Handling

[gramercyjam]

Lower pressure = more grip.

 

Can't say I agree with that as a general rule of thumb Jon.

 

I've noticed some days yes, some days no. It seems to me to have a lot to do with the age of the tires. I find that I run higher pressures in new tires with few heat cycles for optimal grip and handling while tires that have more than a few heat cycles can benefit from lower pressures.

 

Of course this is strictly a qualative assessment of Hoosier slicks from my own personal experience. I'd love to see some graphs.

[JMortensen]

Good to see you John! Where have you been?

 

I haven't noticed newer tires requiring higher pressures, but I've only played one set of new R compound tires before I went to running used slicks. The slicks I'm using seem to like the same pressures consistently through their lifespan, or at least the part of the lifespan they spend with me.

 

The idea though was more for a beginner, when you don't have enough camber you have to jack the pressure up to keep the temps as consistent as possible and keep the tire from folding over, but the more camber you have the less pressure you can run and the temps remain consistent across the tread. You can also get more heat in the tire by running less pressure, which makes it stick better IME. I haven't gotten to the point yet where I've overheated a tire. I've had the track be really greasy when its 105+ out, but the tire temps weren't over 200 ever that I can remember on my car.

[gramercyjam]

I've been lurking. I got sick last fall and had some major surgery and had to take a break. It sucks getting old... Now I put the Z away for a while this year and started driving a 92 E Stock Miata. I got tired of being embarrassed when C Stock Miatii/MR2's beat me when the slicks grip starts falling off. There has got to be a better way of fixing the Z's handling than buying a new set of slicks every 30 runs. I'm hoping to learn the handling secrets of the Miata and improve my driving and improve the Z as a result. I'm picking up an MR2 this weekend too.

[v80z]

I am going to work on tire pressures for push issues. I have adjustable camber plates and run as much neg as they will allow. Even the last car I had had a terrific power on push in the corners. I could get it to turn at the end of a threshold braking session. It would glide through the first 1/3 of the turn fine. But as soon as I floored it she would rock from the FL to the RR, oops thinking of turn one at Summit, and push to track out. Unfortunately the only thing I had at the time was to throttle steer it around cause its track out was much sooner than I wanted it to be. BLAH

 

Now these days I am setting up my son's kart for road course. We had his kart scaled. I watched as the weight was distributed by inserting or removing shims from etiher above or beneath the kingpin bushing up front. Effectively raising and lowering them.

 

One of the first sessions he ran he was loose as all get out. Luckily they have scale in the paddock. We put him up there and there was very little rear grip. Checked the air pressures and I had all the tires at the same air pressure which was not how it was scaled. BAD DAD oh well live and learn. We decreased the rear air pressure from 9 lbs to 7.5 lbs and kept 8.5 up front. LO and behold he went back out and was not loose at all.

 

 

So This tells me if your car is tight run more air pressure in the rear than the front.

 

Whatcha Think?

[JMortensen]

Well, that fits my more pressure = less grip scenario.

[Dan Baldwin]

You probably need:

1) more negative camber up front

2) reduced toe-in at the rear

 

After I lengthened my front control arms and corrected the rear toe with eccentric bushings, I had to remove the rear bar I got so much more oversteer/less understeer.

 

As for tire pressure, too much is bad for grip. Too little is also bad for grip.

[cygnusx1]

I have been busy at work and the weather has been absolutely PERFECT for tearing up the country roads. I didn't want to rip the car apart and start changing parts. I just quickly loosened up the front swaybar endlinks until I could spin the bushings by hand. It made a pretty large difference. It turns in a little slower but once it settles, it now feels like I can drive the rear end out with the gas pedal. Also, when I hit a bump in a turn, the car glides over it much smoother with less interruption to the driving line. Regular bumps are also transmitted less to the steering wheel. Overall, I like the change. I can probably add more turn-in by notching up the front Illuminas and dialing in a little toe-out. Thanks for the advice...it really works!!

[cygnusx1]

Although that's true' date=' its misleading in this example. If you were citing two linear rate coil springs stacked on top of each other I wouldn't argue at all, but in this instance we are talking about 1" tall rubber bushings that in my press take 500 psi of hydraulic pressure to compress 1/4" and 2,200 psi of pressure to compress 1/2" (just checked it). They act as extremely short progressive springs.

 

Lateral load transfer is based on weight, CG, and track width. Chassis roll resistance is provided by the width of the spring base (the distance between the springs on each axle), spring rate, and by the ARBs which transfer load laterally.

 

The chassis doesn't care if the roll resistance is from bushings, the ARB, spring rate, or spring base - it just feels a rate. Softer bushings just slow the initial rate the ARB adds to roll resistance and may allow an additional fraction of a degree of roll in the chassis but the bushings themselves are a very small contributor to roll resistance.

 

On the track you'll feel softer ARB bushings as a little delay in the front end taking a set. If you've had turn in understeer problems then it will delay the onset of understeer enough that the front tires may be able to finish turning the car before the full ARB load is applied. This might keep the front tires from overloading and make the understeer appear to go away. Its not, its just been put off a bit.[/quote']

 

 

Actually I thought about this again after re-reading the thread. I am about to purchase front camber bushings because it's the cheapest easiest way to add a bit of camber to the front.

