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Discussion Starter · #1 ·
I know this isn't pertaining to a Mustang, but since I've been on this particular forum for quite some time I have learned a few things from some knowledgeable people here.

Anyway, this car is a nose heavy, v6, front wheel drive car [lets try to leave the make out of it if we can, its not a chebby] curb weight is 3270 with a 62/38 front to rear weight. McPherson front strut setup with the exception of having struts on the sway bars instead of links.

So, from what I have learned here on this forum is that front heavy cars UNDERsteer. To reduce that several things have to be addressed.

Some of the things to correct this would be a smaller sway bar, and since this particular car is a sport model it has a bigger sway bar than all other models.

I have another car of the same make/model that I'm trying to sell, and its a 4 cyl version with a smaller sway bar, and lighter 4 cylinder front springs.

I was thinking that since I do have the other car it might not be a bad idea to swap parts IF it will help reduce my car's tendency to understeer.

Oh, and for the record this car was hailed in Car/Drive mag as having a very good flat turning going into the curbs in stock form, but I'm thinking thats just the feel you get with a huge front bar, which is misleading.

What do you guys think?
 

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More camber and pay attention to tire pressures can be cheap or free. If it is front steer (tie rod in front of ball joint) then more camber will add toe out, which can be a good thing. The opposite is of coarse true for rear steer.

For autocross type use, a larger front bar can make difference. It will help in transitions, steady state not as much, but since autocross is essentially a string of transitions, a larger bar can be worthwhile. For a while there was a rwd/awd philosophy of a HUGE front bar + tiny rear to get the desired turn in + the rear grip to power out. For fwd, my opinion would be bigger at both ends, front for turn in, rear to help the back end catch up.

John
 

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In my opinion, oversteer when driving spiritedly in a FWD car is a something to be enjoyed. That suggests that it's fairly well balanced, unusual as most cars come from the factory with understeer dialed into their suspension.

If you are experiencing oversteer you can correct it 2 ways.
1. Stay on the gas / brake less aggressively. Controlling vehicle dynamics will reward. The car is already front biased so work with it.
2. If it's a bigger issue then adjust it by following:
a. If the oversteer occurs at the start of a turn, Shocks control transient response, so softening the rear/stiffening the front damping would be correct.
b. If the oversteer occurs past the middle of the turn, Softer rear spring/bar rate or stiffen front spring/bar rate would theoretically be preferable.
This is assuming alignment and pressures are already optimal. Tire pressure adjustments are a great fine-tuning tool especially good for track day when there is no time for other adjustments.
 

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Discussion Starter · #4 ·
In my opinion, oversteer when driving spiritedly in a FWD car is a something to be enjoyed. That suggests that it's fairly well balanced, unusual as most cars come from the factory with understeer dialed into their suspension.

If you are experiencing oversteer you can correct it 2 ways.
1. Stay on the gas / brake less aggressively. Controlling vehicle dynamics will reward. The car is already front biased so work with it.
2. If it's a bigger issue then adjust it by following:
a. If the oversteer occurs at the start of a turn, Shocks control transient response, so softening the rear/stiffening the front damping would be correct.
b. If the oversteer occurs past the middle of the turn, Softer rear spring/bar rate or stiffen front spring/bar rate would theoretically be preferable.
This is assuming alignment and pressures are already optimal. Tire pressure adjustments are a great fine-tuning tool especially good for track day when there is no time for other adjustments.
Its understeer I'm experiencing NOT oversteer, sorry for the mixup in my OP. Of course the best would be a neutral balanced car, with a tad of understeer. [vs snap over steer in a curve].

I'm speaking about a road racer not really an autocross car. Sorry for leaving that out.
 

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So, from what I have learned here on this forum is that front heavy cars over steer.
Front-heavy cars tend understeer, in other words, you get less front grip and vehicle rotation than you'd expect for any given amount of steering input. Also known as "push".

Some of the things to correct this would be a smaller sway bar, and since this particular car is a sport model it has a bigger sway bar than all other models.
Most front-wheel drive under-steering cars respond well to a larger rear swaybar. It's not technically the best way to do it, because you're taking away grip in order to make it happen, but the net result can be better. If you're talking about the front bar, yes, it's possible a softer bar might help.

The bottom line is any time you add roll stiffness (e.g. through stiffer bars), you reduce lateral grip at that end of the car. The exception seems to be when the car has such poor camber curve, or poor dynamic geometry, that the grip lost to load transfer is outweighed by the grip that is no longer lost to positive camber gain in roll.
 

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I thought that it was really unsusal for a fwd to oversteer but his mention that C/D mag lauded the car's handling made me consider it a possiblilty. Funny how one word under vs over makes such a difference in life. ;)
 

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Discussion Starter · #8 ·
Musta been typing before my brain could catch up. I meant under steer.

I know some of the replies weren't making any sense, now I know why.........lol.
 

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Discussion Starter · #9 ·
Would changing out to the 4 cyl springs up front help the understeer issue?

Hey, their free until I sell the car. The 4cyl car I'm selling might feel a bit stiff, but I don't think the new owner would notice.
 

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Assuming the car has a strut suspension and therefore likely has a crappy camber curve, not gaining enough negative camber as the body rolls, I'd be more inclined to stiffen the rear first.
 

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Discussion Starter · #11 ·
Assuming the car has a strut suspension and therefore likely has a crappy camber curve, not gaining enough negative camber as the body rolls, I'd be more inclined to stiffen the rear first.
Ok, got it. The rear has the biggest bar available for that model car so I'm good there. I will play with higher rate springs in the rear, and just leave the front alone for now.

Hopefully I can get my hands on a coil over kit which will make spring changes a bit easier.
 

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Musta been typing before my brain could catch up. I meant under steer.
You could go edit your post to fix that, so that newcomers to the thread don't have to read through the whole thread wondering what the hell you're talking about. :)

Would changing out to the 4 cyl springs up front help the understeer issue?

Hey, their free until I sell the car. The 4cyl car I'm selling might feel a bit stiff, but I don't think the new owner would notice.
I would tend to agree with MFE. The vast majority of my auto-x time is in my Subaru; although Subies are AWD, their behavior is more FWD-ish than RWD-ish (well, expect maybe the STI with it's fancy center diff, but that's neither here nor there...). In the Subaru world guys have gone to bigass front sway bars to reduce the body roll and try to keep the outer front tire from rolling over into positive camber.

Typically to dial out understeer you would soften the front or stiffen the rear, so your thought to try the lighter/softer 4cyl front springs and swaybar would be correct. But in this case, as MFE said, many McP strut cars don't have great camber curves, so if you soften the front you get more body roll which means you go into positive camber on the outside front and you get more understeer rather than less.

So in addition to stiffening the rear you might try a bigger front bar, if one is available.
 

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MacP front? Get as much negative camber as possible and very stiff up front. FWD try 1/4" toe out. If caster is adjustable max that out as well. A tire pyrometer is very valuable here.

Balance the car from that point by stiffening/softening the rear. We race against a lot of FWD cars, they can handle well with the right set-up. An LSD will pay big dividends if available.
 

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My first autocross car was FWD - a 1989 Ford Taurus SHO with the Yamaha V6 DOHC motor. They can be made to handle pretty good.

https://www.youtube.com/watch?v=sKDuoZeikVw

It had MacPherson struts in front and a heavy front ( iirc 65% front distribution ). I was running coilovers with Koni shocks (dont' remember the spring rates) and no front or rear bar. The Quaife differential helped quite a bit as well.
 
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