Mustang severe understeer.

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The Huff
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Mustang severe understeer.

Post by The Huff » Sun Jun 29, 2008 7:30 am

I need advice. Last night I took a 90' turn in my 08 mustang and it plowed straight forward until finally hooking up when the tire blew off the rim & the bare rim dug into the dirt deep enough to get traction. I have Steeda sport springs, Tokico D-spec race springs and a Granatelli A arm brace and it still has this ridiculous under steer problem. After web research on the issue, I am going to order a front sway bar. Does anyone think a rear is necessary as well? Is there one brand better than the other? Does anyone have any other suggestions.
Justin Huffman
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magilson
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Post by magilson » Sun Jun 29, 2008 9:09 am

Unless you are buying a smaller front anti-sway bar you'll make it worse (most likely).

http://www.houseofthud.com/cartech/swaybars.htm
If the car is understeering, decrease front bar size, or increase
rear bar size. This increases front lateral grip and decreases rear lateral grip
giving the car a more neutral to oversteer feel. Reverse the process for
too much oversteer.
It can get more complicated than that but you should consider talking with some of the mustang guys at our events. A lot of those guys have no issue inducing oversteer with stock setups. :lol:
Matt Gilson
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The Huff
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Post by The Huff » Sun Jun 29, 2008 10:42 am

I really struggle trying to understand all of that. Lets say I get the car to over steer before it would under steer. That doesn't necessarily mean that the car is handling a corner better, but that it is breaking the rear tires loose even before the front ones which already break loose way to easily. Does that make since.
Justin Huffman
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Ironhead
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Post by Ironhead » Sun Jun 29, 2008 11:25 am

Absolutely 100% definitely go for a bigger front bar. It's the first thing most Stock class guys do, let alone Street Prepared.

Try to stay away from the internet for "knowledge". Been there / done that too many times when I started out.

Talk to guys who have won or are successful in cars like this.

Locally: talk to Bud
Otherwise: talk to Sam Strano. http://www.stranoparts.com/index.php
He has won multiple championships in Camaro's and Mustangs. He currently runs a Shelby GT. Great guy to talk to.

I would start with the front bar first and then re-evaluate. No need to start throwing unecessary parts at the car. (unless Strano or Bud tells you otherwise)

These cars like more front bar because it reduces the magnitude of body roll. Why does that help? As the car rolls, the front end loses camber (especially with your strut front end). When that happens, your entire tire is no longer in complete contact with the surface. This means loss of grip at the front which means understeer. We can compensate for this somewhat by running more static camber but that comes at the cost of tire wear. And since your car is still a daily driver....

It's possible the car may still push with a larger front bar. This will likely depend on the rest of your setup. I have no idea what those spring rates are or what the newer Mustangs like. If it does still understeer, then it would be time to go up in rear bar size to balance the car. Essentially this larger rear bar will take grip away from the rear of a solid axle car. The car is then faster overall though because it is better balanced and you can drive it hard without turning the front tires to dust.

I can get my car to understeer or oversteer depending on how stupid I happen to driving at that particular time. If I jerk the wheel at high speeds, it'll snap oversteer. If I jerk it around at slower speeds, it'll push. Now, you may roll your eyes and say "duh, no kidding" but what I'm trying to get at here is that you may spend a bunch on money on parts when really it's the driver that needs attention. I know that's my problem right now and I only learned it a few years ago after I had bought a bunch of stuff I didn't need (and has now been taken off the car).

Finally, sometimes less wheel input is more. In other words, if the car gets into terminal understeer, turn the wheel less until the tires regain grip.
Last edited by Ironhead on Sun Jun 29, 2008 11:32 am, edited 2 times in total.
Korry
1996 Camaro Z28 - 96 ESP
Simple and crude, but effective. The car too.

magilson
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Post by magilson » Sun Jun 29, 2008 11:31 am

The Huff wrote:I really struggle trying to understand all of that. Lets say I get the car to over steer before it would under steer. That doesn't necessarily mean that the car is handling a corner better, but that it is breaking the rear tires loose even before the front ones which already break loose way to easily. Does that make since.
In general oversteer means the rear end comes out which points you too far into a turn and understeer means the front end slides rather than pointing in the direction you'd like it points away from the corner.

On a RWD car:

All things being equal with the suspension - Inducing oversteer on a RWD car is relatively easy so long as you either have a lot of power or not a lot of tire. The trick with RWD is getting enough traction in the rear be it with tire or downforce or suspension so that you can continue to power through a corner without inducing oversteer. If a RWD car understeers it is a matter of applying power to induce oversteer and hopefully create a neutral condition. THIS ONLY WORKS IF YOU HAVE ENOUGH ROOM! In your case there was nothing you could do. There wasn't enough room (hence no playing on public roads) to recover properly from the error made going into the corner.

