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

[Bulldogs22]

Yes 19's def closed some of the known gap. Although, it took a couple years and ton of debate to discover that the two models were considerably more different than folks first thought. So who knows what other differences are waiting to be discovered.

This conversation tends to start and end with folks defending why they did or did not buy the R instead of looking at facts.

I knew I would never exploit what the R was made for so I settled for the normal 19 350 and couldn't be happier with how it drives. Luckily my Dad is going to purchase a CFTP 500 for the retirement gift probably next year and we will go to car shows together. We are fortunate to have a great dealer who is a massive volume dealer and will be able to get golden ticket allocations every year the 500 is made. The owner of the dealership has a Ford GT and they have a black CFTP with painted Kona Blue stripes on order right now cant wait to see how sexy that looks.

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[svttim]

I also believe with the 19 updated the normal 350 got the R sway bars and wouldn't say exact but relatively close magnaride tuning. No doubt the CF wheels provide great difference in feel over the normal cast 350 wheels along with a little more downforce from its CF wing compared to the swing with gurney flap.

My understanding was the R was 4 seconds faster initially and I thought that was at VIR. Its now 2 seconds.

 

[Ltsrock]

Now I'm really crying. I stuffed these away and never verified what they were. I had to buy (what I thought were) replacements for my cup2's after I spun on track 360* and flat spotted all four of my almost new tires. It's been an expensive learning curve this year

those are not cup 2s, they are super sports



yep

 

[tbr2001]

Here's a pic of the MPS cup2 325's

Were these the ones they had listed for $199/tire?

 

[lightrules]

anyone got pics of an R on 19" wheels with Ford Perf M-5300-W lowering springs? need to see it before going that route, to see if it is worth it or not.

 

[svassh]

anyone got pics of an R on 19" wheels with Ford Perf M-5300-W lowering springs? need to see it before going that route, to see if it is worth it or not.

50Deep has them, pictures on 2nd page of this thread.

 

[89strok]

anyone got pics of an R on 19" wheels with Ford Perf M-5300-W lowering springs? need to see it before going that route, to see if it is worth it or not.

In the process of installing mine now, front is all set, waiting on my irs bushings to come in to do the rear while its all out. Once im done ill post some pics of it sitting on the 19" signatures

 

[lightrules]

50Deep has them, pictures on 2nd page of this thread.

i saw those already but i believe those are 20" wheels.

In the process of installing mine now, front is all set, waiting on my irs bushings to come in to do the rear while its all out. Once im done ill post some pics of it sitting on the 19" signatures

great thanks. you should probably do an alignment afterwards. looking good though.

 

[Driveway Demons]

based on what I read in this thread 949 is saying that FP is linear? From their specs its legit the same as the GT350R except a tad stiffer front and tad softer rear.

 

[N17]

anyone got pics of an R on 19" wheels with Ford Perf M-5300-W lowering springs? need to see it before going that route, to see if it is worth it or not.

I have the Ford Perf M-5300- installed.
Not an R but i am on R spec wheels. Right now my car sits at about the same height as my buddies R, but i am on 35 tires vs his 30 tires.

 

[Driveway Demons]

I have the Ford Perf M-5300- installed.
Not an R but i am on R spec wheels. Right now my car sits at about the same height as my buddies R, but i am on 35 tires vs his 30 tires.

do you noticed the rear being softer? Someone said it’s soft and bounces/floats over bumps and feels bad on the streets.

 

[ShatterPoints]

Lowering any car, not just specifically the gt350(r) will remove suspension travel. You should also use the correct shock body length, or one with the ability to adjust the spring perch location. Lowering with springs and NOT changing anything else does not in of itself have any sort of performance benefit. You're changing the roll center and its relationship with the roll couple. You would need to change the linkage (suspension geometry) and potentially the ARB in order to realize anything in a spring change as far as performance is concerned. Doing some math for the front of the car since it is a strut and we can be a bit liberal with the assumptions we can look at the regular gt350 and the differences is the FP springs.

This is a neat site:
https://www.drtuned.com/tech-ramblings/2017/10/2/spring-rates-suspension-frequencies

If you plug in 445kg or 981lbs which is 3700*0.53/2 (I am assuming 3700lbs dry weight, 53% front weight divided evenly between each side. I am also assuming a 0.98 MR which is typical of a strut) The result is that our front Wheel Rate is somewhere between 1.3 hz and 1.4 hz with the factory 194lbs spring. If we plug in the 250lbs FP springs were are between 1.5hz and 1.6 hz. Lets make another assumption, we have 1.35hz front WR stock and the FP springs provide a 1.55hz front WR. 1.35 /1.55 = .87. So you get a ~15% increase in stiffness when you swap the front springs. That is easily within the ability of the OEM dampers to adequately control. But there is almost no way to qualify what the increase in stiffness is doing for performance. As a rule the lower your WR the more mechanical grip you are generating. Higher spring rates are a necessity when you are running a lot of downforce so that you do not bottom out. Aerodynamic balance front to rear is also very sensitive to pitch which increased spring rates control.

Holistically there are other things to consider when lowering. Your bump stops need to be changed so that you maintain as much suspension stroke as possible. Most OEM cars are designed to use the bump stops extensively as they are rebound biased which jacks the car (chassis) down onto the bump stops. As that happens you experience an infinite spring rate as the bump stops are more or less solid. However that does control chassis motion, where as if you were 1:1 compression to rebound, or compression biased you would have some chassis movement but be able to be more compliant over bumps. In general on a flat road (tarmac) very little damping is required and so this is all moot as the damper velocity will be between 1 and 3 inches per second (regardless of the spring rate)

If you want to lower your car because it looks cool then awesome, rock on, look bad ass. It's your car, have fun and enjoy it how you like.

If you want lower you car because you want it to perform better then you will need to take into consideration WHAT you are changing and WHY. It is not as simple as moar stiff == moar better.


PS. I find it interesting that we have a front engine vehicle with higher rear rates. Which if the rear motion ratio is reasonable then it would mean that the gt350 has flat ride. This is a suspension strategy employed by GM and is present on many vehicles (corvettes are infamous for it). Flat ride considers the phase delay between the front and rear of the vehicle as it traverses a bump. So the front is slower than the rear which allows the chassis to dampen the oscillation without pitching before the chassis enters a bounce mode.

 

[Driveway Demons]

I’m really confused on the BMR on why it drops the rear more than the front. From what I gathered the ideal setup would be BMR rear with ford performance front.

 

[madlag]

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.

 

[Driveway Demons]

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.

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.

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