islandsoon

I spent the day Sunday here in WI on a nice AutoX parking lot layout running B stock. The track was mostly 2nd gear with a pretty tight first turn and a slow, severe 1st gear hairpin finish. This was my first AutoX event and I found the RX8 to be fast enough and easy to be smooth in (I rec'd a number of comments about how deceptive the RX8 times were), but I sure would like to cure it's understeer. I'm running with ALL traction control turned off. For tire pressure, 42 psi all around and worked down to 38 all around which helped. I'm running stock tires, no CZ stage 1, no aftermarket parts whatsoever.
Any tips without changing out suspension components? Lower tire pressure? Some pre-corner setup I'm missing?
Thanks,
Tom

ZoomZoomH

iTrader: (1)

38 all around sounds like a good starting point.

usually understeer indicates going into a corner a bit too fast, consider slowing down a bit?

oi812

Hey islandsoon, would that have been at the Delevan Dog Track? I was on my way home from the mini-motard race and saw everyone packing up. I didn't know they had planed an event there, I only live about 3 miles from there, I hope they have more soon.

Anyway, to combat the front push I'm planning on getting a non-stock alignment. I'll try a little additional negative camber in the front, zero toe front and rear.

I haven't auto-x my car yet, but I'm in the same boat, car is completely stock at this point and I would prefer a little more overseer. I'm going to try to get to the Miler Park event next Sunday, but not sure if I can get the alignment done in time or not. My alignment shop's gage won't fit the stock wheels, so I have to put the snows back on for the alignment.

Kurt Bob

I second ZoomZoomH's comment. Most novice autocrossers try going too deep in a corner with braking and then can't rotate the car in the right direction on corner exit. By going in slower and and being patient, you'll find you can be much faster. In a car with enough power, trail braking also works well to counter a car that pushes.

islandsoon

That's the one...

The June 27th autox that was scheduled for the Janesville Airport looks to be rescheduled to the Delavan dog track.

http://www.madisonautocross.com/

Tom

islandsoon

Thanks for the notions...

I'll see what coming in slower does.

Tom

RXBob

I know that this is very hard to get used to, but practice some left foot braking. Be careful the first time you try it. I almost kissed the windshield my first time.
Also get autocross tires, it will probably add 3-4 seconds.

RXBob

I mean improve by 3-4 seconds duhhhhh

tpryor

Also, put a bigger bar on the front. Stock, the car has a tendency to "sit down" on the front suspension in a corner, causing it to go to full stiff and set up a push.

The larger bar stiffens the front (in a corner) and allows you a little more time to get the turning complete before it sits down on the bump stops. Doesn't seem right, but it works (I learned this trick from a fast VW driver).

It will still push until you get an aggressive alignment, but it will be significantly reduced from what you are dealing with now.

Autocross tires will lower your times, but it won't change the behavior of the car.

islandsoon

Thanks! This makes sense. The car is deceptively fast and timed well, but the comments above had me wondering if I had one of the two RX 8's in the world that pushed.
https://www.rx8club.com/showthread.p...threadid=28712
Regards,
Tom

rjacobs

OK, I have seen all of this stuff on trail braking, but what is it, is it using the e-brake or what?

dknv

I've heard most new street cars Will push, it's a safety feature that keeps drivers from accidentally oversteering themselves into a bad situation. (I've also heard the Evo is an exception to this rule.)
Regarding front swaybar, I was very glad to get Tim's wisdom in another post about this. When I changed mine out (along with alignment), it really made a difference.

Ophitoxaemia

virtually all stock cars are set up to have understeer, the rx8 is no exception. what i have noticed is sometimes it is much worse- especially on concrete. someone suggested once that the front might be getting on the bump stops, which which certainly cause all sorts of problems, including sudden increase in push.

i have a lot of autox experience in a variety of cars and have trouble getting my stock car to rotate (the ABS doesnt help at all as it tries to straighten the car). i recently drove an rx8 in a fun run that has bars, springs and shock changes. it was better but the springs could be stiffer still.

quite a fun car to autocross, so stable in transitions, and the brakes are amazing. if you can get the rear to come out the right amount it will take a fast drifting set quite nicely. much harder to drive than a miata though.

james

Seenitall

Bigger front bar=more front roll stiffness=more understeer

Kurt Bob

Trailbraking is the act of trailing off the brake (but not completely) as you start to turn the car toward the apex. When you have the car "rotated" sufficiently, you get back on the gas in a progressive manner until you are headed in the direction you want to go on corner exit. By that time, you should be at WOT.

