GT350R Springs for GT (high rate, minimum lowering)

Stuntman · Aug 14, 2017

The lack of compression vs rebound Jacks the car down after hitting a bump, (pulls the sprung mass down to the ground), which makes for a stiff ride. All 4 cars I had Koni yellows on did this as well as most rebound-adjustable coilovers that don't have sufficient compression.

Since Koni yellows are rebound adjustable, stiffening it will make that feeling far worse. Likewise if you have a double adjustable coilovers with a wide range, you can simulate this or try s compression-biased damping curve.

BmacIL · Aug 14, 2017

Stuntman said:
The lack of compression vs rebound Jacks the car down after hitting a bump, which makes for a stiff ride. All 4 cars I had Koni yellows on did this as well as most rebound-adjustable coilovers that don't have sufficient compression.

Since Koni yellows are rebound adjustable, stiffening it will make that feeling far worse. Likewise if you have a double adjustable coilovers with a wide range, you can simulate this or try s compression-biased damping curve.

Yeah I know what you're saying about the jacking down, but what I'm getting at, is that this aspect didn't get worse. It's about the same and wasn't bad with the Steeda dampers. What wasn't quite there was the compression. We are agreeing about the effects of inadequate compression vs. rebound.

Edit: The Steeda dampers actually do have more (about 20%) compression damping, but I was missing enough rebound for my springs.

Stuntman · Aug 14, 2017

BmacIL said:
Yeah I know what you're saying about the jacking down, but what I'm getting at, is that this aspect didn't get worse. It's about the same and wasn't bad with the Steeda dampers. What wasn't quite there was the compression. We are agreeing about the effects of inadequate compression vs. rebound. I'm simply stating that the Koni has more C vs. R at the low end of the adjustment range vs. the Steeda I had, while having a similar R.

I admit that I haven't driven a S550 with Koni Yellows, but 4 different platforms had a severe lack of C relative to R (which maxed out was WAY too much relative to the spring rate and compression. I would be (pleasantly) surprised if the S550 KY had a decent amount of C.

BmacIL · Aug 15, 2017

Stuntman said:
I admit that I haven't driven a S550 with Koni Yellows, but 4 different platforms had a severe lack of C relative to R (which maxed out was WAY too much relative to the spring rate and compression. I would be (pleasantly) surprised if the S550 KY had a decent amount of C.

Fortunately for me, I'm running fairly heavy spring rates and planning on leaving the dampers near full soft (within 1 turn). They seem to match the springs quite well. I don't think anyone runs these anywhere near maxed out. Most in the 1/2 to 1 1/2 turn range, even for autocross/track.

Edit - conclusions with new data: my Steeda Fixed pro actions were more than enough compression damping for my SP085 springs, but do not have enough rebound to adequately control them. For springs above ~850-900 lb/in, I'd recommend Adjustable Pro Action, Koni Yellows or the new Bilsteins (no data yet but I'm sure they'll be there). Butt dyno wasn't quite right.

Stuntman · Aug 15, 2017

BmacIL said:
Fortunately for me, I'm running fairly heavy spring rates and planning on leaving the dampers near full soft (within 1 turn). They seem to match the springs quite well. I don't think anyone runs these anywhere near maxed out. Most in the 1/2 to 1 1/2 turn range, even for autocross/track.

Edit - conclusions with new data: my Steeda Fixed pro actions were more than enough compression damping for my SP085 springs, but do not have enough rebound to adequately control them. For springs above ~850-900 lb/in, I'd recommend Adjustable Pro Action, Koni Yellows or the new Bilsteins (no data yet but I'm sure they'll be there). Butt dyno wasn't quite right.

What rates did you end up with again. Agreed that the jacking is greatly reduced with high spring rates. My comments were on more normal "street" rates. Then again, when a Koni Yellow has a spring rates that is better for the rebound, it starts to relatively lack compression damping. So my problem with them has always been jacking with soft springs or lack of compression on stiffer springs.

BmacIL · Aug 15, 2017

Stuntman said:
What rates did you end up with again. Agreed that the jacking is greatly reduced with high spring rates. My comments were on more normal "street" rates. Then again, when a Koni Yellow has a spring rates that is better for the rebound, it starts to relatively lack compression damping. So my problem with them has always been jacking with soft springs or lack of compression on stiffer springs.

I'm at 240/980, so around 230-235 lb/in wheel rate front and rear, which is about 50% higher than stock rates. That is pretty firm for regular street use but still tolerable.

Ryan1112 · Sep 17, 2017

BMR Tech said:
So, I went ahead and revised our SP084 front springs (the front springs for the SP083 Handling Kit) and they will now be a 7/8" drop and right at 250lb/in. ;)

Figured you guys would like to know this.

So, the SP083 Handling Kit will soon be 250F/980R with 7/8"F Drop and 1/2"R Drop.

