ditch the heavier sway bar?

[ZR8ED]

I currently have a set of tokico sway bars on my 280. 1.25" on the front, and 1" on the rear.

 

I have a stiffer rear spring than the front..maybe more differential than I want. (rear is good.. front maybe a tad light)

 

The car handles very well. It pushed like a son of a gun until I loosened the front sway bar end links. (urethane bushings)

 

I'm wondering if I should stiffen up the springs a bit more, and switch back to a stock bar. (urethane bushings still)

 

I heard that you are best to put in stiffer springs, then to compensate by increasing the sway bar to help cornering.

 

I ask because I just raised the front of the car slightly (old stock cut springs had sagged too much) I now running my old rear cut stock springs in the front. (all I had on hand) I'm still not entirely happy with the ride height, and I think if I change them, i should maybe stiffen them, and reduce the bar at the same time..

 

It is time I revisit some of the older mods on my car..the car is starting to surpass the performance capabilities of my older mods.

 

This mid engine placement, is making searching for a spring combo very difficult. There is just not as much weight on the front of the car compared to stock. this is why I've been able to get away with stock springs that are cut3-4 coils (can't remember for sure)

 

How would I intelligently figure this out without spending huge$$$$ on trial and error?

[260DET]

The circle of never ending mods

 

Re the sway bars, try this experiment. Take a wheel off, disconnect a link from one end, slide a large piece of pipe over the end of the bar, work the bar up and down while watching the mounts etc to see what happens when you load the bar up. Very educational.

 

My thoughts are that ~25mm is the maximum workable diameter for a front bar on a S30, ~18mm for a rear. Going from a 22mm to a 23 front bar improved my best lap time by almost one second, car rides well on the road too with 250lb springs all round and good Koni shocks. Trying a 24mm one next time, rear is 18mm, not touching that.

[blueovalz]

I agree. I've run a 1 1/8" bar up front, and on the heavier 280 (full interior as well), it worked fine, but on my 240, I went to the 1", which works very well on it (running 235F/265R springs). 1/8" difference is quite a bit in regards to a bar, and 1/4 will be a huge change.

[johnc]

I've never heard of anyone running anti-roll bars that big on a 240Z. As suggested, try a 1" front and a 3/4" or smaller rear.

[katman]

What are the current spring rates and what is the application? I'm with JohnC, never been a big fan of big bars- I prefer my wheels to remain somewhat independent.

 

"The car handles very well..."

 

At 8/10ths everything handles very well At 10.5/10ths, well that's when the race engineer gets an earful, and real tuning begins.

[mom'sZ]

Keith:

you know I read this thread and was kind of wondering what would Katman say. My favorite Katman quote on sway bars "personally I don't like how bars wanker the chassis" Still laugh everytime I read that.

[ZR8ED]

Well the car handled very well. (experienced 240 autox'r) when it had the 280 motor, the tokico shocks and large bar that I have on now, and my cut springs. (it had a fairly neutral feel to it, and was pretty fast considering the mods)

 

I now have the vg30et motor in there, and it is stuffed way back in the engine bay.

 

From day one after that, the car pushed like a son of a bitch on the track. I immediately loosened the front bar endlinks, and the car got very neutral feeling..

 

Time goes on...

 

Front springs start to show signs of sagging.. car starts to understeer at next track event.

 

I have a my old rear cut springs (280 springs) I swap them into the front to raise the front of the car back up a bit. I had already did my chevette spring swap into the rear to keep the car from bottoming out with all this new hp and torque.

 

The front of the car is now sitting just about where I want it. Problem is I now carry much more speed at the end of any straightaway. (brakes are the toyota s12w with 300zx vented rotors.) It hauls down just fine, but I do notice now that I can lock up the back wheels sometimes. I also notice the feeling of the car diving nose down more than it maybe did in the past.

 

So.

 

I want to stiffen the front springs, and possibly raise the car another 1/4 inch to make it nice and level.. I know its already pretty close.

