Severe Understeer

[hobbes80]

Ok all... went autocrossing this weekend for the first time. After 3-4 laps I was starting to get the hang of things. The instructor (was an instructor led event) took it around, showed me some cool stuff. by laps 9 and 10 I was really getting a feel for what the car could do...

And what it can't do.

My biggest problems in the event, hands down, were understeer and braking. You can see from my mod list below I'm running pretty good power, and I've done some modest suspension modifications.

The front tires are these crappy, SP9000 Firestone Supersports, my rears are BFG KDs. I feel like the obvious thing to do is ditch the firestones ASAP and put some matching BFG KDs in the front to help keep the front end from sliding forward in the heavy turns. Follow that up (as budget allows) by 13" brakes in the front.

With regards to the brakes, are the Baer/Brembo kits worth the extra jack? If I buy just a front-brake upgrade kit, is there a way to reuse the stock front brakes on the back to reduce the cost of buying a kit for all four corners?

What else can I do to address such a severe case of understeer (other than practice)? The instructor said my biggest problem was braking in the beginning of the turn, as opposed to finishing my braking before the turn. I think this is because A) I was going too fast to fully complete my brake coming up on the turn and B) after 3 runs, I was pushing the brake peddle to the floor and still not slowing down enough to make the turn.

OK, know it was a war and peace post. Looking forward to hearing feed back!

EDIT:
wth... BFG doesn't make KDs in 315/35 anymore? bah... What are people using as substitutes?

 

[DevilGT]

1.) The biggest way to counter understeer is driving technique. You already mentioned it, so it seems like you have an understanding that you're pushing the car too fast into the corners. I know it probably feels instinctive that to be fast at autocross, you have to go as fast as possible but if you're doing a small technical course, it is better to keep a low (as fast as you can go while achieving the desired effect) speed but be consistant instead of FAST - BRAKE - SLOW - FAST - REPEAT.

Remember slow in - fast out. With most autocross courses, you can't afford to really pick up alot of speed but if you are on a large course, I just suggest going in slow and hammering it on your exit.

2.) Your car is extremely front heavy, so you're going to need to do some suspension upgrades if you want to go down this road. I'm going to suggest stiffened front sway bar, as that was one of the major upgrades in my car.

Front Sway Bar. I'll suggest the Steeda one as you can find them very cheap on Ebay if you know where to look.

Rear Sway Bar. The Steeda rear adjustable may be able to help dial in some oversteer but if your power, you need to be careful. It'd still help with the revolution of the car in turns.

3.) Brakes. I'll just suggest getting a Cobra/Mach/Bullitt front kit instead of doing all 4 wheels, as the front is the difference maker. I found my Mach brake kit used for like 250 bucks. The rotors had just been machined too. I think you can talk to uh..what the hell is his name, Red98GT? The guy with the PI SN97 with sidepipes, he built his brakes, I'm sure he could help you.

If you need help PM me.

 

[GDawg]

Try some subframe connectors to stiffen up your car. On my convertible it completely changed my understeer to a bit of oversteer... I can drift now if I want!

 

[DevilGT]

I've heard great things about SFC's, but I've never used them. I also hear changing your control arms helps drastically.

 

[hobbes80]

All sounds like awesome advice. full-length subframes aren't too much $$, so I think I'll look at those early on my list.

I've got a massive front sway-bar that came with the Saleen kit, the springs are fairly stiff as they are and the urethane bushings certainly helped a lot.

I'll definitely look into the mach/bullitt brake kit, as that sounds like an affordable solution for better braking. The root problem I think is that I'm overpowered for my braking and driving technique. I think that the brakes will help off set that a lot, the SFC will help with the body roll on the slalom, and practice, practice practice.

I'm also considering changing gears. I have the stock 3.27s and I found that on the back end of the course when I come out of the corner I'm going too fast for 1st, and too slow to stay in the power-band for 2nd. Not by a lot, just marginally. I'm thinking 3.73s may be too big a jump and put me needing to go to 3rd on the straights, so I'm considering 3.55s.

Thoughts? Everything you guys have recommended so far has been very helpful, I've been pricing out components already, though I may have to wait to buy them until the girl falls asleep so I can spend the money.

EDIT:
Is this the right brake kit?
http://www.buyfordracing.com/shop/product_info.php?products_id=673cPath=6

 

[GDawg]

Do the 3.73 unless you're going with a power adder. I'm going to go from 3.27 to 3.55 cause of my KB. Otherwise, I'd do 3.73. My car is awesome in autocross but 1/4 mile gives me more of a rush.

