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Old 9/22/08, 3:33 PM   #1
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Help me reduce understeer in my car.....

Hi there

I've got my car handling pretty much perfect, but its now so good in the rear its beginning to show up how the Mustang chassis is prone to understeering especially on the Saleens.
My problem mainly comes from roundabouts/islands when taken at high speed I do get understeer, fair enough its not until fairly high speed but the rear end is so planted and could easily sustain much higher tighter corner speeds so I need to look into what I can do to the front-end of the car to try and further reduce understeer or at least dial a bit of if out. Fair enough I get plenty of feel through the steering so can easily drive the car just before where it lets go or allow the car to slide a little when the situation calls for it.

My list of handling modifications so far:-
Saleen Racecraft Suspension (Saleen springs & Shocks/Struts - Factory fit on S281)
Saleen Front Swaybar (Factory fit on S281)
Steeda G-Trac Brace
Steeda Heavy Duty Upper Mounts (Maximum negative camber set)
Steeda adjustable Upper Control arm
Steeda Billet Lower Control arms
Saleen watts-link
Shelby GT500 Rear Swaybar (Part of Saleen watts-link kit)
Lightweight Driveshaft
JDM Engine lowering mounts
Shelby GT500 Brakes
Saleen 20" Chrome Wheels with Pirelli 275/35/20 on front and 275/40/20 on rear (Weigh 71lbs with tyres)

Car does have a Saleen Supercharger fitted and is pushing 480RWHP so obviously the Supercharger adds weight to the front end.

Mods in progress:-
WedsSport or Axis Reverbs 18x10" wheels all round fitted with Michelin PS2 275/40/18. (Weigh 49lbs with tyres)
Stillen 2-piece Shelby GT500 Cross Drilled rotars (4lbs lighter each corner)


1. Do you guys first of all think the much lighter wheels and stickier Michelin PS2's tyres will help to dial out some of this understeer?
2. What else can you recommend to try and improve front-end grip to help dial out the understeer?
I have thought of such things like reducing front-end weight or maybe trying different set of struts/shocks and springs, maybe something adjustable. I would also love to get a strut brace but cannot find anything thats compatible with Saleen supercharger, anybody know of anything else which may help me reduce understeer?
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Old 9/22/08, 4:50 PM   #2
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First things that come to mind are adding more neg camber if possible, like at the strut/knuckle joint, as well as adding a little touch of toe-out. Other than that, try playing with swaybar rates front and rear. You may well find that you just can't plant the front any more, and it'll actually feel better to loosen up the rear some.

You could dump some weight by adding the Steeda lightweight radiator support crossmember, it genuinely helps, particularly that far forward of the front axle. I don't know how much the STB will help, honestly, that's been a pretty hot topic of debate, but I know from factory testing, it takes a LOT of load to get chassis flex...

Also, dumping 20+ lbs per corner in rotating mass will have a profound effect on how the car handles! I would get the new shoes on, then re-assess what you have and what you need.
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Still need more power...
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Old 9/22/08, 10:33 PM   #3
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Quote:
Originally Posted by SoundGuyDave View Post
First things that come to mind are adding more neg camber if possible, like at the strut/knuckle joint, as well as adding a little touch of toe-out. Other than that, try playing with swaybar rates front and rear. You may well find that you just can't plant the front any more, and it'll actually feel better to loosen up the rear some.

You could dump some weight by adding the Steeda lightweight radiator support crossmember, it genuinely helps, particularly that far forward of the front axle. I don't know how much the STB will help, honestly, that's been a pretty hot topic of debate, but I know from factory testing, it takes a LOT of load to get chassis flex...

Also, dumping 20+ lbs per corner in rotating mass will have a profound effect on how the car handles! I would get the new shoes on, then re-assess what you have and what you need.

How much weight does the Steeda drop? Steeda site just says half of stock. I have more important mods to do first, but just curious.
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Old 9/23/08, 4:12 AM   #4
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Quote:
Originally Posted by SoundGuyDave View Post
First things that come to mind are adding more neg camber if possible, like at the strut/knuckle joint, as well as adding a little touch of toe-out. Other than that, try playing with swaybar rates front and rear. You may well find that you just can't plant the front any more, and it'll actually feel better to loosen up the rear some.

