Spudz

Hey All,
I think I am going to try to make the last event of the season. A new baby
and work conflicts kept me away the whole season. I did crew for a friend ,
and his 2 liter Roadster when he ran over here .

My car is suffering from understeer. I am using way to large of front bar ( 1 1/8" ) . If I keep the front tire pressures up and either loosen or shorten/extend the
front end links will this help a bit ?

Any help will be greatly appreciated

Mike

jburge01

I don't think changing the length of the links will change anything. Maybe less front tire pressure, more rear tire pressure, and run the end link bushing real soft/sloppy and loose on the front bar.

zlalomz

I widened the front track with 1/2 inch wheel spacers and ran some toe out to help turn in. Also make sure you are off or are feathering off the brakes when turning.

Spudz

Steve,
I know for a fact that I am still on the brakes a bit when turning in

I can see where this could be a problem trying to turn a wheel that is trying to
stop rolling. Also this could be cured a bit I sure with an adjustable brake bias.

I think I am going to scrub next weekend and try to find a co drive for it. With
all the new ideas floating around in my head , I kind of what things right before
I jumping back into it .

The Seattle guys season start in January , so I think I will focus on that time frame.

John,
I have been running the fronts with more pressure then the rears. With concern for wheels spin on corner exit . NO LSD kills me on corner exit

Thanks,
Mike

preith

I think I may have the answer, which is posted on another thread, Ackerman! Basically, it's turning the inside wheel at a steeper angle than the outside. Carrol Smith says if toe out is needed, which usually seems to be the case on the Z's, then more Ackerman is needed. My project this winter will be making it adjustable by moving the steering rack forward or aft.

jburge01

Ah yes. Of course. How soon I forget. I used to tap, tap, tap the accelerator on and off in corners to try and get grip on the open diff and with the VLSD too. The technique worked somewhat. After getting the R190 LSD, I got a lot slower than even the open diff for a while until I figured out a better transmission to go with it.

I like lots of toe out on autox too, but the steering effort required is beyond me with big wide tires.

Maybe it would help if you could dial in a little more camber in the front too.

tube80z

A little more info please. Alignment, tires, springs, shocks, bars, tire pressures, etc. Then I might be able to give you some idea of how to help. In general any swaybar over one inch will probably lead to terminal understeer. Toe out may help, so may more camber, spring, etc.

Ackerman will help but you're not going to find it easy to fix this. It will require custom fabrication.

Cary

bjhines

Use a little trail braking entering the turns....
Try to unwind your steering wheel as you exit a turn....The scrubbing push that the S30 Z cars suffer from is mostly driver induced...granted the cars have a tendancy to push...but the kind of problematic push I think you are experiencing is just a matter of getting used to the car.

You will find that you can significantly unwind the sterring wheel and you will not decrease your turn radius while exiting the turns...
This is what happens.......as the tires line up with the direction the car is actually moving...you will suddenly get less push and a tighter turning radius....

The tendancy is for drivers to rotate the wheel to begin the turn and then hold that steering angle all the way out of the turn.....THAT IS A MISTAKE.....unwind the wheel just as you apply power...and apply power gradually as the tires begin to get better grip.....This is really a skill gained through experience.....I too had this problem when I first started racing my 240Z....You can eliminate this push with proper technique.

Another more advanced technique is to use hard trail braking to break the rear end loose and then drive the car out of the turn in a 4 wheel drift.....much harder to keep from overrotating....and you really need limited slip to do this right.

Limited slip rear ends will cause the car to push even worse....soo don't even consider LS until you can control slip angles with the stock suspension set up.
LS is for advanced drivers only in an early Z-car.

Even more annoying to me right now is the need to plant the rear end evenly on both sides before I can apply full power exiting turns....inside wheelspin is wasting my exitng momentum advantage. I always run up on the BMWs and Corvetts in the turns only to see them accelerate away in the straights.

tube80z

There are a couple of work arounds for this. The easiest is to limit front droop. You'll need to experiment a little to make this work. The second and hard option is to change the front geometry so that you don't have as much weight transfer from the large SIA of the strut.

Limiting droop works wonders for me. I should point out that you'll need springs that aren't easily squashed for this to work. If you're running really low rates what will happen is you'll pick up the front tire and the car will probably be even worse. I run 400 to 600 pound springs and front droop around 3/4 of an inch. I've tried zero drooping but couldn't make it work.

Cary

bjhines

tube80z... I have 2 different thicknesses of bump steer spacers...I am using the thickest...which seems to actually give more control arm angle than the stock set up. I think it is a 3/4 inch spacer and the front end is only lowered about 1 inch. spring rates are in the mid 200lb range

tube80z

Ideally you want the arms near level. What you have doesn't sound too out of the norm. You could also try lowering the front or raising the rear to balance the car. Camber and tire pressure can be varied too.

Cary

bjhines

well...I was going to try the next event with the spacers removed...but I swear the car felt balanced with the thicker spacer...very predictable trail braking.
Keep in mind that camber is not effectively adjustable on the s30 Z cars. Sure you can add camber bushings and camber plates...but they only give you a degree and a half negative on a straight car....much less one that needs them just to get back to zero on both sides.

bushings are $150rear, $75front, plates for Tokicos cost $200 for the set, add 6 hours labor and set up time....minimum $500.....Dude thats almost $1000 to get very little effect......

Just remember to """"UNWIND THE WHEEL ON EXITS""""... really cheapo mod.
I fly through the carousels....gimme some turns and I show what a light weight car can do.... Miatas move over....and im pushing Porsches...... BMWs beware....the trail of corvette corpses.

preith

The car was unstable because of the increased bump steer. The spacers should technically not be called this. There was another recent thread on this: https://www.zdriver.com/showthread.php?t=10509

Unfortunately everyones trying to kill two birds with one stone. Bumpsteer should be corrected by changing either the steering rack height, or the inner or outer tie rod heights, not by control arm angle. The front arm geometry should be near level.

As far as I know, all the camber needed is available with a good set of camber plates. For the reading I've done, DOT race tires like between 2.5-3.5 degrees camber, easily attainable on a lowered car.