GT500 / GT350R springs on Mach 1

[Mikepol2]

I have a Mach 1 with the handling package, and Steeda adjustable sway bars with the front setting on 2nd stiffest, and the rear on softest. Street use only.

I'd still like less lean / wallowing through corners. Tried the front sway bar on the stiffest setting and it pretty much solves the problem, but it's too harsh for regular use on our crappy western PA roads.

I also have Project 6GR Ten R-spec wheels (19 x 11 front, 19 x 11.5 rear) with 305/30's up front and 325/30's in the back. So I don't want to take a chance on lowering springs rubbing.

The stock spring rates are 211 front / 742 rear. 350R fronts are 240 lbs. 2019-2020 350's have 857 lb rears, and 350R's and 2016-2018 350's are 914 lbs rear.

So I'm trying to decide if the 350R fronts would make a noticeable difference and would they lower the car a lot. Also whether to leave the rears alone, or replace with one of the 350 sizes.

Any advice would be appreciated thanks!

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[NightmareMoon]

Yeah I’d take a shot at the 350R springs. They still arent all that stiff (I run 650# front springs for comparison), but front springs aren’t that hard to swap, so probably worth the effort. However its only like a 15% change and probably less than that in body roll. Body roll isnt a bad thing, you may be a bit too concerned about it. Its only a problem IMHO in very very fast switchbacks or slaloms (which dont occur on streets), and your swaybars fix a big chunk of that by themselves. Springs are a big help when you want to cancel some of the dive/squat.

You can only go to about 350# dual rates (steeda ultimates) before you have to jump to coilovers and ditch the magnaride, which would bee a pain.

Those dual rates may be a good option if you have magnaride but they lower the car 3/4”, and you’d want to do front and rear together. With 11” front wheels and lowered, you’ll get a little rubbing sometimes. Now, without magnaride, I found the dual rates to be kind of annoying on normal imperfect roads. They’d be better with magnaride but still they’re a bit much for just street duty. So the GT350R are a good choice if you arent wanting to lower the car.

 

[Mikepol2]

Yeah I’d take a shot at the 350R springs. They still arent all that stiff (I run 650# front springs for comparison), but front springs aren’t that hard to swap, so probably worth the effort. However its only like a 15% change and probably less than that in body roll. Body roll isnt a bad thing, you may be a bit too concerned about it. Its only a problem IMHO in very very fast switchbacks or slaloms (which dont occur on streets), and your swaybars fix a big chunk of that by themselves. Springs are a big help when you want to cancel some of the dive/squat.

You can only go to about 350# dual rates (steeda ultimates) before you have to jump to coilovers and ditch the magnaride, which would bee a pain.

Those dual rates may be a good option if you have magnaride but they lower the car 3/4”, and you’d want to do front and rear together. With 11” front wheels and lowered, you’ll get a little rubbing sometimes. Now, without magnaride, I found the dual rates to be kind of annoying on normal imperfect roads. They’d be better with magnaride but still they’re a bit much for just street duty. So the GT350R are a good choice if you arent wanting to lower the car.

Great stuff. Thanks!

 

[RobZ71LM7]

GT500 and GT500 CFTP front springs are both slightly stiffer than 350R springs. I've been considering them as I do HPDE but want to keep factory magneride. AND not lose any ride height. I have considered Steeda Dual Rates in the front combined with their spacers to put it back at factory ride height (they make spacers that work with their camber plates which I have already). I'll probably keep HP rear springs or put R springs in the rear. I'm doing this for dive/squat not body roll.

 

[Mikepol2]

GT500 and GT500 CFTP front springs are both slightly stiffer than 350R springs. I've been considering them as I do HPDE but want to keep factory magneride. AND not lose any ride height. I have considered Steeda Dual Rates in the front combined with their spacers to put it back at factory ride height (they make spacers that work with their camber plates which I have already). I'll probably keep HP rear springs or put R springs in the rear. I'm doing this for dive/squat not body roll.

Good call. GT500 fronts are 251 lbs and CFTP fronts are 268 lbs.

