Can anyone explain to me why manufacturers have their spring rates so high. Zeal is making Function R coilovers now in 18K/14K. I have a friend who is a race car driver by proffesion and has a lot of eperience in the Z and states the spring rates are worthless. He states the excessive spring rates are reducing the mechanical grip of the car. Grand Am cars are only running approx 8K/6K spring rates in the Z.

So what gives with these spring rates? Are there any Z race cars running these high spring rates?

JET

 

Perhaps the Zeal setup is ment for running really high down force levels.

I've done my own spring rate trials and while I won't go against the team chassis setup guy, 448lbs IMO is a little to soft in the front. I know that Scott Bush ran some high spring rates on his custom valved Stance coilover setup(exact numbers could be searched by I'm too lazy).

And this is what the new owner of the former unitech Grand Am car had to say about the spring rates on the car.

 

comparing spring rates from one coilover to another is as usless as **** on a bull

 

Zeal doesnt make off the shelf rates in 18/14. thats a custom setup order by a customer. zeal will custom spec out coilovers in whatever spring rate you want and will valve it to match. you can order 22kg rates if you wanted. hence why you see their function xs at 10/8 function X at 12/10-as far as off the shelf rates.


i've seen specs of Z's tuned in japan, and the most of them run ~16kg front and 14kg rear. i have to dig up some info, but i know there was a red tuner z that had the fastest lap around tsukuba circuit and it was in fact a 16/14 setup, beat the amuse, nismo, sunline and whatever other Z's were there tht day.

 

I could have never said it better myself!

 

Why is that?

JET

 

Is it relative to the weight of the car? I was just curious on if that's what you meant or if it was partial. I forgot who told me that weight of the car plays a factor

 

Sure weight plays a factor. So does the track your driving on. Race teams change valving and springs dependant on what track they are driving. Some tracks are fast and straight, some are more technical, some are rough and some are smooth. All these factors play a part in what spring rate you go with.

JET

 

I was just curious if that's what he meant by comparing different cars

 

Jet, alot of it has to do with valving. From what i know valving tells more about a coilover than the spring rates do.


For instance my Tein monoflex's have a way higher spring rate than my Tanabe NF210/Stock strut combo and IMO the Teins ride SO MUCH BETTER. They aren't near as stiff as you would think just by looking at the spring rates.

 

because of the way different setups valve their dampers

 

That's just innacurate. The spring opposes the vehicle weight and does the work. The valving just controls the spring. If the valving is correct for the spring rate then everything is good. If the valving is off for the given spring rate the spring will be over or under dampened. But the spring is what determines the limit of mechanical grip. An under dampened shock can feel very comfortable and an over dampened shock can feel really harsh. But which spring rate you go with has to do with the weight of the vehicle, the track layout and conditions.

JET

 

exactly Larry...and you just answered your own question

You cannot evaluate coilovers in a vacuum - the only meaningful comparison is several of the same coilovers with various rates vs one another. Comparing brand x with a rate of 1, vs brand Z with a rate of 2, won't really tell you very much without a shock dyno.

 

I have a shock dyno from the manufacturer on the shocks I purchased, but it was not a dyno from my particular set of shocks. Is there a place I can send my shocks to to be dyno'd?

It seems like I have to have a full time R&D team with suspension telemetry to pick the right valving/springs for the given day and track, and have a shock team to buiild, dyno and install them and then I need a test and tune day to iron out the bugs and set the car up.

I NEED A SPONSOR!

JET

 

I would think a stiffer spring, the better the handling(with the right valving).

Stiffer springs = less body roll = less force driving you to the outside of the track. Also you keep more of a equal amount of downward force on the driver side and passenger.

 

On a rought track like Sebring stiff suspension casues tires to lose contact with the ground. If suspension is too stiff it will not absorb the bumps, rather it will transmit the energy into the chasis which upsets the vehicle dynamics.

Here's a perfect example. Turn 17 at Sebring is pretty rough. You can see this Porsche hit a rough spot and upsets the chasis. Then he's just a passenger in the drivers seat along for the ride. This guy is off the line. He went too wide into no mans land and this is how you pay. He almost destroyed a $200,000 GT3. The porsche behind him taking this video took the correct line and hit the apex.

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JET