TheCheeksMcDuke
That guy
Re-post, Blah blah blah
Original Thread here
http://www.moddedmustangs.com/forums/99-04/239965-un-official-suspension-guide.html
This was compiled as a companion, or Cliff Notes, to Official Suspension Guide and major portions of the information found here was copied DIRECTLY from that thread. I have received permission from ModMustang97GT to do so and has been on several other forums for since July '09. This was done due to the information contained in ModMustang97GT's thread is wonderful, but spread out over many pages, as it was compiled over many months. THIS thread was compiled at a single sitting, more or less, and therefore able to take relevant items and place them in an easy-to-access format.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
HOW I SEE IT
Before we begin, I would like to touch on a few things about suspension and its modification. I don't see suspension mods as ONLY for auto-cross or the 1/4 mile or even the race track. I see a well operating suspension as a way to improve the driving experience every time you get behind the wheel. If you go to the store for a 1/2 gallon of milk or over the hills and through the woods to grandmas house, you should enjoy your drive. If one installs a Kenne Bell or Whipple to get the rush of quick acceleration, does this mean that he/she romps on it at every stop light? Anyone that is running 350+ HP can "feel" the energy and power under the hood and most of the time, it's enough just knowing it is there. I see a nice suspension in the exact same way. I don't rip around every corner and push the limits of man and machine everytime I head out. But... I have the ability to take a nice corner and "feel" that my car and I are capable of soo much more and that, my friends, is enough most of the time. Now... down to bidness!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I would like to state that this is NOT a completely original post. I have received permission from the orginal author to copy/paste his information into this thread. I have contributed very large portions of information, so would be safe to say I am a co-author and would appreciate any/all input to its accuracy and completeness.
The information in this post has been gathered from many peoples questions/input over the course of several years and compiled here for convenience. Furthermore, this post deals specifically with geometry issues as they pertain to fuction of the suspension components as they work together in a general manner. Issues of roll center and roll axis are effected with some of these modifications and are beyond the scope of this post, so therefore, not addressed.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
What is the ULTIMATE goal for your ride?
Before we get started here, I would like to mention two things that are VERY important for those considering modifications found within this thread. The first being that suspension can be quite difficult to do efficiently, as one often ends up replacing parts that were thought to be great and only to find out later needs have changed or the decision was a bad one. A real good example of this is the common purchase of aftermarket lower control arms (LCA's). This is great, but depending on the design, additional problems can arrise due to how they interact with other components within your suspensions travel. I have much information explaining the differences between designs so that one can better understand how your car will respond to such modifications. Secondly, with maybe one or two exceptions, the modifications listed here will create addtional Noise Vibration Harshness (NVH) to your driving experience. There is really no way to build a Mustang that eats corners for breakfast and rides like it's just off the showroom floor. That being said, one does not have to use earplugs to drive a corner-killer, just turn the stereo up a bit louder to overcome it! If you would like a car that will hold its own with a higher-end BMW or Corvette... you will need to spend some money for coil-over shock (CO's) with serious modification to the rear axle geometry to compete. This means, your OEM located springs are no longer needed and your existing shocks and struts will very likely need to be replaced.
This info is really focused on the Fox Body ('79~'93) and SN95 ('94~'04) Mustangs. Much of this information is relative to the '05+ models (S197), but does not apply in some cases. The '99~'04 Cobra is also an exception, to some degree, as it is has independent rear suspension (IRS).
Glossary of terms:
AX ~ auto-cross
CC ~ caster/camber
CO ~ coil-overs
Fox Body ~ '79~'93 Mustang
Fox chassis ~ platform used by '79-'04 Mustangs. Used on many '80s era Ford RWD cars. Full list can be found here. '94-'04 use a revised version called "Fox-4".
