Wondering about suspension after V8.

[QWKDTSN]

Here's the setup I have:

 

GC coilovers, struts sectioned 2". 10" springs, 150# front 175# rear. Illumina 5-way adjustable strut inserts. No camber plates. Stock front swaybar, no rear swaybar. Stock front arm mount (not JTR bumpsteer mod). Urethane bushings. Rear strut brace. 15" 300ZX wheels with 215/60/15 Yokohama AVS Intermediate tires.

 

My car rides.. well, okay, I guess. It was always really rough over patchy roads, shaking me up a lot and getting a lot of rattling from the suspension. Over big bumps it bounced even with the struts set at a high setting. basically it didn't soak up bumps like it should, like any factory stock car does. I can't figure it out because my springs really aren't that stiff and shock settings, while they did change the way things felt, didn't help soak up bumps. The worst thing about this is that with my tall-profile tires and non-bumpsteer-mod, I get a lot of steering wheel kickback. A lot, like where in any corner with bumps I don't have much confidence in the roadholding of the car. The body doesn't roll all that much that I can tell, it corners nice and flat, but bumps are a big problem. There's one corner by my house with a manhole right in the middle that I always take at 35 in my daily driver with no problems, and taking it in the 240 was annoying because my awesome performance car with the upgraded suspension bounced off this little dip in the road like a pinball, the wheel kicking back hard against my hands and everything. On the autocross track, I really think I need some swaybars because the car doesn't take corner transitions well. it pushes pretty hard. I'm hoping the V8 will help take care of this, along with a rear-mounted battery, but I am definitely going to be installing the swaybar kit from MSA either before or after I get the car running with the eight. Do you guys think that the bumpsteer mod is anything I should look at? Why the hell do they want you to tack weld that washer over the old hole once you've drilled a new one? I doubt you're compromising any rigidity and by welding over it you can't ever go back to the stock setup. I've seen other guys drill the new holes and weld over the stock hole and it doesn't make any sense to me.

 

Basically, how can I get my suspension to soak up bumps and still keep the car cornering flat? Swaybars should help, but don't necessarily mean that by setting my shocks softer that I'll get any more dampening because swaybars are basically just big torsion bars. Would different springs help? I usually have my car set on 3/4 front and rear on the illuminas and 4/5 for the track. I've tried switching the settings, but that stiffens the front and makes it push more.

 

One major problem may just be that my tall sidewalls are rolling over in quick corner transitions - but shorter sidewalls certainly won't help soak up bumps! When I ordered my tires I wasn't really thinking straight, and I ordered the stock size for a 300ZX, which is where my wheels are from. They're 215/60/15s. I have a set of 205/50/15s that came with the wheels (they were on a 510) and was thinking that the reason they were so short is that the 205 makes the 50% aspect ratio really small... the 215 makes the 60% aspect ratio on my current tires really tall.. maybe a wider tire would fit if I had a 55% ratio? 225 or 235? And this would not be quite as tall... or maybe even a 50 series with the wider tread would fit and not be so tall. I don't know. Stupid planning on my part to get the tires I did. Anyone want them? Brand new, maybe 500-700 miles on them. Still have 'molding fuzzies' on the sidewalls.

 

I'd love for this to be a car that I can autocross with a turn of the dial on the Illuminas and still take out on bumpy streets without rattling myself to death. It's probably wishful thinking, but is there any way to accomplish this without spending too much? Ideas needed

[Guest scca]

first i think the springs are too soft. and will be far too soft for a v8. IMO.

secondly the settings on the illuminas may not work too well with real soft springs.

 

make sure the suspension up front has full movement. IE that its not hanging up anywhere and that the lower a-arms are not sticking in their movement and that the geometry is actually correct.

 

how low is the car? those are pretty small tires OD wise and i wonder how far off your steering really is. with 15" rims you might need the bump steer spacers. ( i have some used ones)

with the 16" rims on my car i dont use the spacers but that is also due to that i use camber plates and my geometry is pretty good as it is.

 

i'm running 225 and 250 rate springs and my car with regular tokiko (not adj) and its smooth thru sweepers at 40mph even with bumps.

 

it does ride rough on rough roads though.but i try to avoid real bad roads- drive down the middle

[QWKDTSN]

You think I should get some stiffer springs? I probably need some new ones anyway because the guy that sectioned my strut in the rear put the threaded sleeve down too low and the car sits low even with the adjustment nut all the way at the top. Ugh. I was under the impression that I wasn't getting any bump damping out of the car because the springs were too stiff, though I know for a fact that 150 and 175 are really soft. So it was sort of a contradiction. The alignment on my car seems okay but I guess I'll get it checked again. The camber's off a little, of course, because of the sectioned struts but it's okay for the autocross. Just a little too negative for regular driving around town.

