corner exit traction
 

I've noticed the brz rotates very well under throttle, better than the mr2 I used to own. the mr2 being mid-engined tended to push under throttle. I didn't "tune it out" because I wanted the stability for a rear heavy car.

The main difference I'm noticing on corner exit is how easy it is to get the brz's tail to slide under power. In the mr2 that had a lot more torque, with the right alignment and tires, it was almost impossible to break the rear lose. It just hooked up and went.

I see 4 main differences though between the cars.
1. weight distribution favors mid-engined cars on corner exit traction
2. suspension setup - mr2 had aftermarket shocks and camber bolts
3. tires - 235 width fk452 vs 215 width prius tires
4. differential - mr2 had open diff that would spin the inside tire, a limited slip would dump the power on the outside tire if the inside tire had no weight on it.

Now, I want to say the brz is actually very good on corner exit. It's just a different kind of experience from the mr2 where I had absolutely no worry about losing rear traction on dry pavement. Wet pavement is a completely different story. :bellyroll:

So can any of the above differences be addressed?
1. no
2. yes
3. yes
4. I've never driven a car with a limited slip before. I can say it definitely helps on the very tight corners where an open diff would just spin the inside tire. On higher speed corners, I might like the an open diff better for the added slip allowance or I just need to drive better. :)

corner entry and transitions is where the brz really shines above everything else though...

I'm assuming you are just talking about 1st and 2nd gear? Or maybe 3rd gear on a less than ideal grippy surface, since the car doesn't have enough power to slide the tail at a high speed.

Also please stop referring to the tires as "prius" tires. They are Summer Grand Touring tires with a W (186mph) speed rating and a 240 wear rating. Just because they're offered as an option for the Prius in EUROPE doesn't mean they're whimpy crap tires:sigh:

If you want it to grip better on corner exit use a staggered tire set up, with 225, 235, or 245 section width tires in the back instead. Just be aware that under other situations your car will be more prone to understeer.

yes, I'm talking about 1st and 2nd gear.

I don't mind being able to break the rear loose. it's actually pretty fun to do once in a while. I did notice the 240 wear rating which surprised the heck out of me when I looked at the tires. Let's see how long they last with rotation. :)

I'm wonder though does the rear have enough camber gain stock? Anyone with experience have studied their tire wear? If not, I might have to go out and drive really hard for a while with the right amount of air pressure to see if the rear needs more camber because it could be the tires have more traction, it just doesn't have the contact patch.

I like the tail out antics in 1st and 2nd gear as well. It's much more controllable than doing the same thing in my previous car (S2000). That car would snap back too quickly (prob b/c of it's 255 section width rear Dunlop Z1 Star Specs, haha).

I'm looking forward to taking the car to the track with these Michelins, for some oversteer fun :P

Keep in mind the BRZ also comes with almost zero toe in the rear from the factory ;)

After checking the track forum, it doesn't look like many people are dialing in rear camber and also saw report of a lot of camber gain for a little bit of lowering. They're mostly going with a stiffer front sway bar which I hate for driving feel. I would only go the direction of losing the rear sway bar or going stiffer springs up front because if you've driven a car with more spring vs a car with more sway bar, you will understand. But class rules must be followed in order to stay competitive :burnrubber:

in the wet, you can break the rear loose in any gear if the tires have enough lateral load... it's physics

Furthermore, I believe they are OEM tires on some Audi, BMW, and Mercedes models.

Bet you can't do that in SIXTH gear in the automatic! :D

Have you looked at that ratio? Lordy! I figure you guys need to change down from sixth when encountering a slight grade on the interstate. ;)

Yep. Changing class can REALLY up the ante to remain competitive! :D

I bet if I get to top speed in 6th in the auto, I can just turn the steering wheel a little bit and get the rear to slide :lol: something about increasing speed and the tendency to oversteer... not sure how to explain it... :lol:

FINAL oversteer? At top speed of around 140 mph?

It should not be designed to permit that; it should understeer at high speeds when cornering.

But you might be right.

And since you have an auto, whereas mine's a manual ... you go first!

We'll watch.

Tell us what happened. ;)

Actually, you cannot reach top speed in SIXTH gear in the auto, I don't believe. It's too tall a gear and that 2 liter just hasn't got the grunt to pull top speed in sixth.