FWIW I used those Steeda spacers on my 2018 GT, I think I still have a couple lying around somewhere. Was able to use the stock strut studs and new shorter profile nuts with just 1 or 2 of them I believe. Using the whole stack required replacing the strut studs with longer ones.

 

[WItoTX]

Look at AJ Hartman's coil over conversion kit. I'm using stock dampers and standard 7" coil over springs. Up front I'm at 400 lb springs, and I retain the factory mag ride/dampers. The plan is to jump to the 500 dampers.

Now, you will lose some ride height. I'd say I'm about 12-15mm lower than stock.

I think the ride you are looking for would be in AJs conversion kit, especially if you did front and rears. Just another option.

 

[Schwerin]

How do they compare to FP springs? I've dailied those on PA roads for the last 5yrs with no problem.

 

[Mikepol2]

Should also add, I have about 80 lbs more than stock hanging off the front end of the car with the supercharger and intercooler, wonder if that has any effect that would make a little higher front spring rates a good idea.

 

[GTP]

My 2019 GT is PP with magneride. I am putting on GT500 front springs at 250#, but keeping my rear OEM springs at 728#. This is a DD + Track car.

I insist on stock ride height, and so we will find out if I have to space up the front a little. Also planning on putting on Steeda camber plates since my current ones don't go negative enough.

 

[RobZ71LM7]

Good call. GT500 fronts are 251 lbs and CFTP fronts are 268 lbs.

FWIW I used those Steeda spacers on my 2018 GT, I think I still have a couple lying around somewhere. Was able to use the stock strut studs and new shorter profile nuts with just 1 or 2 of them I believe. Using the whole stack required replacing the strut studs with longer ones.

I’m probably going to order GT500 CFTP springs, but if you get them before I do let me know before and after ride height. I hear rumors they are lower than regular GT500, but I don’t know if I trust that after my M1 experience. I never experienced a height change after going from non-HP to HP springs while some claim there is a ride height change outside of the different tire sizes.

 

[RobZ71LM7]

Look at AJ Hartman's coil over conversion kit. I'm using stock dampers and standard 7" coil over springs. Up front I'm at 400 lb springs, and I retain the factory mag ride/dampers. The plan is to jump to the 500 dampers.

Now, you will lose some ride height. I'd say I'm about 12-15mm lower than stock.

I think the ride you are looking for would be in AJs conversion kit, especially if you did front and rears. Just another option.

Are you on the factory VDM or DSC Sport? I’ve considered the AJH conversion but I don’t know if the stock VDM would dampen rates that high. I’m trying to avoid the DSC since their support as well as technical knowledge has become poor according to others.

 

[GTP]

I’m probably going to order GT500 CFTP springs, but if you get them before I do let me know before and after ride height. I hear rumors they are lower than regular GT500, but I don’t know if I trust that after my M1 experience. I never experienced a height change after going from non-HP to HP springs while some claim there is a ride height change outside of the different tire sizes.

Dave in Nashville has CFTP and he said the ride height is a little lower than regular GT500.

 

[WItoTX]

Are you on the factory VDM or DSC Sport? I’ve considered the AJH conversion but I don’t know if the stock VDM would dampen rates that high. I’m trying to avoid the DSC since their support as well as technical knowledge has become poor according to others.

AJ ran his kit on the stock vdm and said it was great. All you have to do is get forscan and reprogram your ride height sensors, which is pretty straightforward.

 

[VictorH]

Since you are street only, I would suggest NOT using the coil-over conversion. I think you're on the right track with a stiffer OEM Ford spring set up.
You can maintain near stock ride height with a coil-over type set up, but for street use I think it's really overkill. The stock suspension is SOFT but unless you track a moderate amount or more going to a really stiff set up probably isn't worth it.
I'm running 325 in lb front and 1200 in lb rear and the car is firm but not harsh. Again, I think this is too much for most public road use unless you have super smooth roads in your area.
Picture of how I was able to maintain near stock ride height, i.e. lots of shims.

 

[VictorH]

Also, any time you remove stock factory bushings or isolators you will get more suspension noise.
I've since added urethane bushings under each spring front and rear which provides just a bit less noise and vibration, the change is very modest but worth it.

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