Got new Penske shocks. Which springs to order ?

[HUBBSTER]

Just got my pretty new Penske shocks. I didnt realize you have to order springs seperately.

They have 225 or 275 # springs available

I mostly drive it on the road. I would imagine the 225# are more comfortable for road use

Would that be correct ?

Thanks

 

[BlackICE]

The spring rates are different front to back. Also the shock settings will be different with different rate springs.

 

[sahlman]

Just got my pretty new Penske shocks. I didnt realize you have to order springs seperately.

They have 225 or 275 # springs available

I mostly drive it on the road. I would imagine the 225# are more comfortable for road use

Would that be correct ?

Thanks

Stock FGT springs are ~190 lb/in front and ~230 lb/in rear. You will want to keep about that 40 lb/in split fornt to rear for ride quality and balance.

However, I am not sure how the Penskes you purchased are valved and if they kept a similar to stock damping split front to rear as well, which affects the ride and handlign balance and quality. 225 lb/in fronts and 275 lb/in rears may be OK, but will free the car up a hair (looser/oversteer) and make it ride a little harsher than stock, but have less roll and pitch on the track.

I would check with your shock supplier on spring recommendations for your shock...spring diameter (2.25" or 2.5") and rate.

Scott

 

[KJD]

Stock FGT springs are ~190 lb/in front and ~230 lb/in rear. You will want to keep about that 40 lb/in split fornt to rear for ride quality and balance.

However, I am not sure how the Penskes you purchased are valved and if they kept a similar to stock damping split front to rear as well, which affects the ride and handlign balance and quality. 225 lb/in fronts and 275 lb/in rears may be OK, but will free the car up a hair (looser/oversteer) and make it ride a little harsher than stock, but have less roll and pitch on the track.


I would check with your shock supplier on spring recommendations for your shock...spring diameter (2.25" or 2.5") and rate.

Scott

Is this place great or what?

The guys who designed, built, and test drove our cars are right here.

Providing info, advice, guidance, perspective, etc.

Only on this car board. THANKS!!!

 

[BlackICE]

Stock FGT springs are ~190 lb/in front and ~230 lb/in rear. You will want to keep about that 40 lb/in split fornt to rear for ride quality and balance.

However, I am not sure how the Penskes you purchased are valved and if they kept a similar to stock damping split front to rear as well, which affects the ride and handlign balance and quality. 225 lb/in fronts and 275 lb/in rears may be OK, but will free the car up a hair (looser/oversteer) and make it ride a little harsher than stock, but have less roll and pitch on the track.

I would check with your shock supplier on spring recommendations for your shock...spring diameter (2.25" or 2.5") and rate.

Scott

Should the front rear split be an absolute 40 lbs or a percentage 190/230=0.826, where the fronts are 82.6% of the rears?


Probably a minor difference for reasonable spring rates.
KW sells shocks.

•Spring Rates: 286lbs/in Front / 400lbs/in Rear

Is that much too high for a street high? The front rear spring rates seem way off?

 

[sahlman]

Should the front rear split be an absolute 40 lbs or a percentage 190/230=0.826, where the fronts are 82.6% of the rears?


Probably a minor difference for reasonable spring rates.
KW sells shocks.

•Spring Rates: 286lbs/in Front / 400lbs/in Rear

Is that much too high for a street high? The front rear spring rates seem way off?

Simple answer…keep the absolute split of 40 lb/in.

More detailed answer…

Within 100+ lbs/in on springs keep the delta/ the split of 40 lb/in. This will stay very close to the stock ride frequency ratio rear to front of 1.05 (5% higher at the back versus the front), which accounts for spring motion ratios, tire rates and sprung mass.

It will also maintain the roll couple distribution (the roll resistance distribution front to rear) just due to the springs of about 40% front / 60% rear, which affects the handling balance.

The springs you note of 286 lb/in front and 400 lb/in rear would hurt the ride frequency ratio and roll couple distribution front to rear (the ride and handling). These would result in a ride frequency ratio of 1.12…7% higher than stock for the rear versus the front. These springs would also free the handling balance up because the roll couple distribution just due to springs would change to 36% front / 64% rear. None of this sounds like a lot, but these are fairly significant differences.

