Front Suspension Springs and Shocks

tsheakley · Sep 12, 2024

Hi, My Mustang has a spongy front suspension and had a front high bias. I'd prefer level or slightly rear high bias.
So I just lowered the front of my 1973 351 2v convertible.
First I cut the height of the sprint by 1/2 inch which was about 1/2 a coil. This lowered the front about 1 inch at the top of the wheel arch.
And then I replaced the old shocks with KYB Excel-G shocks.

Now when I drive the car, the front end bottoms out with the slight dip in the road. Like transitions going up or down a hill where the cross road is level.
The suspension still feel spongy.
I was thinking of change the springs to: 1, Scott Drake Performance Coil Springs C7ZZ-5310-P OR 2,1967-73 Mustang Shelby High Performance Front Coil Springs.
They both are rated at 600 lbs.
I was thinking of changing the shocks to: 1, QA1 Stocker Star Shocks 1964-1973 Ford Mustang, OR 2, First Generation 1971-1973 Ford Mustang BILSTEIN STREET F SHOCK OEM Part #55-R047

I would appreciate your thoughts about what to change or keep and what you think the bottoming out of my suspension problem could be.

Thank you,
Tony

giantpune · Sep 12, 2024

tsheakley said:
I would appreciate your thoughts about what to change or keep and what you think the bottoming out of my suspension problem could be.

Thank you,
Tony

Well, you cut your springs, man. Can't really be surprised when it bottoms out.

Were these the 51yr old worn out springs you cut?

I'm running the QA1 TS601 and TS402 on one of my cars. I put both of them on the setting it says in the instructions for a starting point and haven't felt the need to move it from there. I'd buy some appropriate springs for the weight of your front end in in the length you need and dont cut them.

tsheakley · Sep 12, 2024

Thank for your thoughts Giantpune.
I thought the stiffer shocks and the minimal cut would have that much of an effect.
It bottoms out so easily I don't thing its all just because of the cut. Since the car only has 61,000 miles on it I didn't think the springs would be worn out.
I don't like the stock ride height so I have to do something to get the front down and not bottom out.

Hemikiller · Sep 12, 2024

Balljoints contribute a lot of friction to the front suspension. If they are well "worn in" and rotate easily, it can contribute to the problem you're having. They don't have to be worn out and sloppy to cause this problem.

midlife · Sep 12, 2024

Your original high profile up front may be due to your rear springs being worn and thus, the rear sags a bit. Sounds like your front springs were OK, but when you cut them, they don't have enough travel anymore...just my thoughts.

72conv · Sep 13, 2024

When I restored my car back in 1990-91, I went with a set of 600 lb., 1-1/2 in drop springs. I always use KYB Gas-A-Just shocks (just replaced them recently as the old ones were leaking from age). Never had a problem with the suspension bottoming out and the car sits "just right".

Stanglover · Sep 13, 2024

I've said this many times and from my own experience with badly made (Scott Drake) springs, front and back.
Do your self a favor and buy Eaton Detroit Springs springs. If you want, they can custom make what you want or you can buy lowering front springs I believe. At least with Eaton springs, you get the correct material for springs and not some crap made from scrap ships!!
I actually still have the original front springs in my car and I'm using KYB Excel G shocks with out any issues. I do have an ADDCO 1 1/18" sway bar that really helps with handling too.
For the rears, I chose Eaton Boss 351 heavier springs, BUT the stock 138 lbs rate would have been better for normal street driving. Eaton have 1" longer shackles, but they only raise the back about a 1/2" at center wheel arch. You can buy springs with different eye positions.

Stanglover · Sep 13, 2024

72conv said:
When I restored my car back in 1990-91, I went with a set of 600 lb., 1-1/2 in drop springs. I always use KYB Gas-A-Just shocks (just replaced them recently as the old ones were leaking from age). Never had a problem with the suspension bottoming out and the car sits "just right".

Just my personal experience; I found Gas-A-Just shocks a bit too harsh and changed them for Excel-G and like them better. Nothing wrong with G-A-J's for a firmer ride.

Sheriff41 · Sep 13, 2024

How did you cut your springs? The safe way is with a cutoff wheel since it doesn't overheat the steel. Using a torch can overheat the steel and affect its strength.

tsheakley · Sep 13, 2024

tsheakley said:
Thank for your thoughts Giantpune.
I thought the stiffer shocks and the minimal cut would have that much of an effect.
It bottoms out so easily I don't thing its all just because of the cut. Since the car only has 61,000 miles on it I didn't think the springs would be worn out.
I don't like the stock ride height so I have to do something to get the front down and not bottom out.

Hemikiller said:
Balljoints contribute a lot of friction to the front suspension. If they are well "worn in" and rotate easily, it can contribute to the problem you're having. They don't have to be worn out and sloppy to cause this problem.

I hadn't thought of that. The next time I get it on the rack with my mechanic, we'll check it out.
Thanks Hemikiller

tsheakley · Sep 13, 2024

tsheakley said:
Thank for your thoughts Giantpune.
I thought the stiffer shocks and the minimal cut would have that much of an effect.
It bottoms out so easily I don't thing its all just because of the cut. Since the car only has 61,000 miles on it I didn't think the springs would be worn out.
I don't like the stock ride height so I have to do something to get the front down and not bottom out.

