So I've been studying my autocross videos with a comb, getting a bit antsy with the -40 degrees and snow dump. One thing I've noticed is the car nose dives hard now with the SN95 brakes and hawk HP+ pads, and it seems to maintain that dive through most of the morner if not all.
Now I'm running H&R race springs up front and Superrace springs in the rear, car is stiff. on slaloms or portions where I dont need to touch the brakes the car stays mostly flat and runs very quick and I like the feel.
My car isnt balanced well, its a fox mustang so heavily front biased. battery already relocated to the rear, I've gone since my last videos to aluminum heads so I have done what is simple to change the bias
Now looking at photos the car also has a significant forward rake to it as well, probably from the different series of H&R springs. Now would it be worth my effort to pull the fronts out and add a spacer on top of the spring, maybe 1/2" tall to jack the nose up slightly. I've also struggled with being able to put any sizable amount of caster into the car, would decreasing the forward rake also fix this issue?
I can see having the center of gravity in the front being lower then the rear for the rear weight transfer during hard braking to transfer even more because the rear already has a sort of head start on transferring forward. As well as it may effect it during turns as well.
Im just trying to wrap my head around the mechanics of it, hopefully someone could put in their insight. thanks
The rake does not alter your weight distribution but you are correct in thinking it will cause more oversteer with the rear end higher.
If you're getting that much brake dive you likely need to swap to stiffer front springs. I would recommend going to the super race springs on the front then adjusting the rear sway bar to get your balance back where you want it.
Raising the front of the car will gain you more caster, but it could also be achieved by lowering the rear. Are you using adjustable camber plates?
Between the rake, higher spring rate in the rear, and how front heavy these cars are I'd imagine it has way too much oversteer in it's current configuration.
What sway bars are you using?
In reply to Patientzero :
Its actually the opposite, it pushes hard in corners. The heavier rear springs were a plan to try and help the car rotate around a corner better. Infact watching videos lately Im noticing the only time the car seems to turn well/at all is throttle induced oversteer, or snap oversteer. The car turns well on throttle but off it really struggles.
I'd like to raise the front at least 1/4-1/2" at the moment in hard turns I have a bit of a tire to fender rub up front, and I think the bit more height will remedy this. Maybe get it truly flat by trimming a bit of rear coil as well. I dont have weight jacker rear control arms, only M/M rear lowers
Currently Im running a factory 1-5/16" front bar and its a factory SN95 rear bar, solid 24mm I think
The Car has M/M caster camber plates with camber bolts, the alignment is 1/8" toe out, 3 degrees camber and its maxed out the caster at about about 1.8-2.0 positive.
Thank you
"Infact watching videos lately Im noticing the only time the car seems to turn well/at all is throttle induced oversteer, or snap oversteer."
This I think is telling, without having experience with that body style I don't know where I'd start.
But it certainly is too tight if it snaps loose, this makes it difficult to drive because you have to force oversteer and it is easy to go too far, and leaves little margin for corrections.
Maybe a combination of adjustments, you have not mentioned messing with tire pressures.
Yes, I would lower the rear raise the front maybe a smaller front sway bar and heavier front springs.
My Challengers all wanted reverse rake. If you daily the car you will not like stiffer springs and it will eventually soften the FoMoCo Origami.
Which brings another question regarding stiffness of the front half of the car does it have adequate bracing? Many of the off_the_shelf bolt on braces I have seen place form over function and have insufficient rigidity. A bent tube needs a lot of diameter to retain any kind of rigidity. https://www.youtube.com/watch?v=CKgCh6ttDGc Is lower bracing needed on those models?
In reply to bentwrench :
Tire Pressures i've played with significantly, usually using a tire marking pen to find when the tire is getting a slight bit of roll over, usually to the edge of the actual tread itself without spreading onto the sidewall. That I use as my baseline. Usually I find the car will get faster with about 3-4psi less then my "baseline" in the rear and leave the front alone. If I remember correctly the average pressures I was running was 38-40psi front and 26-30psi rear.
Car has 275/40R17 BFG GForce Comp2 tires front and rear.
Def going to level the car out and see if it helps, hopefully will be able to get 4 degrees of caster
The car does have weld in subframe connectors, front strut brace and a K-member brace. These cars are a bloody wet noodle if I say so myself lol, I do plan on adding a few strength gussets onto the strut brace in the near future
I seem to recall that the camber curve is so bad that the the fast guys run astronomical front spring rates.
I would assume that the snap oversteer is due to the rear suspension going into bind (it doesn't have to travel much at all for this to take place) and the already stiff spring rates are effectively much more stiff when that happens. Front has roll center issues, I think, along with bump steer and some other things from the factory.
I think the car should be at factory ride height if you haven't done anything serious to the front and rear suspension, like going to an aftermarket SLA kit on the front and a 3-link on the rear. Folks here have autocrossed Fox/SN95 Mustangs quite a bit so hopefully they show up to help provide good first-hand experience in what worked for them.
In reply to mfennell :
Yes that is very typical. Another way I've seen to counter it is to run a lot of static Camber and max caster. As the suspension compressess it looses camber very quickly 
stock front springs are 425Lb front and 180lb rear
Average lowering springs are 475-525lb front and 225-250lb rear
H&R race springs are 980lb front and 340lb rear
H&R Super race are 1060lb front and 360lb rear
I've got what should be considered the common place stock coil location heavy autocross style spring
What is your differential set up? A locked Diff will most certainly produce the results you're getting of plowing when off throttle, and ass out when on throttle
In reply to _ :
3.73 ratio, factory Limited slip. Packed using 6 of 8 friction disks. it will spin both reliably but it is on the lower tolerance of the stock spec
By using stiffer springs in the rear to help it "rotate" you're just reducing grip on that end to compensate which is lowering your total grip. To get more front end grip on these cars you need more front spring and stiffer front sway bar.