You could dump some weight by adding the Steeda lightweight radiator support crossmember, it genuinely helps, particularly that far forward of the front axle. I don't know how much the STB will help, honestly, that's been a pretty hot topic of debate, but I know from factory testing, it takes a LOT of load to get chassis flex...

Also, dumping 20+ lbs per corner in rotating mass will have a profound effect on how the car handles! I would get the new shoes on, then re-assess what you have and what you need.

Hi there

The Steeda piece looks great.

What do you mean by STB?
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Old 9/23/08, 8:34 AM   #5
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IIRC, the Steeda piece saves something on the order of 14-18lbs, is a direct bolt-in swap, and will take far less than an hour to do. You'll need to zip-tie the brake lines and the belly pan to the crossmember, but no issue there, either.

STB= Strut Tower Brace. There has been a LOT of debate about exactly how much they actually do on the S197 chassis. FACT: The S197 chassis, stock, has a LOT more torsional strength than and SN95 or Fox, and has been called equivalent to a fully caged Fox with subframe connectors and torque box reinforcements. One school of thought is that there is sufficient stiffness that the bar will have minimal to no effect in maintaining tower geometry, assuming that the A-arm brace is in place. The other school is that ANY additional stiffness is a good thing. Personally, I think that the benefit just doesn't justify the cost of materials and weight addition at my level of driving skill. I reserve the right to change my opinion if my skills increase to the point where I'm flexing the chassis. I don't think it will happen any time soon, though! Also, if you're doing a brace, make sure it's a solid bar type, and not the bling-tastic kind with heim joints, and lots of bends. If you want to see if the brace is actually doing anything, try this: solidly mount the brace on one side, coat the bottom on the other side with a thin sheet of grease, and leave the mounting nuts loose. This assumes a 2-bolt mounting scheme, obviously. Now, go out and beat on the car (carefully!) then come back in and see if you have any visable grease on the top of the tower. If you do, that implies that the brace has moved in relation to the top of the tower, and you do indeed have flex. If you don't, then the tower did NOT move in relation to the bar, which implies that there is no need for a brace!

I'd still suggest re-evaluating what you have with the new shoes, though, they'll change your chassis dynamics substantially. Once you have the tires on, what I would do, in order: tire pressure tuning, camber tuning (watch your temps and wear patterns!), toe tuning, swaybar tuning, spring rate and damper tuning.
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'06 Silver GT coupe, auto: C&L CAI,Tuned by BamaChips, Mezeire water pump, Roush UDPs, Steeda deletes, Setrab oil cooler, ARH headers, Spydershaft, FRPP 3.73 gears, BMR(springs, bars, UCA, LCA, antisquat)/Tokico/Steeda suspension, Steeda front fascia and race cowl hood, etc.

Still need more power...
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Old 9/24/08, 3:07 PM   #6
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Quote:
Originally Posted by SoundGuyDave View Post
First things that come to mind are adding more neg camber if possible, like at the strut/knuckle joint, as well as adding a little touch of toe-out. Other than that, try playing with swaybar rates front and rear. You may well find that you just can't plant the front any more, and it'll actually feel better to loosen up the rear some.

You could dump some weight by adding the Steeda lightweight radiator support crossmember, it genuinely helps, particularly that far forward of the front axle. I don't know how much the STB will help, honestly, that's been a pretty hot topic of debate, but I know from factory testing, it takes a LOT of load to get chassis flex...

Also, dumping 20+ lbs per corner in rotating mass will have a profound effect on how the car handles! I would get the new shoes on, then re-assess what you have and what you need.
I agree totally. That is going to make a HUGE change in the way it feels. Definently the place to start.
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Old 9/24/08, 10:54 PM   #7
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At the risk of sounding too simplistic, I would work on tire pressures first. Go just a tad bit lower on the fronts and a bit higher on the rears, and that should help stick the front just a smidge, while adding enough rear pressure should help loosen the rear end to make the car neutral in the corners. Again, very simple adjustment that is 100% free.
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Old 9/25/08, 3:40 AM   #8
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Originally Posted by Five Oh Brian View Post
At the risk of sounding too simplistic, I would work on tire pressures first. Go just a tad bit lower on the fronts and a bit higher on the rears, and that should help stick the front just a smidge, while adding enough rear pressure should help loosen the rear end to make the car neutral in the corners. Again, very simple adjustment that is 100% free.
Funny you should mention that, I was about to give the same advice.