 

The car sits low but the tires are tall... I mean, they're not low profile by any stretch. They were made for a bigger car and look big on the little 240. I was under the impression that bumpsteer spacers would mess up the roll center with the sectioned struts. I don't think anything's hanging up, I've put everything through its full movement.

 

picture of the car's stance

 

But do you think the swaybars will make a significant improvement all around? That's what I'm hoping for because it's a major component of the suspension that's being left stock with all these other parts being stiff.

[Guest scca]

i didnt mean that type of geometry. not alignment.

 

the alignment of the rack in relation to the angle of the lower a-arms and what sort of angle the steering arms are being pulled in.

 

after looking at the car pic i would guess that the steering is along way off of straight. the cars pretty low (rocker to ground) and when i had 14" tires with 225/55/15 P7's i needed bump steer spacers.

if its 240 strut tubes you can just put the longer sleeve on yours to get more adjustment. i have 6" and 8" sleeves to fit a early sized tube.

 

if the car doesnt have urethane in teh lower a-arms then they can bind up with the original rubber bushing as the arm moves - this is more common as the car is lower as well. as the angles it moves thru are much greater than stock height

[PaulR]

I think the 300ZX wheels have quite a bit of offset (+40mm ?) That might contribute to the steering pulling hard when you hit a bump.

 

As for spring rates, I think the stock 240Z is around 110 lb/in. I would think 150/170 would be OK for a atreet car. Competitve autocrossers are in the 250 range.

[jeromio]

That is a really low car. But other than that, and the wheel/tire combo, you have almost the same setup that I have: sectioned struts, 150front 175 rear, stock front sway, no rear. I have the non adjustables though.

 

My car rides like a skateboard. It's a kidney abuser. Corners insanely and has very quick steering. I have done the JTR hole relocation mod on my car. And yes, you do have to remove the old washer and spot in a new one. The washers are there to both reenforce the pivot hole and to provide a nice "pocket" for the bushing to fit into. The mod I did, 15/16 up and 1/4 out seems to have eliminated bumpsteer (by a seat of the pants estimation). But it also really increased negative camber. With fresh tires, the car is like a mosquito - darts back and forth, turns in if you even think about moving the wheel. Once the tires settle in, it's easier to manage. Eventually I'd like to get some adjustable control arms to fine tune things a bit.

 

I would think that with your sectioned struts and lowered car, you'd actually have little or no negative camber left. (Negative is the wheels making an "A" shape, Positive is a "V" shape which is not good for handling)

 

I keep hearing people talking about 250, 300 and even 500lb springs. Madness. Maybe for a track only car. These cars are light. My experience has been that 150/175 is too stiff for a reasonable daily driver. I'm actually considering swapping in some softer springs. Expansion joints are just too murderous right now. My next formula is going to be a slightly larger front bar (perhaps a stock 280Z bar) and a smallish rear bar with a change to 125lb in front (if I can find them) and the 150lb springs moving to the rear. In theory, this should get me some more compliance without adversely affecting cornering.

[johnc]

I think Mike is on to something.

 

With the softer springs I think you're suspension is bottoming. I might add to his suggestion by trying a set of 12" long springs. Hyperco and Eibach make them. Try going up 25 lbs all around (175 front, 200 rear) and putting in a good set of the cone shaped poly bump stops.

[QWKDTSN]

HybridZ'ers rule. This is the only forum that I've ever encountered where every post includes really useful information and there's not a lot of trash talking and joking around going on. Okay, so yes, My car's low.. I like it that way I can always raise it once I get some longer springs. I guess I will try a 175/200 since that will allow me to use my rear springs in the front and just buy a longer set of 200s for the rear, where I need them long. Will this be enough to compensate for the V8 or should I go to 200/225? The thing is about the spring length is, the guy that sectioned my strut cut the tube right where the threaded collar needs to go. There wasn't room above the weld for it, so he ended up putting the collar down at the bottom of the strut, so it's wedged under this weld. It makes it impossible to just put on a longer collar. But some longer springs will fix things nicely. I don't think my car's bottoming out. I can usuall tell when it does (not often, unless I'm totally wrong and it does nothing but bottom out). I do have poly bushings in the front arms, Mike, and I do have the cone-shaped poly bump stops. I will try the zip tie trick once I get the car back on the road. Yes, the 300ZX wheels do have a +40mm offset. I think I'd need to hear an explanation of how that affects things because they fit like they were made for the car. They could even be offset more, you can see that there's a fingertip between the tires and the UNrolled fender.

 

I'm just sort of wondering about all this right now, since there's no way for me to drive the car and do different modifications to see the differences. I will put on stiffer springs and maybe raise the car a little, add some swaybars and see if I need to do the bumpsteer mod or add bumpsteer spacers.

