Autocross street tire question

Front bar will keep the front tires from positive camber as badly and will likely make it oversteer more under all conditions except under throttle.

See Sam Strano, he knows about setting up Mustangs.

Too much tire for your wheel isn't helping things. 225s suck on a 7. 8 or 9 will let them work better.

General rule of thumb is , under steer- stiffen the rear or soften the front. Negative camber on the front also helps.

He can't go with a wider wheel and stay in GS, the biggest wheel a 2000 V6 Mustang came with were 16x7's. So he could go to 17x7's if he wanted, but there wouldn't be much point in doing that. 225's fit finde on 16x7's. Remember that he's still running a fair amount of sidewall here. I believe the OE size for a V6 equipped with 16's was a 225/55/16.

I understand the cases people are making for stiffening the front bar, but they are forgetting that this car currently has NO rear bar. I think adding a rear bar would do far more to improve the car's overall composure than to stiffen the front bar.

I autocrossed a 97 Mustang for over 10 years and I suggest adding the rear sway bar and playing with the tire pressures. I usually ran with higher pressures in the front because I wanted the rear end to come around on a tight autocross course.

exactly the opposite for my FWD … I run HIGHER pressures in the rear to help the car rotate …

even with having driven a couple of E30's in Lemons races … I don't know squat about RWD

There's no difference in the effect tire pressures have on FWD vs. RWD. Tire pressures that are higher or lower than optimal will both decrease grip, but overinflating is better for wear, safety, and handling than underinflating.

So if bumping up the front pressures on a RWD car made the car oversteer more, it means all four tires were too soft in the first place.

In reply to pjbgravely: Yes, that's true, but remember, Grassroots Motorsports did extensive testing with just using one size tire on different wheel widths on the same car for a purely scientific finding. For street use, it's not as important.

In reply to wbjones: With a solid rear axle, you can't adjust toe or camber, because it's fixed. A small plus is that you can't get positive camber or toe in with it.

Mustang50 wrote: I autocrossed a 97 Mustang for over 10 years and I suggest adding the rear sway bar and playing with the tire pressures. I usually ran with higher pressures in the front because I wanted the rear end to come around on a tight autocross course.

Ok maybe that is where I went wrong. I inflated the tires to max to help them lose traction. I run the fronts at just above roll over which is 41 I believe last time. I keep deflating each run until the chalk says I went to far.

I thought the idea was to have the lowest pressure possible without roll over to increase traction.

Last year on all 4 seasons I basically drifted through the tight corners, all 4 wheels pumped up to max. I wasn't fast. This year with the Comp 2's I am the same speed, the tires seem to slow down my acceleration, and prevent the back-end from rotating in the curves.

My engine might be down on power as I don't seem to squeal the tires accidentally like I used too. I am going to change the plugs tonight, they are worn but not real bad. They only have 60K on them.

This weekend is probably my last event for the year so any changes like a rear bar will be next year.

I do have adjustable struts and shocks. I set the fronts to max and the rears to 1/2. I don't know if that setup is close. Hopefully next year we will have another tune and test.

As for the driver, I have had people ride with me, I thinks I am a lot smoother than before, but not any faster. I might just be a bad autocross driver. Next year my daughter should be driving my car, we will see who is faster.

Add a rear sway, as much negative front camber as you can and practice. It makes sense that you get lots of understeer if you dont have a rear sway bar at all, doh!

Mr_Clutch42 wrote: In reply to pjbgravely: Yes, that's true, but remember, Grassroots Motorsports did extensive testing with just using one size tire on different wheel widths on the same car for a purely scientific finding. For street use, it's not as important. In reply to wbjones: With a solid rear axle, you can't adjust toe or camber, because it's fixed. A small plus is that you can't get positive camber or toe in with it.

my bad .. I didn't make my point … that is what I was trying to say without telling someone that they didn't know what they were talking about

pjbgravely wrote:

Mustang50 wrote: I autocrossed a 97 Mustang for over 10 years and I suggest adding the rear sway bar and playing with the tire pressures. I usually ran with higher pressures in the front because I wanted the rear end to come around on a tight autocross course.

