More 240z Suspension Questions

[Tom Donnelly]

Reference: Carol Smith....changing spring length changes the natural frequency of the spring. If you get the natural frequencies off front to rear, strange things happen. Chuck

So a 12" spring would act differently than an 8" spring. Right? So how does more or less free travel change things?

And Paul, its not so much that the shocks need adjusted around, I was just thinking of going to either 8, 10 or 12 inch springs all around.
To make it easier to change things without re-scaling the car. But if there is an advantage to longer in front, say, smoother transitioning / less twitchy and shorter in the rear, (why, I dunno), then I shouldn't change the results of prior testing. I know my driving style isn't like the former owner. Larry Stepp liked a stiffer suspension if I remember right. His BMW was stiffer than Chet's. But Chet ran the ARRC in the 240 with 400/350 f/r. So, like I said, I dunno.

[Tom Donnelly]

Of course, maybe I should quit thinking so much and just shut up and drive.

[chuck baader]

Two identically built cars will usually use two different sets of springs and bars. Read Carol Smith's book and he explains the relationships. That is way advanced and over my head...I just changed and lucked out to get the balance very good front to rear. I finally am just driving. Chuck

[TomL]

Paul -
I realize you can move the center of travel a bit by adjusting strut tube length and the size of the spacer (or not using one) under the insert. I just don't see how that is influenced in any way by the length of springs you use, which was the original question. Or was I reading to much into your response - that centering the shock is a good thing in general (and you weren't addressing the spring length question?)

[pballance]

TomL and Tom, my last response about centering the shock was more for TomL than TomD. Too many Toms around here I guess we just need some "Harry's". I'm not going looking for "Richard's"

TomL, I think maybe I wasn't clear enough and maybe you read a little too much into it. Get the shock where you need it, then figure out the length of the spring from that based on your artificial (mocked up assembly) ride height. If you have a delta that might allow you to use springs of 2 length's, let's say 9" or 10" and still get ride height and adjustability, then go with the shorter i.e. lighter of the 2 springs.

TomD, I have only seen different length springs on struts that used the OEM perches for the lower mounting point of the springs. Some tubes had been sectioned, others not. If I were in your shoes, and could use 4 springs of equal length and get the car set, that is what I would do. Otherwise SHUT UP AND DRIVE! didn't we have that conversation?

[kthomas]

If I were in your shoes, and could use 4 springs of equal length and get the car set, that is what I would do. Otherwise SHUT UP AND DRIVE! didn't we have that conversation?

That.

The natural frequency of the suspension springs for the rates and dimensions commonly used on 240Z's is inconsequential. Now you want to talk about spring harmonics when it comes to valve springs on and L24 and we have something worth discussing. We always used 10" free length springs on cars I prepped because I didn't have to worry about stack up for any reasonable rates, and it put the spring perches in convenient places relative to the strut tube to not cause any issues or clearance problems.

We won a ton of races back in the day with rates under 250 on both ends. Big springs, remember, are going to require more consistency and precision on the part of the driver, and may not be as much fun to drive, or drive well, depending on how regular your track days are.

[Tom Donnelly]

We won a ton of races back in the day with rates under 250 on both ends. Big springs, remember, are going to require more consistency and precision on the part of the driver, and may not be as much fun to drive, or drive well, depending on how regular your track days are.

Keith,

Glad you're still around! My plan was lower spring rates and increase them as my track time, consistency and precision goes up. The lower spring rates are more forgiving right? And not necessarilly slower. I need to run newer than 8 year old tires too.

Tom

[gira]

Good Day folks,
My two cents on this topic real quick. First off, a coil spring is only considered 36% unsprung weight, so buying an IT spring with this as the main criteria might not be that great. Some people think a longer spring produces more reliable results. I like trying to use the same size springs so that I'll have more choices to change my chassis setup. Once the front tubes are sectioned, changing the shock body length and shimming up and down inside the tube could only change your droop travel since the top of the strut and the bump stop will not change location. Once you get the components in the right location at your normal ride hide, you shouldn't have to change it that much. We use 10's and 12's I believe and incorporate a 2" space sometimes.
Hope this helps.

greg ira