This technique takes practice, and is more useful in autox situations than in road race settings. Autocrossers can use a couple different ways to get through a corner (with success).

The reason I'm so familiar with the technique is that I use it a lot in tight corners with my early model Miata. The early Miatas have a viscous limited slip that makes the car push on tight corners when you try to accelerate hard. Autocrossers with FWD do a lot of trailbraking with their left feet to get their car to rotate as if they were driving a RWD car.

dknv

Hi James,
so this was not your RX-8, someone else's? Who cares, bring it up to Reno autox anyway!
-Debbie

julian

trailbraking keeps/shifts weight on the front tires (thus lightening the rear) so the car will rotate, ie oversteer more or understeer less. motorcycle racers use this too, if you watch them brake hard into a turn you can see the rear wheel step out or fishtail slightly until they get back on the throttle.

clyde

Not in a softly sprung, underdamped, front camber limited street car like an RX-8.

PUR NRG

It was my wife's Pikachu car. Although now that she's preggers she won't be autocrossing for a while.
________
Chilis Gift Card

tpryor

Nope.

If the car sits down on the bump stops, the spring rate goes to infinity. By increasing the size of the bar, the spring rate does not go to infinity, as the stiffer bar forces it to stay on the spring, thereby EFFECTIVELY reducing the rate, and the push is diminished.

You have heard other members say it works also. So, the proper equation would be:

Bigger front bar=more front roll stiffness=less effective spring rate=less understeer

dknv

Pikachu car?? Cool!! Yellow? (I s/b doing a search, huh?)
Early congrats on the upcoming event!

trex8

A bigger bar in the front won't help a RWD car with understeer. The VW's front wheel drive can/will create understeer through wheelspin, especially with an open diff when the inside tire is unweighted, which is entirely different from what you're getting. In fact, you could disconnect the front bar completely and you'll probably find the car turns in better in the situation you described. (Won't be good on higher speed turns on tarmac, though.) Maybe try messing with more negative camber on the front, maybe even a bigger bar on the back... different tire pressures might help.

Lawerence

Um actually that will make the understeer worse.

A larger bar in the rear would help rotate around more though.

Or you could just take of the front bar alltogether.

Gord96BRG

trex8, Lawerence:

Nice theories you have there. Have you actually tested them on an RX-8? (Both of you state categorically that a bigger front bar will result in more understeer).

From a strictly textbook approach, I would have agreed with you. However, Tim (tpryor), the one suggesting that a bigger front bar on an RX-8 decreases understeer for autocrossing, actually has an RX-8 that he autocrosses very successfully, and HAS experience with that mod, and explained why it works.

Hmmm, who should we listen to - the guy who has actually run a bigger front bar on an RX-8 and is winning his class in autocrosses, or the guys who haven't tried it and are just stating generic theory?

Regards,
Gordon

trex8

Hey, I'm for whatever gets you around the course the fastest... it's a race! You're right, I haven't raced my RX8. It does defy conventional wisdom & my experience with racing other RWD cars though. But what works is what matters...

Another way to overcome understeer on very tight twisties is to drive more aggressively and toss the car into the corner more, using the weight of the car to rotate. Could it also be the tighter feel of the bigger bar inspires the driver to attack the corner more? (The biggest variable is the guy behind the wheel, IMO).
You won't roll an RX8, I don't think..

Any easy way to test this before spending any money is to set up a series of very tight, acute turns in an open parking lot or something. Run 'em with the bar on and then with one side unhooked. See which turns in the fastest - if its quicker without the bar hooked, a bigger bar 'should' only make it worse.