Lowering GT350R ...is it worth it? (Eibach, FP and BMR)

[madlag]

They say the 2015-2018 GT350 rear is stiffer than the GT350R I wonder if that is true. My 2020 GT350 says the rear springs are 6% softer which is why it doesn’t bounce around.

I just wish I could figure out how to lower the car and keep the suspension as good as it is now or better. Some people say the Ford Performance lowering springs are too soft in the rear.

I know people that run the FP springs and they're very happy with the performance. And thats on the twisty mountain roads. I think T has the FP springs all the way around and was happier on track with his.

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[ShatterPoints]

my opinion is the R suspension was WAY too stiff for non perfect roads like, off track lol. Regular roads under aggressive driving caused major wheel hop and general traction issues. I use DCS suspension controller to help and it made a huge difference. I'm going to FP springs/sways sometime this year.

To be accurate, springs transmit stiffness. Shocks transmit harshness. The OEM springs are actually pretty good they are not too soft or stiff. The dampers / shocks on the other hand... while magnaride is nice, in the 300mi I have put on my car since purchase I am starting to understand the issues with it. The DSC controller IMO is not worth anything until TPC gives us a shock dyno since their controller only changes a % of the damper's capacity at a certain acceleration. I am not told what lb per inch force is being generated at any given % of damper force. The driving behavior you are describing is 100% all damper setup. I would agree that the shocks are too stiff at low speed, low impulse bumps. High speed the shocks are actually pretty great. Springs and sway bars are displacement activated, so in a turn once the weight moves your sway bar is not doing anything, same with your springs.

They say the 2015-2018 GT350 rear is stiffer than the GT350R I wonder if that is true. My 2020 GT350 says the rear springs are 6% softer which is why it doesn’t bounce around.

I just wish I could figure out how to lower the car and keep the suspension as good as it is now or better. Some people say the Ford Performance lowering springs are too soft in the rear.

If you want to lower the car and keep the suspension as good as it is you need to go custom, or at the very least move the OEM spring perch. You might look into cutting the OEM perch and then getting a ground control coilover adapter. https://groundcontrolstore.com/coll...djustable-ride-height-kit?variant=35982436419

You are not salved to choosing BMR, Vorshlag, etc if you know the spring rate you want. You can get the spring size which fits the adapter you choose (eg ground control) and you can make your own "coilover".

 

[madlag]

To be accurate, springs transmit stiffness. Shocks transmit harshness. The OEM springs are actually pretty good they are not too soft or stiff. The dampers / shocks on the other hand... while magnaride is nice, in the 300mi I have put on my car since purchase I am starting to understand the issues with it. The DSC controller IMO is not worth anything until TPC gives us a shock dyno since their controller only changes a % of the damper's capacity at a certain acceleration. I am not told what lb per inch force is being generated at any given % of damper force. The driving behavior you are describing is 100% all damper setup. I would agree that the shocks are too stiff at low speed, low impulse bumps. High speed the shocks are actually pretty great. Springs and sway bars are displacement activated, so in a turn once the weight moves your sway bar is not doing anything, same with your springs.



If you want to lower the car and keep the suspension as good as it is you need to go custom, or at the very least move the OEM spring perch. You might look into cutting the OEM perch and then getting a ground control coilover adapter. https://groundcontrolstore.com/coll...djustable-ride-height-kit?variant=35982436419

You are not salved to choosing BMR, Vorshlag, etc if you know the spring rate you want. You can get the spring size which fits the adapter you choose (eg ground control) and you can make your own "coilover".

Yea I know how the suspension components work. DCS made measurable track gains and I could tell instant difference between the modes and the harshness of the car ride from cruising to WOT. The biggest area of improvement for me was being able to put more power down to ground because the body controller detects rear end squat and opens the dampeners. And yes, I agree, thats all damper related. And yes springs def too harsh at low speed tho too. If you haven't had the pleasure or experience before/after with DCS then you need to spend some time with it before passing judgement. It's prob the best thing I've done to the car. I ran the car stock for 18 months and have been on the DCS set up for around 18 now as well. No regrets.

