I need suspension help

[Matt 78Z]

Trying to at least help reduce understeer with what i have.

 

I've read where people say you shouldn't run the rear sway bar on a autoX car, well even a track car. Supposed to keep both rears planted and reduce understeer...

Well I've been messing with mine. Unhook it, feels ok, not as tight and does not transition as fast or flat. I don't know that I can tell any difference in the understeer, still pushes I'd say the same. But now leaving the turn my back is rolling/pitching. I have to wait for the car to settle back down before getting on the gas or I just burn the tires off. I don't remember it doing this with the sway bar. It always felt settled and seemed to rotate easier.

 

Here's what it is;

78 3.0L

illuminas

200lb front and 225 rear springs

1" front 7/8" rear SB's

urethane

strut braces

I know I need camber plates, right now I'm at -.7 all I can get at the moment

I'm running a 1/4" total toe OUT in front and 1/8" toe IN on the rear.

Ball and socket TC bushings - so I guess that leaves it around stock castor? Maybe I should shim for more?

I have not modded the subframe yet. I"ve read to move the pick up points 5/16th up and 1/4 out - good idea?

I can notice a difference adjusting the illumina's and make it understeer less but I'm still plowing trying to turn with the miata's and M3's.

I also adjust tire pressures and was able to help a decent bit that way, by taking air out of the front.

Oh yeah, with the bar unhooked I'm getting more 1 wheel peels and slower launches also. Yes I need the OBX unit, that is coming soon. I'm not sure how that will play into the understeer issue?

 

I'm considering doing the subframe mod and using stock rubber bushings in my front control arms, thinking that it will be more compliant and allow for more castor adjustment and negative camber via the subframe.

 

Can I do anything until I buy camber plates and a bump steer kit and LSD?

Thank you

Matt

[JMortensen]

OBX shouldn't add much understeer. I think if I were you I'd add adjustable TC rods to your list. Caster made a big difference in my car.

[Matt 78Z]

Thank you Jon,

Any advise to the subframe mods? How about the sway bar debate? I've been reading about droup limiters, might be a good alternative to the sway bar.

 

As you can probably tell I'm just getting into moving past the basics, I'm reading the sticky thread for the 3rd time now!

 

adjustable TC rods and arms are on the list.

[RebekahsZ]

You sound just like me a year ago. I had both problems. John Coffey at Beta Motorsport solved my problems. 1) EMI or DP bolt-in camber plates: amazing. Car totally stopped pushing even with stock TC rods. This was a true bolt-in camber plate without any tower mods or cutting. There is no reason to put off installing these plates. Took a few hours to install, then go get alignment. 2) WRx CLSD with Beta Motorsport snap-in stub axles. Another easy bolt-in job. Budget a day for this mod. PM John and spend about $1500 total and your problems will be fixed. My car is SOOOO much faster AutoX-ing; a totally different handling machine. LSD is amazing! Now I need to learn how to drive up to the car's potential!

[Leon]

The ARB does not affect traction on launches, but only in cases where there is lateral weight transfer. More bar means more weight transfer, thus a greater tendency to lose traction with a rear bar since you are taking load off of the inside tire.

 

You mention understeer, but when do you understeer, during transients or steady state (think slalom or sweeper)?

 

I would experiment with different setups as you've begun to. Try with/without rear bar and with/without front bar, with having rear bar and no front bar being most prone to oversteer. Also try different alignment settings. Set rear toe to zero and see how it feels, then set front to zero and see if behavior improves.

[JMortensen]

I wouldn't do droop limiters on a car with that light a spring rate. There's so much droop that you probably won't get to limit much. Just to show the problem, figure a 2800 lb 280 with 50/50 weight distribution and perfect corner weights. With 700 lbs per corner and 200 in lb springs, you're going to have 3.5" of droop. This means the limiter isn't going to do anything until the roll is 3.5" up on the inside.

 

For the subframe mod, you'll see different people quote different numbers. I've never heard 5/16" up, always 3/4" or 13/16". What I did was to remove the little washers on the crossmember then drill another hole directly up from the stock hole on the crossmember. Then I cut a slot between the two holes. Using a bumpsteer gauge I moved the control arm pivot up until the bumpsteer was minimized. In my case I think it was 7/16" up to fix.

[Matt 78Z]

Camber plates are my 1st priority.

 

Leon, not arguing just wanting to figure this out. I understeer on 180 turns. At our current autox there is 1 turn where you have a small box and single inside cone to basically pivot around. I understeer here it seems no matter how slow I go. I'm watching many other cars just rotate right around it while going faster. Then on a larger radius 180 I still plow but in this turn the box is much larger so I have room to kick the back around with the throttle. However after doing such my back end is rolling up enough that the inside tire is totally unloaded and spins till I let off (this is what I was told would not happen). In the slalom it turns good, gets into oversteer easy now.

