[blackstangt]

Hi all,

1990 Mustang GT Hatchback:

I installed a Ford Racing Spring / Tokiko Shock/Strut kit 10 years ago, the ride height has always been low in the back and high in the front. It has C springs in the Front and B springs in the rear.

I cut a decent amount of weight by removing AC, Smog Pump, Fog Lights and Brace, using aluminum heads, fiberglass hood, 15 lb AGM battery. Maybe 150 lb total off the front.

I'm not sure if the weight reduction is playing a large part in the front end being high, or if the advertised 7/8" drop in the front and 1/2" in the rear was inaccurate, but I'd like to drop the front 1/2" or so and maybe raise the rear slightly to level the car.

Does anyone have a similar front-rear weight car with a set-up I can copy that rides well? I'm looking for a little better ride comfort than C/B springs as well, since I'd like to drive the car more than to and from a track and I'm not 18 anymore, my body is beat up enough.

Trying to figure out spring rates has led me to believe it's mostly marketing nonsense, and my experience with the previous set-up makes me concerned that the estimates are inaccurate, so I'm just looking to copy someone's setup that works well.

 

[thadude]

Coilovers and call maximum motorsports to set up rates.

 

[indy2000]

recommend you go to the Max Motorsports site

and read the FAQs section

 

[Mustang5L5]

C/B rear springs are the same, it's the front that differs between the two kits. The C springs are notorious for riding terrible, and i ran the same combo with Tokico blue shocks/struts. Car handled reasonably well, but it jarred over bumps. My drop was closer to 1" in the front and barely anything in the rear. Car had a rake, which i solved with Max motorsports adjustable rear arms. I used to bottom out my front struts badly, and eventually blew them. I did swap to a set of bullitt springs after getting sick of having the car so low.

That was 20 years ago (when i was 18 as well). Now i run coil-overs from Maximum Motorsports. I have rates more suited for street driving and the car rides so well that I am still impressed every time i get behind the wheel...even with it lowered.

I recommend reading through MM's tech articles which will answer many questions as well as give you an idea on what you would need to do.

https://www.maximummotorsports.com/Struts-and-Shocks-Tech-C568.aspx

 

[Jack Hidley]

There is a new section of the Tech section on the MM website with more articles on springs, coilovers and other subjects.

https://www.maximummotorsports.com/Good-Handling-Is-Fun-C723.aspx

 

[blackstangt]

Went to MM website. Good info.

What about the ride height issue? Is this something anyone has had to correct? I imagine coil-overs would be the easiest way to adjust, but am a bit worried about putting all the weight on the strut towers, which weren't designed for that.

The fender gaps are:
DSF: 1-3/4"
PSF: 2-1/4"
DSR: 1"
PSR: 1-1/4"

The suspension is now 13 years and 100k+ old, so new components should help, but the front has always been about 3/4" higher since 2006 when installed.

 

[blackstangt]

C/B rear springs are the same, it's the front that differs between the two kits. The C springs are notorious for riding terrible, and i ran the same combo with Tokico blue shocks/struts. Car handled reasonably well, but it jarred over bumps. My drop was closer to 1" in the front and barely anything in the rear. Car had a rake, which i solved with Max motorsports adjustable rear arms. I used to bottom out my front struts badly, and eventually blew them. I did swap to a set of bullitt springs after getting sick of having the car so low.

That was 20 years ago (when i was 18 as well). Now i run coil-overs from Maximum Motorsports. I have rates more suited for street driving and the car rides so well that I am still impressed every time i get behind the wheel...even with it lowered.

I recommend reading through MM's tech articles which will answer many questions as well as give you an idea on what you would need to do.

https://www.maximummotorsports.com/Struts-and-Shocks-Tech-C568.aspx

What's the exact setup you're using now? I assume regular shocks/springs in the rear?

 

[Mustang5L5]

What's the exact setup you're using now? I assume regular shocks/springs in the rear?

Correct. H&R super sport springs, Bilstien
HD shocks and MM adjustable arms


I had the same concern about the strut towers. I added a strut tower brace when I did the coil overs.

Here's a good read on the topic

http://corner-carvers.com/forums/showthread.php?t=670&highlight=coil-overs+shock+towers

 

[Jack Hidley]

Regarding post #6 from above.

One very common problem we run into are customers who want to adjust the ride height of the car so that it is the same at all four corners. This is impossible to do in the vast majority of cases.

The car body is not going to be built perfectly flat. It doesn't matter what adjustments you make between the ground holding up the chassis at each of the four corners. If the car body is not built flat, the four ride heights will never all be the same.

One way to visualize this is with a flat piece of metal. If the metal is flat and you hold it over the ground, you can tilt it at an angle in any direction. When you do this, the four corner distances from the corners of the metal to the ground will always be unequal. It is possible to adjust the angle of the board to make all four of these distances equal.

