GTU_FAN

What causes understeer in an FC? Just collecting input to better adjust my setup. As it is I have zero oversteer moderate understeer w/the following.

-Eibach springs w/Ground Control adjustable perches (375lbs ft, 280lbs rear) 1.5" drop front .5" drop rear. Springs have approximately 1/2 travel of stockers so about 3" vs 6".
-Tokico HP's (ft)
-KYB AGX (rear, set on "6"... HP's are about a 3-4 compared to that).
-Front Strut Brace (generic w/pre-load)
-Racing Beat Sway Bars.
-Energy suspension bushings (ft lwr control arms and swaybars only)
-Mazdatrix dual rear camber links
-Racing Beat DTSS elliminators
-BBS "vert" wheels w/225/50/r15 Toyo Proxes T1-R's
-Overall lowering is about 2.5" from stock.
-Allignment is stock setup for good tire wear w/zero added camber or toe

I want to lessen the understeer so it will distribute grip more equally and drift naturally on all 4 wheels when pushed beyond the limit. Basically I want better skidpad performance which should translate to faster lap times with my driving style.

I do not want to throw more parts at this problem or bandaid it by adding oversteer. I want the grip threshold to increase overall and have more balanced tire slippage when it occurs. I'd also like to maintain a decent compromise for tire wear since this is my daily driver.

madaz07

i have the same problem is very bad in wet conditions.ive got dtss bushes. koni adjustables king springs. stock sway bars. front strut brace, its lowered about the same camber is stock on front but has lots on the back due to lowering etc

im keen to get rid of the understeer too.

GTU_FAN

The rear-camber issue is why I had to fork out so much for the mazdatrix links. I still have to keep the rear spring perches up all the way. I dont think anyone has an actual kit to get rid of all camber in a full drop in the rear...

trainwreck517

iTrader: (1)

I would add a bit of camber in the front, and loose weight in the rear when you run at the track.. no spare, no rear speakers, carpet.. etc.

I would also run rider tires/better tires.. Of this is auto cross run some hosiers A6's or track days run some R6.

fc3s-infini

If your sway bars are adjustable, then set the rear a bit stiffer.
Or if your dampers are adjustable, maybe set them on a harder setting.

Or you could just pop the clutch to induce oversteer

spot_skater

When I put on a front strut brace, I noticed a big change in the handling characteristics of my FC. It tended to understeer A LOT more. Try adding a rear strut brace, and it may tighten the rear up enough to give you more neutral handling.

Before you go spending money though, take off the brace in front, and see if things change.

Also... when entering a corner if you completely lift off the throttle, weight transfer goes from the rear of the car to the front, and helps induce understeer. I'm sure you know about this, but I'm just throwing it out there. Powering through should help the rear slide out a bit more, as well...

Also... I think your tire size may be off a little. I run 225/50 tires on my 16" wheels.

Sideways7

iTrader: (7)

I thought making the rears sways weaker or the fronts stiffer would get rid of understeer. I have the stock front sway bar and rear one removed and it is quite neutral. From the way I understand suspention tuning, you might benefit from stiffer front dampers.

fc3s-infini

I agree with this, but from what i gather GTU_FAN already has front and rear sway bars....


Its the other way around. Stiffer rear = more oversteer. Stiffer front = more understeer.

Having said that tyres also make a BIG difference as well! Having good tyres front and crap ones rear also will help to induce more oversteer.

CrackHeadMel

iTrader: (2)

Ive hurd many times that fixing a problem at one end of your car by adjusting something at the other end is wrong


Try making the front softer first

scrip7

iTrader: (6)

I was taught long ago that on a rear drive car, stiffening the rear sway bar would typically increase understeer, and vise-versa. I have played around a lot with front sway bars by, for instance, using a rubber bushing at the top of the link and a urethane at the bottom, etc. to get the roll stiffness the way I like it.

Sideways7

iTrader: (7)

We need to get someone with a lot of experience in here to straighten this out. Maybe reted or someone will drop by.

stevensimon

iTrader: (11)

have you played with tire pressure yet? 5 or 10 psi can make a huge difference in characteristics. try max in rear and 10 below max up front. helps with rotation tons

rotarydelight

add a little camber in the front,
adjust the front sway bar or damper (more soft)

Mr.LD

The FC is a bit hard to drift in at first. takes some time to get used to it since its balanced out with the engine near the firewall. From my experience of changing to an FC from an AE86 getting it oversteer more is harder. Stiffening the rear , in theory would make it oversteer a bit more. Depends on how you plan to make it turn , your mods will differ. You can do alot before having to swipe out parts unless your gear is 18yrs old n etc.