IN a FWD car we generally "push" or understeer. This is not necessarily the default condition of a FWD car, only that it is most frequently correctly reacted to condition by your average driver and so many manufacturers design the car to react this way. A FWD owner who wants to improve the handling of their car by increasing the size (or more correctly the torsional rigidity) of their rear anti-sway bar. Increasing the size of the rear ASB in effect decreases your slip angle or the max angle your tire can handle before it slips. So it makes your rear tires more likely to slip. Why is this good? Because unlike RWD I still have a useful way of putting down power and so you will often see, when racing head-to-head, that FWD cars will oversteer around a corner and continue to apply power. I have my car pretty neutral when my tires are warm and when I go on my first run I tend to oversteer )which is increadibly fun for a FWD driver :D ) In the case of really good drivers, like Scott in his white rabbit, he can induce oversteer in a stock FWD car with the proper technique (and camber thrust :wink: )

In the end, no slip is best. It means you are sacrificing traction which means you are sacrificing speed. I have a feeling with some practice you can improve your driving with the stock suspension but otherwise consider this:
Here's where it gets really tricky.
If decreasing the size of the rear bar doesn't help enough the next thing you do is
increase the size of the front bar. When the outside front compresses in a corner, it
causes the inside front to compress and may actually lift that tire completely off the
ground. The car is now sitting on 3 tires and guess where the weight that was on
the inside front goes? Outside front? Some of it. The rest goes to the inside rear
where we need more grip. The total weight of the car hasn't changed. It's just been
redistributed, and a sway bar at one end, actually transfered weight to the other
end of the car. Here it is in action on a RWD car.

Image

See the inside front tire off the ground. That translates into more motive grip
at the rear, and thus more acceleration, and believe me, that car rockets
out of corners.
In this case increasing the size of the Front ASB helped by compressing the inside spring so much that it came off the ground. When that happens the weight has to transfer to the inside rear wheel (since the car's center of gravity is still low enough to the ground to make it want to roll back down again) which translates to more grip. So a bigger front anti-sway bar helped.

I wanted you to see the whole story before you just went and bought a bigger front ASB. That way when you do put it in you can know what happens and go from there. In most cases once you start to mess with suspension the game never ends. This is why most people say that you have to really learn your car first before you spends thousands on a car you can't drive to the limits to begin with (and I'm 100% guilty of this!).
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Post by Ironhead » Sun Jun 29, 2008 11:53 am

magilson wrote:
If a RWD car understeers it is a matter of applying power to induce oversteer and hopefully create a neutral condition.
Yes, as you pointed out these cars can be driven quite a bit with the throttle but the above will make it understeer worse. If the car is already pushing and you give it a big dose of throttle, you're going to unload the front tires and it'll push even more than before. Rolling out of the throttle will unload the rear and get it to rotate once the car is understeering.
magilson wrote: In the end, no slip is best. It means you are sacrificing traction which means you are sacrificing speed.
In general, these big cars have to slither around for them to be fast. I don't mean the "Tokyo Drift" type of sliding around but they do need to slide. If you're not slithering around the course, you'll never be fast in one of these things. Also, if you're sliding around too much, you'll never be fast. Note that I'm not just talking about hanging the rear out. You need both ends sliding just a bit.

I used to strive for neat and tidy, slip free runs because I thought the same thing. Then one day I got to ride with Sam Strano. I was shocked at how fast and in control he was and how much the car moved around at the same time. I've been working on finding that sweet spot ever since.

Just a few observations from a big pony car driving guy..... :wink:
Last edited by Ironhead on Sun Jun 29, 2008 12:52 pm, edited 1 time in total.
Korry
1996 Camaro Z28 - 96 ESP
Simple and crude, but effective. The car too.

The Huff
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Post by The Huff » Sun Jun 29, 2008 12:43 pm

I have know problem purchasing a sway bar but do you think it would be worth me just adjusting the rear suspension softer to see if that will correct anything? Or, will that do what I had said in my previous post "break the rear loose sooner than the front" and slow me down even more?


Korry, Thanks for the link to that web site I couldn't remember it after we spoke last week.
Justin Huffman
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Post by Ironhead » Sun Jun 29, 2008 12:50 pm

Softening the rear will give you more grip there. That will make the understeer worse.

