Datsun Roadster Forum-311s.org

I'm about to do a front end rebuild and am thinking about doing a comp. spring, comp. swaybar and some soft shocks. Now hold on, I know what you guys are thinking, WHY soft shocks?
Well I'm hoping to get a lowered ride and better cornering but not as hard a ride as with racing shocks or is that just crazy thinking?
Is there a way to split the difference or is it all or nothing?
Thanks!
Todd-

I'm no expert, but stiffer springs and soft shocks will give a harsh and sharp ride with the added bonus of uncontrolled bouncing. You want a balance. To keep ride quality as good as is possible, you want to retain as much suspension travel as is possible. Comp springs are shorter and must be stiffer to avoid bottoming out.

Mike Young makes a good spring, shorter than stock and not overly stiff.

Lowering the bottom spring perch allows you to keep the stock springs, retain all of the spring travel and lower the car. This gives the desired look with stock feel, but increases the chances of bottoming out. Trimming the bump stop decreases the number of times you will bottom out, but makes it more violent when you do...

Most off the shelf shocks (KYB and such) are also spec'd for huge domestic cars. I doubt the leverage ratio is greatly different, so I would bet that these shocks are too stiff for a 2000lb car. I run the white KYB's in the front and they handle great, but the ride could be better.

Maybe try to find tune-able shocks that fit and tweak them for your liking (and let us know what you find!)...

Also, do not overlook the vast improvement in handling and ride offered by stiffer rear leafs. I was amazed at how much more predictable and better my car handled with the "add a leaf" springs. TR

Many people think that the shocks are what make race cars ride so rough. It is actually the stiff springs.

The purpose of the shock is to dampen the spring. There are two motions that need dampening. There is compression dampening and rebound dampening. Rebound dampening controls the speed at which the compressed spring can extend. With too much rebound dampening the spring does not extend all the way after a bump. When the next bump is hit then the spring extends even less. This effect will eventually compress the spring until there is no travel left and you are on the bump stops. When you hit the bump stops then you load the tire to infinity and lose all traction. If too little rebound damping is present then the spring is free to oscillate. The wheel and tire can rebound at great speed after a bump and pogo off the ground. This will cause the tires to leave the ground and lose all traction. As you can see the shocks must be tuned for rebound to the spring.

Compression dampening is not so much tied to the spring rate but to the rebound dampening setting. The springs provide resistance to bumps. As stiffer springs are installed the ride will get stiffer. The compression dampening can tune the speed at which weight is transferred from the front to the back during acceleration or from side to side during cornering.

Adjustable shocks frequently are only adjustable for rebound since it is the most critical for handling. Double adjustable shocks include compression and rebound adjustment. There are also four way adjustable shocks that dampen high speed bump rebound actions separatly from low speed weight transfer actions.

Commonly available for the roadster are a few types of shocks.
Hydraulic shocks are very basic. They are a tube with a piston and oil inside. As the piston moves in the tube the oil is forced through a hole. This is how the shock dampens the motion of the spring.
These are what came on the car from Nissan.
Adjustable hydraulic shocks can vary the size of the hole in the piston allowing oil to flow faster or slower. Koni adjustable shocks are this type.
Low pressure gas shocks are similar to hydraulic shocks except that they are pressurized with nitrogen which keeps foam and bubbles from forming in the hydraulic fluid. KYB GR2, Gabriel, Monroe, and a few more are like this.
High pressure gas shocks use much more gas pressure. The gas pressure adds spring rate. KYB Gas-Adjust are this type.

By choosing a higher spring rate you will automatically get a rough ride. The high pressure gas shocks will only make it rougher because of the increase in spring rate. My suggestion is to buy the Koni adjustable shocks. You can set them as hard or soft as you want. An added bonus is that you can fine tune the handling of the car. Stiffening one end of the car makes that end looser in the corner. Stiff rear shocks promote more fishtailing and stiff front shocks make it push.

One minor issue with your suggestion Andy - Konis are supposedly NLA which means getting used ones and having them rebuilt. Not many used ones out there that I have found.

One theory on handling is to use SOFT springs, BIG sway bars and stiff shocks. That way, you get the soft ride while the bars and shocks keep things in control during maneauvering. I did see an article on a Firebird with just such a setup, and he was pulling WELL over 1.0 on the skidpad in street trim. It was an interesting article. Wish I had kept it...

I agree Sid. Koni's may be hard to find. I'm sure there are still some out there. One day a vendor will find a bunch in a closet. Probably in the same closet that they found all the NLA timing sets.

My take on swaybars is that they are a spring. The stiff shocks are working to dampen the stiff swaybar.

The drawback with swaybars is that hitting a bump with one wheel will effect the other. The bigger the swaybar, the bigger the effect. It might make for a good skidpad number but in the real world it makes the car dart and follow on bumpy and rutted roads.

My thoery is that you tune body roll and weight transfer with spring rates and fine tune oversteer, understeer, and weight transfer with swaybars and shocks.

Another option I just heard of is too just cut the stock springs down a little. Probably not as good as lowering the spring perch but maybe a little easier?
I have adjustable shocks on my leaf sprung 85' 4runner, they are great! I use that offroad with alot of equipment on board so I can really use the adjustability depending on my load.
Would be great to find the adjustable koni's for the roadster, at least for the front.
Any ideas on price if I find them?
Other wise I'll go with the KYB's, unfortunately no one seems too satisfied with them.
What is their drawback?
I'm not looking to race, just a lowered and solid ride.
Thanks for all your input!
Todd-

On the topic of springs does anybody know how to contact Mike Young via another way rather than phone. I am trying to track down a pair of his springs but find it difficult to contact him with the time differance and everything. If there is anyone in Australia with another option for a similar spring or someone also after a pair of Mikes springs please contact me and we might be able to sort something out.
Regards Andy.

Guys,

Koni's are still readily available via Dann at Rallye and Dean Fairlady Parts.

Just bought a set a couple of months ago.

Wade

What??!!! Konis are still available??!! Oh, cra...er, crud! I have KYB GR-2's coming from Summit this week.

OTOH, the price difference leaves money for Mike Young springs and front sway bar...and a six-pack or two to install 'em.