Ok maybe that is where I went wrong. I inflated the tires to max to help them lose traction. I run the fronts at just above roll over which is 41 I believe last time. I keep deflating each run until the chalk says I went to far. I thought the idea was to have the lowest pressure possible without roll over to increase traction. Last year on all 4 seasons I basically drifted through the tight corners, all 4 wheels pumped up to max. I wasn't fast. This year with the Comp 2's I am the same speed, the tires seem to slow down my acceleration, and prevent the back-end from rotating in the curves. My engine might be down on power as I don't seem to squeal the tires accidentally like I used too. I am going to change the plugs tonight, they are worn but not real bad. They only have 60K on them. This weekend is probably my last event for the year so any changes like a rear bar will be next year. I do have adjustable struts and shocks. I set the fronts to max and the rears to 1/2. I don't know if that setup is close. Hopefully next year we will have another tune and test. As for the driver, I have had people ride with me, I thinks I am a lot smoother than before, but not any faster. I might just be a bad autocross driver. Next year my daughter should be driving my car, we will see who is faster.

(bolded) for the fronts … you're wanting them to grip, and you're wanting the rears to rotate … so for them = not to grip … but since they are your drive wheels, you don't want to loose forward grip

again … maybe soften the fronts and stiffen the rears …

but then again, it might be better to wait and hear from a RWD guru

In reply to wbjones: It's all good.

chiodos wrote: Add a rear sway, as much negative front camber as you can and practice. It makes sense that you get lots of understeer if you dont have a rear sway bar at all, doh!

Everything I have read, and everyone I have talked to says you don't want a rear bar for a live axle car.

Nevertheless, some of my problems may be that the bushings are worn on the rear support system. Possibly a light rear bar may help that without changing all the bushings.

*Update*** For anyone who cares. On the first day the coarse was long with some tight chicanes and an off camber almost hair pin curve.

The car cornered fine, the rear end came around like I wanted. I had some competition, I beat a V6 Dodge charger, but the Focus ST's still beat me by 12 seconds. I ran 40 pounds front and back.

The second day the coarse was even straighter with only 2 sharp turns. The gates were so far apart that I could turn most of the turns into long sweeping corners.

This time the rear tires had no traction at all. People thought I had stalled because my launch was just spinning tires, they wouldn't even squeal. I ended up dropping to 25 pounds rear and I finally got rear grip. The afternoon was hot, everyone was cooling tires and complaining about sliding, and I just kept getting faster. I have no idea what caused this change and I probably never will. It was the first time I had to add air to get home

My only class competition the focus st beat me by 9 seconds. 2 first timers in H class cars beat me by 3 seconds.

So all in all the car handling they way I want I am still slow. But I get to change my sig.

jstein77 wrote: Though you can certainly try to improve your setup, changes in driving technique make more difference than all the legal mods put together. I highly recommend soliciting the help of an instructor or an experienced driver in your group. Have them ride along with you, look for potential areas of improvement, and then drive you through to demonstrate those techniques. That's what I do for novices at every event I attend, and it never fails to improve their times by leaps and bounds.

This.

You can learn a lot sitting in the passenger seat of our own car with someone who really knows how to drive pedaling your car through the cones.

That will be my goal for next year. After the last event, I am sure I am the cars worst problem. Having someone else drive will prove that.

this guy pretty much has written the book on RWD autoX setups … now he can be a bit of a PITA to deal with if you're not buying stuff form him … but if you do use him for your parts goodies, he'll help in any way he can

ha and his setups have many national championships and nationals trophies to their credit

http://www.stranoparts.com

add this guy to the list of live axle gurus .. http://www.vorshlag.com/forums/showthread.php?t=7806 (he also posts on here occasionally)

one more resource for your type of car (Evo School) Mike Junior Johnson … https://www.facebook.com/MikeJuniorJohnson