IIRC one needs fifth gear for top speed in the auto. Even that gear is taller than sixth in my manual gearbox BRZ.

But go ahead and max it out in sixth, whatever the speed, and make it oversteer if you can with additional throttle. Bet you can't. ;)

Not without doing something dumb.

Again ... we'll watch! :)

alright.. which video game has the brz in it..... I have to buy a game system just to test this... :lol:

I bet a Scandinavian flick at high speed would do it, if the front tires still have enough traction to do a Scandinavian flick at 140mph :lol:

GT5 :)

I can slide the ass out in 3rd in the wet too. On racing slicks. Must be some crappy tires....

Driver error ;)

The drivers who are less comfortable with a loose rear use stiffer front sways. And the Autocrossers.

We hold a lot of the local records (and Evasive/Robispec are local to us), and we run HIGHER rear spring rates and stock sways.

More camber in the front than rear.

I don't know about 140, but the car will oversteer at 125+. I've done it.

Game? What game?! That's cheating! We don't need no stinkin' game!

Get your butt out on the road and SHOW us! LOL! :lol:

Yeah, I'll bet it would. But that fails to observe the requirement to avoid doing something dumb, doesn't it?

Still, I'd like to watch you do it.

Video, please... :lol:

I'm reminded of Niki Lauda who said, in his thick Austrian accent, "Bazzickly, I don't like OVERSTEER!" :)

My point here, to resume a more serious tone, is merely that a BRZ off the showroom floor, as setup by Subaru for street use, unmodified, should not display final oversteer characteristics in high speed cornering.

I was also making a point about the astonishingly tall sixth gear in the AUTOMATIC BRZ and the unlikelihood of generating power oversteer at high speeds with that enormous gear.

Now, that's an assumption on my part, untested on the road by me. I could be wrong about this assumption, but it will take some convincing for me to believe Subaru would market a car with "dangerous" handling traits. High speed oversteer is unstable, undesirable, and dangerous, even for the most skilled professionals, notwithstanding guys like the young Jody Scheckter or Gilles Villeneuve, all of whom I was privileged to watch.

This is not to say oversteer cannot be GENERATED at high speed, especially in the wet on a racetrack. And remember, I'm talking straight stock car as supplied by Subaru for the street. A track-prepped car can be made to behave pretty much as you'd like; pick your poison. I'm not talking about the possibility of generating oversteer in a race car. That's certainly possible.

But, at high speeds ... better you than me. I'm with Niki on this one, even if I'm not exactly in the same talent pool. ;)

Power oversteer is fun at low speeds in lower gears, but less and less fun and increasingly dangerous as the speeds mount.

Again, I'm quite prepared to be shown wrong, but it would certainly surprise me to learn that ANY manufacturer of a modern car would, or could AFFORD to, market such a car to the general public for street use. They could go broke paying off the subsequent lawsuits.

I could be wrong, but somebody's going to have to show me.




************************




P.S. Speaking of Niki, Ron Howard's film, Rush, will be out in a few months. It chronicles the battle for the 1976 World Championship between Niki Lauda and James Hunt. You can see the previews on youtube. It looks promising. I was at Mosport for the Canadian Grand Prix that year and saw Niki shortly after his horrific accident that, but for Marlene's help, might well have killed him. Lauda's an impressive man. Those interested might wish to read his autobiography. I enjoyed it.

It's funny cause one of the little complaints I have about my car is that the front end feels too loose. Particularly on fairly tight, second-gear type corners it often feels like when I try to get it to rotate with the throttle, both ends feel a bit squirmy. It reminds me a little of the stock setup on our 135... when I get done with school I want to make some little changes to make the front end feel more planted.

It feels good in really slow corners where you can trail-brake it in and then just kick the back out with the throttle if you want. It feels fine in faster, third-gear corners where you don't get as much torque to play with, but in fast-ish second gear corners the car just feels a bit nervous to me, like the back wants to go but the front is yelling, "No! Me first!"

The front needs more camber. The front tire is probably rolling over and riding on the sidewall. Once you give the front more negative camber though, you will experience way more grip and way more oversteer :lol:

I believe the fr-s is more oversteery than the brz and that is at lower speeds. I've never seen a car that becomes more understeery at higher speeds. It always becomes looser as the speeds increase. Can't explain why though.. as far as lawsuits, the vsc does a pretty good job of keeping the car on the road and going in the intended direction.

