Let's compare Steeda Magneride Dual Rate Ultimate Springs on my S550 to a Dark Horse with HP

[MCS]

Ok, so reaching out to my M7G folks to make sure I am not going crazy (and also provide info for others who I know are looking at the same questions/options as I am).

OBJECTIVE/CONTEXT

• My new ride is Dark Horse (with HP)
• Shopping between Steeda Sport Progressives (0.8125" all corners) and Steeda Dual Rate Ultimate Handling (1.31" front / 0.75" rear) springs
  • The goal here is to NOT smash things as I drive down the road
• NOTE: My old S550 had 19" rims and the Dark Horse has 20" rims

DETAILS AND VISUAL COMPARISONS

So let's compare front ends and see if my old eyes are missing anything; do these cars look about the same drop even though the wheel size is different and the drop rate between S550 and S650 are different?

2021 GT Premium (with PP and Supercharger)

Had DUAL RATE ULTIMATE HANDLING SPRINGS

• Drop the S550 0.5" on all four corners
  • Not sure if the supercharger stuff would have made this a bit more or not. Maybe 0.6? 0.7?
  • Never had issues with it hitting anything.
• 275/35R19 in the front
• 305/35R19 in the rear

CHRIS C's DARK HORSE (spliced together from his Insta)

Has DUAL RATE UTLIMATE HANDLING SPRINGS

• Lowers the Dark Horse 1.3" in the front and 0.75" in the rear
• 275/35R20 in the front
• 315/35R20 in the rear
• Stance and Wheel fitment looks awesome!

THE TIRE MATH

So basically....

• The S550 had a 0.5" drop (may be more with the Supercharger kit installed) + a 26.6" tall tire
• The Dark Horse would have a 1.3" drop but with 27.6" tall tire
  • a 1.0" height delta = 0.5" above the axle and 0.5" below the axle
• Net drop would be 0.8" which is only very slightly lower than the 0.5" (before Supercharger) on my S550.

Is the math mathing here or am I missing something?

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[Jmatech]

Following! Math sounds right to me though

 

[MCS]

I ended up going with the Sport Progressives and the 285/35R20 front and 315/35R20 rear.

The hasn't been any rub as far as I can tell.

 

[Ken H.]

I ended up going with the Sport Progressives and the 285/35R20 front and 315/35R20 rear.

The hasn't been any rub as far as I can tell.

Are you having any problems with Pre-collision assist & cruise control since you changed to 20” rims & those tire sizes?

 

[MCS]

Are you having any problems with Pre-collision assist & cruise control since you changed to 20” rims & those tire sizes?

No I did not. I'm back on 19" for now (LMR rims with PS4S tires) but may go back to 20s. I haven't had a single issue with either tire size.

For cruise control just know your rim size and adjust accordingly.

 

[Ken H.]

No I did not. I'm back on 19" for now (LMR rims with PS4S tires) but may go back to 20s. I haven't had a single issue with either tire size.

For cruise control just know your rim size and adjust accordingly.

I had 285/35/20 fronts like you. Pre-collision assist & Cruise went out. Got it back with stock setup. Come cold weather, put 285/30/20’s on (26.6” diameter stock, 26.8” diameter for 20’s). Worked fine for a month, then problem recurred. 305/35/20 rears. I’m confused. I seem to be the only person in the forum getting this problem except one guy who had it without changing wheels/tires & found wheel sensor bad.
Back to the dealer!
Thanks for the info

 

[Dark Sprite]

I ended up going with the Sport Progressives and the 285/35R20 front and 315/35R20 rear.

The hasn't been any rub as far as I can tell.

Hi MCS, how was the ride comfort with the progressives and the 20” compared to stock and 19”? Also, any clearance problems driving over speed bumps?

 

[MCS]

Hi MCS, how was the ride comfort with the progressives and the 20” compared to stock and 19”? Also, any clearance problems driving over speed bumps?

Comfort was fine. I mean it's not a C class Mercedes but an 800hp muscle/sports car.

With the 20s I had no issues at all with most clearance. Remember; lowering the car 1/2" (springs) but raising the car (1" larger rims) sort of makes it stock ride height. I sold those 20' rims about a year ago and am running LMR 19" rims now.

Now lowering it with the 19" rims? That is a different story. I have had to be VERY careful.

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