 

Like you say with the weight transfer taking load off the inside with the bar, I seem to be opposite. I'm doing more 1 wheel peels than ever, coming out of turns even sweepers and launching. So this has me confused. I guess I don't understand the physics enough but I thought the ARB would actually keep the back tires more planted by not allowing the body to shift. Thought that was their whole point really.

 

I wish someone would talk about the subframe mod, I actually have time to do that this weekend if it's worthwhile. Right now my control arms are parallel with the ground, as I understand they should be angled more like stock with the chassis side higher than the wheel side. Plus I know I can gain some - camber. Since no ones talked about that portion of my novel here it leaves me wondering if it's not a good thing to do.

 

Also does it help any to have a slight rake with the front being at most 1/2" lower than the rear? I used to have that, now I'm using the 240 upper rear strut mounts so the rake is gone.

 

My driving needs to improve also, I'm entering many of the corners too fast leaving me with an upset car - I'm working on that as well - alot!

 

I really appriciate yall's advice and experience.

[johnc]

What sub frame mod?

[Matt 78Z]

Moving the front control pickup points. Redrill the bolt holes up 5/16" and out 1/4". As I read this helps correct bumpsteer on a lowered car and gives you a little more negative camber. I've seen this mod mentioned for years, I believe it comes out of the JTR manual also.

 

Thanks John

Edited June 3, 2011 by Matt 78Z

[Leon]

Leon, not arguing just wanting to figure this out. I understeer on 180 turns. At our current autox there is 1 turn where you have a small box and single inside cone to basically pivot around. I understeer here it seems no matter how slow I go. I'm watching many other cars just rotate right around it while going faster. Then on a larger radius 180 I still plow but in this turn the box is much larger so I have room to kick the back around with the throttle. However after doing such my back end is rolling up enough that the inside tire is totally unloaded and spins till I let off (this is what I was told would not happen). In the slalom it turns good, gets into oversteer easy now.

 

Like you say with the weight transfer taking load off the inside with the bar, I seem to be opposite. I'm doing more 1 wheel peels than ever, coming out of turns even sweepers and launching. So this has me confused. I guess I don't understand the physics enough but I thought the ARB would actually keep the back tires more planted by not allowing the body to shift. Thought that was their whole point really.

 

I don't mean to be overly critical, but I think you need to slow down and work on driving technique. Have an instructor ride along with you and see what they think. I think that will do much more for you than trying to play with suspensions settings. Tune the driver first, then the car.

 

My driving needs to improve also, I'm entering many of the corners too fast leaving me with an upset car - I'm working on that as well - alot!

 

Good!

[260DET]

What follows may or may not be relevant here but it's something that noone in the US seems to do, or at least talk about. And which I keep forgetting to mention. Which is welding a bridge across from the lower inside part of the front strut tube to the upper top part of the front stub axle forging/casting. A friend of mine races nationally and has proven this works with his historic 280Z, allowing a reduction in static front camber and dramatically reducing front wheel lateral movement under severe cornering loads.

 

Probably more applicable to circuit racing but its a cheap and easy mod.

[RTz]

What follows may or may not be relevant here but it's something that noone in the US seems to do, or at least talk about.

 

I believe Mortensen has a picture to share with you...

[260DET]

If it's anyone it would be Mortensen

[RTz]

I've read where people say you shouldn't run the rear sway bar on a autoX car, well even a track car. Supposed to keep both rears planted and reduce understeer...

 

For my autocrossing, I try to run as little rear bar as possible. Not because it reduces understeer (opposite actually), but because it helps with corner exit bite. S30's are not great at putting power down on corner exit... running a V8 in lower gears exaggerates the problem. For what it's worth, I've been pretty successful in my region running a stock rear bar. Our local courses are typically pretty tight. The only time I've been able to do well with no rear bar is on faster courses.

 

Are you running stock length struts?

 

 

 

Caster made a big difference in my car.

 

Ditto that.

[wheelman]

Heres my setup, how I drive the elements you are referring to and a few questions:

 

73 240Z

LT1 V8,T5 5-Speed, JTR mount location, huge torque (353ft/lbs) , lots of HP (320).

R200 3.54:1 CLSD, 300ZX CV axles

DP bolt in camber plates

Same ARBs as the OP

Kumho V710, 265/45-16 (sticky DOT legal race tires)

Camber -2* front, -1.5* rear (approximate values)

Caster ~3.5* (I'd really like more but its not possible with my current setup)

Koni Yellow single adjustable struts (softest setting front and rear)

350 lbs/in front, 325 lbs/in rear springs

Ride Height: ~4.5" at bottom of frame rail

 

My car is pretty neutral with a tendency toward oversteer, especially with generous throttle application, I like it this way, some people find it hard to drive.

