FRPP P Spring Rates

[cm581978]

Ive searched, without much luck. Does anyone know what the spring rates are of the P springs?

 

[csamsh]

170 front, 120 rear? I think that's about right.

 

[kcbrown]

Vorshlag tested the spring rates for the P springs. Here's the results:




Seems a bit low to me. I'm presuming that Ford Racing hasn't changed the springs for that kit, and that there isn't a different version for later S197 cars than for earlier ones.

With those rates, I'd think you'd be on the bump stops all the time.

 

[sheizasosay]

The car weight is gonna collapse a coil or more. The working range probably starts at the 1.5" range in the chart which is typical 200ish in/lbs.

 

[kcbrown]

The car weight is gonna collapse a coil or more. The working range probably starts at the 1.5" range in the chart which is typical 200ish in/lbs.

For those specific springs, at 1.5", the rates are 147 lb/in for the front and 109 lb/in for the rear.

Considering the Boss 302 springs are 148 lb/in for the front and 186 lb/in for the rear, and that's for a ride height that is half an inch higher in the front and at least an inch higher in the rear, the P spring rates seem low, especially for the rear, which doesn't seem to change its rate until 3.5".

The rear P springs don't ever reach even the rate of the base GT (156 lb/in).

A car with P springs might not, while cornering hard, be riding on the stops in the front, but I don't see how it wouldn't ride on the stops in the rear...

 

[sheizasosay]

For those specific springs, at 1.5", the rates are 147 lb/in for the front and 109 lb/in for the rear.

Considering the Boss 302 springs are 148 lb/in for the front and 186 lb/in for the rear, and that's for a ride height that is half an inch higher in the front and at least an inch higher in the rear, the P spring rates seem low, especially for the rear, which doesn't seem to change its rate until 3.5".

The rear P springs don't ever reach even the rate of the base GT (156 lb/in).

A car with P springs might not, while cornering hard, be riding on the stops in the front, but I don't see how it wouldn't ride on the stops in the rear...

I read it wrong. You guys got the rate right.

 

[cm581978]

Good info! Reason I ask is I have K springs on my car, but I have P springs in a box. Was going to order some Konis this weekend and am looking for a less teeth chattering ride. the streets here in NJ arent exactly in the best condition. I believe the K springs are closer to a spring rate of 225 or so in the fronts.

 

[csamsh]

I think the low spring rate is probably a good thing. Switching from theory mode to experimental here for a second...the Shelby GT and its P Springs was the unquestioned master of SCCA F Stock until the coyote existed.

 

[frank s]

I thought the Shelby Mustang GT had the "K" springs.

Any road, the "P" springs on my '09 GT/CS never hit the bump stops either in careful road driving, or on autocross (Bridgestone Re-01s) or Chuckwalla Valley Raceway (Goodyear F1 Supercars). Koni yellow struts/shocks.

 

[cm581978]

Yes, the Shelby GT does come with the K springs. Id have to believe the P springs, with a lessor spring rate are more ride compliant

 

[sheizasosay]

I wish I would have bought a Shelby GT instead of my Roush Sport. Just having the 6 speed would have been worth it. I like the styling better too for that matter.

 

[69Mach1-409]

Shelby GT was a regular GT with a CAI, axleback, some suspension, and tune. They had the stock GT powertrain.

 

[Whiskey11]

Shelby GT was a regular GT with a CAI, axleback, some suspension, and tune. They had the stock GT powertrain.

You left out the "And it's a real Shelby" from the list of changes! That does matter to some people. FWIW, the Shelby GT is still a strong contender for F-Street R and F-Street. I'd venture to guess that it's the better F-Street car but the half inch of wheel width deficit to the Brembo stangs is a buzz kill.

 

[sheizasosay]

Shelby GT was a regular GT with a CAI, axleback, some suspension, and tune. They had the stock GT powertrain.

I couldn't believe it when you typed it. I been sitting here googling to verify. I must have just ran into a rash of modders that dropped 6 speeds in and I called it the norm. Hell I was even gonna buy one and it had a 6 speed, but it was wrecked. Well I feel better about the Roush now .

 

[69Mach1-409]

The GT500's all had 6spd.

 

[csamsh]

delete please...

 

[BMR Tech]

It would help if we knew the free height of the springs.

Anyone have these springs laying around, that can measure how tall the spring is - as it sits on the floor?

Until I know those heights, I won't try to guess the effective rates of these springs.

 

[BMR Tech]

Actually, I'm going to guess and say the "rate" that people are looking for, with these springs, is around 180F / 140R.

 

[cm581978]

Sounds about right, as I believe the K springs are 225F/190R or so. I'm assuming there has to be a noticeable right difference between those rates.

Actually, I'm going to guess and say the "rate" that people are looking for, with these springs, is around 180F / 140R.