I'd like to tame the understeer in my Zed a bit. I'd like it if the front had a bit more grip and was a little bit more willing to pull the car around the corner (instead of trying to go straight).

I am playing with the tyre-pressures, and allignment (as much as one can) to see if and how much that helps. It looks like that it helps, but nowhere close enough so I'm thinking either about getting:
a) a thinner front swaybar
b) or a thicker rear swaybar

I'm wondering if anyone has replaced one or the other (or both)? If so, what make/type and what was the effect? Also which one would you recommend changing ... front or back?

Thanks for all the input in advance.

 

My advice is to change the front and leave the rear bar alone. The higher suspension frequency should go at the rear of the Z, ideally on a smooth track run withour a rear bar altogether and increase the spring rates out back. For the real world, to reduce understeer run a smaller bar in the front. Unfortunately, I cannot recommend any as I have not changed my suspension at all ...yet

 

Well, here is what I read on F1 website about tuning the performance of the car. Most road racing cars, as well as formula 1, are set up to understeer a little bit because unlike oversteer, understeer is not loosing you as much time during cornering. Of course, you have to be patient in the turn with adding gas. I was taking a class at autocross school and the instructors told us to watch how much the car will be pushing (under/oversteering) in the beginning of the day VS. the end of the day. Interesing enough, as soon as I learned patience rather then jumping on the gas, my times became faster and the car "stoped" understeering as much. Don't get me wrong, there might be a way to cure the understeer using different car setup but it's easier to start with driving habits IMHO.

 

i agree with madmax, practicing with your car to learn how to deal with the understeer is always educational.

you'll have to do a little investigating to find out which sway to replace. is it understeering because there's too much camber change in the front tires as the body rolls, or is it because there's too much weight transfer to the outside front tires and it's pushing because of that? if it's the former, add a stiffer sta bar in the front to keep the body from rolling. if it's the second, add a thinner one in the front or a stiffer one in the rear to get both ends to break at the same limit.

 

The understeer a car exhibits is safer, and as Madmax stated, is not as detrimental to lap times as oversteer. However, the car could certainly use more neutral turn-in and utilize any understeer only upon corner exit to help pull to the outside under throttle. Julian, the Z gains (-)camber under body roll, the beauty of not having struts The car understeers because of too much weight transfer, and in any case, adding a stiffer bar up front will only increase the tendancy to undertseer. I would not add a thicker bar in the back, but use higher spring rates for any track use. As I stated earlier, the higher frequency needs to go on the driven end of the vehicle, or the rear of the Z. Anti-roll bars' affect with weight transfer inherently cause the inside wheel to be lifted, this is not what you want for your drive wheels. On a berfectly smooth track where the primary purpose of the springs to allow travel over irregularities is minimum, stiffer springs can be used to control body roll more effectively than a bar without lifting either tire in weight transfer. For a daily driver, the rear bar is a neccessary evil in order to run softer spring rates to maintain contact over road irregularities. David, you'll have to decide the best compromise for your pursuits. In the front of the Z, the stiffer bar will again lift on the inside tire during weight transfer, causing more understeer. A smaller bar will allow the tires to stay planted and the use of stiffer springs will help control roll couple, while sacrificing "bump control". Again, the compromise will be up to your pursuits and goals. But remember, while the primary purpose of the springs is to control the tires over bumps and dips, the motion ratios on this car allow the use of stiffer springs and damping for roll couple without delivering an ultra stiff ride, so don't automaticaly assume stiffer springs will be too much for street use.

 

Thanks guys, I track my cars a fair bit so I'm talking here about being able to extract better laptimes. In that respect I see the understeer in the Zed as detrimental (it just stays too long 'in' he corner). It does not mean I want to remove the understeer totally and turn the car into a tail-happy monster. It just means that (to me) the front does not have enough grip turning into corners as well as mid-corner. If I can sustain more entry and mid-corner speed, then that should see the laptimes improve.

I do realize that you can drive aroud the understeer simply by just slowing down the car for the croner and waiting longer to get on the power, but I ultimatelly want to go faster and the Zed does not sustain the entry/mid-corner speeds that I'm (in a way) used to.

That's why I'm looking at making a change to the car ... ideally a smaller change as I don't want to upset the car's 'natural balance' too much ... it seems pretty good up to 8/10th, but seems to be tuned primarily for safty and starts pushing the front way too early for my liking (ie. at 8/10th instead of 9 - 9.5/10th). The thinner front swaybar and/or thicker rear swaybar should help with this (IMHO). Also a camber-kit for the front so that I can dial in more camber, but that alone will not be enough (IMHO) to give the front a bit more grip, which is what the car needs.

So, please keep the comments coming and if anyone has already changed any of the swaybars, then I'd love to hear about it.

 

I tracked my Z with Cusco bars at 7 events this year. No other suspension mods. Front set full soft, rear is non-adjustable. This will minimize understeer. Cusco's are I believe the stiffest bars out so far. I loved the set-up on the tracks I ran.....mainly 3rd & 4th gear. Tail end NEVER came loose. At the autocross I ran, and on the street, it seemed a bit easier to induce power oversteer.

