As many of you know, I'm into handling in a big way. Straight-line acceleration is sweet, don't get me wrong, but I just love the feeling of a slow entry into a fast sweeping turn and feeling the lateral G-forces trying to pull you out the window. Doing 130 and feeling the tires bite into the road as you hover on the edge of control... The audible protest of the rubber as you beg just another mph out of them when you're already far beyond the sane limits of speed... It's a much greater rush than nailing your first 11.99 time slip in my own humble opinion. Everyone has his or her performance thing, and that's one of mine.
With that in mind, most of my current modifications have been suspension related in some way (click on link in sig for details). I've already a fat stack of receipts for the bits and pieces under my car and now I've added a couple more. Introducing the Evolution Motorsport (EvM) Tri Link and Watts Link:
For more pics, including install photos, see their site:
http://www.evolutionmsport.com/index.php
(If you're familiar with the problems with the Mustang rear suspension, you can skip this part)The main problem with the Mustang suspension is in the rear. It's been covered many times and so I won't go too deep into it, but the stock 4-link design is junk for any serious type of handling. The upper control arms (UCA) have two jobs. One is to control axle torsional movement in conjunction with the lower control arms (LCA). The other is to control lateral (side to side) movement. This is where it runs into problems.
As the axle rotates relative to the chassis during a turn, the design requires the UCA to lengthen and shorten. Of course the steel isn't going to do this very easily and so the soft rubber bushings are required to compress to make up the length difference. Unfortunately, as the axle rotates more and more, the force required to compress the bushings increases. This acts as a false spring rate and increases the wheel rate. Wheel rate is the force required to move the suspension at the wheel center itselfand consists of spring rate, friction, and bind.
So basically speaking, as you get deeper into a turn, your wheel rate increases (unpredictably so). Mustangs, from the factory, are designed to understeer (push) into a corner for safety. Back off the gas, you straighten out. It's a basic response to an adverse situation that most people follow. This is why Ford (and most manufacturers) design passenger vehicles this way.
Now as you add spring rate in the rear, the vehicle tends to oversteer (spin). This is why Mustangs are known for "snap-oversteer." Entering a turn with speed will result in understeer followed by "snap-oversteer" as the UCA create bind and increase the wheelrate.
(More suspension design here, but getting out of the Mustang specific area)The closer the UCA are to each other, the less of a length change they must make. So UCA that are all the way out towards the wheels will have to lengthen/shorten more than if they were located halfway in towards the differential. As they get closer and closer, the requirement to compress keeps reducing until the UCA are in the same location, 0" apart, i.e. one UCA instead of two. This is known as a 3-link (note: 3-links and torque arm suspensions are two separate things; don't confuse the two).
However, since one link cannot control the lateral axle movement like the two splayed links do, another device must be added. This is where a panhard bar (PHB) or watts link (WL) come into play.
Both devices control lateral axle control in two separate ways. A PHB consists of a single bar that mounts to the chassis on one side and the axle on the other. A WL consists of a bellcrank (pivot point) and two bars. The bell crank can be mounted to either the axle (like the Griggs design) or the chassis (like the EvM design). Whatever the mounting position, the bars will mount to the other side (i.e. axle or chassis) in both the left and right sides.
The PHB and WL (as well as how they're mounted) both have their pros and cons that I won't get into for the sake of brevity (if someone really wants to know, I'll discuss it). Suffice it to say that I believe the WL is the better performer and that's why I'm using it.
So now, instead of the stock UCA taking care of both torsional and lateral movement (and doing a barely adequate job of both), I'll be removing them entirely and using a 3rd link to take care of the torsional and a WL to control the lateral. Each device, since it has only one job, does what it's supposed to do very well.
This brings me almost to the end of my suspension modifications, as I've only one or two things left to do (adjustable rear swaybar namely). My rear suspension will now be all heim joint (rod-end) suspended with the exception of the polyurethane in the shock mounts. Currently, the only thing not solid in the front suspension is the delrin control arm bushings (which will eventually be heim joints as well).
Unfortunately, it's going to be a little bit before I can get this stuff installed. It comes down to money. I've got a full T56 conversion sitting in the shop that needs to go in first so I can sell the stock T5 and related parts. I'll probably sell it all to someone wanting to do an AOD to T5 conversion as I'll have 75% of the parts for it. With that money, I'll be buying a side exit catback (SS Bassani). I'll have so much rear suspension now that I don't want to fight with interference problems (note: the EvM pieces do allow the use of stock pipes or you can do slight modifications for an aftermarket catback). I've got no desire to take a hammer to a (rather pricey) Bassani quiet thunder catback. Instead, the side exit will go on and I'll sell the old setup. Once that's done, the new suspension will go on. And actually, now that I think about it, I'll use the money from the catback sale to buy the adjustable rear swaybar and install it at the same time! Woohoo! Assuming the world calms down for a while and I don't get sent out of town, I'm looking for a mid February install.