If it dont wanna turn when u hear it go Vrraaawww , maybe punch the clutch when its like VRRAaaWWWWWWW. some people can get it @ just Vraww.

Ld

toplessFC3Sman

iTrader: (1)

gotta love the sound effects. I agree with taking off the front strut brace and seeing if that helps, some camber in the front will help with maintaining lateral grip, but wont do as much for initial turn-in. You have the rear dampers at 6 and the fronts at about 3-4? try softening the front dampers and sway bar, but be careful not to over-soften the dampers so the car doesnt start really bouncing around

madaz07

will try taking out the strut brace if that is part of the problem how do i fix it or what do i change ???

gabe30

isn't the e-brake an obvious solution to all understeer?

i did like the idea of clutch kicking

spot_skater

I was talking about his front strut tower brace, not sway bars.

Wankel7

Could any of this have to do with adjusting the preload on the sway bars with adjustable end links? Making sure you have zero preload?

stevensimon

iTrader: (11)

have you tried tire pressure yet? it sounds stupid but that is one of the biggest factors in suspension setups. i have owned driven and drifted 86 s13 and fc for a few years now. all with suspension similar to yours and it always came down to getting the tire pressure right. what size tires are you running and what are they set at now?

Black91n/a

Here's what I'd do (in order of what I'd try first):

-Play with tire pressures, this has a large impact on handling
-Stiffen the rear shocks
-Take out some rear camber (if not maxed out already)
-Raise the rear ride height a bit
-Put the rear bar back on

GTU_FAN

Thanks for all the imput guys... but it dosen't seem like most of you even read my post. Most of your suggestions are just wrong. If you read it you'd realize that.


-Remove weight... Sure I'll try it out but I would think that reducing weight on the front would help with understeer not the rear...

-Add camber... Sure I'll try it out. But I want to get some decent mileage out of my tires.

-Better tires... for the track sure I'd like better tires. I plan on having a set of track/wheels tires as soon as I can afford it. But on the street my tires are better then 95% of the competition as it is.

-You are correct I could benefit from less preload. But that isn't as big of a problem as the size of the swaybar itself.

-Stiffen my rear struts? Not any more on the street. They are stiffer then they need to be on "6". I get absolutely no squat on launches and hardly any give over curbs and what not. On the track though I dont mind stiffening them more.

You also mentioned driving style changes. I didn't say... dont mention driving style changes but I should have. I've had this car long enough to have tried many different methods of corner entry. When its helpful I will induce oversteer. When its not I wont. That dosen't change the fact I want my car to be capable of less understeer. If I wanted advice on how to drive I would have asked for it. But thanks anyway you were only trying to help.

Correct. I realize this is one mistake I've made in my cars setup. Larger diameter sway bars make the suspension stiffer and transfer more weight to the end of the car where they are installed. If the car is understeering, you can increase rear sway bar diameter or decrease front sway bar diameter to restore balance. Anti-roll bars should be chosen to match your springs. If you are planning on installing stiff springs, there is no need for a large diameter sway bar.

-Remove my strut brace? No... I put it on there for a reason. It makes the chassis much more responsive. Both because of less flex keeping the front tires on the ground and helps steering response. I could literally drive 10mph faster on a challenging touge because of the strut brace. If I remove it the car might be more neutral but it'd be slower. No thanks.

-You described the weight-transfer thing wrong... but I catch your drift... like I said though I dont need advice on how to drive.

-Toyo tires offers that size in a 15" as well...check out their website if you dont believe me. I said I ran vert wheels so there's no doubt about how big my rims are.

-Stiffen my front struts... yes I already plan too thanks for the good advice.


-Soften my front struts? No... they are already too soft for the higher spring rates. I get lots of bounce on a touge. Not so much on the track of course. I agree with your statement in theory though.

-That's cool that you experiment with links that way but mines an s5 and I dont think you can press bushings in and out of those plastic ones so easily? I may be wrong.

-
-Screw with tire pressure... Sure I'll try it out as long as it dosen't make wear much worse. I told you what size tires I have. I should probably loose some pressure in the front tires to help with understeer.

-The tire pressure thing is the only thing you mentioned that makes any sense in regards to my car. Were you trying to comment on Sideways7's car?

spot_skater

Thanks for the correction. Since you don't seem to be getting the answers you're looking for, why don't you bring this over to the suspension/wheels/tires section. Or the race car/auto-x section.

There's guys there that REALLY know their stuff, and might be able to point you in the right direction.

EDIT: And just because a tire is made in a size, doesn't mean it's the correct one for your particular car.

GTU_FAN

So your saying its not?

spot_skater

Yeah, that's what I'm saying. On a 15" tire I would run a size 55 sidewall, with your width. The guys in the suspensions section will be able to point you in the right direction though, for sure.