Ford Racing Boss 302 Springs...

[Boss 738]

Boss 738
Do you have the trans scoop installed?

Yes currently it is still installed

 

[VoodooBoss]

Boss 738

Do you have the trans scoop installed?

The scoop is pretty stout and can take several scraping with no major damage. I only know of one owner that has replaced their scoop because of damage...so far. ;D

 

[mardis]

Lots of talk here on springs and thought I would add my $.02.

I could not wait for Ford, so we went with the Steeda Sport/Comp Boss specific springs. Steeda claims a .800" drop in the rear and a .200" drop in the front. I took my measurements off a flat concrete floor, with all tires at 34PSI, and a full tank of fuel. Measurements were made from floor through spindle/axle centerline to wheel lip opening. Did a before, and an immediate after the Steeda spring install. Right height was lowered 1.000" in the rear. Fronts, there was no change at all. I have had the springs installed for about 6 weeks, and fronts have "settled" approx. .062" or a 1/16".

Panhard bar was a necessity, and we installed the BMR adjustable. Rear end settled to the drivers side just a hair under 1/2" after the spring install. Was able to get the rear back to within 1/16" of what I feel is center. Took my measurements from face of rear brake discs, to a plum bob taped to rear fender arch.

A before and after...pardon the indoor photos.

 

[2012-Boss]

Looks good. What brand wheels, model, and size are those in the "after" photo? TSW's?

Thanks.

 

[DGRacing]

They look like RTRs to me !

 

[steveespo]

Ford Racing '12 GT 500 wheels. Very nice.
Steve

 

[ford20]

My guess is TSW, they aren't concave so they can't be RTR or Avant Guarde M310s. They definitelyn aren't SVE Drifts or the AMR wheels, they could be the SVTPP wheels but they spoke spaces seem a bit big though.

 

[steveespo]

I rescind my vote, I zoomed in and think AMR now. Good eye Ford20, still like the look.
Steve

 

[Justin]

any word on the spring rates yet on these springs?

 

[mardis]

Those that guessed TSW's are correct. I went with the stock sizes...19 X 9.5 for the rear and 19 X 9.0 for the front.

I re-mounted the stock Pirelli's for now.

 

[DGRacing]

I think the spoke pattern and finish on those wheels are replicated by a few brands (AMR, RTR, Ford, BBS) etc. ;D

 

[ford20]

any word on the spring rates yet on these springs?

My bad, I missed the post. I will PM Kelly tomorrow and see if he can get me the spring rates for you. Sorry about that.

 

[Justin]

My bad, I missed the post. I will PM Kelly tomorrow and see if he can get me the spring rates for you. Sorry about that.

thanks!

 

[Orange]

Nice. I'll add a couple.

Mustang GT (2011+) Stock: Ft 122 lbs/in Rr 154 lbs/in *
Brembo Stock: Ft 131 Rr167 lbs/in
Boss Stock: Ft 148 Rr 185 lbs/in
Boss LS Stock: Ft 137 Rr 191 lbs/in
Eiback Pro-Kit: Ft 159 Rr 193 lbs/in *
M- 5300-K rate: Ft 173-248 lbs/in – Rears 195-236 lbs/in
Steeda Competition: Ft 225 Rr 185 lbs/in
Steeda Sports: Ft 200 Rr 175 lbs/in
Steeda Boss Springs Ft 225 Rr 195 lbs/in
Steeda Ultra-lite (pn 555-8206) 1.25/1.5 front: 195lb/in / rear: 175lb/in

* Sourced from Maximum Motorsports website.

Can someone please explain why the front springs are all so much harder compared to stock than the rear springs which are sometimes even softer?

Wouldn't something like that not be a good setup: For example only taking the rear springs of the Steeda Boss package and not changing the one in the front?

 

[Brandon302]

Can someone please explain why the front springs are all so much harder compared to stock than the rear springs which are sometimes even softer?

Wouldn't something like that not be a good setup: For example only taking the rear springs of the Steeda Boss package and not changing the one in the front?

It may be for the same reason that, even though Ford recommends shocks at 5 all around, I was faster with the rears softer then the front since it allowed for a little movement instead of being so stiff it slammed.