 

[ShatterPoints]

Yea I know how the suspension components work. DCS made measurable track gains and I could tell instant difference between the modes and the harshness of the car ride from cruising to WOT. The biggest area of improvement for me was being able to put more power down to ground because the body controller detects rear end squat and opens the dampeners. And yes, I agree, thats all damper related. And yes springs def too harsh at low speed tho too. If you haven't had the pleasure or experience before/after with DCS then you need to spend some time with it before passing judgement. It's prob the best thing I've done to the car. I ran the car stock for 18 months and have been on the DCS set up for around 18 now as well. No regrets.

I don't doubt the DSC does make a change. Or that it could make a good change. My problem is I do not know what it is changing for example, what force in lbs per inch is generated at 45% damper capacity? It cannot give me that number, so the changes to me are unable to be evaluated. Otherwise you're chasing your tail forever waiting for their "next firmware upgrade" or the never ending cycle of adding or removing low or high speed damping force. Short of throwing a set of potentiometers on the car I am not sure how to get that data. It would be worth while to go traditional monotube dampers where you can control the shim stack exactly and then dyno the damper to know what is going on.

 

[Driveway Demons]

I know people that run the FP springs and they're very happy with the performance. And thats on the twisty mountain roads. I think T has the FP springs all the way around and was happier on track with his.

I have heard the same thing but I hear on the street the rear is too soft. That’s what I am trying to figure out.

many choices right now are:

1. oem GT350R springs (2019+ has gt350R rear sway bar and identical shocks and everything else.

2. ford performance springs

3. ford performance springs front and BMR linear rear.

 

[ShatterPoints]

I have heard the same thing but I hear on the street the rear is too soft. That’s what I am trying to figure out.

many choices right now are:

1. oem GT350R springs (2019+ has gt350R rear sway bar and identical shocks and everything else.

2. ford performance springs

3. ford performance springs front and BMR linear rear.

What specifically do you want? If you make a suspension change to fulfill a subjective want/need then there is not much we can do to offer advice aside from so-n-so said this one brand was good. If you're looking for stance, then there are lots of options. If you want the car to perform better, the available spring rates mentioned in your options are fine it is the damper/ shock that you need to address.


*edit*
Read all of this:
http://farnorthracing.com/autocross_secrets5.html

 

[Driveway Demons]

What specifically do you want? If you make a suspension change to fulfill a subjective want/need then there is not much we can do to offer advice aside from so-n-so said this one brand was good. If you're looking for stance, then there are lots of options. If you want the car to perform better, the available spring rates mentioned in your options are fine it is the damper/ shock that you need to address.


*edit*
Read all of this:
http://farnorthracing.com/autocross_secrets5.html

I want to lower the car a bit without compromising the ride now. I want it equal to or better. The campers on the GT350 have the same settings as the GT350R and the R is 0.5” lower than the non R. So I figured the dampers would be identical in settings.

That’s why I was looking at the R springs or ford performance. It’s just that a lot of people say the FP springs are too soft in the rear as it takes 3” of travel to get to 700+ lbs/in where as stock R is 900

 

[ShatterPoints]

I want to lower the car a bit without compromising the ride now. I want it equal to or better. The campers on the GT350 have the same settings as the GT350R and the R is 0.5” lower than the non R. So I figured the dampers would be identical in settings.

That’s why I was looking at the R springs or ford performance. It’s just that a lot of people say the FP springs are too soft in the rear as it takes 3” of travel to get to 700+ lbs/in where as stock R is 900

Then use the spring measurements published by vorshlag, order custom length linear springs which match the FP front and the BMR rear spring rates. I'd recommend Eibach as when I was building a custom suspension for my 997tt they were the only spring manufacturer who's published spring rates matched the actual spring which was delivered to me. Hyperco and swift are other good alternatives.

 

[madlag]

I don't doubt the DSC does make a change. Or that it could make a good change. My problem is I do not know what it is changing for example, what force in lbs per inch is generated at 45% damper capacity? It cannot give me that number, so the changes to me are unable to be evaluated. Otherwise you're chasing your tail forever waiting for their "next firmware upgrade" or the never ending cycle of adding or removing low or high speed damping force. Short of throwing a set of potentiometers on the car I am not sure how to get that data. It would be worth while to go traditional monotube dampers where you can control the shim stack exactly and then dyno the damper to know what is going on.