FRPP ~ Ford Racing Performance Parts
IRS ~ independent rear suspensin
ISOS ~ spring isolators
LCA's ~ lower control arms
NVH ~ Noise Vibration Harshness
PHB ~ panhard bar
POLY ~ polyurethane
S197 ~ '05+ Mustang
SFC's ~ sub-frame connectors (FLSFC's = full-length)
SLA ~ short-long arm
SN95 ~ '94-'04 Mustang ('99-'04 often referred to as a "New Edge")
SRA ~ solid rear axle
TA ~ torque arm
UCA's ~ upper control arms
WL ~ Watts link
The Mustang suspension: The Mustang suspension was poorly designed for high performance driving, therefore is good, but not great. The 4-link design that was incorporated in to the rear suspension between '79~'04 ('99~'04 Cobras excepted). It uses two lower control arms (LCA's) and two oddly angled upper control arms (UCA's) to position the axle side to side, prevent axle wind up and transfer force from the wheels to the chassis. Axle articulation is the main issue with the 4-link and leads to geometry problems in addressing the bumps and ruts of your everyday street. Axle articulation is seen when one wheel is up inside the wheel well and the other is down and out of the wheel well. This happens most aggressively when going up a steep incline at an angle and, to a lesser degree, upon body roll when turning sharply at higher speeds around a corner.
The front suspension is not much better, but does not introduce such bind. With a flimsy sheet metal "K" member (or craddle) that weighs double what tubular parts do, it offers half the rigidity and prevents easy access to just about everything. The strut design also leaves something to be desired with caster/camber needing to be carefully monitored and tweaked to optimize handling. The modified Macpherson strut is the design of putting the spring about half of the distance from the pivot point on the "K" member to the ball joint at the spindles, while the strut being placed on the spindle it self. This leads to a slow and clumsy wheel rate (the speed the wheel reacts to changes in the road) and a poor ride. You can’t get good handling without punishing your low back. The body is also flimsy and allows for huge chassis twist and rebound. But HOLD ON!, it may sound like you are screwed, but your not. In fact, you are actually in a pretty good place. The Mustang, once fixed and a very good start for $2K, will begin to out handle just about any car around and includes Ferrari’s.
Griggs Video
The solutions are as follows:
Chassis Rigidity: The first thing you need to fix for your safety and any kind of racing is the chassis rigidity. Poor chassis rigidity leads to poor weight transfer, sloppy handling and poor ride. Not to mention the inability to take advantage of any mods that affect the movement of your car. Think about it... that’s everything! (see overall stiffness below) Solution: Subframe connectors and/or a roll cage. A good set of subframe connectors (SFC's) will connect the front and rear suspension to form a strong and continuous steel subframe, kind of like every other good car in the world. You can also do a cage, which will work better, but not required for your average Joe. I recommend any good companies kit, such as Maximum Motorsports, Griggs, even Steeda makes a decent set. They are welded to either end of your cars subframe and limit the flex across the length of your cars body. Not only does it make your car safer, it will help to keep your car doors keep from getting out of alignment after a couple years of hard driving. For less than $200, I believe this is the single most sugnificant mod and the beginning of a much improved suspension system. The SN95 is much improved over the Fox Body and the S197 is gererally accepted to not need any subframe uprades at all.
The Macpherson strut: The true Macpherson strut is what you would normally see on a car. The shock is inside the spring. This links the recoil and spring rate together. It also means that you can place a smaller spring a lot closer to the wheel, giving you a better wheel rate and a smoother ride and all the while reducing weight. A coilover, is simply a Macpherson strut that allows you to adjust the height of the spring and allowing you to adjust the ride height of your car to the application. In the case of our cars, converting to coil-overs actually means you get a better designed suspension component and adjustability. This, my friends, is a Double Wammy! I recommend coil-overs all around if within your budget and require no more modification than the parts them selves.
Coil-overs: This is a shock or strut with a coil spring encircling it (CO's) and will require the use of caster/camber plates (see CC plates). The shock/strut and spring are installed as a complete assembly and able to replace either independent of each other. This provides for optimal damping without torsional loads while using lower spring rates for nicer ride and improved handling (see wheel rate). CO's are infinitely adjustable for ride height using a simple threaded spring perch located at bottom of the spring. Stiffness can be modified by use of a replacement spring, but needs to be paired properly with the shock or strut (see matching springs/shocks). Please note, that not all shocks/struts can be used in a CO application!