 

[boro92]

It may be for the same reason that, even though Ford recommends shocks at 5 all around, I was faster with the rears softer then the front since it allowed for a little movement instead of being so stiff it slammed.

This, and also a strut front end car benefits from a higher front spring rate (proportional to the rear). Most track and race cars you'll find stiff front rates vs the rear on a Mustang. Crisper turn in, and less understeer (counter-intuitive I know). I've written about this at length in another thread.

Don't be dismayed by the higher rates though. 225lb/in front is still very mild. Some people run higher than 225lb/in in the rears alone on the track--let alone the front.

FWIW if I recall correctly, the 302s was somewhere near 500lb/in up front. Which honestly I'm not sure about that being enough in our street weight cars (302s is much lighter, so it get's away with less spring). My old track car was 300 to 400lbs lighter than the boss, and despite running 460lb/in and I could have gone stiffer (but FWIW, I didn't run a large front bar either).

What matters most is the wheel rate--not spring rate. Each end of the car has an effective motion ratio. So although the spring can be a stiffness of X lb/in, the stiffness drops down to Y lb/in where the wheel is mounted. This is due to geometry, mounting points and ultimate design of the car.

 

[captdistraction]

Am I crazy, boro92 or do you have that backwards?

I was always under the impression Audi lowers the rears of their cars more (reverse rake) to help with the engine being past the front wheels in most of their cars.


I could be crazy though.

 

[boro92]

Am I crazy, boro92 or do you have that backwards?

I was always under the impression Audi lowers the rears of their cars more (reverse rake) to help with the engine being past the front wheels in most of their cars.


I could be crazy though.

Rake would affect weight distribution as well as roll center. But for purposes of spring rate discussion on a macpherson strut car, a stiffer front end actually reduces understeer. A higher front rate is a compromise, like many things in suspension tuning.
On a strut car, the higher rate prevents/reduces the camber from going positive because the spring is compressing less (so the car rolls less). The spring rate becomes especially important once roll center drops, as the car will have a greater tendancy to roll.

The traditional wisdom of "whichever end is softer will have more grip" is true, but is also a generalization. It doesn't consider geometry and suspension design.

 

[Orange]

This, and also a strut front end car benefits from a higher front spring rate (proportional to the rear). Most track and race cars you'll find stiff front rates vs the rear on a Mustang. Crisper turn in, and less understeer (counter-intuitive I know). I've written about this at length in another thread.

Don't be dismayed by the higher rates though. 225lb/in front is still very mild. Some people run higher than 225lb/in in the rears alone on the track--let alone the front.

FWIW if I recall correctly, the 302s was somewhere near 500lb/in up front. Which honestly I'm not sure about that being enough in our street weight cars (302s is much lighter, so it get's away with less spring). My old track car was 300 to 400lbs lighter than the boss, and despite running 460lb/in and I could have gone stiffer (but FWIW, I didn't run a large front bar either).

What matters most is the wheel rate--not spring rate. Each end of the car has an effective motion ratio. So although the spring can be a stiffness of X lb/in, the stiffness drops down to Y lb/in where the wheel is mounted. This is due to geometry, mounting points and ultimate design of the car.

Thanks for the different feedbacks, but why has Ford not done that already instead of selling track ready cars with such a low spring rate?

And yes, as you see I am newbie in this area. :

 

[boro92]

Thanks for the different feedbacks, but why has Ford not done that already instead of selling track ready cars with such a low spring rate?

And yes, as you see I am newbie in this area. :

I think street cars have strict NVH requirements that they must adhere to, so it's difficult to spec out a properly suspended street car.
In addition, as rates go up, so does wear. I suspect many people would be bummed to be replacing bushings, balljoints etc in what is perceived as premature intervals due to the extra stresses chassis components take with stiffer suspension.

Most street macpherson strut cars are sprung so that the rear rates are higher than the fronts. This is to bake in some safety understeer at the limit. BMW does this as well, and takes it a step further and specs some wimpy factory recommended tire pressures (IIRC it's 31psi front, 34psi rear on my old M3).

Ford's true track ready cars have diffrerent spring rates, and you'll find the ratio/balance of front rate vs rear rate differs greatly when compared with our street cars.