I get it. I’ve never updated the firmware on mine. I have it set and don’t plan to mess with it much again. I’ve thought a few times to add some dampening stiffness back in in normal bc it might be a touch too soft when you start to get rowdy. But I never have. Interstate or cruising in normal is real good now.

What specifically do you want? If you make a suspension change to fulfill a subjective want/need then there is not much we can do to offer advice aside from so-n-so said this one brand was good. If you're looking for stance, then there are lots of options. If you want the car to perform better, the available spring rates mentioned in your options are fine it is the damper/ shock that you need to address.


*edit*
Read all of this:
http://farnorthracing.com/autocross_secrets5.html

Agreed

I want to lower the car a bit without compromising the ride now. I want it equal to or better. The campers on the GT350 have the same settings as the GT350R and the R is 0.5” lower than the non R. So I figured the dampers would be identical in settings.

That’s why I was looking at the R springs or ford performance. It’s just that a lot of people say the FP springs are too soft in the rear as it takes 3” of travel to get to 700+ lbs/in where as stock R is 900

You’ll be fine with the fp springs. It will lower the stance and you’re prob not going to be able to tell on the ride at alll. What Shatterpoints is saying is it’s the dampeners that affect what you’re taking about. Change your springs. Besides, what does too soft on the street mean? We talking going over railroad tracks, cruising around town or raising hell on the mountain twisties?

 

[Driveway Demons]

I get it. I’ve never updated the firmware on mine. I have it set and don’t plan to mess with it much again. I’ve thought a few times to add some dampening stiffness back in in normal bc it might be a touch too soft when you start to get rowdy. But I never have. Interstate or cruising in normal is real good now.



Agreed



You’ll be fine with the fp springs. It will lower the stance and you’re prob not going to be able to tell on the ride at alll. What Shatterpoints is saying is it’s the dampeners that affect what you’re taking about. Change your springs. Besides, what does too soft on the street mean? We talking going over railroad tracks, cruising around town or raising hell on the mountain twisties?

Someone was saying the rear was unpredictable when going over bumps the rear would float and if he hit a bump while in the back roads turning it would go from float to soft and then stiffen in the turn. Kinda unpredictable is what he meant where as the stock R and stock Non R springs are completely linear and dual on the rear which are in the stiffest form 95% of the time so very predictable and not much change.

 

[madlag]

Someone was saying the rear was unpredictable when going over bumps the rear would float and if he hit a bump while in the back roads turning it would go from float to soft and then stiffen in the turn. Kinda unpredictable is what he meant where as the stock R and stock Non R springs are completely linear and dual on the rear which are in the stiffest form 95% of the time so very predictable and not much change.

Someone had a bad install or something lol. You’re not going to experience that by changing over to those FP springs. Also that sounds like a dampening issue not a spring issue. Maybe they had a magnaride issue idk... that description is def not the norm.

 

[Driveway Demons]

Someone had a bad install or something lol. You’re not going to experience that by changing over to those FP springs. Also that sounds like a dampening issue not a spring issue. Maybe they had a magnaride issue idk... that description is def not the norm.

Good to hear! I guess what worried me is many people have been saying “FP springs are great for the track, on the road a different story”. You think the FP springs are better than the R?

what do you think I will feel/see between the stock 865 lb/in spring rate and FP 500 lb/in progressive to 900lb/in at 3” travel?

 

[ShatterPoints]

Good to hear! I guess what worried me is many people have been saying “FP springs are great for the track, on the road a different story”. You think the FP springs are better than the R?

what do you think I will feel/see between the stock 865 lb/in spring rate and FP 500 lb/in progressive to 900lb/in at 3” travel?

It's hard to say without know exactly how the dampers are valved for that velocity. In general you wont feel much from the springs, they respond to displacement and so the feeling will be subjective from bump to bump. On a flat road with few bumps you wont really feel any difference. You will feel the car be softer over low speed, low to moderate impulse bumps like a speed bump and stiffer over higher speed, higher impulse bumps like a rumble strip.