Short long-arm: The SLA is the extreme end of your Mustang front suspension upgrade. This is an unequal length double "A" arm set-up and offers improved grip under aggressive cornering. The SLA applies ever-increasing negative camber to outside front wheel and increasing positive camber to the inside front wheel to improve the tires contact patch during a hard corner. The SLA requires removal of the stock struts or traditional CO's and replaces them with a coil-over shock assembly and has fixed caster/camber settings. These settings can be modified, but much work to do so and certainly not on the fly. It is generally upwards of $4K for installation after tube "K" and other upgrades, to run the SLA. It’s a worth while change if your car is a track only monster or hardcore AX, but not for just about anyone else. The two big players in SLA are Agent 47 and Griggs Racing (seen below)
Griggs
Agent 47
Springs: Stiffer springs can improve handling, but only to a point and depends on the application. For a drag car, there are many spring combinations available. Generally, soft springs in front and semi soft in rear are the desirable set up. There are some differing opinions for exactly what spring rate you should get for drag, so do some further research. You will find many locations to purchase springs so hit up one of the sponsors here on Mustang Forums and just remember with stiffer springs, comes a harsher ride. The following items are highly recommended when going with a 2" drop for proper suspension geometry. Caster/camber plates (CC plates, see below), specialized springs or coil-over kit, new shocks/struts to match coil-over or springs rate, new "K" member and "A" arms to support the new geometry and a bump steer kit (see bump steer below). There are several stiffness factors that need to be considered and add up to your overall handling. Idealy, your car would be perfectly flat, always have equal downforce on all 4 tires and even grip on the road. Your wheels would dip into and out of every bump on the road and get maximum traction at all times. Obviously this is impossible, so here are the key points to consider:
Overall Stiffness - This, I will use to define the stiffness of your car as a whole. This is what your are adding by getting subframe connectors (see chassis rigidity above). You are tying the front and rear of the car together better. This makes all parts work together to attain a specific goal. The ultimate solution to this is a 10 point roll Cage. A 10 point roll cage is a cage that attaches the strut towers and rear shock towers to the central cage. A 6 point cage would be the central cage. It helps in stiffness a bit, but is mostly for safety. A 10 point stiffens the entire car.
Front Stiffness - The stiffer your car is, the better it will handle... if the roads were always smooth as glass. The problem is, if you stiffen the front of your car a whole bunch, it won't adhere to the road as well due to poor conditions of most streets. This means you won't absorb those potholes and your car won't lean as much, but is even more problematic if not balanced to rear suspension. When the rear end is not as stiff, the car will tend to understeer. This is when your front end will slide out before your rear end does in a hard corner and does not follow steering input.
Rear Stiffness - Your Rear stiffness works exactly like the front does. The stiffer it is the more the rear end will slide when upset by poor road conditions. When matched to the front, it will handle better, but when out of balance, you will have a hell of a time in corners. If you ever watch drift cars, you will notice the front end seems to be almost soft, it seems to glide a little more, absorbs the bumps. This gives them superior traction over the rear (see oversteer). The rear end, is SUPER STIFF as it is tied down as tight as they can be. This makes the car have excellent front end traction and a rear end that feels like its constantly on ice. There is no play for the suspension to absorb the bumps and shifts of the road the rear wheels receive every bit of the energy. It's like taking the clutch out of the transmission, but for your tires. They are either not going, or they are going 2000 RPM. Essentially, getting a drift car to peel out takes as much effort as it does to turn your car on. Overall stiffness is the most important aspect of your car once you have gotten the power and suspension bugs figured out. When your front and rear are equally stiff, or at least set up to work together, your car will be a whole new machine. But... if done incorrectly, you will think your car will be worthless if not dangerous.