Questions?
Yeah, I got your road feel right here baby.
With that in mind, most of my current modifications have been suspension related in some way (click on link in sig for details). I've already a fat stack of receipts for the bits and pieces under my car and now I've added a couple more. Introducing the Evolution Motorsport (EvM) Tri Link and Watts Link:
For more pics, including install photos, see their site:
http://www.evolutionmsport.com/index.php
(If you're familiar with the problems with the Mustang rear suspension, you can skip this part)The main problem with the Mustang suspension is in the rear. It's been covered many times and so I won't go too deep into it, but the stock 4-link design is junk for any serious type of handling. The upper control arms (UCA) have two jobs. One is to control axle torsional movement in conjunction with the lower control arms (LCA). The other is to control lateral (side to side) movement. This is where it runs into problems.
As the axle rotates relative to the chassis during a turn, the design requires the UCA to lengthen and shorten. Of course the steel isn't going to do this very easily and so the soft rubber bushings are required to compress to make up the length difference. Unfortunately, as the axle rotates more and more, the force required to compress the bushings increases. This acts as a false spring rate and increases the wheel rate. Wheel rate is the force required to move the suspension at the wheel center itselfand consists of spring rate, friction, and bind.
So basically speaking, as you get deeper into a turn, your wheel rate increases (unpredictably so). Mustangs, from the factory, are designed to understeer (push) into a corner for safety. Back off the gas, you straighten out. It's a basic response to an adverse situation that most people follow. This is why Ford (and most manufacturers) design passenger vehicles this way.
Now as you add spring rate in the rear, the vehicle tends to oversteer (spin). This is why Mustangs are known for "snap-oversteer." Entering a turn with speed will result in understeer followed by "snap-oversteer" as the UCA create bind and increase the wheelrate.
(More suspension design here, but getting out of the Mustang specific area)The closer the UCA are to each other, the less of a length change they must make. So UCA that are all the way out towards the wheels will have to lengthen/shorten more than if they were located halfway in towards the differential. As they get closer and closer, the requirement to compress keeps reducing until the UCA are in the same location, 0" apart, i.e. one UCA instead of two. This is known as a 3-link (note: 3-links and torque arm suspensions are two separate things; don't confuse the two).
However, since one link cannot control the lateral axle movement like the two splayed links do, another device must be added. This is where a panhard bar (PHB) or watts link (WL) come into play.
Both devices control lateral axle control in two separate ways. A PHB consists of a single bar that mounts to the chassis on one side and the axle on the other. A WL consists of a bellcrank (pivot point) and two bars. The bell crank can be mounted to either the axle (like the Griggs design) or the chassis (like the EvM design). Whatever the mounting position, the bars will mount to the other side (i.e. axle or chassis) in both the left and right sides.
The PHB and WL (as well as how they're mounted) both have their pros and cons that I won't get into for the sake of brevity (if someone really wants to know, I'll discuss it). Suffice it to say that I believe the WL is the better performer and that's why I'm using it.
So now, instead of the stock UCA taking care of both torsional and lateral movement (and doing a barely adequate job of both), I'll be removing them entirely and using a 3rd link to take care of the torsional and a WL to control the lateral. Each device, since it has only one job, does what it's supposed to do very well.
This brings me almost to the end of my suspension modifications, as I've only one or two things left to do (adjustable rear swaybar namely). My rear suspension will now be all heim joint (rod-end) suspended with the exception of the polyurethane in the shock mounts. Currently, the only thing not solid in the front suspension is the delrin control arm bushings (which will eventually be heim joints as well).
Unfortunately, it's going to be a little bit before I can get this stuff installed. It comes down to money. I've got a full T56 conversion sitting in the shop that needs to go in first so I can sell the stock T5 and related parts. I'll probably sell it all to someone wanting to do an AOD to T5 conversion as I'll have 75% of the parts for it. With that money, I'll be buying a side exit catback (SS Bassani). I'll have so much rear suspension now that I don't want to fight with interference problems (note: the EvM pieces do allow the use of stock pipes or you can do slight modifications for an aftermarket catback). I've got no desire to take a hammer to a (rather pricey) Bassani quiet thunder catback. Instead, the side exit will go on and I'll sell the old setup. Once that's done, the new suspension will go on. And actually, now that I think about it, I'll use the money from the catback sale to buy the adjustable rear swaybar and install it at the same time! Woohoo! Assuming the world calms down for a while and I don't get sent out of town, I'm looking for a mid February install.
Questions?
Yeah, I got your road feel right here baby.
awesome man
If I actually thought that anyone paid much attention to the FAQ, I’d write up a much more complete report on the Mustang 
Ah yes, the infamous coilovers growing out of the driveway thread. Let me type up a detailed report about it and I'll post it. As far as where I learned about it, lots of book reading, lots of talking with road racers, lots of overnight flights with nothing to do but draw pictures with forces/vectors/load paths etc.
