Surprising differences in Motor Trend testing: GR86 vs. BRZ
 

Motor Trend has recent solo tests of both the BRZ and GR86 I haven't seen referenced here yet. Of interest here are the varying results of a few of the instrumented tests MT ran, as they are substantial and highlight the real impact of the differences in how these two cars' suspensions have been set up. (All cars were tested with the Pilot 4s at the same location under similar conditions.)

The BRZ (manual) averaged .93 g on the skidpad test and posted a 25.7-second, 0.71 g (average) on their figure eight test. The GR86 did significantly better at .98 g (manual) and 1.00 g (auto) on the skidpad, with figure-eight times of 24.7 seconds (manual) and 24.8 (auto) at an identical 0.76-g average.

These results seem a bit surprising given the general view that the BRZ is set up for a more neutral handling balance, from which one would infer it should have a higher maximum grip. But it appears likely that the GR86 is in fact more neutral at the limit and the BRZ loses out due to more understeer. As R&T notes, "Each car has its own front and rear damper settings, with the Toyota utilizing a 7-percent lower front spring rate and an 11-percent higher rear spring rate compared to the BRZ, respectively. " So the GR86 sacrifices a bit of sharpness on initial turn-in with those softer front springs for higher ultimate grip?

That is surprising, and it's very different BRZ numbers than the C&D skidpad results which had the BRZ at .99g and the GR86 at .98. Interesting.

https://www.caranddriver.com/feature...-toyota-gr-86/

Maybe the tires on Motor Trend's BRZ were shot.

It seems like there had to be something else going on. The difference between .93 and .98 is more than I would expect from just spring rate tuning right?

Like a difference that big would have been mentioned by all or most of the reviewers.

The C&D numbers are just .01 different, and I could believe that, but .05 seems like a lot for nearly identical cars of the same weight with the same tires.

Maybe some of our track rat experts could weigh in here. I've been wrong before lol.

Maybe the variability in these tests are larger than you think. You are looking a low N as well.

I doubt MT would be that sloppy in their testing, they have been at this for a while. But obviously the varying C&D results raise questions.

I wonder if they tested on different surfaces. I highly doubt any OEM suspension tuning differences would be responsible for a delta that large on the same tires.

Pretty interesting find though.

I was going to suggest differing alignments between the C&D and MT cars as a potential cause.

But ultimately it doesn't matter to me since I'll probably be slapping some crash bolts in the first thing next spring.

+1 that this feels more like a mistake in the MT testing protocols (as compared to the "industry standard" C&D).

On top of that, IMO all the peak handling performance test results are irrelevant with stock alignment. Anyone who cares about handling performance of these cars should get as much camber up front as their budget allows.

Loose is fast. Tires need a certain amount of slip angle to produce maximum grip.

Most likely tested on different days. Temperature, people, tire life, humidity, etc.

BRZ has more stability, GR86 is more neutral. Stiffening one end typically reduces grip on that end relative to the other. The opposite is generally true for softening one end.

If I'm not misunderstanding, MotorTrend measures "lateral acceleration" on their "figure eight skipad" which combines 2-300 foot diameter circles connected by a short straight. So the the car travels around half of each circle, accelerates down the short straight, then brakes into the other half circle. They then average this.

Car and Driver, on the other hand, uses either a 200 or 300 foot diameter circle without straights.

https://www.motortrend.com/features/...trend-testing/
https://www.caranddriver.com/feature...-we-test-cars/

So perhaps MT's test better highlights the differences when you introduce acceleration and braking to the turn. Whereas with C&D, both cars are settling on their suspension and are holding the corner identically.

Or, yes, alignment or something else could be off.

The duel figure 8 introduces more inconsistency - you are going to have slight approach and departure differences and your are never doing more than 1/2 to 3/4 of a circle, giving you less of a chance at achieving perfect balance and maximum grip angle.

You can test more things with it though, and your changing direction.

I don't know, I don't see how that layout difference alone would affect the maximum lateral G by so much. Maybe one could transition slightly better than the other (I doubt it, no reviewers said it, but maybe) but even if that were true by the middle of the 180 degree curve it would just be tires and grip.

The MT numbers were in separate articles dated more than a week apart, it's pretty obvious they tested the cars on different days. Temperature and humidity and possibly driver differences exist.

The C&D numbers are in the same article in a chart meant to be directly compared. They even have pictures of both cars on the road right next to each other. I trust that more.