What's up with these springs?

[John Coffey]

Interesting that you mention this. Whatever springs that were put on my newly purchased Z are amost completely bound. It seems that I may have at max 2" of compression travel. Those will be replaced soon.

The lack of compression travel has to do with how much your car is lowered. Keeping the same spring and shortening the strut will get you back some of that suspension travel.

Lowering a 240Z any more then 1.5" requires strut shortening IMHO.

[HAZELNUTRACER]

FYI2... shock compression damping has a much larger affect on felt ride harshness (impact harshness) then spring rate. A really good shock with stiff springs is a much better ride then a crappy shock with soft springs

John, thanks for stating this. This may be my problem as the smallest bumps and dips in the road cause harsh jolts. Any ideas on testing the condition of my tokico illuminas?

[John Coffey]

Any ideas on testing the condition of my tokico illuminas?

Take them off the car and put them on a shock dyno. If that's inconvenient then put all 4 shocks on setting 1 and drive the car around a curvey/bumpy road for about 5 minutes. Put both fronts on setting 5 and drive the car around for 5 minutes. You should notice a big difference in how the front of the car feels. Put the fronts back to setting 1 and set the rears to setting 5. Drive the curvy/bumpy road again.

If you don't notice a difference or one side of the car (left or right) feels different then the other then you've got one or more bad shocks.

[HAZELNUTRACER]

Thanks John, the driving test is simple and to the point

[Arne]

But if flipping the rear springs will soften up my ride, that is a simple solution to save my aching spine and also some $$!!

Flipping the springs is the correct thing to do, but don't expect a big difference in ride quality. A small one at best, and probably un-noticeable at normal road speeds. Will have increasing effect the harder you work the suspension.

[jmortensen]

Flipping the springs is the correct thing to do, but don't expect a big difference in ride quality. A small one at best, and probably un-noticeable at normal road speeds. Will have increasing effect the harder you work the suspension.

Arne is correct. As I originally stated, it won't make much of a difference at all (I too doubt you would be able to notice it), but technically, those are upside down. I probably shouldn't even have mentioned it, but it's a bit of a pet peeve of mine.

[jmortensen]

Is a coil spring, with "0" clearance between the coils really a "spring" or is it just a "coil of spring steel".

Is it possible that someone has heated these springs, to let them collapse? Maybe to lower the ride height?

Eibach sells progressive springs, and that's what is pictured. It is true that there are hillbillies out there that will lower their vehicles by taking a torch to the spring, but that's not what we're looking at here. In terms of the spring function, yes, if the coils are bound then they aren't doing anything. But when you're actually driving the suspension doesn't just compress, it also extends as the wheels go down into depressions in the road, etc, and when this happens those springs will open up a bit and that will lessen the spring rate for the first part of the travel. If the coils didn't bind at some point, then your spring wouldn't be "progressive". It would just be a lighter weight spring.

[Nigel1943]

Pic of progressive spring (with helper spring on top) on a UK rally car.

[HAZELNUTRACER]

In terms of the spring function, yes, if the coils are bound then they aren't doing anything. But when you're actually driving the suspension doesn't just compress, it also extends as the wheels go down into depressions in the road, etc, and when this happens those springs will open up a bit and that will lessen the spring rate for the first part of the travel. If the coils didn't bind at some point, then your spring wouldn't be "progressive". It would just be a lighter weight spring

Thanks for this explanation and shedding more light.

[five&dime]

In regards to the springs being ok either way.... That is incorrect. When we did my dad's car, we installed the eibachs upside down. Turns the Z into a truck. When we flipped them, it was low (correct).

Always install springs with the writing right side up.

[jmortensen]

In regards to the springs being ok either way.... That is incorrect. When we did my dad's car, we installed the eibachs upside down. Turns the Z into a truck. When we flipped them, it was low (correct).

Always install springs with the writing right side up.

That don't make no sense. ;-) To what do you attribute difference?

Spring rate is determined by the wire size and number of coils, and has nothing to do with which end of the spring is up. The springs act exactly the same, the only difference is the increase in unpsrung weight with the tight coils on the bottom and a slightly higher cg with the tight coils on top. Those things are both very minor differences, and if one was going to have a greater effect, it would be the unsprung weight. Reducing the unsprung weight would make the suspension more reactive to bumps in the road and would allow the shocks to have better control over since there would be a very slightly lighter mass to damp.

[Arne]

I'm with Jon on this one. The ride height can't be affected by whether the springs are upside down or not. I say this not only from theory, but also from several years of experience selling and installing Eibach springs. I've done them both ways - no difference.