Shocks: They are an important part of buying aftermarket springs or going coil-overs. As with traditional springs, shocks should be matched to the rate, but high quality coil-overs will be customized to your shocks. There are many choices for shocks and many are specific to certain applications. Regardless, do NOT buy suspension components from an exhaust company. The shocks you get also has just as much to do with your ride quality as the springs. Your shocks are what keep the spring from bouncing after absorbing a shock. This means that you can over or under dampen your springs very easily. If you buy some amazing springs and keep your stock struts/shocks, you will hate life. The springs will overpower your shocks and you will spend all day bouncing down the road. Good companies for shocks/struts are harder to find and they cost more money. As mentioned above, you should always get new shocks/struts to match your springs. Although the budget minded modder might do otherwise. Most aftermarket springs are not a ton different in spring rate than your stock springs. Making it possible to swap them out without hugely affecting your shocks/springs and handling. Lower than about 2" of drop or a good 30% softer or harder spring rate and you should definitely be buying new shocks. The OEM shocks on your car will not be able to support the new limits of the travel for long with that much drop. Your suspension geometry will also be greately affected by that much of a drop without several other supporting mods. I will break it down for you in a few different ways. I don’t recommend adjustables unless you truly plan to adjust them a lot.
Drag adustable – Tokico Illuminas, best adjustable drag shock out there. Its been proven many times.
Road course adjustable – Starting with Konis, Penskes, Ohlins and Tokico D spec, are best adjustable shocks/struts out there and not horribly expensive either.
Road course non-adjustable - Bilstein HD’s, and Bilstein custom valved from Maximum Motorports for coil-overs. Also Koni Yellows are amazing shocks, but expensive and require very good springs.
Cheap shocks - There are lots of cheap ones out there. Tokico HD’s and KYB’s are OK if you want a stock replacement. Not generally that great for high performance though.
Matching springs/shocks: The job of a shock is to dampen the movement of the suspension or the springs. If you had no shocks, the car would just bounce around like a spring. Most shocks have a range of movement so think about an air pump, like you used for a bike tire. The harder/faster you push on it, the more resistance. Vice versa, the slower/easier/less you pushed on it, the least resistance is given. This is how a shock thinks or knows the difference between a bump in the road and you taking a corner at 120 mph. More importanly, you swerving suddenly because someone cut you off or a dog ran out in front of you. When you have over-compressed that shock all times, it's out of its normal stroke range. When you hit a bump, it responds as if the bump is larger, so it's tighter then what it should be. This causes the shock to wear out faster as it's always working hard... even under normal conditions! You feel bumps more then you would otherwise and this makes for a worse ride then need be. Handling wise, the shock was setup for a certain spring rate. It's set-up, in some cases with gas pressure, to address a specific amount of force or energy from the spring to dampen this movement and help with controling the car. Now you have a stiffer spring, basically a stronger spring pushing on the shock, its not setup for that spring, so it doesn't dampen the movement of the spring and the car is more easily "upset" by bumps and the handling is poor. Either way, the spring and shock should be "tuned" to work together for optimum ride/handling.
