TRev's BRZ RTR Autocross Build

[torqdork]

I called Tire Rack yesterday to find the publishing date of their new Extreme Summer Tire comparo in progress now. The helpful rep said the raw data collection will be done in about two weeks and another two weeks to crunch, so estimated early June.

He didn't mention all tires being compared but said the ones I'm interested in (ZII, Rival and RE-11A) are nearly complete. So far, they're most excited by the Rival's performance, think it's a fine all-around tire that performs well in dry or wet conditions.

Exciting, but my inner skeptic wonders if having a monopoly on Rivals might somehow influence outcomes.

Anyway, my car doesn't arrive until sometime in June so timing should be good and hopefully by then Rivals will become available from other retailers.

[xwd]

GRM just published their street tire test and the Rival came out as a clear winner this time around. However the test was on a 2000lb car running narrower 15" tires. Wish they had a heavier car to test with.

Chris Harvey who autocrosses a bit and works at Tirerack said today on another forum early June for the tire comparison article. They were also hoping to have the new Yoko AD08R in the test as well.

At this point it seems like a crapshoot still. I have the 225/45/17 Rivals as my daily driver/RTR tires and may run them at our next event on the 18th to save the A6s. I did one practice run in them a couple events ago and I was surprised how close they actually were to the A6... on a 42 second course I was about .9 slower and had that was never having autocrossed on them before.

[TRev]

I got the Konis and the Ferodo DS2500 brake pads in this past weekend. BIG thank you to Defyant Motorsports for all the help.

Took the afternoon off to drive up to the cities and have Jeff (www.thealignmentguy.com) do the alignment. Jeff does awesome work and it is worth the 5 hour round trip drive. Went with a slightly more conservative alignment with regard to toe.

Left Front Camber: -1.2
Right Front Camber: -1.4
Front Total Toe (out): -0.06
Caster: 5.5

Left Rear Camber: -0.6
Right Rear Camber: -1.2
Rear total toe (in): 0.08

I did a bit of testing with the Rivals on the car. I saw 1.4 longitudinal G's and 1.3 lateral G's. Temperature is 60 degrees and the tires only had a minimal amount of heat in them.

I rotated rears to front so the fronts have minimal scrub in. The car feels very balanced with the exception that it has a slight push on corner exit. Once the tires scrub in better, I think this will probably go away. If not, I will soften the Konis in the front to see if I can get the push dialed out.

The Koni adjustment range is 2 full and 1/4 turns from soft to hard. I currently have the fronts at 1 1/2 turns starting at full soft. The rears are at 1 turn starting at full soft.

The other change I made after reading the GRM street tire test was to drop pressure on the rivals to 32 psi front and rear. They definitely provide more audible feedback at that pressure. The rollover up front is a hair below the triangles at the lower pressure.

[SVThis]

I've been running the Koni fronts at 1 turn out from soft and the rears at 1/2 turn out from soft. Since everyone has been keeping a secret on their settings I'm not sure where the sweet spot is. The only time the rear has kicked out at all was at an event where the pavement was damp. I think I need to loosen up the rear a bit. Am I running the shocks too soft to begin with? BTW the tire pressures I am using are 36 front 34 rear.

[TRev]

Originally Posted by SVThis

I've been running the Koni fronts at 1 turn out from soft and the rears at 1/2 turn out from soft. Since everyone has been keeping a secret on their settings I'm not sure where the sweet spot is. The only time the rear has kicked out at all was at an event where the pavement was damp. I think I need to loosen up the rear a bit. Am I running the shocks too soft to begin with? BTW the tire pressures I am using are 36 front 34 rear.

I am still learning myself though I believe this is representative of what changes should be made based on entry, mid corner, and exit behavior.

Corner entry over steer: Soften rear rebound
Corner entry under steer: Stiffen rear rebound
Corner exit over steer: Stiffen front rebound
Corner exit under steer: Soften front rebound
Mid corner over steer: Stiffen front bar
Mid corner under steer: Soften front bar

The recent article in GRM mentioned that the Z2 could deliver almost the same lap times anywhere from 24-40 psi with the exception of 36 psi where it was slower for some reason. Since the front is at that not so magic 36psi number and rear is at 34psi it could be attributing to the under steer and it would be good to try varying the pressures. I would bump the front up to 38psi and then start increasing the rear by 2psi to see what effect it has.