FWIW over the years I swapped rear bars back and forth (between stock and larger than stock) as I changed things up front. Basically you need to get yourself as much front grip as you can and use the rear bar to fine tune the balance.
Korry
1996 Camaro Z28 - 96 ESP
Simple and crude, but effective. The car too.

budweeks
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Post by budweeks » Sun Jun 29, 2008 1:43 pm

Well, I'm not real sure I can shed any light on this discussion as I've never tried to set up a street prepared car. I have always been challenged enough to try to get a stock class car right. I have talked to Sam Strano and I agree that he has a lot of good insights into what makes a car fast. And then, he is a fast driver too, but they have to go together.

Having said that, I have learned some things from two sources that you might try. One is from doing skidpad work. Find an empty parking lot, set up a circle maybe a hundred feet in diameter, maybe more depending on how fast you think you should be going, set your pressures to customary, and then go around at a steady speed, smooth but at the limit, and see what happens. This also helps you to find out what the limit feels like. Use the highest gear you can so you can be smoother. Soften the shocks first so you get a baseline, and then you can play with pressures, shocks, maybe camber, etc. You could time it for the fastest speed or just try to get it neutral and to "feel" right. I've done this on many of the cars I've autocrossed. Sometimes I asked permission and went out early in the morning. You also can use a tire pyrometer to check tire temps to get pressures more or less dialed in. I have one you can borrow.

The other source of info is the column by Randy Pobst in SportsCar. He throws out pearls of wisdom just about every issue. Even though he is a road racer now, he started out in solo and continues to respect solo racers in his advice. There is a lot of common ground. A column he wrote in March 2006 (I save stuff like this) addressed cornering set-up. He said think of every corner in terms of entry, middle, and exit, and speed of turn. And he said that most handling issues occur only in one part of the turn, and that is your best clue. I'll quote a bit here: "The middle of a corner is the best place to judge your spring and swaybar setup. The entry is highly affected by brake bias, wheel toe-in and shock settings, especially front compression and rear rebound, because weight is tranferring foward as you slow. The exit is infuenced most heavily by the differential in the drive axel, and by shocks--but now it's the front rebound and rear compression. because weight is shifting to the rear under acceleration." You might be able to get the entire article online through Fastrack (SCCA.com).

Having said all that, I agree that it is easy to change too much too soon. Auto engineers have a lot of resources at their disposal and have put a lot of work into a stock car. They can be improved, but there's nothing wrong with a cautious approach. After all, the aftermarket is in the business of trying to separate us from our hard-earned money. I'll be happy to talk with you more about all this. Send me a pm and I'll give you my phone #.

Bud

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scoTT
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Post by scoTT » Sun Jun 29, 2008 5:28 pm

if I was you... I would give it a season and learn as much as you can from your car... Its amazing what tire preasure, stearing input, throttle input or throttle lift will do on a stock supension car...

I can make my rabbit push like a freight train.... or be as loose in the rear as my dads corvette... its all in what you tell the car to do... and it has taken me a few years to figure that out... and now Im just trying to learn as much as I can with the stock suspension.... I really want sway bars but they will probably slow me down........haha
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2007 VW Rabbit 2.5l

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RacinAlt
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Post by RacinAlt » Mon Jun 30, 2008 11:19 pm

Sounds like too much speed, or b/c the tire blew, I would say a very low tire pressure would have caused this.

Street tires for performance driving is around 40-44psi on most tires. Doesn't do much fo the tread wear patten, but helps with side wall roll.

With suspension, if you make one end STIFFER than the other, the end of the car that you are siffening will NOT be the end of the car that will benifit with additional traction.

Remember slow in and fast out!
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Post by drivehard » Wed Jul 16, 2008 10:52 am

I put a bigger front swaybar on my Integra, and it made a drastic difference, on the understeer. Turn in is awsome.
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Post by The Huff » Wed Jul 16, 2008 3:24 pm

I was going to put a bigger bar in my car but I was advised by Sam Strano "Parts supplier/Racer" and he advised against it. So for now I am just going to try and figure out my car with the upgrades I already have.
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Post by JimR » Wed Jul 16, 2008 3:56 pm

Sam Strano has proven he is the fastest '05+ Mustang driver in the country by winning in F-Stock. He is willing to share setup advice, and I imagine it's pretty good. But, definitely, the universal truism is to learn to be a fast driver before you try to make a fast car.

Another pearl of wisdom I heard from National champion Gerry Terranova: "Most problems begin with too much speed." When the front end washes out in a corner, entry speed was too high, or you rolled on the throttle too early. Swaybars, tires, alignment, spring rates, etc., can only do so much. Everything is still transmitted to the four small contact patches by the driver's inputs.
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The Huff
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Post by The Huff » Wed Jul 16, 2008 4:09 pm

Well put, and I will definately be focusing on my speed into the u turn if there is one this weekend. BTW Who is designing the course on Sunday?
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