If you get subframes, be sure to have someone that knows what they are doing when it comes to the welding. Lift on the tires/wheels and not the frame.

 

[hobbes80]

I'm doing full-lengths, have an appointment with Excessive on Saturday to have them welded in.

Definitely on a wheel lift, not on an chasis lift. Want that frame nice and straight when they weld it in.

Check my sig, my car is S/C with a vortech. Hence the reason I am looking at 3.55s... I have a pair of 4.10s in the garage, I'm going to see if I can convince someone to do a straight swap with me.

 

[Spreadman]

Adjustable struts and shocks will help a lot. Also, change all of your bushings to urethane.

Brakes, change all of your rubber hoses to stainless braided lines. That will help with pedal feel. The Cobra brakes are good, but I would upgrade to some slotted rotors. If you plan on autocrossing a lot, get some Hawk race pads. They dust a ton but they will stop you hard.

 

[hobbes80]

I think I should probably clarify my sig, for the record.

the "getting started" suspension kit on my car is:
1.3" lower springs, front and back, the Saleen springs are I believe Motorcraft Springs.
Front Tubular Sway bar, urethane bushings all the way around, and bilstien Struts/Shocks/quad-shocks, all the way around. I've got caster camber plates to get a near-perfect alignment.

Not interested in getting a negative camber to reduce understeer because I like having SOME life to my tires.

Currently, I'm looking into:
Full Length Sub Frame Connectors (being installed Saturday)
Better Front Tires
Upgrade front brakes to 13" rotors with new calipers (probably mach1/bullitt, unless I go nuts and go brembo or baer)
Adjustable Rear Sway bar
3.55s to get out of the turns quicker and stay in the power band
Oh yeah, and practicing.

Thoughts that have crossed my mind:
Tower brace
Lower control arms
Steering bushings

Am I missing anything?

 

[40oz]

you might consider going back to the stock front swaybar. Generally speaking, a stiffer bar makes that end slip more.

A really stiff front swaybar is useful if you had *too much* grip up front so the car really leaned over in turns. If you put too stiff a bar on the rear, it gets tail-happy. Too stiff on the front and you get understeer.

Since your front tires are not as sticky as your rears as well as being narrower, you need a softer bar in front than if you ran the same tires at all four corners. Better tires will lessen the problem but won't correct it.

Also check your tire pressures. You give up traction if your tires are rolling over when you turn. This can be fixed with more air pressure. Too much pressure and the fronts will be too hard and slide, but this is a different feeling than rolling over - you'll be able to tell.

I know parts get sold as kits, but obviously people run all different kinds of set-ups. A kit that works awesome on one car won't necessarily improve things on every car.

I would agree with SFC's - stiffer is better. A strut brace will be my own next upgrade. It's hard for the tires to hold a line when the strut tower flexes. In other cars I had it didn't make the car handle better so much as make steering more solid and consistent esp. over uneven surfaces - less wandering over bumps and slightly sharper turn-in.

 

[Flghtmstr1]

These cars understeer simply because of all the weight up front. If you truly want a balanced, neutral-handling car, deal with the weight issue by getting an aftermarket k-member with coilovers, AC delete, aluminator block, etc. I have the same tires on all 4 corners, good subframe connectors, and full suspension, and the car still understeers at low (i.e. autocross) speeds.

As for the brakes, I don't see why the stock GT brakes would be insufficient for stopping from <70 mph, but if you're encountering problems, I would highly recommend the Cobra brake upgrade. Even the factory Cobra pads and rotors are more than sufficient for providing fade-free stops at autocross speeds.

 

[007]

Theres good advice here. The adjustable shocks and tire pressures really help dial your car in. The only thing I would stress that wasnt really emphasized above, is that you MUST get some better front tires. The tires have a HUGE impact on grip. If you have nice KDs on the ass, and POS tires on the front, then it will obviously cause bad understeer.

The Cobra brakes, front only, would be my recommendation for brake upgrade unless you have lots to spend. Its cheap and very effective.

Personally I'd do front tires first, then brakes. I'd do SFCs but wouldnt go for the STB yet. It wasnt anywhere near as effective for me. Have you relocated your battery to the trunk? Thats a nice easy way to move a load of weight off the nose and over the rear wheel.