Dampers dampen, and so the feeling at a distance of travel is quantifiable but hard to qualify. Take my 997 shock dyno for example(blue and green are my final valvings):

You can see that there is a force generated at a given damper velocity. So at 3ips there is maybe 110lbs of compression damping(top left). There is a whole lot of math for the dampened and undampened natural frequencies, for the 997turbo critical damping is ~ 43lbs per inch so 110/129 = .85 or 85% of critical. What this means for you and to best answer what you will feel is the car will hit a bump, bounce and then in more than one oscillation it will return to equilibrium.

If you look at this graph you will see the closer to critical and beyond you get the slower the system will return to equilibrium until that time is infinite translating to a harsh "crashy" ride.

Less than critical and the car will return to equilibrium faster BUT too little damping and you overshoot your static ride height and you feel that as a soft, numb "bouncy" ride.


You want to compromise to reach equilibrium in the least amount of time with the least amount of overshoot. Usually that is somewhere between 65% and 85% of critical.

However WHAT that number is for you is different than it is for me. I could take you for a ride in the 911 and you would agree it rides really well but that there still may yet be a preference of stiffer or softer from you to be "ideal" for you specifically. In other words we could run around the track and you could put down fast times in a setup that you actually don't like the feel of. And so we move away from a performance target and into something more tailored to your subjective experience. I know I am sort of on repeat, but I put in YEARS of time trying to find out how to represent this info in a way that makes sense of why suspension seems like a black box AND why it is so different person to person.

 

[Inthehighdesert]

Talk about analysis paralysis. Spring sets are cheap. Buy them, try them, swap them if your not happy.

 

[Driveway Demons]

It's hard to say without know exactly how the dampers are valved for that velocity. In general you wont feel much from the springs, they respond to displacement and so the feeling will be subjective from bump to bump. On a flat road with few bumps you wont really feel any difference. You will feel the car be softer over low speed, low to moderate impulse bumps like a speed bump and stiffer over higher speed, higher impulse bumps like a rumble strip.

Dampers dampen, and so the feeling at a distance of travel is quantifiable but hard to qualify. Take my 997 shock dyno for example(blue and green are my final valvings):

You can see that there is a force generated at a given damper velocity. So at 3ips there is maybe 110lbs of compression damping(top left). There is a whole lot of math for the dampened and undampened natural frequencies, for the 997turbo critical damping is ~ 43lbs per inch so 110/129 = .85 or 85% of critical. What this means for you and to best answer what you will feel is the car will hit a bump, bounce and then in more than one oscillation it will return to equilibrium.

If you look at this graph you will see the closer to critical and beyond you get the slower the system will return to equilibrium until that time is infinite translating to a harsh "crashy" ride.

Less than critical and the car will return to equilibrium faster BUT too little damping and you overshoot your static ride height and you feel that as a soft, numb "bouncy" ride.


You want to compromise to reach equilibrium in the least amount of time with the least amount of overshoot. Usually that is somewhere between 65% and 85% of critical.

However WHAT that number is for you is different than it is for me. I could take you for a ride in the 911 and you would agree it rides really well but that there still may yet be a preference of stiffer or softer from you to be "ideal" for you specifically. In other words we could run around the track and you could put down fast times in a setup that you actually don't like the feel of. And so we move away from a performance target and into something more tailored to your subjective experience. I know I am sort of on repeat, but I put in YEARS of time trying to find out how to represent this info in a way that makes sense of why suspension seems like a black box AND why it is so different person to person.

from everything you stated I gathered the following information in short:

1. the 565 lb/in for performance springs were engineered that way to return to equilibrium slower (on time I guess) to prevent bounce on the road courses to keep the rear end more stable, for better traction. Which will mean less bounce on the street at lower speeds and sharp bumps. Allowing them to get progressively stiffer at faster bumpe. Effectively removing sloppiness or bounce. Pretty much trying to eliminate anything that would not allow full control or traction of the rear.

2. ford should have use these springs in the cars oem setup but didn’t do so to make extra money and they sit to low due to warranty claims.

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