Constant vs. progressive coil springs

Red50Fox

Active Member
May 6, 2019
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Hello all. As I look at what I'm preparing to do this spring, 5 lug / disc brake conversion with new shock/strut and bushings etc. I've come to the startling realization that the coil springs in this gem are ~32 years old. So, given that "everything" old is coming out from under the car and everything new is going back in, I started looking at springs. I'm not looking to lower the car, stock ride height is fine with me (concerned about tire clearance) but I've seen a lot of info regarding constant vs. progressive and the benefits of each. So now that the internet has confused me I'm reaching out to people that have first hand experience (and opinions) on the subject. The Gem is an 88 5.0 GT, convertible, automatic, with air.

Thoughts?
 
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2000xp8

SN Certified Technician
Aug 8, 2003
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I don't know if you are really going to tell the difference (typically we refer to them as linear and progressive).
I've had both kinds. It's just hard to compare when multiple parts are swapped out at once.
I'd also be surprised if you had a choice when choosing stock ride height.
If you are trying to keep ride quality, me personally i'd just call Maximum motorsports and let them pick you a set of H&R springs.
If budget allows, i'd probably go to coil overs in the front.

I'm not sure what kind of clearance issues you think you are going to have, but I would expect any set of aftermarket springs to lower the car.
I think the h&r sport springs only lower the car about an inch. That really isn't all that much especially if you combine them with new energy suspension isolators.
 

Red50Fox

Active Member
May 6, 2019
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Thank for the info. I hope to tell the difference overall, but you're right probably would not be able to tell new vs. old springs with all the other changes. I was looking at springs on Rock Auto, which has listings for variable rate and constant rate springs and a quick trip around the internet left me with more questions.

I'm not looking at taking it to the track, just some fun street driving. So if there's more info out there please share your thoughts.
 

2000xp8

SN Certified Technician
Aug 8, 2003
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You may want to strongly consider what the car is going to look like with different wheels (which are likely an inch or maybe 3 taller) with lower profile tires.
Foxes tend to not look right when you change the wheels and there is a significant gap. Fresh new springs with no sag, could leave it looking like an offroad vehicle.


Better springs aren't necessarily for race cars (out of the thousands of fox members here, only a couple actually race on road courses)
A set of subframe connectors, decent shocks and struts and good springs can significantly change how the car feels and drives without really altering the ride quality all that much or adversely affecting value. I'd probably go as far as calling the car safer to drive.

I know this, the rear of my car had eibach progressive rate springs and when I switched to h&r's (forgot which set) the car rode notably better.
Some companies engineer their springs, some just stiffen the hell out of them to get better handling.

I don't know how much feedback you are going to get on stock replacement springs around here.

What size wheels and tires are you going to when you do five lug?
 

Red50Fox

Active Member
May 6, 2019
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Hey, thanks for the feedback. As far as rims and tires go. Moving from 16" to 17" and 225/55/16 to 245/45/17 (same diameter). I'm hoping that it won't look like a baja racer, but will be ok. Time will tell.

Thanks again
 

Essn95

Active Member
Jun 21, 2017
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Progressive is typically more comfortable. It adapts to the roads with the spring rate progressing upwards as the compression is increased. A Constant Spring rate will be a certain stiffness permanently. Pair progressive springs with some full length sfc and some quality shocks and you should be on your way to a great ride. If you’re after more performance like twisty roads, go constant.
 

2000xp8

SN Certified Technician
Aug 8, 2003
6,827
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Hey, thanks for the feedback. As far as rims and tires go. Moving from 16" to 17" and 225/55/16 to 245/45/17 (same diameter). I'm hoping that it won't look like a baja racer, but will be ok. Time will tell.

Thanks again
They will be a hair shorter most likely, nothing major.
That 17 inch size shouldn't be a big deal, lowered or not. thought you were going to say something crazy like 295, lol.
 

revhead347

I have face herpes.
15 Year Member
Jun 14, 2004
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Acworth, GA
Live anywhere near North Georgia? I have at least 2 full sets of factory springs in good condition that I haven't thrown out yet. At least one pair has been on the shelf for 20+ years now.

Kurt
 

Red50Fox

Active Member
May 6, 2019
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They will be a hair shorter most likely, nothing major.
That 17 inch size shouldn't be a big deal, lowered or not. thought you were going to say something crazy like 295, lol.
Not going crazy with rims and tires. Just got a bunch of work to get done and with everything else wanted to give serious consideration to springs. Thanks
 

96pushrod

Advanced Member
May 15, 2018
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I feel like I’m one of the few who can’t really tell the difference in ride with linear or progressive springs.
 

7991LXnSHO

Mustang Master
Sep 1, 2010
2,325
353
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Kearney, NE
I rescued my latest Mustang from some stock appearing class. The famous brand, light blue lowering springs rode like a slot car, not quite like a go cart. It was also low enough to scrape the X pipe going to get an oil change. So rather than just put thicker poly isolators for a little more height and kidney rescuing bounce, I replaced them with Ford “B” springs. I kept the same recent struts and shocks. The first two times down my local local twisty road, I was quite surprised. I had to get used to a little unsettling body roll as the weight switched onto the stronger rated part of the spring. I would not put it back on the linear rate too rough springs now, and no longer feel uncomfortable cruising or throwing it into curves, but there was definitely a noticeable difference. I also have a nice rake and a little extra lift for a load or passengers in the back.
 
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