Perfection in my eyes! This is approx 4% stiffer front and 6% stiffer rear - compared to the GT350R springs.

Any update on when the new front springs will be available? I'm dying to get my hands on a set. Also, will these have the helper coils in the middle like the last version?

saf1 · Dec 8, 2017

Anyone running these setups change the front and rear sway bars? It is about the only thing I've not looked at yet with regards to the setup(s) we have been discussing here. With my 15 GT/PP I'm in the camp that has:

GT350R fronts
BMR SP085 rears
BMR CB005 cradle lockouts
BMR jacking rails
Steeda billet shock mounts
Steeda Pro Action Adjustable shock/struts

Most of it is still in boxes in the garage due to work/travel but since that is slowing I figured I'd ask the question about sway bars. I'm not sure I want to throw those into the mix yet but figured I'd ask. Hope everyone is doing well and enjoying the ride.

BmacIL · Dec 8, 2017

saf1 said:
Anyone running these setups change the front and rear sway bars? It is about the only thing I've not looked at yet with regards to the setup(s) we have been discussing here. With my 15 GT/PP I'm in the camp that has:

GT350R fronts
BMR SP085 rears
BMR CB005 cradle lockouts
BMR jacking rails
Steeda billet shock mounts
Steeda Pro Action Adjustable shock/struts

Most of it is still in boxes in the garage due to work/travel but since that is slowing I figured I'd ask the question about sway bars. I'm not sure I want to throw those into the mix yet but figured I'd ask. Hope everyone is doing well and enjoying the ride.

I would do the primary stuff first and do bars later if necessary for tuning aid. Doing too much at once means you won't know what did what.

Norm Peterson · Dec 8, 2017

Agreed ↑↑↑

Find out what the car - and at least as importantly your driving preference - wants first. If it needs bars, choosing adjustable bars will give you the widest variety of tuning options.

Too understeerish will have a slightly 'heavy' feel about it, oversteerish will feel too "lively". You'll want something in between, which might not be the same as what I might choose. Bmac might prefer something different still. Plan on a little experimentation.

Norm

keltymd · Dec 8, 2017

I found mine, with my driving style, works great with
gt350R front and rear
Steeda fixed valve dampers
Steeda toe link bearings
Steeda rear control arm bearings
BMR vert links
Steeda camber adjusters

I had the gt350r front and rear sway bars installed and the car would work great for drifting but found the slightly softer GTPP sway bars let it grip a bit more in the corners. Now that is running street tires I am sure the GT350R bars would do better with some comp rubber.

BmacIL · Dec 8, 2017

keltymd said:
I found mine, with my driving style, works great with
gt350R front and rear
Steeda fixed valve dampers
Steeda toe link bearings
Steeda rear control arm bearings
BMR vert links
Steeda camber adjusters

I had the gt350r front and rear sway bars installed and the car would work great for drifting but found the slightly softer GTPP sway bars let it grip a bit more in the corners. Now that is running street tires I am sure the GT350R bars would do better with some comp rubber.

Yes, with grippier rubber, and the resulting higher Gs and roll angle it would bring, the stiffer bars would keep your roll control in check along with giving you a tuning aid. I still stand by leaving them alone till after you've done your big list so far, [MENTION=29413]saf1[/MENTION] :thumbsup:

saf1 · Dec 8, 2017

BmacIL said:
Yes, with grippier rubber, and the resulting higher Gs and roll angle it would bring, the stiffer bars would keep your roll control in check along with giving you a tuning aid. I still stand by leaving them alone till after you've done your big list so far, [MENTION=29413]saf1[/MENTION]

I am. It was more of a Christmas list thing ;) I'll find a T or Polo shirt from one of the venders I purchased from then - lol.

Thanks!

2015Etrac · Dec 9, 2017

I just purchased front and rear GT350R sway bars. I probably won't have a chance to install them for a few weeks though. If I had PP sway bars, I probably would have left them on the car, but I have a non-PP GT.

Tmason · Dec 10, 2017

BMR Tech said:
So, I went ahead and revised our SP084 front springs (the front springs for the SP083 Handling Kit) and they will now be a 7/8" drop and right at 250lb/in. ;)

Figured you guys would like to know this.

So, the SP083 Handling Kit will soon be 250F/980R with 7/8"F Drop and 1/2"R Drop.

Perfection in my eyes! This is approx 4% stiffer front and 6% stiffer rear - compared to the GT350R springs.

Curious when these will be available as well as I currently have the handling springs and will be adding some weight to the front and am worried I might be a little low.

GT350R Springs for GT (high rate, minimum lowering)

Stuntman

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BmacIL

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Stuntman

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BmacIL

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Stuntman

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BmacIL

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Ryan1112

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saf1

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BmacIL

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Norm Peterson

corner barstool sitter

keltymd

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BmacIL

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saf1

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2015Etrac

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Tmason

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