Quad-shocks: These were an afterthought by Ford to address wheel hop issues of the Fox Body and SN95 Mustangs. They are installed in a horizontal position behind the rear wheels and connect between the frame and axle behind the brake rotor. Due to the flexabilty of the stamped-steel OEM LCA's and the soft rubber bushings at each end, wheel hop issues can result if ones right foot should get *clears throat*.... suddenly very heavy! When oporating properly, they will dampen wheel hop and decrease a bit of "waggle" in the rear end. If looking to install 10.5" or wider wheels, they can sometimes rub on the tires, so flipping them 180° may do the trick to avoid it. Your 4-link suspension bind can be reduced a bit further by completely removing these shocks (yes.... I said COMPLETELY REMOVE THEM). To do so, it is best to install a set of aftermarket LCA's that will not have the flexabilty found in the OEM ones, so render the quads un-necessary. To find a "Jazzer approved" LCA', read the section on them below:
Original Thread here
http://www.moddedmustangs.com/forums/99-04/239965-un-official-suspension-guide.html
This was compiled as a companion, or Cliff Notes, to Official Suspension Guide and major portions of the information found here was copied DIRECTLY from that thread. I have received permission from ModMustang97GT to do so and has been on several other forums for since July '09. This was done due to the information contained in ModMustang97GT's thread is wonderful, but spread out over many pages, as it was compiled over many months. THIS thread was compiled at a single sitting, more or less, and therefore able to take relevant items and place them in an easy-to-access format.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
HOW I SEE IT
Before we begin, I would like to touch on a few things about suspension and its modification. I don't see suspension mods as ONLY for auto-cross or the 1/4 mile or even the race track. I see a well operating suspension as a way to improve the driving experience every time you get behind the wheel. If you go to the store for a 1/2 gallon of milk or over the hills and through the woods to grandmas house, you should enjoy your drive. If one installs a Kenne Bell or Whipple to get the rush of quick acceleration, does this mean that he/she romps on it at every stop light? Anyone that is running 350+ HP can "feel" the energy and power under the hood and most of the time, it's enough just knowing it is there. I see a nice suspension in the exact same way. I don't rip around every corner and push the limits of man and machine everytime I head out. But... I have the ability to take a nice corner and "feel" that my car and I are capable of soo much more and that, my friends, is enough most of the time. Now... down to bidness!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I would like to state that this is NOT a completely original post. I have received permission from the orginal author to copy/paste his information into this thread. I have contributed very large portions of information, so would be safe to say I am a co-author and would appreciate any/all input to its accuracy and completeness.
The information in this post has been gathered from many peoples questions/input over the course of several years and compiled here for convenience. Furthermore, this post deals specifically with geometry issues as they pertain to fuction of the suspension components as they work together in a general manner. Issues of roll center and roll axis are effected with some of these modifications and are beyond the scope of this post, so therefore, not addressed.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
What is the ULTIMATE goal for your ride?
Before we get started here, I would like to mention two things that are VERY important for those considering modifications found within this thread. The first being that suspension can be quite difficult to do efficiently, as one often ends up replacing parts that were thought to be great and only to find out later needs have changed or the decision was a bad one. A real good example of this is the common purchase of aftermarket lower control arms (LCA's). This is great, but depending on the design, additional problems can arrise due to how they interact with other components within your suspensions travel. I have much information explaining the differences between designs so that one can better understand how your car will respond to such modifications. Secondly, with maybe one or two exceptions, the modifications listed here will create addtional Noise Vibration Harshness (NVH) to your driving experience. There is really no way to build a Mustang that eats corners for breakfast and rides like it's just off the showroom floor. That being said, one does not have to use earplugs to drive a corner-killer, just turn the stereo up a bit louder to overcome it! If you would like a car that will hold its own with a higher-end BMW or Corvette... you will need to spend some money for coil-over shock (CO's) with serious modification to the rear axle geometry to compete. This means, your OEM located springs are no longer needed and your existing shocks and struts will very likely need to be replaced.
This info is really focused on the Fox Body ('79~'93) and SN95 ('94~'04) Mustangs. Much of this information is relative to the '05+ models (S197), but does not apply in some cases. The '99~'04 Cobra is also an exception, to some degree, as it is has independent rear suspension (IRS).
Glossary of terms:
AX ~ auto-cross
CC ~ caster/camber
CO ~ coil-overs
Fox Body ~ '79~'93 Mustang
Fox chassis ~ platform used by '79-'04 Mustangs. Used on many '80s era Ford RWD cars. Full list can be found here. '94-'04 use a revised version called "Fox-4".