 

As far as softer front sway bar bushings...by loosening them, the front bar reacts later in the lean so the front appears softer on entry. However, once the car has taken a set, because of the "play" in the front endlink bushings, the rear bar is loaded more heavily than it was before thus giving more oversteer or less understeer. In other words, with the car at a static 3degrees of lean, the front bar sits in a less twisted state with softer or looser front bushings passing more work to the rear bar. (loose condition or oversteer)

[zguitar71]

I am running camber bushings on all 4 corners. With AZC heavy duty springs that lowered the car 1.25" and the bushings I got just over 2 deg of neg in the front and 1.5" in the rear. I could have gotten more in the rear but I kept the rear bushings turned out the max amount and the front (on the rear) turned a little less so I could get 1/8" of toe in on the rear wheels. So over all I run 1/8 toe out in the front 1/8" toe in in the rear and 2.25 neg in front and 1.5 neg in the rear. I just bought new (very crappy) street tires. The old tires were bald on the inside edges and to the tread bar on the outside. I got the crappy tires because the aligment eats up tires pretty fast (along with my driving style) but I works pretty good on the autox course considering I have springs that are too soft and very little chasis stiffining. I run Goodyear 23x9x15 cantilever r250 slicks with 1 less pound of air in the front (21 to 24 pounds, I vary the inflation amount with the air and track temps, even on a hot day the mornings start out in the 40's here in MT). The car stays fairly neutral with that set up.

[katman]

I would endeavor to one day be able to run near zero toe in the back. No sense in dragging the tires around all the time if you don't have to. On the front, unfortunately, 1/8 toe out is about what we found was required to get good low speed turn in, even after exhaustive changes to springs and bars and shocks.

[260DET]

In my experience some Ackermann is a good substitute for front toe with the S30, although with that front rack its hard to get much of that. More caster should help too but I never worked out how to do that without messing up other important settings. If I was doing a S30 from scratch the strut towers would be severely modified to allow up to 7-8 degrees caster.

 

Then power steering would probably be required

[tube80z]

More caster should help too but I never worked out how to do that without messing up other important settings. If I was doing a S30 from scratch the strut towers would be severely modified to allow up to 7-8 degrees caster.

 

Then power steering would probably be required

 

In order to use more caster without power steering you need to move the spindle forward on the strut. Increased steering effort is caused by the lever from the actual turn center to the tire's contact patch. You can do a little of this with custom RC/bumpsteer spacers and moving the lower balljoint.

 

Cary

[260DET]

In order to use more caster without power steering you need to move the spindle forward on the strut. Increased steering effort is caused by the lever from the actual turn center to the tire's contact patch. You can do a little of this with custom RC/bumpsteer spacers and moving the lower balljoint.

 

Cary

 

At one stage the whole front Xmember with rack was moved forward to give more caster. But that did not help things at all, I believe because it increased the wheelbase and particularly shifted weight towards the rear wheels. It does not take much sometimes to make a difference with the S30.

 

Anyway, with some Ackermann, a bit of toe in, a ATB diff and some trail braking where possible it turns in nicely now, medium to slow corners.

[cygnusx1]

Well I did it. I ordered the front and rear camber bushings from MSA. This morning I installed the front bushings and set them to max camber. I must say that the wrench they supply is totally inadequate for adjusting the bushings. It is only good for using as a template to make a real wrench.

 

After putting the front end back together and doing a few tape measure toe alignments, I made a jig with a steel bar and a level to measure the camber at the rim. I leveled the car best I could and measured the wheel camber.

 

The fronts are now running 1.25 and 1.35 degrees negative as best as I can measure and calculate. I took it for a drive and right away noticed that the tire temps were more even across the tread.

[col]

Hi Im not sure if its ok to ask a question here thats about something a bit diferent, but here goes .I would like to run a v8 and am concerned that the weight will cause handling problems.my car is a std 280zx old tyres old suspension etc it handles surprisingly good ,if you brake late and feed throttle through corner it just flattens and grips.new bushes and low profile tyres can only make it better.Will a v8 ruin this?Can you change anything to compensate?Thanks col.,

 

 

 

 

 

 

 

 

 

 

 

 

 

i.

[Wiisass]

Cygnusx1, do you still have the sway bar on the car? Or have you completley removed it at this point. From your previous description is seems like a spring and bar problem. You said that it happens at the middle of the turn when the car is closest to its steady state performance. This would mean that the shocks weren't adding much to the effect. So removing the front bar or softening it, if adjustable, would be what I would suggest. The camber thing is also probably an issue, but I don't know S30s well enough to say whether or not. But since it seems like you increased your camber and your still only running 1.25 degrees, I would definitely say you aren't running enough. How much lower than stock is your car? Lowering the car, especially on a strut suspension greatly effects the camber curves. If you lower the car enough, the front view IC will actually be outside of the car giving positive camber gain with jounce.

 

Oh and btw, are you Supra guy as well?

 

Col, how much will the weight of the V8 effect the overall weight and distribution of the car? The weight distribution change will cause the greatest effect. But I don't know how much it will change things. But then again, if you're doing the engine swap before you redo the suspension, all of the effects changing engines can be tuned out through selection of different springs/sway bars/dampers/tires.

[Pop N Wood]

.I would like to run a v8 and am concerned that the weight will cause handling problems. Will a v8 ruin this?

 

You have committed the #1, unforgiveable sin on Hybridz. The short answer is, if done right, the V8 will reduce the weight of the car and will position the weight lower and more toward the center of the vechicle. Some people think that is a good thing.

 

Spend some time reading through the stickies at the top of each forumn. Especially rule #2 in this announcement

 

http://forums.hybridz.org/announcement.php?f=65&a=2

[col]

Hi sorry to annoy ,Im new and will try to go by the rules ,thanks for leting me know.I value your opinions.thanks col

[col]

Hi sorry to annoy ,Im new and will try to go by the rules ,thanks for leting me know.I value your opinions.thanks col

[col]

just to be sure the problem was asking twice ?