Check out my avatar to see the amount of lean in a 3rd gear, tire screaming turn.

 

From what I've heard, going to a stiffer bar in front will help somewhat. Going to a stiffer bar in front and a stiffer bar in the rear will help even more. This is my current feeling based on comments that I've heard from some of the AutoXers and trackers that post and others whom I've met at events.

My experience is limited, since my car is still stock. However, I have noticed that I wear the outside edges of my front racing tires far more than the outside of the rears. This tells me that even though the Z may gain some neg camber, it is still rolling over the edges more than it should. This is part of what makes a stiffer front bar seem like a good solution.

Now, in order to combat the understeer in a very minimalistic way, I have simply gone to 245/40 tires in front, instead of 225/45 (and my racing tires are 265/35 on all corners). This simple changed has helped quite a bit, and if I can get the turn in right, I find that the Z is decently balanced through a long sweeper. If I go into a corner too hot, and don't get off the brakes in time, I will still plow, but I think that will happen to pretty much any car if driven poorly. Now, if I keep the speeds down and really turn in hard, the REAR will really want to brake loose (at least on occasion - and I will admit that I'm still not exactly sure when it will happen). This again leads me to believe that things are better than before.

Anyway, I just drove at Thunderhill yesterday with street tires (245/40 Yokohama AVS ES100 in front and Hankook Ventus K104 245/45 in back) and the car felt much better than it did back in January when I did my first track day @ Laguna Seca (still on stock tires). Of course, I've had a few AutoX's between those events, so that may have helped a bit as well. Also, I did loose some nerve (since I spun out at Laguna and almost hit a wall), and was unable to get confident enough to turn VDC off yesterday. I did notice however, that it seemed to allow a little more freedom with the better balanced car than it did stock. I had it activate almost as often for slight oversteer as it did for understeer (and, if I was doing well, I could balance the car with the throttle and slide just a bit without having it turn on).

Anyhow, sorry to go with the whole dissertation here, but I just wanted to share my thoughts on the subject, which basically are - Do anything you want, because at the stock stage, almost nothing seems to make the understeer worse.

Take care,
D'oh!

 

ok guys to "cure" under steer or to move the suspension to a neutral or over steer setup you need to make the REAR bar stiffer. Adding more front bar will only make matters worse. So if your out on the track and the car pushing through turns going straight or “under steers” you need to add a stiffer rear bar or just adjust your rear sway bar to a stiffer setting (making the bar shorter makes it stiffer). Depending on spring rates and type of adjustable sway bars you will need to find out exactly which setting works best to your liking.

Soooo here are a few setups we have run on track if you want a more neutral or a car that slightly over steers which means the back end will come out rather than push through corners here is what we have track tested.

Stillen sways and stock springs front full soft and rear full stiff. This car had 265/295 tire setup.

Hotchkis Springs and Sways was front soft and rear set to the middle setting. With 255/275 tires.

Stillen Sways with Eibach sways needs to be set to front middle setting and rear i want to say both holes we one notch back from stiff but I can't remember right now for sure. Car had 245/255 tire setup

 

Simple answer. YES YES YES YES

 

Since it sounds like you're getting on the throttle too early and causing understeer through weight shifting to the rear, why don't you try trail braking a tiny bit more to help keep the weight over the front wheels for a tad bit longer? That will also help rotate the rear as well. If that still causes you to understeer too much at exit, then you should think about putting in stiffer sways.

 

There is a suspension tuning article that I have posted along with alot of other general suspension information in the suspension section on this forum. Look for the Suspension FAQ/Review thread stickied at the top of the suspension section.
Jon

 

I guess I'll chime in, my car feels very neutral on corner entry and mid corner and has the slightest but of oversteer on corner exit. I'm sure there are 50 ways to accomplish this. You could get an alignment and non staggered wheel/tire setup be 90% there. A little toe out in the front 1/8 in. and some toe in in the back 1/4 in. This will doa tremendous amount toward getting your car to handle properly.

I have to run a stock rear bar for auto-x but I do run a huge front bar. The larger front bar help hold static camber through a turn and gives you a better contact patch in the front, causing more grip.
Here is how my car is setup suspension wise.
275/40/17 kumho 710s 36psi front 33psi rear
Koni SA usually set on full hard for dry asphalt.
Hotchkis front swaybar on full stiff
Alignment
-1ish camber in front (not adjustable)
1/8 in toe out in front
-1.4 camber in rear
1/4in toe in in rear
We are having a new front bar made that is slightly bigger than the hotchkis bar.

The car has feels very good, I've had several people compete in my car in the last few months and all of them where very happy with how the car handled.

 

Sounds like your setup is working for you for autox, but it is not an appropriate setup for a road course. You'd get major understeer at entry and possible mid corner~late corner oversteer at speeds you'd experience on a road course.

 

Have anyone tried running bigger tire on the front? "Bigger" as in 245 to match the rear, or whatever size that matches the rear. I have not tried it yet but it seems to be a much easier fix than suspension changes.

 

Guys, never mind, sorry, too eager to post. Just read the whole thread and saw the answer.