 

I have no spare bars or springs. So when I do this its gonna cost me, and I don't want to do it wrong and have to experiment too much.

 

Should I weigh the front of the car? would this help me figure out some spring rate requirements? Its easy to just say "switch to coil overs", but what rates? and If I do, I may need to upgrade my shocks as well. (shocks are a several years old)

 

I can try and find some locals with other bars that may let me try out.

 

I know I know my suspension seems weird, but Trust me.. the car handled very predictably and very tight, and I could dive in deeper into a turn than your average Z with a set of kyb's upgraded lowering springs, some urethane and some nice wheels and rubber and similar braking setup. (lots of Z club lapping days under my belt with lots of Z cars to compare with..)

[ZR8ED]

oh and yes I did say Chevette springs in the back. They fit very nice in there.

 

1980 front chevette springs 4dr heavy duty with powersteering. (please do not quote me on this.. I'd have to look it up again before I said this was the "be all end all"

 

I have a few friends running hopped up l28's in 280z's with identical brake and suspension mods brakes/sway bars/urethane and shocks.. except they are running chevette springs on all 4 corners. I had stock cut springs, but had better rubber. I have chased them around the track (back when my car was l28 carbed) When we swapped cars, it was surprising how similar, and neutral feeling each of the cars was. I really thought that was a killer street setup. not too harsh on the street, and plenty of handling for my skills at the time.

[mom'sZ]

I'm no race engineer, but one thing you said in your last post got my attention. You said:

 

Its easy to just say "switch to coil overs", but what rates? and If I do, I may need to upgrade my shocks as well. (shocks are a several years old)

 

Well I don't want to sound like I'm suggesting you just 'switch to coil overs' but... one of the cool things about switching to coil overs is you are no longer stuck having to find similarly sized ones to the stock springs that have a better rate then stock and cutting them down to get ride hieght where you want, or purchasing expensive lowering springs that only come in a few rates, or having custom springs wound. With coil overs any 2.5 inch spring will work. And there are TONS available!!! Some of them really cheap, check out some of the circle track web sites on the net. I've seen them as cheap as 70 buck per pair! Now the initial investment for the coil overs is a pretty lot, but, once you get the struts set up for them, you can swap rates relativly cheaply until you're blue in the face. And the threaded collars make ride hieght adjustment a simple on the car thing! If your serious about autoXing or road racing, I think you'll find varing conditions or tracks require varying spring rates. If you want to set it up once, get it to you liking, then leave it alone, then not so much. You can get any spring rate wound in any size from a number of spring shops. I found a rate calculating excel spread sheet once somewhere on the net, I'll try to dig it up. And like I said, I'm no race engineer, and your set up is ... ah ... unique. I think your going to need to know overall weight and front to rear weight distribution.

Strut inserts: all I can say there is from what I've heard the tokicos are only good to about 200 or 250 lbs. spring rates. So if you intend to go much higher, you might want to factor them in to this as well.

By the way... NICE LOOKING CAR!!!!!!!

[katman]

I've done some really nice handling 240Z street cars using cut 280Z springs, so nothing wrong there. 'Tis a bear to get ride heights where you want them exactly without coilovers, and every time you hack the springs to adjust the height you're changing the rates. Seems like using the 280Z rear spring cut about 3.5 coils is around 185 lb/in rate which is still streetable and enough for occasional track. I've heard of the Chevette spring mod but still don't have enough info to guess your current rate setup. Bottom line, loosening up the front bar seems to be working, and it's the cheapest route to go. Unfortunately, IMHO, balancing understeer/oversteer on a first gen Z is tough because roll center changes a lot with ride height (which affects what rates you need front to back), as does the requirements of the application- low speed corners like autox and Mid Ohio require significantly different spring setup than high speed corners like Road America and Road Atlanta. With your setup I see Trail and Error in your future...sorry. Good looking car, BTW.