FRPP ~ Ford Racing Performance Parts
IRS ~ independent rear suspensin
ISOS ~ spring isolators
LCA's ~ lower control arms
NVH ~ Noise Vibration Harshness
PHB ~ panhard bar
POLY ~ polyurethane
S197 ~ '05+ Mustang
SFC's ~ sub-frame connectors (FLSFC's = full-length)
SLA ~ short-long arm
SN95 ~ '94-'04 Mustang ('99-'04 often referred to as a "New Edge")
SRA ~ solid rear axle
TA ~ torque arm
UCA's ~ upper control arms
WL ~ Watts link
The Mustang suspension: The Mustang suspension was poorly designed for high performance driving, therefore is good, but not great. The 4-link design that was incorporated in to the rear suspension between '79~'04 ('99~'04 Cobras excepted). It uses two lower control arms (LCA's) and two oddly angled upper control arms (UCA's) to position the axle side to side, prevent axle wind up and transfer force from the wheels to the chassis. Axle articulation is the main issue with the 4-link and leads to geometry problems in addressing the bumps and ruts of your everyday street. Axle articulation is seen when one wheel is up inside the wheel well and the other is down and out of the wheel well. This happens most aggressively when going up a steep incline at an angle and, to a lesser degree, upon body roll when turning sharply at higher speeds around a corner.
The front suspension is not much better, but does not introduce such bind. With a flimsy sheet metal "K" member (or craddle) that weighs double what tubular parts do, it offers half the rigidity and prevents easy access to just about everything. The strut design also leaves something to be desired with caster/camber needing to be carefully monitored and tweaked to optimize handling. The modified Macpherson strut is the design of putting the spring about half of the distance from the pivot point on the "K" member to the ball joint at the spindles, while the strut being placed on the spindle it self. This leads to a slow and clumsy wheel rate (the speed the wheel reacts to changes in the road) and a poor ride. You can’t get good handling without punishing your low back. The body is also flimsy and allows for huge chassis twist and rebound. But HOLD ON!, it may sound like you are screwed, but your not. In fact, you are actually in a pretty good place. The Mustang, once fixed and a very good start for $2K, will begin to out handle just about any car around and includes Ferrari’s.
Griggs Video
The solutions are as follows:
Chassis Rigidity: The first thing you need to fix for your safety and any kind of racing is the chassis rigidity. Poor chassis rigidity leads to poor weight transfer, sloppy handling and poor ride. Not to mention the inability to take advantage of any mods that affect the movement of your car. Think about it... that’s everything! (see overall stiffness below) Solution: Subframe connectors and/or a roll cage. A good set of subframe connectors (SFC's) will connect the front and rear suspension to form a strong and continuous steel subframe, kind of like every other good car in the world. You can also do a cage, which will work better, but not required for your average Joe. I recommend any good companies kit, such as Maximum Motorsports, Griggs, even Steeda makes a decent set. They are welded to either end of your cars subframe and limit the flex across the length of your cars body. Not only does it make your car safer, it will help to keep your car doors keep from getting out of alignment after a couple years of hard driving. For less than $200, I believe this is the single most sugnificant mod and the beginning of a much improved suspension system. The SN95 is much improved over the Fox Body and the S197 is gererally accepted to not need any subframe uprades at all.
The Macpherson strut: The true Macpherson strut is what you would normally see on a car. The shock is inside the spring. This links the recoil and spring rate together. It also means that you can place a smaller spring a lot closer to the wheel, giving you a better wheel rate and a smoother ride and all the while reducing weight. A coilover, is simply a Macpherson strut that allows you to adjust the height of the spring and allowing you to adjust the ride height of your car to the application. In the case of our cars, converting to coil-overs actually means you get a better designed suspension component and adjustability. This, my friends, is a Double Wammy! I recommend coil-overs all around if within your budget and require no more modification than the parts them selves.
Coil-overs: This is a shock or strut with a coil spring encircling it (CO's) and will require the use of caster/camber plates (see CC plates). The shock/strut and spring are installed as a complete assembly and able to replace either independent of each other. This provides for optimal damping without torsional loads while using lower spring rates for nicer ride and improved handling (see wheel rate). CO's are infinitely adjustable for ride height using a simple threaded spring perch located at bottom of the spring. Stiffness can be modified by use of a replacement spring, but needs to be paired properly with the shock or strut (see matching springs/shocks). Please note, that not all shocks/struts can be used in a CO application!