You are going to find 180* elements to be the most challenging auto-x element no matter what car you're in, period!! It takes a lot of practice to get them right.

Those other cars may look totally composed with no under steer, I bet if you ride along in one you'll find they push just like your car (maybe not as much) when trying to navigate the element with too much speed.

The best technique I've found for 180 elements is to over brake just a bit just as I enter the element, get the car settled in the turn, try to backside the cone and slowly add throttle until either the front or rear just starts to wash out. Trail braking can also be used effectively to get the car to rotate but it's really hard to get the speed right. Being as tight as possible on the cone is not always the fastest line. Carrying too much speed into the turn and expecting the front to hold is always an exercise in frustration, you'll never tune that out with suspension mods or sticky tires, its a driver cured problem.

 

Some questions:

1. When you say your car under steers are you saying the front tires are sliding or you have to crank the wheel tighter and tighter in a corner to maintain the line?

2. What tires are you running? Tired good or new crappy street tires are not going to work no matter what you do.

3. What pressures are you running? Front? Rear?

4. Have you tried adding pressure to the rear to free it up a bit?

5. Have you tried a bit of toe out in the rear? Be careful with this, it can make the car very tail happy if you over do it.

6. Have you tried running the rear bar but with the end links a little loose, not torqued all the way down? This has worked well on my car.

7. Are you shifting from 2nd into 1st for 180* elements? Experiment with staying in 2nd if you are shifting down.

8. What setting are your Illuminas set on? Have you tried a stiffer setting in the rear than the front? Again, be careful with this, it can make the car tail happy.

 

A word of warning, the DP camber plates may not be as bolt in as you think, most likely you'll have to expand the hole in the top of the strut tower to clear the Illumina adjustment knob.

 

EDIT: Also does it help any to have a slight rake with the front being at most 1/2" lower than the rear? I used to have that, now I'm using the 240 upper rear strut mounts so the rake is gone.

I ran my car like that for a couple of events, made it real squirrelly so I set it back to level.

Edited June 4, 2011 by wheelman

[RebekahsZ]

I messed around with connecting and disconnecting my rear bar last year and it did not help me connect my rear wheels with the ground. I even took my front bar off to try to help with understeer and did all kinds of tire pressure changes. Didn't help. Unless you are restricted to an open diff, go with the Wrx CLSD and you will solve your tire spin problem immediately-and it is soo easy. Even if you are restricted by class, no one will care unless you beat last year's champion at Nationals. The DP camber plates are So easy, and you just can't screw it up. I'd go that way before taking a drill to my cross member (I would screw it up and drill it crooked! Do what you want though, either way it is pretty easy to back-track and put it back the way it was. Go for it! I'm just afraid that you will do that mod and not accomplish anything significant. The camber plates will solve your pushing problem unless you are just going too darn fast into the turn. Last driving tip: are you braking as you are turning? Try braking, then turning. Go really slow-you only lose time in a 180, you never gain time there.

[mark]

Try swapping your springs front to rear. Stiffer springs up front and softer on rear.

[JMortensen]

If it's anyone it would be Mortensen

Yep. Can't remember where I heard about this, but it seemed like a good idea and literally took about an hour to do both struts. Really easy. Too bad there isn't a way to do something similar in the rear...

[tube80z]

Yep. Can't remember where I heard about this, but it seemed like a good idea and literally took about an hour to do both struts. Really easy. Too bad there isn't a way to do something similar in the rear...

 

It was a discussion we had some time ago about increasing installation stiffness. I tried searching but couldn't find it. This mod was quite common on many of the higher end Zs that raced in the 80s. I'll have to see if I can get you a picture of the rear mod they did. It was a bridge plate similar to the front. It might have been in the same discussions where the rear suspension braces were talked about (bridging tranverse link to the mustache mount).

[tube80z]

EDIT: Also does it help any to have a slight rake with the front being at most 1/2" lower than the rear? I used to have that, now I'm using the 240 upper rear strut mounts so the rake is gone.

I ran my car like that for a couple of events, made it real squirrelly so I set it back to level.

 

Rake is a powerful tuning tool. You can use it to balance different spring setups Generally you want to lower the end that isn't sticking but you mustn't overdo it. Most cars will respond to 2 to 3 turns on the spring mounts.

 

For the understeer problem you've been given many things to think about. If you can get some pictures of your car under load in a corner where it is pushing that would really help us point you in the right direction. If you haven't noticed almost all the suggestions are around making sure the front tire has proper camber when loaded. On a Z roll is something you need to aggressively control or the tires will end up in a positive camber placement to the road and you will lose traction.

 

Cary