 

The car does have some negative camber. Imagine the A-arm sitting level and the body as a vertical line connected to it. The strut is the hypotenuse, forming a triangle. Shorten the strut and you shorten the hypotenuse (well, it's not really a hypotenuse anymore, since that would make it no longer a right triangle, but let's just pretend). The wheel hub attached to the strut leans over more, then, since the stut's shorter. There's a little negative camber up front and a bit more in the rear. But it's not bad like most of the lowered 510s that are around whose rear tires literally do look like this: /

 

Thanks again.

[jeromio]

Yes, but shortening the strut has nothing to do with camber. IOWs, 2 cars at the same rideheight, one with sectioned struts, one with stock struts, both will have identical camber. The sectioned strut car has more bump travel, but that's the only difference.

 

It's the lowering that affects the camber. Lowering causes the control arm to angle up. Since the top pivot is fixed, the relative distance between the hub and the chassis is effectively reduced and its equivalent to the whole strut angling more towards the car, thus resulting in positive camber gain. (ie, wheels like | | or slightly / - not good)

 

Ideally, in a Mac Strut susp, the control arm should angle slightly downward when the car is at rest. That way, when the strut compresses during corning, the arm angles up causing that hub to chassis distance to increase, effectively "swinging" the strut outwards and resulting in negative camber increase. Lowering the car flarnks up the whole equation. Thus the JTR pivot point relocation, which corrects a bump steer problem but also helps this camber problem on a lowered car. Of course, moving the pivot outwards helps too (maybe too much ).

 

I'm a little confused by your explanation of the strut sectioning and why you can't use longer collars? It sounds like maybe the collars were slipped on, then the struts were sectioned, and then the resulting weld bead was left alone "trapping" the short collars in place?

 

I hope that's not the case, but I can't imagine another reason why you couldn't switch to longer collars . At any rate, grind that bead down, and stick some longer collars on there.

 

Also, why're you switching to stiffer springs since it pretty much sounded like you're not very happy with the harsh ride quality you've got with those 150/175s?

[QWKDTSN]

Yep Jeromio, that's exactly how my struts are. The guy who did them works at Dave Turner Motorsports and does a ton of 510 struts. His name is Eric (so avoid him if you need this done.. ) I guess he doesn't do too many Z struts because he screwed them up... I think what he did was cut both of the struts, weld one together, and try to put on the collar. The collar wouldn't fit over the weld, so he ground it down and wedged the collar down over it. The second strut, he just put on the collar and then welded above it. He took so long to get them done that I didn't complain much, since it works. Mostly, I didn't complain because he hooked me up for a quarter of what he's supposed to charge me (which is why they took so long, he had other things to do that were full price so mine were on the back burner).

 

 

 

Well, I don't know about the springs. Mike and John C. make it sound as though my springs are too soft for the struts, and I respect them both very very much. Can anyone else give some input to help clear this up? Are my springs too soft or too hard?

[jeromio]

I could possibly agree that Nion's car might be bottoming since it is so low. Maybe.

 

But mine most assuredly is not. I have lots of suspension travel and an expansion joint is certainly not going to cause bottoming.

 

Jumping up and down on the front bumper for instance, yields maybe 1 inch of maximum displacement of the car. It's just stiff. Really, really stiff.

[Modern Motorsports Ltd]

Nion, you've got lots of fine feedback.

 

I'd put some zapstraps/tiewraps around your strut insert pistons at the bottom and drive it as per normal to see how much travel you're getting. This could quickly tell you if bottoming is an issue or not.

 

For the wandering I'd be quite curious to see the results of your last alignment.

 

Don't sweat your tire OD, at 25.2" it's larger than many of us at 245/45/16 (24.7), 225/50/16 (24.9) and is similar to stock (slightly taller).

 

Good luck and let us know how it goes.

[jeromio]

Yikes. I think we all assumed you had the short collars on there already. Those look like the 8 inchers. Mounted waaaay too low . Here's a shot of mine,

the collar is the same length as yours but it almost goes to the top of the tube.

 

As to the spring issue, the strut carts are there for rebound damping. Their stiffness will contribute to a harsh ride since they will help cause the suspension to resist movement when absorbing the impact of a bump. But, since you have the adjustables, try this: set those Tokicos on 1 and then go drive on a bumpy road.

 

My guess (only a guess - not an expert here) is that you'll still get hammered by the bumps and the car will tend to not recover from each bump as nicely.

 

Regardless, I can't see how going to a stiffer spring can do anything but cause the car to be more brutal over the bumps.

[johnc]

Tokico Illuminas work well with springs in the 150 to 300 lb in range. Anything below that and compression/rebound doesn't let the spring work. Anything over that and compression/rebound cannot control the spring.

 

Jeromio's suggestion about testing your setup at the lowest Tokico settings is a good one. The collar setup and the strut sectioning job are not the best, but you can work with it. Longer springs in the rear are a must.

[Guest scca]

best bet would be to buy some more sleeves and install some on top of the weld as well.

you'll probably find the rear lower sleeve you wont use at all.