Short long-arm: The SLA is the extreme end of your Mustang front suspension upgrade. This is an unequal length double "A" arm set-up and offers improved grip under aggressive cornering. The SLA applies ever-increasing negative camber to outside front wheel and increasing positive camber to the inside front wheel to improve the tires contact patch during a hard corner. The SLA requires removal of the stock struts or traditional CO's and replaces them with a coil-over shock assembly and has fixed caster/camber settings. These settings can be modified, but much work to do so and certainly not on the fly. It is generally upwards of $4K for installation after tube "K" and other upgrades, to run the SLA. It’s a worth while change if your car is a track only monster or hardcore AX, but not for just about anyone else. The two big players in SLA are Agent 47 and Griggs Racing (seen below)
Griggs
Agent 47
Springs: Stiffer springs can improve handling, but only to a point and depends on the application. For a drag car, there are many spring combinations available. Generally, soft springs in front and semi soft in rear are the desirable set up. There are some differing opinions for exactly what spring rate you should get for drag, so do some further research. You will find many locations to purchase springs so hit up one of the sponsors here on Mustang Forums and just remember with stiffer springs, comes a harsher ride. The following items are highly recommended when going with a 2" drop for proper suspension geometry. Caster/camber plates (CC plates, see below), specialized springs or coil-over kit, new shocks/struts to match coil-over or springs rate, new "K" member and "A" arms to support the new geometry and a bump steer kit (see bump steer below). There are several stiffness factors that need to be considered and add up to your overall handling. Idealy, your car would be perfectly flat, always have equal downforce on all 4 tires and even grip on the road. Your wheels would dip into and out of every bump on the road and get maximum traction at all times. Obviously this is impossible, so here are the key points to consider:
Overall Stiffness - This, I will use to define the stiffness of your car as a whole. This is what your are adding by getting subframe connectors (see chassis rigidity above). You are tying the front and rear of the car together better. This makes all parts work together to attain a specific goal. The ultimate solution to this is a 10 point roll Cage. A 10 point roll cage is a cage that attaches the strut towers and rear shock towers to the central cage. A 6 point cage would be the central cage. It helps in stiffness a bit, but is mostly for safety. A 10 point stiffens the entire car.
Front Stiffness - The stiffer your car is, the better it will handle... if the roads were always smooth as glass. The problem is, if you stiffen the front of your car a whole bunch, it won't adhere to the road as well due to poor conditions of most streets. This means you won't absorb those potholes and your car won't lean as much, but is even more problematic if not balanced to rear suspension. When the rear end is not as stiff, the car will tend to understeer. This is when your front end will slide out before your rear end does in a hard corner and does not follow steering input.
Rear Stiffness - Your Rear stiffness works exactly like the front does. The stiffer it is the more the rear end will slide when upset by poor road conditions. When matched to the front, it will handle better, but when out of balance, you will have a hell of a time in corners. If you ever watch drift cars, you will notice the front end seems to be almost soft, it seems to glide a little more, absorbs the bumps. This gives them superior traction over the rear (see oversteer). The rear end, is SUPER STIFF as it is tied down as tight as they can be. This makes the car have excellent front end traction and a rear end that feels like its constantly on ice. There is no play for the suspension to absorb the bumps and shifts of the road the rear wheels receive every bit of the energy. It's like taking the clutch out of the transmission, but for your tires. They are either not going, or they are going 2000 RPM. Essentially, getting a drift car to peel out takes as much effort as it does to turn your car on. Overall stiffness is the most important aspect of your car once you have gotten the power and suspension bugs figured out. When your front and rear are equally stiff, or at least set up to work together, your car will be a whole new machine. But... if done incorrectly, you will think your car will be worthless if not dangerous.
