Rear spring rates for Fox body

[David Love AI27]

I think my rear springs are to big (the car was built for drifting)... what rates are you Fox chasis guys running????

[SmackDaddy]

FYI - 225lb and 275lb depending on the upcoming track event.

All depends on the other suspension parts though. One combination might not net the same or desired results as another one on a different Stang.

Spring rubbers can be the ticket also...especially during testing sessions.

[GlennCMC70]

you need to give some front rate info. the springs need to be matched front to rear. for example, the 4th gens like a 3:1 ratio. that means if you have a 900 front rate, the rear needs to be around one 3rd of that (300). things that will affect that ratio are things like, rear sway bar size, rod ended or poly bushing rear control arms (changes roll rate), rear downforce, and personal driving ability and driving style. tire age is also a big factor in how well the car works. old tires make the car feel as if it has too much spring rate - it feels like it has no grip.
but even if you stick w/in, for example, the 3:1 ratio a 4th gen f-body likes, too much spring rate is a bad thing. your better off w/ too soft than too stiff.
so, unless you fill us in on what front rates you have that your trying to balance the rear rates too, there is no correct answer. i know guys running 1300 lb all the way down to 600 lb fronts on a 4th gen and 325 lb to 175 lb rear rates. getting the car to balance and be nuetral is what is key here.

push = too much rear grip. drop front rates or increase rear rates
overly loose = too much front grip drop rear rates or increase front rates.
dont exclude wheel spacers when tuning your set-up. they can be added to soften a given rate, removed to stiffen a given rate.

so, what is a good ratio w/ a Fox? i do not know. i'm sure the same rules apply and there is one. what is a good rear rate for a Fox? same again, who knows w/out front rate info.
mmmmmmmkkkkaaaaayyyy? :wink:

[jeffburch]

Don't those things use a single pigtail 5.5" just like the f-cars in the rear?
Try the cheap streetstock dirt track springs from Day Motorsports online.
They come in 25# increments and are only like $45 each.
Come in 11 and 12 inch lengths.
http://www.daymotorsports.com/


jb

[SmackDaddy]

From the H&R website:
http://www.hrsprings.com/site/about/manufacturing.html

Another issue that adds to the debate between "Linear" and "Progressive" rate springs, is that when most spring manufacturers say that their springs are progressive they are not! Springs may be wound progressively, but that does not mean that they function progressively. Some suspension springs are wound progressively but function as a linear spring. These springs can be called "dual-stage" coils, but are generally referred to as springs with "dead" or "inactive" coils. Dead or inactive coils are coils that are in contact with adjacent coils at loaded height.

Inactive coils do nothing but give the spring enough free-length to stay tight in the spring perches at full rebound (when the tires and wheels are hanging in the air like when the car is on a lift). A spring that is wound with inactive coils and no progressive coils that are active, is actually working as a linear-rate spring. This is why when you call a spring manufacturer for spring rates for your application you must ask, "What is the actual working spring rate?" This ensures that you do not just get numbers quoted from a design sheet.

For example: A design sheet may have rates of 69lbs. per inch, to 160lbs. per inch, to 220lbs. per inch. When the actual rate is 170lbs. per inch to 220lbs. per inch. As you can see, getting the correct information is important in making a true comparison.

[EV] Read the entire article to get you going and it has a lot of information in it. A lot factors come into play when addressing the Fox body suspension. Besides springs, struts, shocks, chassis stiffness and other geometrical parts, don't forget the TIRES! They are the secondary set of springs on the car!! Set the pressue too high and you just made a nice susupension setup into garbage. Set the pressure too low and it will be more than a handful! Keep this in mind....all the time.

[GlennCMC70]

you shouldnt use a progressive rate spring in a racing application.
although some progressive rate springs will use up all its progressive section from just the weight of the car alone. in that case, they are o.k., but i would avoid them if at all possible.
stick to a linear spring.

[SmackDaddy]

you shouldnt use a progressive rate spring in a racing application.
although some progressive rate springs will use up all its progressive section from just the weight of the car alone. in that case, they are o.k., but i would avoid them if at all possible.
stick to a linear spring.

2nd that one for sure.

[Rob Liebbe]

Too much rear spring in the back can be very bad. Well more correctly put an improper front to rear suspension stiffness ratio is bad. Too stiff in the rear can give the undesireable snap "oversteer" that sent me off of Hallet #1. That was with the H&R Race spring set. The rear was way too stiff. I ended up keeping the H&R Race springs in the front and use a set of Eibach street (10% stiffer than stock) in the rear as well as a stock GT front and rear sway bar setup. So many factors go into this as Glenn has stated. I think that my H&R problem was linked to the fact that the car is a stripped down race car with a lot less weight on the rear than a street car. My street/track car with full interior and spare tire in place never had any problems running a very similar suspension setup with H&R Race Springs but it still has a lot of weight on the rear. That's my theory anyway.

You're doing the right thing by asking. Keep asking and also trying different things. Just go conservative on rear rate. And remember, the Camaros don't have anywhere near the rear suspension bind that the Mustangs do. This will change the 3:1 ratio that Glenn stated. Crappy Mustang rear suspension!!!!!

Best of Luck. Call if you want to talk more - early evenings and weekends are best.

[Boudy]

David: I am currently running linear springs at 900 lb front and 200 lb rear. Not sure if they are right or wrong but that's what it came with and now that the front end is a couple inches wider and the rear is not slapping 1" side to side, it feels pretty good. I was loose on exit @ TWS and RP suggested I remove the rear sway bar which worked well.

Hopefully this summer will lend some time to test other combinations.

Rob: I've got a rotor for you. Thanks.

Boudy

[GlennCMC70]

i've heard Robs means of setting up spring rates all too often. you guys are aware that jumping up and down just 25lbs in the rear rate is a considerable move, right? by limiting yourself to H&R, or Eibach, or MM springs, your moving all over the map in front or rear rates.
why do you guys not get what you need from the dirt track shops in specific rates? we sell off what we dont need at almost zero loss so there is no major risk to doing this.
just wondering.