If I were going in that region of springs I would go 300 lb/in front and 345-350 lb/in rear. The springs you refer or these springs I note as an option will result in a much stiffer and harsher ride. Great for the track. Not so bueno for the road.

Scott

 

[fjpikul]

Bueno? Is that Wisconsin talk for ?

 

[BlackICE]

Bueno? Is that Wisconsin talk for ?

That is CA, AZ an TX talk, for sure.

Scott thanks for the insight into the spring rates. I wonder how companies like KW come up with their spring rates? Not having access to development data is like working in the blind! KW spring rates sound much too extreme for street use. How would the increased ride frequency ratio affect handling?

 

[Wwabbit]

Is this place great or what?

The guys who designed, built, and test drove our cars are right here.

Providing info, advice, guidance, perspective, etc.

Only on this car board. THANKS!!!

+1 !

 

[sahlman]

That is CA, AZ an TX talk, for sure.

Scott thanks for the insight into the spring rates. I wonder how companies like KW come up with their spring rates? Not having access to development data is like working in the blind! KW spring rates sound much too extreme for street use. How would the increased ride frequency ratio affect handling?

Last trip to Cabo must have rubbed off...

Glad to help.

As I tried to note, not so elegantly, the KW springs would aslo free up/loosen and head towards oversteer for handling. I don't know what they did to the shocks as well, which could compound issues.

I am looking at performance set of FGT shocks for my own project...may have to sell a few...with good setup info/recommendations so you guys know what you are getting!

Scott

 

[BlackICE]

Last trip to Cabo must have rubbed off...

Glad to help.

As I tried to note, not so elegantly, the KW springs would aslo free up/loosen and head towards oversteer for handling. I don't know what they did to the shocks as well, which could compound issues.

I am looking at performance set of FGT shocks for my own project...may have to sell a few...with good setup info/recommendations so you guys know what you are getting!

Scott

Thanks, I get oversteer, not a good thing to increase for a rookie driver like me.

 

[sahlman]

Thanks, I get oversteer, not a good thing to increase for a rookie driver like me.

10-4...dealing with a car that tends toward spinning is not good for most...especially on the street, when we are typically not as focused with lots of immovable objects in our path. And it will bite many on high speed and aggressive "Esses" at the big tracks.

 

[Ed Sims]

Who did the set up/valving on your shocks? Are they set up for a street FGT? Penskes use o-rings instead of seals so be prepared for more maintenance than Ohlins, Motons or OEM. I have SPD in AZ do my Penske maintenace but I bought them from T&A.

Ed

 

[Wwabbit]

Hubbster- did you get adjustable Penske's?

 

[Ed Sims]

The Penskes are all adjustable for the FGT. Either the 2 or 3 way adjustable I believe (rebound for 1 adjust but choice on compression). All with remote reservoirs. There are piggy back Penskes but I don't think they will fit the FGT.

Ed

 

[Gulf GT]

I have Hypercoil 225lb front and 300lb rear on my three way Penske's for the past 5 years. Feels right to me.

 

[cobra498]

I run 450lb/in fronts and 700 lb/in rears and the ride is not bad, the car is much more responsive now and does not have that lazy stock car feel.

 

[BlackICE]

I run 450lb/in fronts and 700 lb/in rears and the ride is not bad, the car is much more responsive now and does not have that lazy stock car feel.

Wow, those are the stiffest spring I know of on a street driving FGT. Are you using them with the Penske shocks? If so, did they need to be re-valved to match the springs, or did you just have to turn the adjustment knobs?

 

[RALPHIE]

I have Hypercoil 225lb front and 300lb rear on my three way Penske's for the past 5 years. Feels right to me.

I run 450lb/in fronts and 700 lb/in rears and the ride is not bad, the car is much more responsive now and does not have that lazy stock car feel.

Have you guys ever tried closer settings such as what Scott suggested - say, a 40-60 lb difference from front to rear? What testing did you do to come up with your numbers?

I'm very curious, as I am thinking of getting some shocks from Alex, and would like to know the testing you went through to establish your numbers. How many different combinations did you try? Did you test it on skid pads, tracks, etc.? Did you push each setting past the points of adhesion?

 

[dbk]

I run 450lb/in fronts and 700 lb/in rears and the ride is not bad, the car is much more responsive now and does not have that lazy stock car feel.

Holy cow! Pretty stiff. Whatever works!