Shocks: They are an important part of buying aftermarket springs or going coil-overs. As with traditional springs, shocks should be matched to the rate, but high quality coil-overs will be customized to your shocks. There are many choices for shocks and many are specific to certain applications. Regardless, do NOT buy suspension components from an exhaust company. The shocks you get also has just as much to do with your ride quality as the springs. Your shocks are what keep the spring from bouncing after absorbing a shock. This means that you can over or under dampen your springs very easily. If you buy some amazing springs and keep your stock struts/shocks, you will hate life. The springs will overpower your shocks and you will spend all day bouncing down the road. Good companies for shocks/struts are harder to find and they cost more money. As mentioned above, you should always get new shocks/struts to match your springs. Although the budget minded modder might do otherwise. Most aftermarket springs are not a ton different in spring rate than your stock springs. Making it possible to swap them out without hugely affecting your shocks/springs and handling. Lower than about 2" of drop or a good 30% softer or harder spring rate and you should definitely be buying new shocks. The OEM shocks on your car will not be able to support the new limits of the travel for long with that much drop. Your suspension geometry will also be greately affected by that much of a drop without several other supporting mods. I will break it down for you in a few different ways. I don’t recommend adjustables unless you truly plan to adjust them a lot.
Drag adustable – Tokico Illuminas, best adjustable drag shock out there. Its been proven many times.
Road course adjustable – Starting with Konis, Penskes, Ohlins and Tokico D spec, are best adjustable shocks/struts out there and not horribly expensive either.
Road course non-adjustable - Bilstein HD’s, and Bilstein custom valved from Maximum Motorports for coil-overs. Also Koni Yellows are amazing shocks, but expensive and require very good springs.
Cheap shocks - There are lots of cheap ones out there. Tokico HD’s and KYB’s are OK if you want a stock replacement. Not generally that great for high performance though.
Matching springs/shocks: The job of a shock is to dampen the movement of the suspension or the springs. If you had no shocks, the car would just bounce around like a spring. Most shocks have a range of movement so think about an air pump, like you used for a bike tire. The harder/faster you push on it, the more resistance. Vice versa, the slower/easier/less you pushed on it, the least resistance is given. This is how a shock thinks or knows the difference between a bump in the road and you taking a corner at 120 mph. More importanly, you swerving suddenly because someone cut you off or a dog ran out in front of you. When you have over-compressed that shock all times, it's out of its normal stroke range. When you hit a bump, it responds as if the bump is larger, so it's tighter then what it should be. This causes the shock to wear out faster as it's always working hard... even under normal conditions! You feel bumps more then you would otherwise and this makes for a worse ride then need be. Handling wise, the shock was setup for a certain spring rate. It's set-up, in some cases with gas pressure, to address a specific amount of force or energy from the spring to dampen this movement and help with controling the car. Now you have a stiffer spring, basically a stronger spring pushing on the shock, its not setup for that spring, so it doesn't dampen the movement of the spring and the car is more easily "upset" by bumps and the handling is poor. Either way, the spring and shock should be "tuned" to work together for optimum ride/handling.
Quad-shocks: These were an afterthought by Ford to address wheel hop issues of the Fox Body and SN95 Mustangs. They are installed in a horizontal position behind the rear wheels and connect between the frame and axle behind the brake rotor. Due to the flexabilty of the stamped-steel OEM LCA's and the soft rubber bushings at each end, wheel hop issues can result if ones right foot should get *clears throat*.... suddenly very heavy! When oporating properly, they will dampen wheel hop and decrease a bit of "waggle" in the rear end. If looking to install 10.5" or wider wheels, they can sometimes rub on the tires, so flipping them 180° may do the trick to avoid it. Your 4-link suspension bind can be reduced a bit further by completely removing these shocks (yes.... I said COMPLETELY REMOVE THEM). To do so, it is best to install a set of aftermarket LCA's that will not have the flexabilty found in the OEM ones, so render the quads un-necessary. To find a "Jazzer approved" LCA', read the section on them below:
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