Now take a flat piece of metal, but bend one corner up one inch. It doesn't matter what combination of angles you put this metal with respect to the ground at, the four corner heights are never all going to be the same. It is IMPOSSIBLE for ANYTHING in the suspension to have caused this problem. The problem is in the body of the car. When the car is at stock ride height with 3" between the tires and top of the fender arch, no one notices the variation. Once they lower the car down to around 1" from the tops of the tires, the variations in the heights becomes much more apparent.

In this case, I took the gaps that the poster posted above and did a little analysis on them.

His initial numbers are:

1.75 2.25
1.00 1.25

Note that all numbers are in the format below:

LF RF
LR RR

If you make the following adjustments to the ride height at each corner:

-0.25 -0.63
0.63 0.25

You will end up with the following gaps:

1.496 1.621
1.628 1.503

If you correctly make the recommended adjustments above, the corner weights of the car will not be completely messed up and the car will be as level as it can possibly be. This is super important to realize. If you have the ability to adjust the ride height at all four corners of the car, it is very easy to get the car close to level, but have a massive amount of weight on one diagonal and very little weight on the other diagonal. This will make the car ride, handle, brake and accelerate very poorly in most cases.

 

[toddturbo]

Jack is once again absolutely correct. I've had this issue on my drag car. With it "level", it's impossible for the car to leave straight unless I purposely leave some air out of one tire to once again level it. At that point, it becomes, well quite frankly dangerous. Getting the car to leave properly requires adjustments to the suspension,which makes the body to lean slightly to the right, which puts a little more weight on the RR tire, which looks kind of weird to those who don't know any different. In some cases (such as mine) "looks" take a back seat to function.

 

[qtrracer]

If corner weighting isn't of prime importance, I resolved the ride-height variations with combinations of poly and stock rubber isos.

As Jack suggested, my 86 had a badly deformed rear chassis Passenger side spring pocket. This was factory as far as I could tell. The deformity caused the spring to ride high in the pocket (meaning it didn't sit flat in the grove) causing that side of car to ride substantially higher than the other side (as measured by ground to fender lip). To overcome the deformity, I cut a poly iso into a "C" shape so that the deformity sat in the mouth of the "C". This allowed the spring to rest in the pocket without any effect from the deformity, but it was still higher on that side. On the DS rear, I used a rubber and poly iso which effectively leveled the car in the rear. But it was still too high in the rear with the "C" springs. So using MM adjustable RLCAs, I put the height where I wanted and still had roughly the same adjustment left for both sides. On the front, I used a combo of poly and rubber isos to get the car as close to level as possible (level defined as +/- .25"). Eventually I swapped to C/Os up front making the process much easier to accomplish with adjustments at all four corners.

Ultimately, I went to rear C/Os which eliminated the deformed spring pocket as a variable. But during the several years before I discovered the deformity, ride height issues drove me nuts.

 

[blackstangt]

Regarding post #6 from above.

One very common problem we run into are customers who want to adjust the ride height of the car so that it is the same at all four corners. This is impossible to do in the vast majority of cases.

The car body is not going to be built perfectly flat. It doesn't matter what adjustments you make between the ground holding up the chassis at each of the four corners. If the car body is not built flat, the four ride heights will never all be the same.

One way to visualize this is with a flat piece of metal. If the metal is flat and you hold it over the ground, you can tilt it at an angle in any direction. When you do this, the four corner distances from the corners of the metal to the ground will always be unequal. It is possible to adjust the angle of the board to make all four of these distances equal.

Now take a flat piece of metal, but bend one corner up one inch. It doesn't matter what combination of angles you put this metal with respect to the ground at, the four corner heights are never all going to be the same. It is IMPOSSIBLE for ANYTHING in the suspension to have caused this problem. The problem is in the body of the car. When the car is at stock ride height with 3" between the tires and top of the fender arch, no one notices the variation. Once they lower the car down to around 1" from the tops of the tires, the variations in the heights becomes much more apparent.

In this case, I took the gaps that the poster posted above and did a little analysis on them.

His initial numbers are:

1.75 2.25
1.00 1.25

Note that all numbers are in the format below:

LF RF
LR RR

If you make the following adjustments to the ride height at each corner:

-0.25 -0.63
0.63 0.25

You will end up with the following gaps:

1.496 1.621
1.628 1.503

If you correctly make the recommended adjustments above, the corner weights of the car will not be completely messed up and the car will be as level as it can possibly be. This is super important to realize. If you have the ability to adjust the ride height at all four corners of the car, it is very easy to get the car close to level, but have a massive amount of weight on one diagonal and very little weight on the other diagonal. This will make the car ride, handle, brake and accelerate very poorly in most cases.

What method are you suggesting will get me those adjustments without screwing up corner weights?