shock and spring modifications

[Guest Anonymous]

Hi all

 

I have a 260z that i am restoring for street and occasional track work. I have had the front struts shortened by approx 1.5 inches to retain bump travel while lowering the car approx 1.5 inches. The inserts used are a koni adjustable design of shorter stroke (custom, not a Z insert). The springs recommended (by a Z specialist) for these modifications are cut springs of approx 180 lb/in that have a static length that is slightly less that the length between the lower and upper spring seats. This allows them to be loose under full droop.

 

This concerns me for safety and an engineering reasons. i have heard of solutions for this including spring clips to secure the spring but this seems like a bodge fix to me.

 

The alternative is a 260z aftermarket spring which will be lesser stiffness (30% over stock)and may end up causing the bump to droop ratio to be comprimised (> than 60/40).

 

I'm a little lost as i have spent money on shortening the struts and the shorter koni inserts and really want to make the most of what i have done. I dont want to have to drop the car on its rails to retain acceptable suspension geometry and i want to avoid the cut springs advised by the z specialist. Adjustable spring seats is an option but is expensive and maybe a little overkill and also has the problems with registering the vehicle due to obvious modifications.

 

Any ideas guys or experience with my situation. I havent tackeld th rear yet as i want to make sure the front will be acceptable.

 

Regards

 

Kim

 

1976 260Z

[Dan Baldwin]

I just let mine flop around with the car in the air, and then make sure they seat properly when I let the car back down. No biggie, been doing this for 7 years, 50+ track events. I've heard of folks using safety wire, and some coilover setups offer "helper" springs, but I don't see the need for either.

[jeromio]

Or, if it's really buggin you, measure the the distance between perches at full droop, and then buy a set of 180lb springs with that length, maybe slightly longer.

 

I have pretty longs springs up front, such that to do suspension work, I have to unlock the lower perch and spin it down several inches (to remove the strut for instance.

 

It's another benefit of coilovers, no spring compressor required!

[blueovalz]

I do like Dan does too. Always loose at full droop, but once the car is dropped down onto the springs, they settle into the perches on top fine. Once in a while you'll hear them seat the first time you turn the wheel up front. With a light car and even moderate springs, the springs will not compress very much (mine with 200lb springs only compress 1.875"). Obviously the suspension geometry will move much more than this, so even with the adjustable perches you will still have this problem. The only thing that I can think of that would fix this is a dual rate spring that is long. This way it will keep the spring seated at full droop at a lower rate, but once the car reaches its static ride height, the heavier rate then dominates the charateristics of the handling. I would try to find one that has the largest spread between the rates (or as is commonly done, stack two springs of different rates on top of each other with again, the coil over set-up you were trying to avoid) to allow for more length on the spring.

[ZROSSA]

I belive that once the car is on the ground the anti roll bar will load up the oposite side so the spring wont be loose when cornering. It will only be loose if the whole front or rear is off the ground. I have even cosidered mounting a tab in the center of the anti roll bar that when loaded with enought dive will work againt a bump rubber or stiff sping to give more dive stiffness. Thus would be a race car only mod, done to allow me to run very low to the ground without having to run really stiff springs. Single seater single and 3 spring set ups work similar.

 

Douglas

[Synlubes]

Hey kspunner

I to am getting ready to shorten some strut tubes, ? for you is, What koni`s are you using???

2nd, my springs are also loose with car up, Same as others I have been runing car for some time with no problems!

Thanks