 

[Spreadman]

And I would go with 3.73's instead of 3.55's. I had them on my NOVI'd GT and it helped a TON.

 

[40oz]

These cars understeer simply because of all the weight up front.

Personally, I call this a myth. Lots of cars have less than ideal designs. Porsche 911 comes to mind as just one example of famously imperfect layout yet widely acclaimed results. There are plenty of car makers that ignore the 50/50 mantra with success. The suspension and driver are a bigger factor than chasing theoretical ideals for their own sake.

I have the same tires on all 4 corners, good subframe connectors, and full suspension, and the car still understeers at low (i.e. autocross) speeds.

Just a question - what's the point of the "full suspension" if your car still doesn't handle the way you prefer? I'm not knocking you, I'm just asking.

I've been able to all but eliminate understeer on a FWD Civic with simply more air in the front tires, a strut tower brace, and a stiffer rear swaybar. And that's with a car with inherently more strikes against it than a stock Mustang GT of any era. And my current Mustang is so much more capable than that Civic ever was it's silly. I've not had to fight the same kinds of issues with handling, so when I read about someone talking as if the Mustang has some inherent issue, I have to laugh a little.

Sure there are cars that have a better set-up out of the box, but we aren't talking about those cars here. And things like changing tire stagger, engine output, etc. ARE going to change how "better" cars behave. Bolting on new parts more or less randomly will change the character of the car's handling, and there is nothing to suggest random changes will always improve things. On the other hand, one has a greater chance of success by identifying a problem then addressing it appropriately.

I'm not saying the same steps to fix a Civic will work on any Mustang, but they both obey the same laws of physics. And if a new part doesn't improve the car, I take it off. I gain nothing by having expensive parts if the car still won't do what I ask. I *don't* take the view that if a part is expensive and doesn't work for me it must be the car's "nature." Rather, if it doesn't fix *my* problem, it's not designed for *my* car. And if there isn't a problem, I don't go looking for a solution.

That said, moving the battery and taking weight off the front *are* good things. I just don't buy the "front heavy" excuse. Most cars understeer from the factory - oversteer scares people. Simple changes are often all that's needed to fix it. But the tendency for Mustang owners is to put wider tires out back and increase power - a recipe for more understeer. If one does that, one also needs to make changes to the suspension to balance the car. Or tolerate poorer handling than stock.

 

[san~man]

Just remember that if you're going to compete in auto-x, there are classes in which your car falls into. Changing the suspension components can/will push you into the higher classes. Just something to think about if you're planning to do this on a regular basis.

 

[hobbes80]

Just remember that if you're going to compete in auto-x, there are classes in which your car falls into. Changing the suspension components can/will push you into the higher classes. Just something to think about if you're planning to do this on a regular basis.

Yeah, I was reading through the SCCA rules, and basically I'm screwed if I want to compete because I already have a blower on the car. I think my current plan, is to auto-x for fun, and if I decide I really want to compete, I'll buy a POS that is really light weight and can qualify for the beginner class levels without putting a lot of cash into it... like a 95 miata or a used Z4 or something along those lines... once I've gotten my skill level up to where I feel I could compete, then I'd put money into the mustang with the skills to know exactly where my shortcomings are (and the shortcomings of the car).

Mostly I'm just out there to enjoy myself, the thought of competing has not yet been a high priority... besides, the girl is already looking at low-cost, light-weight cars that she could learn in... which means I may end up having one at my disposal

the tendency for Mustang owners is to put wider tires out back and increase power - a recipe for more understeer. If one does that, one also needs to make changes to the suspension to balance the car. Or tolerate poorer handling than stock.

I agree completely. I feel like my understeer problem is mostly self-induced. I've added a lot of power, put sticky tires in the back, crappy ones in the front, and done very little to stiffen the chasis or rear-end. I did it all out of different motivations than what I'm looking for now. All the mods I've done up until now have been done with "look and feel" in mind instead of a specific goal.

So it looks great, sits well in a parking lot, and will light tires on fire all day long. When I first bought it, those were all I really cared about. It isn't set up to win drag races, it isn't set to win auto-x... just generally a fun car to drive that sounds/looks awesome pulling through the Friday Night cars in the Lowes parking lot... And there is nothing wrong with any of that.

I'm just ready for something else, and the steps to get there involve some trial an error along with the experience of those who have gone down this path before me.

