoshoobaroo]

Originally Posted by wparsons

Nope.

Huh, reading fail on my part.

The heavier steering then doesn't make sense either, as the scrub radius is unchanged. I'm starting to think this is all placebo.

[rvoll]

Originally Posted by wparsons

That's not understeer at all. If you're feeling more effort in the wheel, I'd check tire pressure again. There's simply now way that putting spacers on the rear axle made the steering heavier. IMO, you were expecting it to do something and it was all placebo or something unrelated to the spacers.

Checked tire pressures again and they are fine. Perhaps I'm not explaining it properly (that is entirely possible). Let me try again. When the spacers are on, and I'm turning a corner, I have to turn the steering wheel more to accomplish the turn. Could it be a placebo effect? Possibly, as I'm considered partially human. I do understand your theoretical argument, so I'm puzzled as well. Perhaps since the outer driving wheel must make more rotations around a corner that is, in some way, affecting how it corners. The car did feel different enough that I noticed it immediately. I'll put them on again tomorrow and this time pay more attention to whether it's real or in my mind.

After some of you raised this issue, I did a Google search and here is what was posted:

https://rennlist.com/forums/964-foru...ndersteer.html

http://www.mycarforum.com/topic/2691...he-real-truth/

https://www.6speedonline.com/forums/...teristics.html

https://www.evolutionm.net/forums/ev...ndersteer.html

https://forums.vwvortex.com/showthre...-or-understeer

http://www.maseratilife.com/forums/g...nly-wheel.html

I admit I don't know as much about the BRZ suspension as you guys, but it seems the general consensus is that adding rear spacers very slightly increases understeer. What I've found over the years is that a car's geometry is quite complex and what seems to be simple answers aren't quite that. I'll report back and try to take real measurements this time.

[churchx]

@Racecomp Engineering: can you tell how spacers - in rear - affect grip bias? In my eyes it should only change slightly suspension motion ratio and again only slightly increase track and load on rear wheel bearings and that's it, doesn't sound to me as something drastic. But if change in rear grip is that noticeable, i guess there is more to it?

[JimmyMac]

Widening the rear will cause more push and less rotation in the corner.