What are your alignment specs?

[Kido1986]

I need to go measure my current shock settings and then Ill report them. More knowledge is better

Now to just get the decision down between Z2 and Rivals as my RS3s are about 5-6 events from dead it looks like.

[Biggins]

I ran .5 turn from full soft in the front and .75 turn from full stiff in the rear at the Dover Tour. I have the Hotchkis bar but no alignment yet. It was my first event with the Konis (finished the install in the paddock), so I have lots of testing to get it right. I don't want to muddy-up TRev's thread, but I'm always up for sharing! My alignment will probably be close to TRev.

I just hope I get off the waitlist for the DC Pro to see where I'm at...

[DylanFRS]

Hey Trev, what do you think of the Whiteline 20mm front bar. That is looking to be my next mod but I am debating between the 20mm and the 22mm. I notice most people are running the 20mm but most of the autocrossers seem to have picked the BRZ. Since the FRS tends to be more tail happy from the factory, I was thinking that 22mm bar may compensate for that a little. But will it be too stiff in the front? With the 20mm bar on the BRZ are you wishing you had more front bar or less?

[SVThis]

Originally Posted by TRev

I am still learning myself though I believe this is representative of what changes should be made based on entry, mid corner, and exit behavior.

Corner entry over steer: Soften rear rebound
Corner entry under steer: Stiffen rear rebound
Corner exit over steer: Stiffen front rebound
Corner exit under steer: Soften front rebound
Mid corner over steer: Stiffen front bar
Mid corner under steer: Soften front bar

The recent article in GRM mentioned that the Z2 could deliver almost the same lap times anywhere from 24-40 psi with the exception of 36 psi where it was slower for some reason. Since the front is at that not so magic 36psi number and rear is at 34psi it could be attributing to the under steer and it would be good to try varying the pressures. I would bump the front up to 38psi and then start increasing the rear by 2psi to see what effect it has.

What are your alignment specs?

Front: -1.0 camber
0 Toe
5.7 Caster
Rear: -1.0 camber
.2 total toe in
Strano front bar
225/45/17 Z2's

[TRev]

Originally Posted by Biggins

I don't want to muddy-up TRev's thread, but I'm always up for sharing!

No worries, this thread is all about sharing what works and what doesn't...please share away!

Originally Posted by DylanFRS

Hey Trev, what do you think of the Whiteline 20mm front bar. That is looking to be my next mod but I am debating between the 20mm and the 22mm. I notice most people are running the 20mm but most of the autocrossers seem to have picked the BRZ. Since the FRS tends to be more tail happy from the factory, I was thinking that 22mm bar may compensate for that a little. But will it be too stiff in the front? With the 20mm bar on the BRZ are you wishing you had more front bar or less?

I am right in the middle of the bars range (soft setting with end links as short as possible) so I have quite a bit of adjustment. The car feels good mid corner. I think the 22mm would be too much for the FRS. I would recommend the 20mm bar with the adjustable end links and start with the stiffer hole and the end links extended as far as you can get them and then shorten as needed.

[TRev]

Originally Posted by SVThis

Front: -1.0 camber
0 Toe
5.7 Caster
Rear: -1.0 camber
.2 total toe in
Strano front bar
225/45/17 Z2's

I could definitely see the .2 toe in keeping the rear more planted. Does the car push at all? If yes, what part(s) of the corner?

[qoncept]

Planning on doing any more Iowa region events? Just picked up my BRZ last week and my wheels and tires are on the way. I'll be running in stock class on Z214s (the harder compound C51s for the first set at least). Holding off on Konis as long as I can.

[DylanFRS]

I don't know if there is one already but maybe we could start a CS RTR or just CS general thread for us to all chat discuss on if anyone else is interest. That way we can have our discussions in one consolidated thread instead of a bunch of thread-jacked builds.

On a side note, I am going to go with the 20mm bar Trev, the jump in stiffness from the 20mm to 22mm is ridiculous.

[Kido1986]

There have been previous ones but a new one would be good. Also link to each person's CS/RTR Build thread in the first post as a shortcut for people researching