GT350R Springs for GT (high rate, minimum lowering)

BmacIL · Oct 28, 2016

sredish said:
I'm seeing mention of FR3Z-5560-T in the beginning of the post as the "R" spring, then I also see mention of the FR3Z-5560-S as a 350 spring. Is one the R and the other the std350 or are they fully interchangeable as the left rear spring.

Reason I ask... I ordered FR3Z-5560-S x 2

Those are GT350 (non-R) rear lefts. FR3Z-5560-N is the GT350 (non-R) rear right. FR3Z-5560-P is the GT350R rear right.

Rebellion · Oct 28, 2016

BmacIL said:
Looks perfect.

I has been possible thanks to the information you have shared...really appreciate it!

BmacIL · Oct 28, 2016

xXANCHORMONXx said:
Track pack

This is interesting, though one thing that sort of makes that progressive part of the plot irrelevant: The car will compress the spring at least 1" at ride height, probably closer to 2", therefore taking the spring into the linear part of the curve right away.

Rebellion · Oct 28, 2016

BMR Tech said:
BOOOOOM!

Perfect!

No. Leave it alone.

That is a handling machine right there. Bet!

If the BMR authority says it looks cool...it must! :cheers:

Thanks for coming up with all these good products and helping folks here and on the phone.

Rebellion · Oct 28, 2016

BmacIL said:
This is interesting, though one thing that sort of makes that progressive part of the plot irrelevant: The car will compress the spring at least 1" at ride height, probably closer to 2", therefore taking the spring into the linear part of the curve right away.

I find it curious that the R rears are actually a tad softer at max compression, a wee bit less than 10%. When combined with the wheel rate, I don't think the difference can be felt.

BmacIL · Oct 28, 2016

Rebellion said:
I find it curious that the R rears are actually a tad softer at max compression, a wee bit less than 10%. When combined with the wheel rate, I don't think the difference can be felt.

That's almost in the noise (2126 lb vs 2133 lb). What I find interesting is the 'linear' average rate differences in the range 1.5" to 3" of compression:

GT350: 930 lb/in
GT350R: 834 lb/in

The R rear springs are slightly progressive, going from 814 lb/in to 874 lb/in between 2" and 3" of compression, and the GT350 springs go from 915 lb/in to 960 lb/in in the same range.

BmacIL · Oct 28, 2016

Conclusion on linear vs. progressive on the Shelby springs: Both of them are extremely close to linear in the working range of the springs. They have a trend line that is nearly a straight line, though it has a slight curve. Manufacturing tolerances can and do make a difference here. The point is that they are engineered to be linear springs. See the below chart that's scaled for just the rear springs, in their working range.

I'm a little surprised by the rate differences between the two, but the R is a stiffer spring.

Rebellion · Oct 28, 2016

Vernichtung said:
I think it looks great as-is. How's she drive and handle?

Thanks. It drives a tiny bit harsher than PP, but reacts much quicker. Corner very well, body roll is improved a ton. I have only cornered with a max of 50-60 mph and it handles well, barely any roll on the front.

Getting out of corner, the throttle responds instantly. I haven't lost grip yet, not that I have tried to. With the base GT stock suspension, it would understeer quite frequently, I haven't had any understeer with the new setup. Not that it won't I, the limits are just waaay higher.

The rear grip is improved vastly. There is no oscillation on the rear, it completely eliminated the infinity-sign oscillation and bobble it had when stock. The dampening is pretty much on point after break it...at first it was super harsh, but after two days it rides a lot better. I would say that finally this feels like a 400+HP car, just on the rears alone.

To be objective, the BMR CB005 and CB006 were also added at the same time. A portion of the grip and cornering ability is due to those two.

If I was really nitpicky, the rears are ever-so-slightly underdampened, I feel. I think it sort of makes the ride more comfortable vs the opposite scenario. I would leave the rates as it, as they handle well, reacts quick, and rides decent.

Honestly, I'm more amazed at the fronts...I think the rear could use a new sway, for this setup the stock base GT rear sways seem to not be adequate. The fronts seem to be good enough for my level of skill.

xXANCHORMONXx · Oct 28, 2016

BmacIL said:
Conclusion on linear vs. progressive on the Shelby springs: Both of them are extremely close to linear in the working range of the springs. They have a trend line that is nearly a straight line, though it has a slight curve. Manufacturing tolerances can and do make a difference here. The point is that they are engineered to be linear springs. See the below chart that's scaled for just the rear springs, in their working range.

I'm a little surprised by the rate differences between the two, though.

You know more about this stuff than me. I'm glad I posted it.

The GT350R sway bar is stiffer due to being shorter which is apparently why the spring rates are the way they are.

Also the spring on the R is slightly shorter at free load

Rebellion · Oct 28, 2016

BmacIL said:
That's almost in the noise (2126 lb vs 2133 lb). What I find interesting is the 'linear' average rate differences in the range 1.5" to 3" of compression:

GT350: 930 lb/in
GT350R: 834 lb/in

The R rear springs are slightly progressive, going from 814 lb/in to 874 lb/in between 2" and 3" of compression, and the GT350 springs go from 915 lb/in to 960 lb/in in the same range.

I was referring to the lbs per inch, the fourth column, its almost a 10% difference. If anything, I expected the R to be stiffer or equal.

BmacIL · Oct 28, 2016

Rebellion said:
I was referring to the lbs per inch, the fourth column, its almost a 10% difference. If anything, I expected the R to be stiffer or equal.

I would've too. That said, the force at each increment is higher, which is ultimately what matters. As pointed out, the rear bar is stiffer because it has shorter arms vs. the GT350, so overall roll stiffness is a decent amount higher.

sredish · Oct 28, 2016

xXANCHORMONXx said:
You know more about this stuff than me. I'm glad I posted it.

The GT350R sway bar is stiffer due to being shorter which is apparently why the spring rates are the way they are.

Also the spring on the R is slightly shorter at free load

Do you by chance have the individual part numbers for those?

Rebellion · Oct 28, 2016

sredish said:
Do you by chance have the individual part numbers for those?

FR3Z-5A772-E non R rear sway bar

FR3Z-5A772-G R rear sway bar

Needs PN for bushing, bracket, maybe arms, and confirm fitment.

Was thinking about getting this, I don't think it tops 100$ for all four parts, sounds like a damn good deal compared to 200$+ for an aftermarket.

BmacIL · Oct 28, 2016

sredish said:
Do you by chance have the individual part numbers for those?

The GT350 rear bar is part number FR3Z-5A772-G
The GT350R rear bar is part number FR3Z-5A772-E

BmacIL · Oct 28, 2016

Rebellion said:
FR3Z-5A772-G non R rear sway bar

FR3Z-5A772-E R rear sway bar

Needs PN for bushing, bracket, maybe arms, and confirm fitment.

Was thinking about getting this, I don't think it tops 100$ for all four parts, sounds like a damn good deal compared to 200$+ for an aftermarket.

OD is the same as the PP bar, so the existing bushings & brackets will work (if you have the PP ones).

GT350R Springs for GT (high rate, minimum lowering)

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