Good to know. My first thoughts were to play with tyre pressures, add some more camber at the front and change the rear toe, but I gather from a previous post that there's almost no toe-in on our cars?

I don't think so.

Obviously, your personal experience has convinced you that this is true. I cannot argue with your personal experience, nor would I.

But your general assertion that modern cars suffer increased final oversteer as the speeds increase is simply false. You are mistaken.

It would be a disservice to the readers of these forums to allow this to go unchallenged.

I ask you to produce authoritative proof of your assertion on a broad, general scale.

Perhaps you could provide the links to, and quotes from, major automobile magazine road test reviews that support your assertion about road cars sold to the general public. The writers would surely warn the general public about such a dangerous and undesirable trait, were it present in ANY road cars they tested. They would surely say so.

Quote them, please, if you can find any such reviews.

I have never seen such a description of a road car in more than 50 years of reading automobile magazines. Probably because road cars are NOT sold with such a setup, not to the general public they're not.

Even Mark Donohue said he would steer clear of a loose setup until he'd done a ton of testing, felt truly comfortable with the car at speed, and then would change the setup to just a bit loose, and that would be for a flat-out attempt to gain the pole. It's not the ideal race setup. Too twitchy, too dangerous, too foolish. (Donohue was one of America's finest racing drivers.)

Having to "save your life" at every fast corner gets tiring and slows one down over the course of a race.

Street cars are setup FAR more CONSERVATIVELY than race cars. I trust that requires no explanation.

Average street drivers haven't a hope of keeping up with a car that oversteers in fast corners.

Fortunately, they don't need to.

USA-spec Prius Five (the top-of-the-line model) comes with 215/45/17 Michelin Primacy HP. Same exact tire in the same exact size as the 86.

Correct---being on the Prius doesn't make them whimpy crap tires. They're just whimpy crap tires, period ;)

Hey look my vehicle dynamics textbook is online!
Vehicle Stability

Basically in the section linked Figure 6.11 illustrates that a car setup for oversteer (like the FRS) will likely be more unstable at high speeds and a vehicle set up for undeersteer is stable at higher speeds. It's why 911's are so successful in racing but have a reputation for being hard to control for everyone else. It also explicitly states in the paragraph below the figure that a car that understeers will understeer MORE at higher speeds when comparing similar steering inputs (the graph shows the understeer line dropping off, representing unresponsiveness).

This is simplified and doesn't delve into specifics but I think it shows nicely that depending on the setup, some cars are stable, some aren't, depends on the car. And like you explained, not many people are willing to test this, much less journalists borrowing cars.

Don't you just love it when everybody is right?

That's most cars....

Interesting thread. Subscribed.

The FRS doesn't oversteer by itself. It oversteers due to driver input. It will understeer at static turns.

You're the author? :)

Thank you!

Final understeer in high speed bends, a stable and relatively safe status, setup that way by the auto manufacturer for keeping the public safe. Anything less is bordering on insanity for a street car being sold to the general public.

This is NOT to say, however, that a determined driver cannot send it off the road tail first with sufficient provocation. I expect the aforementioned Scandinavian Flick should do the trick. (Again, video, please, @autobrz) :)

:bellyroll: I wish, he is a cool guy. He taught the class I took.

:thumbsup:

Cool! :thumbsup:

My first car was a Mk1 MR2 which I drove almost 30 years ago. I'd say that the BRZ has similar rotation characteristics on turn-in but the biggest difference is of course that the MR2 was quite a handful in an oversteer situation whereas the BRZ is easy to catch (VSC off). On corner exit, the MR2 was more hooked up under acceleration due to the extra weight on the rear.

On a related note, I just replaced the stock tires with Michelin Pilot Super Sports in the stock size. They are pretty close to R compound tires like the Hoosiers and Kumhos I used to autocross on, in terms of grip and steering feel. I am super impressed. FYI, the wear rating is misleading because while the stock tires have a rating of 240, the PSS rating is 300. However, Michelin has a 35,000 mile wear warranty on the stock tires vs. 30,000 for the PSS. Anyway, highly recommend the PSS -- and there is a $70 rebate right now.

If you think the PSS is good.... try something a bit stickier, but still a street tire.

yeah EVERYTHING starts at the road contact patch!