On my stocker 17bullits I run nearly 38-40psi rear and 35-36 front. I find that on takeoff it sticks less but in the corners the car stays neutral. The fuel economy has gone up and the car is less bouncy around corners and more predictable. Next up is a watts link for me. Thinking of fays or saleen. Then some 18x9 asa rims with 275x40xr18 rubbers all around.
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Old 9/25/08, 11:51 AM   #9
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Funny you should mention that, I was about to give the same advice.

On my stocker 17bullits I run nearly 38-40psi rear and 35-36 front. I find that on takeoff it sticks less but in the corners the car stays neutral. The fuel economy has gone up and the car is less bouncy around corners and more predictable. Next up is a watts link for me. Thinking of fays or saleen. Then some 18x9 asa rims with 275x40xr18 rubbers all around.
Hi there

Please help me find lightweight wheels that fit out cars, I am pulling my hair out.

Can't get WedsSport TC-005 and now struggling to find Axis Reverbs in stock anywhere and been told those are no longer made any more.

I have found some Enkei RPF1 in 18x9.5" with 40mm/45mm offset but not sure if they will fit or clear the GT500 brakes on my car.

I never though buying a set of wheels would be so hard....
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Old 9/26/08, 2:26 AM   #10
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Hi there

Please help me find lightweight wheels that fit out cars, I am pulling my hair out.

Can't get WedsSport TC-005 and now struggling to find Axis Reverbs in stock anywhere and been told those are no longer made any more.

I have found some Enkei RPF1 in 18x9.5" with 40mm/45mm offset but not sure if they will fit or clear the GT500 brakes on my car.

I never though buying a set of wheels would be so hard....
Well, im going for an all around package. The stock wheels on my 07 are around 51lb. With the rim being quoted @ 26lb. The wheels im looking at getting are the ASA AR1 that are 18x9 and weigh in at 23.8LB witch by far is not the lightest weight wheel but it should be light enough for what im looking for. The tires im looking at are the goodyear eagle f1 all season tires, as my car is a daily driver. The tire weigh in at 30lb as well. So im looking at gaining a coulple of lb per corner but gaining allot more traction and stiffer sidewalls. Coupled with a watts rear and a few tweaks with a tire pressure gauge and im set. I know what you mean about finding the right package, but when your on a budget like I am, the options are allot smaller. I could have bought some 17lb volk wheels for about 800per rim and couple them with some extreme performance sumer tread and be done with it but chances are the volk wheels and extreme tires will hurt me in the wallet in the long run with frequent tire changes and god forbid I crack or hurt one of the volk wheels and im stuck at spending allot of cash for nothing.
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Old 9/26/08, 6:02 AM   #11
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put bigger tires on the front than on the rear. That should fix it
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Old 9/26/08, 8:08 AM   #12
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put bigger tires on the front than on the rear. That should fix it

I wouldn't go bigger front than rear.. if going down that path, put stickier tires on the front.. that might actually help to get closer to even wear front and back... soft front tires wear quickly, harder rear tires but 480rwhp means wear quickly as well.

Another option would be to go to adjustable shocks/struts, favorite for S197 are the Tokico D-specs (what I run) and run the front softer than the rear.

Basically to reduce understeer:
1.) Add negative Camber
2.) Reduce toe-in/add toe-out dependant on current
3.) Soften front shocks/stiffen rear shocks
4.) Play with tire pressure
5.) Play with tire compounds
6.) Play with swaybars
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Old 9/26/08, 5:11 PM   #13
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Originally Posted by Gibbo_UK View Post
I would also love to get a strut brace but cannot find anything thats compatible with Saleen supercharger, anybody know of anything else which may help me reduce understeer?
Not that I think it's all that helpful (honestly don't know), but there is one STB out there made for the Saleen supercharger, but it's way pricey, has joints instead of being solid, but it does only weigh 3.5lbs:

Chicane Series VI Tower Brace

Click the image to open in full size.
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