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What is your opinion progressive springs?

AmericanLegend

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My belief is the dampers.


This is also why I believe people who upgrade to linear lowering springs aren't satisfied with the handling compared to those who upgrade both the shocks and springs.

Unless you pair BMR SP080 lowering springs with the Performance Pack shocks. Perfect match.
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I've always been surprised by this, since they offer two sets (one for street, one track-focused, supposedly). The only reason I can think they did this was because the rates they chose were deemed too harsh for the street OR wouldn't be a great match to the dampers. It's hard to know the exact reason.
I read an article about their track package on the Ford Racings website. They said designed it to be a track car that they could still drive home on the street and not beat themselves up too much. So maybe the initial spring rate helps ride on the street to a certain extent and I guess the dampers are obviously designed to suit.
 

Burkey

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I've only run the one set of springs under my car, swapping out the factory PP springs on the second day of ownership. Now on Vogtland 35mm drop, linear front, progressive rear.
When I first started punting the car HARD, I found it to be quite unpredictable, mostly when on opposite lock (track junkies look away)
Fitted BMR CB005 and then sway bars. MASSIVE improvement.
Fitted a heap of other bits (look below) and she's now an animal. Completely predictable, even at extreme slip angles.
I don't think progressive springs are a bad thing at all, however, I can see that having progressives in the front MAY have a much larger influence on handling than it does in the rear.
It's also possible that the actual level of progression on offer will be a major contributor too.
I'm not about to throw these in the bin, they are far from trash.
Obviously wider stickier tyres are going to push the springs that bit harder and perhaps this is where the debate REALLY stems from :shrug:
 

EricSMG

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Unless you pair BMR SP080 lowering springs with the Performance Pack shocks. Perfect match.
That doesn't make sense as the PP shocks are under damped in rebound for the stock PP springs, particularly up front. Add a marginally stiffer but linear spring while reducing travel seems like a step (or two) backwards if you really want true performance.

In other words, the stock PP setup is limited by its shocks, not its springs, and so adding a more aggressive spring isn't the solution.
 
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BmacIL

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That doesn't make sense as the PP shocks are under damped in rebound for the stock PP springs, particularly up front. Add a marginally stiffer but linear spring while reducing travel seems like a step (or two) backwards if you really want true performance.

In other words, the stock PP setup is limited by its shocks, not its springs, and so adding a more aggressive spring isn't the solution.
It's more nuanced than that. 1) cutting the rear bumpstops more than is required to maintain the same travel with the 0.5" lowering improves the bounce/float because this car is using its bumpstops all the time. 2) the PP shocks have a tight bleed setting, a big contributor to the boince. A slight increase in rate will push through this faster. I confirmed this with a Ford Vehicle dynamics engineer and he said they'd look into it. 3) the lower CG improves handling, roll and pitch control.

Most report a ride improvement with the SP080 or SP089/SP082 setup. I'm not going to call probably 70-100 people who have provided feedback on this forum regarding this setup liars. You're not wrong that logically, increasing rate on an underdamped car wouldn't normally help, but a lot is in the details.

Anything else [MENTION=9985]BMR Tech[/MENTION]?
 

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valentinoamoro

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It's more nuanced than that. 1) cutting the rear bumpstops more than is required to maintain the same travel with the 0.5" lowering improves the bounce/float because this car is using its bumpstops all the time. 2) the PP shocks have a tight bleed setting, a big contributor to the boince. A slight increase in rate will push through this faster. I confirmed this with a Ford Vehicle dynamics engineer and he said they'd look into it. 3) the lower CG improves handling, roll and pitch control.

Most report a ride improvement with the SP080 or SP089/SP082 setup. I'm not going to call probably 70-100 people who have provided feedback on this forum regarding this setup liars. You're not wrong that logically, increasing rate on an underdamped car wouldn't normally help, but a lot is in the details.

Anything else [MENTION=9985]BMR Tech[/MENTION]?
Wow. Incredibly useful and insightful answer. Thanks. I learnt something new. Wondered why folks using lower stiffer springs on PP shocks were claiming better ride.
 

ansibe

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I sacrifice my street comfort for track performance, so I insist on linear springs. Spring rate front to rear affects balance, and I personally don't want my car's balance to change on the track.

I got the Eibach Pro rates from the suspension sticky:
.........................F......R
Eibach Pro (low) 200 800
Eibach Pro (high)315 915

You can see that in the transition from low to high rate, the front rises about 50%, and the rear about 12%. Higher front rates generally cause under-steer. When pushing the car hard on a grippy track with reasonable tires, the the loaded (outside) springs will be in the high range, tending to under-steer. The unloaded (inside) wheels will be in the low range, tending to slight under-steer. If you're slithering about, the rates could change from high to low and back again pretty quickly as the suspension oscillates, which might be a very entertaining ride, but not exactly predictable. This effect will be worse on under-damped shocks. On a slippery track (or wet road) the car should tend to over-steer much more easily which could be unsettling.

Blah, blah, blah ... A good fried of mine let me drive his GT PP on the road and track with Pro springs and MT tires (hey, he's a drag racer, don't hold that against him!). It was great. Street performance was stellar, quite a bit better than stock imo. On the track it was fine, but I didn't push his car at all - no braking deep into corners, and no sliding at entry, apex, or exit.

