Boss 302 front springs/change rear too or leave V6?

[Duane Black]

I'm the poor high school teacher out here making due in a world if coil overs and GT350 cars so just bear with me...

I've tracked for 4 years now on stock v6 springs. If i ever had a set of 14" brakes and coil overs I'd never know what to do with myself.

So i found the boss 302 springs in our very own classified section and pounced. While i await the ups man eagerly next week, I'm I'm wondering....

Should i put in the whole setup, or just the front? I would be tempted to say the whole setup since the Boss 302 is alleged to be the quintessential Mustang in regards to its handling. To run that spring setup would be essentially be to have an underpowered slightly lighter Boss 302, rightttt?

In tuning stages in the past, i have two major experiences regarding rear rate changes. In 2017 when i ran 3-4 track events a year and 12-15 autocrosses, i bought a set of koni yellow struts and shocks. Several autocross events later, unablw to find a balance, i removed the rear shocks in favor of the OEM stuff and left the koni adjustable front strut in. The rear end was too unpredictable and i couldnt get back to throttle and lean in the rear of the car again until the factory shocks were back in. Im still running said struts/shocks setup, and it restored a neutral feel to the car again.

I understand springing a car and damping a car are different. My second experience regards that lateral spring we have, the sway bar. Last year i hooked up a set of Strano bars. A member here whom i cant recall predicted since my car was so soft, id likely prefer both bars at full stiff and they were correct and i run both bars at full stiff today, rain or shine... to me, the car was too understeerry at medium and is near neutral/slight oversteer at full stiff in the rear.

I suppose the correct answer may be to swap in the front and experiment with the back

For what its worth, when im driving a simulator, i generally prefer a stiffer front to rear setup as it seems to let me lean on the rear end more.... which supports my preference concerning shocks a couple of paragraphs ago.

So in conclusion, your honor, the debate point is to put in the front boss 302 and leave the back alone, which would put them near equal to the rear springs in rate (148F/156R) or swap in both as theyre designed to work together? (148F/186R, numbers per @Grant 302 pinned post in this subsection compiling all the rates for us, for which i count myself among the many who owe him gratitude)

 

[Mad Hatter]

I think those spring rates for the Boss are due to the OEM 255 and 285 size staggered tires... What size are you running now?

 

[Grant 302]

I’d try it both ways, but would do the fronts alone first. Maybe go one softer on the front bar for the first test.

And thanks for the kind words...but nobody owes Grant anything!

 

[Duane Black]

@Mad Hatter , i run 255 squares in the wet, 285 square in the dry

 

[Mad Hatter]

Grants to modest!!! He is way behind in updating his OPM total!!!

 

[Grant 302]

Grants to modest!!!

False.

He is way behind in updating his OPM total!!!

True.

 

[Duane Black]

@Mad Hatter , curious, how does tire width and stagger impacr yiur spring recommendations?

 

[Mad Hatter]

its all related!! When you go square you add grip up front which means you can go to a stiffer front bar and go to a smaller or no bar in the rear for grip on corner exit. Same goes for the springs, Most of the track mustangs here have 450# to 800# front coil over springs and 250# to 450 rears... Followed AJ's setup with 500F/300R springs while Terry Fair method has had success with 800# up front. Tried 600# upfront but made jumping curbs too hard on the suspension (at least for me).

Tons of info here on TMO.
https://trackmustangsonline.com/threads/going-square-what-is-needed.7928/

The fact you have a V6 means you have less weight over the front wheels and and can probably get on the throttle a little sooner since you have less power. I would guess that you could do spring rates that would be little closer front to rear.

 

[Duane Black]

@Mad Hatter , I agree and understand that even with Boss springs, I'm running half the rate of the real pros around here.

I wonder if Billy Johnson would be around to tell us why Ford upped the spring rate in teh front AND rear for the Boss 302. They also dropped it just a touch up front for the Boss 302 Laguna Seca vs "regular" Boss... and upped the rear rates a touch again.

Perhaps on the stock rates, you haven't gone hard enough on the back to make it so that it causes oversteer anyway. I understand the Boss 302 from the factory eliminated a lot of brake dive and felt more "sure" of itself when steering into a corner.

This info makes me think I'd be best off with both springs swapped in. Chassis dynamics and what I've liked in simulators, however, tells me to run Boss 302 front/factory rear to achieve a better balance.

It's odd to me that over 45 years, Ford has similar characteristics across multiple cars. When going over bumps in the road at least, it seems like my 1968 Torino and my fiance's 2012 Focus have a similar feel with a stiffer rear, and my Mustang has a stiffer rear.... very odd. IT's apparently part of the Ford way...



.... edit: perhaps part of putting in stiffer rear springs in the S197 is that the performance models (Boss 302, GT, etc.) often had a staggered tire setup? Or was that just the S550 track pack and performance packs? Stiffer rear springs/sway bar would offset the understeer of the tires....

 

[Mad Hatter]

Yes, too

edit: perhaps part of putting in stiffer rear springs in the S197 is that the performance models (Boss 302, GT, etc.) often had a staggered tire setup

I would say that brake dive in the Boss is anything but eliminated!!! For springs I really liked the Ford P setup. they go well with the Koni yellows as well.