In reply to Patientzero :
could I maybe try stuffing my old eibach pro-springs in the back with the H&R up front and see if it helps it rotate?
When I raced my Mustang (1993 Cobra) I used a 1 3/8 front bar. Their not common but their out there.
In reply to jimbbski :
It seems from what I've seen many people actually claim the front bar is too big on these cars.
This may solve some issues in my trying to explain, this is one of the videos Ive been studying and remembering the sort of troubles I was having
Patientzero said:
By using stiffer springs in the rear to help it "rotate" you're just reducing grip on that end to compensate which is lowering your total grip. To get more front end grip on these cars you need more front spring and stiffer front sway bar.
This. Rake may play a factor, but the immediate issue that jumps out to me is your spring & bar setup.
Rushcanuck said:
In reply to jimbbski :
It seems from what I've seen many people actually claim the front bar is too big on these cars.
I was running a 1 3/8" Steeda front sway bar with 425lb front springs and 325lb rear springs. I went throught a several day long email conversation with Jack at Maximum Motorsports about how to get more front end grip. He recommended I drop back to 275lb springs on the rear and upgrade to an Eibach front sway bar with MORE rate.
Obviously our setups are different so the specifics will change but the premise is the same. People on the Road Race and Autocross Mustang page on Facebook have echoed these same thoughts.
Patientzero said:
Rushcanuck said:
In reply to jimbbski :
It seems from what I've seen many people actually claim the front bar is too big on these cars.
I was running a 1 3/8" Steeda front sway bar with 425lb front springs and 325lb rear springs. I went throught a several day long email conversation with Jack at Maximum Motorsports about how to get more front end grip. He recommended I drop back to 275lb springs on the rear and upgrade to an Eibach front sway bar with MORE rate.
Obviously our setups are different so the specifics will change but the premise is the same. People on the Road Race and Autocross Mustang page on Facebook have echoed these same thoughts.
I'll defidently try running my old rear springs then, they are 250lb. And if I remember correctly they also made the car sit a bit lower in the rear might solve my forward rake issue too and give me a better starting point before dumping more money into it without proper reasoning.
I don't think you get what we're trying to tell you. You need to change the FRONT. Going to a lower spring rate on the rear will make it grip better and cause more understeer.
You need to STIFFEN the FRONT.
Also, the spring rates running are on coilovers. This is going to be very different for stock location springs. Plus my car is just over 3000lbs.
In reply to Patientzero :
last post you stated M/M said for you to drop your rear rate from 325lb to 275lb AND change the front bar. I thought it was a bit odd that they said to change the rear spring to lighter as well because that will cause an increase in grip and thus make the car understeer worse. I guess i just went with it and decided to jump to the conclusion to trying my old rear springs I've already got.
I do understand the difference with a coilover vs a standard spring location its nearly half the rate due to the position of the coilover vs location of the stock spring. Ex. your 425lb front spring is effectively/approximately a 850lb spring in a stock location. Im currently running a 960lb front spring.
I'll look into upgrading the front bar, sorry for any confusion, thank you for the help
In reply to Rushcanuck :
Close, it's probably better to look at it in terms of wheel rate. The front is 25% for a stock spring and around 85% in a coilover setup. So if you were aiming for a wheel rate of 300lb/in it would require a coilover rate of 345lb/in but a stock location spring would have to be 1200lb/in. The rear springs are 50% due to the location on the lower control arm with a coilovers setup actually being 110% because it's located behind the axle centerline.
Your front H&R race springs have a wheel rate of about 200lb/in and and with the super race springs in the rear the wheel rate is about 140lb/in.
Compared to my coilover setup with 425/275. My wheel rates are 360lb/in front and 300lb/in rear on a lighter car.
My point about reducing the spring rate in the rear is that my line of thinking was the same as yours. I thought I could use more spring rate in the rear to help the car rotate to offset the lack of grip in the front. This may make the car more "balanced" but you're not gaining grip on the front, you're just reducing mechanical grip on the rear to compensate. Making your total available grip less.
In actuality you should keep your Super Race springs on the rear and get the matching springs for the front because what you have is already too soft.
This is the info I found for H&R Foxbody springs.
H&R Sport Springs= Front: 490-575 lb/in, Rear: 250-285 lb/in
H&R Super Sport Springs= Front: 700-760 lb/in, Rear: 275-300 lb/in
H&R Race Springs= Front: 750-850 lb/in, Rear: 260-280 lb/in
H&R Super Race Springs= Front: 950-1050 lb/in, Rear: 260-300 lb/in
The reasoning behind adding more spring rate to the front is that these cars have very bad camber gain. Meaning as the shock is compressed(such as body roll going through a corner), the body rolls more than the strut gains camber due to it's arc. So the more body roll you have, the more camber you loose which in turn loses grip. You want a stiff spring to keep the wheel in it's "sweet spot". Increasing your caster will also help increase camber when the wheels are turned. Your 2 degrees is not enough. You need to be in the 4-7 range. Really as much as you can get.
In reply to Patientzero :
that makes more sense. this car is already nearing becoming difficult to street drive with the coils it has, I might have to start looking into going to a coilover setup, basically havent because the tires will rub the coil. I've got about 3/8" of clearance as it sits right now. But the fact you have have a higher wheel rate without the massive increase in road harshness is becoming something I've got to look in to as well.
Right now for unknown reasons I've got the caster camber plates absolutely maxed out for caster. hoping that that maybe solving my rake issue might be the culprit to why the car cant get any more caster out of the car. I've even tried pulling the K-member as far forward as I could and cut the strut tower hole as big as there is still structure.