On the street these springs would be hard to beat, and on the track they worked pretty damn well.
 

BmacIL

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I sacrifice my street comfort for track performance, so I insist on linear springs. Spring rate front to rear affects balance, and I personally don't want my car's balance to change on the track.

I got the Eibach Pro rates from the suspension sticky:
.........................F......R
Eibach Pro (low) 200 800
Eibach Pro (high)315 915

You can see that in the transition from low to high rate, the front rises about 50%, and the rear about 12%. Higher front rates generally cause under-steer. When pushing the car hard on a grippy track with reasonable tires, the the loaded (outside) springs will be in the high range, tending to under-steer. The unloaded (inside) wheels will be in the low range, tending to slight under-steer. If you're slithering about, the rates could change from high to low and back again pretty quickly as the suspension oscillates, which might be a very entertaining ride, but not exactly predictable. This effect will be worse on under-damped shocks. On a slippery track (or wet road) the car should tend to over-steer much more easily which could be unsettling.

Blah, blah, blah ... A good fried of mine let me drive his GT PP on the road and track with Pro springs and MT tires (hey, he's a drag racer, don't hold that against him!). It was great. Street performance was stellar, quite a bit better than stock imo. On the track it was fine, but I didn't push his car at all - no braking deep into corners, and no sliding at entry, apex, or exit.

On the street these springs would be hard to beat, and on the track they worked pretty damn well.
The Pro Kit are actually a linear spring, but have intentional and increased bumpstop use included in the rate.
 

JamesinLittleSilver

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Ford springs are Eibach springs rebranded perhaps slightly different. But I would bet pretty close. The track pack comes with pretty decent size sways(as are Eibach I think). I think as a package for the price it cannot be beat. I think overall the balance much better even as a DD, and while I only track occasionally it certainly fits and is more than a match for my driving skills.

Get no complaints from the wifey in fact she likes it better so if you are doing DD.
 

BMR Tech

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One reason I am asking is that my Ford Racing springs are progressive and i don't feel any lack of consistency? But maybe because I am just on the street. But why else would Ford Racing design these for their track pack? Unfortunately their specs are not published.

I'm not thinking of changing, I just want to learn more.
Here is food for thought.

Ford (and all OEMs) put an extreme amount of engineering into their production vehicles.

"aftermarket" parts, even endorsed OR offered by Ford may be tested in similar fashion...but are not required to meet specific NVH and Ride Frequency requirements.

With that said, no S550 trim offering comes from the dealer with a truly progressive coil spring.

That is right. An EB, GT, GT350 or GT350 of any trim level - none have a true progressive spring rate in factory form.

One thing to ask yourself after considering the above. If Ford could make a car ride just OMG super awesome from the factory, THEN have the ability to outperform a Camaro.....why do they use 240F/914R linear spring rates on their current flagship production GT350R?

The answer is simple. There are other factors at play, such as bump stops..bushing deflections..dampers/valving..durability etc.

Often times aftermarket companies try and re-invent the wheel. Ford has the ability to out spend, out-engineer, and make a product with the highest level of ride quality AND performance - yet they do not use a Progressive Spring. Weird.
 

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BMR Tech

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*But they will sell an aftermarket "track" package that when outfitted to a GT Mustang, still does not provide the level of performance their production GT350s provide.

^Forgot to add that tid-bit ;)
 

SteedaTech

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Here is food for thought.

Ford (and all OEMs) put an extreme amount of engineering into their production vehicles.

"aftermarket" parts, even endorsed OR offered by Ford may be tested in similar fashion...but are not required to meet specific NVH and Ride Frequency requirements.

With that said, no S550 trim offering comes from the dealer with a truly progressive coil spring.

That is right. An EB, GT, GT350 or GT350 of any trim level - none have a true progressive spring rate in factory form.

One thing to ask yourself after considering the above. If Ford could make a car ride just OMG super awesome from the factory, THEN have the ability to outperform a Camaro.....why do they use 240F/914R linear spring rates on their current flagship production GT350R?

The answer is simple. There are other factors at play, such as bump stops..bushing deflections..dampers/valving..durability etc.

Often times aftermarket companies try and re-invent the wheel. Ford has the ability to out spend, out-engineer, and make a product with the highest level of ride quality AND performance - yet they do not use a Progressive Spring. Weird.
Your information is incorrect, the GT 350R has progressive springs in the rear and linear in the front.

I will provide great technical info from our engineers next week regarding this post.
 

Rebellion

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Your information is incorrect, the GT 350R has progressive springs in the rear and linear in the front.

I will provide great technical info from our engineers next week regarding this post.
Aren't they dual rate? I think someone posted the Vorshlag test report some while ago.
 

BmacIL

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SteedaTech

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First inch of travel from curb if so,then it is progressive. Most progressive springs go linear after a inch of travel from curb.

Dual rate springs remains the same linear rate from curb to jounce or full compression. Dual rate springs have decreased rate from extension past curb to induce less roll.

I will have some of the best vehicle dynamics spring engineers to explain some of our test data and give some great info for everyone. We work with several OE spring engineers on a daily basis.
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