So yeah.
Tires, SFCs, Rear Sway bar, Brakes... not necessarily in that order.

 

[40oz]

So it looks great, sits well in a parking lot, and will light tires on fire all day long. When I first bought it, those were all I really cared about. It isn't set up to win drag races, it isn't set to win auto-x... just generally a fun car to drive that sounds/looks awesome pulling through the Friday Night cars in the Lowes parking lot... And there is nothing wrong with any of that.

defintely nothing wrong with that

My car is *my* fun daily driver, not a car intended to impress all the various breeds of snobs lol.

 

[Flghtmstr1]

Personally, I call this a myth. Lots of cars have less than ideal designs. Porsche 911 comes to mind as just one example of famously imperfect layout yet widely acclaimed results. There are plenty of car makers that ignore the 50/50 mantra with success. The suspension and driver are a bigger factor than chasing theoretical ideals for their own sake.



Just a question - what's the point of the "full suspension" if your car still doesn't handle the way you prefer? I'm not knocking you, I'm just asking.

I've been able to all but eliminate understeer on a FWD Civic with simply more air in the front tires, a strut tower brace, and a stiffer rear swaybar. And that's with a car with inherently more strikes against it than a stock Mustang GT of any era. And my current Mustang is so much more capable than that Civic ever was it's silly. I've not had to fight the same kinds of issues with handling, so when I read about someone talking as if the Mustang has some inherent issue, I have to laugh a little.

Sure there are cars that have a better set-up out of the box, but we aren't talking about those cars here. And things like changing tire stagger, engine output, etc. ARE going to change how "better" cars behave. Bolting on new parts more or less randomly will change the character of the car's handling, and there is nothing to suggest random changes will always improve things. On the other hand, one has a greater chance of success by identifying a problem then addressing it appropriately.

I'm not saying the same steps to fix a Civic will work on any Mustang, but they both obey the same laws of physics. And if a new part doesn't improve the car, I take it off. I gain nothing by having expensive parts if the car still won't do what I ask. I *don't* take the view that if a part is expensive and doesn't work for me it must be the car's "nature." Rather, if it doesn't fix *my* problem, it's not designed for *my* car. And if there isn't a problem, I don't go looking for a solution.

That said, moving the battery and taking weight off the front *are* good things. I just don't buy the "front heavy" excuse. Most cars understeer from the factory - oversteer scares people. Simple changes are often all that's needed to fix it. But the tendency for Mustang owners is to put wider tires out back and increase power - a recipe for more understeer. If one does that, one also needs to make changes to the suspension to balance the car. Or tolerate poorer handling than stock.

The weight distribution of a vehicle has a large effect on every dynamic motion. The excess weight (combined with Ford's factory suspension tuning) IS what causes understeer. Adding a stiffer rear swaybar will cure it, but it does so by limiting lateral traction in the rear, not by addressing the underlying issue. Removing weight from the front will not only help the car's handling, but will increase acceleration and fuel economy as well.

As for your question:

what's the point of the "full suspension" if your car still doesn't handle the way you prefer?

I have modified my car to be a jack of all trades. I enjoy autocross, occasional drag strip passes, and just tearing it up on the street. Those three disciplines necessitate compromises when it comes to suspension tuning, and my suspension handles all of these counter-productive goals admirably: competitive in autocross (with my buddies, not in my class), great weight transfer at the strip (1.8 second 60' time on my regular street tires), and a balanced, taut feel for the street. However, as the saying goes: "Jack of all trades, master of none." There are inevitable compromises that must be made if I want to take my car in a particular direction, and those are compromises I don't want to make.

 

[hobbes80]

So the full length sub-frames are in, and must say the difference is huge. I must say that I was always aware that the car had significant body roll, but the reality of what that meant was never more solidly underscored to me then the first 10 minutes driving around after having SFC installed.

Basically, the SFC allow the suspension on the car to actually serve its purpose. Before hand, the whole car would kind of dip with the lay of the road, now you can feel the suspension more evenly keeping the car balanced on the rougher road, and keep everything together for a tight turn. Just in my daily driving I've almost curbed the rims a few times taking right-hand turns as it is turning tighter then I expected.

Very pleased with them as an inexpensive mod to affect the overall handling.... can't wait to see how this affects driving on the course.

 

[007]

Good to hear. The SFCs got rid of a lot of creaks in my car when going over bumps.

Did you order tires yet?

D