Thanks for your thoughts on shocks too.
Since I've already cut the springs, I'll be making a change to new springs. Any thoughts on stiffer springs with the QA shocks?

tsheakley · Sep 13, 2024

midlife said:
Your original high profile up front may be due to your rear springs being worn and thus, the rear sags a bit. Sounds like your front springs were OK, but when you cut them, they don't have enough travel anymore...just my thoughts.

Hi Midlife,
The car only has 62k miles. It looked like the original stance. The rear didn't look low or too low. I'll post some before and after photos. I wouldn't have thought 1/2 inch would have caused such a drastic change in travel.
Thanks for your thoughts.

tsheakley · Sep 13, 2024

72conv said:
When I restored my car back in 1990-91, I went with a set of 600 lb., 1-1/2 in drop springs. I always use KYB Gas-A-Just shocks (just replaced them recently as the old ones were leaking from age). Never had a problem with the suspension bottoming out and the car sits "just right".

Hi 72conv.
I've seen 1" drop 600lb springs I would prefer 1 1/2" drop if I could find them. If you know a part number I'll check them out.
Thank you

tsheakley · Sep 13, 2024

Stanglover said:
I've said this many times and from my own experience with badly made (Scott Drake) springs, front and back.
Do your self a favor and buy Eaton Detroit Springs springs. If you want, they can custom make what you want or you can buy lowering front springs I believe. At least with Eaton springs, you get the correct material for springs and not some crap made from scrap ships!!
I actually still have the original front springs in my car and I'm using KYB Excel G shocks with out any issues. I do have an ADDCO 1 1/18" sway bar that really helps with handling too.
For the rears, I chose Eaton Boss 351 heavier springs, BUT the stock 138 lbs rate would have been better for normal street driving. Eaton have 1" longer shackles, but they only raise the back about a 1/2" at center wheel arch. You can buy springs with different eye positions.

Hi Stanglover.
Thanks for you experience with Scott Drake springs. I'll look into Eaton. I'm very happy with the rear. I'll also check my sway bar/bars for measurement. The power steering doesn't give me that real positive feel in handling. I also have a 69 390 cougar where I increased the spring stiffness and larger front and rear sway bars. It drives tight as can be expected with the power steering. I'd Like to get at least that feel with this mustang. I don't know why my Excel G shocks feel so soft. The rebound feels good when I push down on the fender.
Thanks for your thoughts.

tsheakley · Sep 13, 2024

Sheriff41 said:
How did you cut your springs? The safe way is with a cutoff wheel since it doesn't overheat the steel. Using a torch can overheat the steel and affect its strength.

We used a cut off wheel.

c9zx · Sep 13, 2024

Cutting 1/2 coil should not cause it to bottom out easily. Mine are cut 1/2 coil with no problems. Hemi's suggestion is a good one. I'd suggest checking the part number on the front shocks to make sure the travel length is correct. I've found incorrect travel length shocks that would bolt on but, bottom the shock out prematurely. I would check everything thoroughly before buying parts that you may or may not need. As a side note, all of the 65-73 Mustangs were a bit lower in the rear from the factory. Chuck

Don C · Sep 13, 2024

tsheakley said:
Hi Midlife,
The car only has 62k miles. It looked like the original stance. The rear didn't look low or too low. I'll post some before and after photos. I wouldn't have thought 1/2 inch would have caused such a drastic change in travel.
Thanks for your thoughts.

You can look up your car's original spring rates and ride heights to the bottoms of the bumpers in the AMA Specifications manuals.
The ride heights are listed on page 2, the key sheet is on page 27.
https://7173mustangs.com/threads/1971-73-ama-documents.23433/

The Ford assembly manual shows the stock ride heights measured from the axle centerlines to the center of the wheel well lip. The front ride height, with 351 and standard suspension is 14.66". The rear is 14.48"

giantpune · Sep 13, 2024

tsheakley said:
Thanks for your thoughts on shocks too.
Since I've already cut the springs, I'll be making a change to new springs. Any thoughts on stiffer springs with the QA shocks?

Nope. On the car with the qa1 stacker shocks, i'm still rocking the worn out 50yr old springs. On my other one with the qa1 coilovers, i went with their 500lb shock option.

Stanglover · Sep 13, 2024

After you play with the front end, you'll need a re-alignment.
Most suggest using the specs below for radial tires.
If you like spending money, you could upgrade your PS box with a fast ratio. Lots of posts on this.

tsheakley · Sep 17, 2024

c9zx said:
Cutting 1/2 coil should not cause it to bottom out easily. Mine are cut 1/2 coil with no problems. Hemi's suggestion is a good one. I'd suggest checking the part number on the front shocks to make sure the travel length is correct. I've found incorrect travel length shocks that would bolt on but, bottom the shock out prematurely. I would check everything thoroughly before buying parts that you may or may not need. As a side note, all of the 65-73 Mustangs were a bit lower in the rear from the factory. Chuck

Thanks Chuck,
I'll check the part number and compare to what the stock travel lengths should be. Since the front is now lower, maybe I shouldn't use the stock specks for the shocks.

Front Suspension Springs and Shocks

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