S13 Racers.... Need help with understeer

[slider2828]

Hi Everyone... I have an S13 SR and during heavy front breaking, the car doesn't really want to turn. Here is my setup

15/16 new booster and new brake MC
Megan Racing Race C/O
Suspension Techniques F/R Sway Bars
Whiteline Bushings all around
Rear CUSCO 3PT OST
Front Greddy Triple Tube STB
Stock Tenshion Rods with New Whiteline Bushings
Toe and Castor - Basically Stock
Camber is .5 degrees over top of alignment spec
Inner tie Rods are stock, but have Moog Tie ends
So i think 1.7degrees in the front and 2.5 in the rear I believe is the camber spec.....

You think I should Toe-In the front like 4 threads? Will that help? Please let me know what you guys think.....

[Dousan_PG]

what tires are u using?? thats the most important!

[slider2828]

I have 235/45R17's on FN01RC 17x8's..... with FUSION ZRI... (Maybe crappy tire?)

[Saisoku]

I personally dont like the fusion tire line... then again it could be just me also because my chassis is about as stiff as bubble gum.

[slider2828]

Yah for a Z rated tired, it doesn't really even hook up, but does have a 280 treadlife, which ima drift the hell out of? hahaha

[Angel]

I would flip the camber settings. ie: 2.5 front and 1.7 rear and start playing around with little toe changes to see if you can get it to rotate a bit better. Do you have an lsd of any type?

[HaLo]

Get same tire size all around.
Get -2.5 to -3 degrees camber in the front
Get -1.5 camber in the rear.
I run 0 toe all around.

No understeer. :)

[n2motorsports]

things you can try

-increase front tire pressure, decrease rear tire pressure
-if the megan's C/O are adjustable, set the fronts softer vs. rear

also get new tires

[tre]

Stiffen up the rear end IE: stiffer springs
OR soften the front.

You're car is a balancing act. Put back on the stock front sway bar is another suggestion.

You dont need all the goodies you can buy on the shelf. In fact most people screw up their set ups, by buying everything they see on the shelf and expecting it to work.

Just like your engine you have to tune your suspension.

My car pushes just a hair. So i'm putting 450lb springs in the rear instead of my 350lbs atm and going to see how it reacts to that.

[RightWheelDrive]

How are your sway bars set up? IIRC, ST sways are adjustable, so set the front softer in relation to the rear sway bar. However, your biggest problem is your tires.

[slider2828]

Ok... will try to run more camber in the front, but I don't have adj. RUCA's so ima screwed there... I will soften the front and stiffen up the rear because I had it the other way around. I guess soft rear and stiff front is for drag and more for neutral steering cars? I have a welded diff as well so that shouldn't be the problem.... Thanks guys....

Do all of you run aftermarket tie rods? Granted my car isn't that low compared to most people and this is for running street as well...

I can't run castor nor too much toe because I have 45's on my rims so they will rub.....

[95zilvia]

How about... Put back stock sway bar in the front, less camber in the rear, more in the front, better tires in the front.

Understeering under braking? What brakes are you running?

Megan Racing Coilovers? Just camber all the way in and experience with that, adjust the camber out a little at a time til your car feels about right.

[slider2828]

I am running project Mu's Bforce in the front Z32 calipers/Rotors, and stock rears with Satified ceramics in the rear.... I think it could be from the brake bias as well..... You think that is the problem? because it doesn't understeer when I am not braking.....

[tchenku]

are you braking while turning? this also cause understeer. halo's the autocross man! he can elaberate more on this, or anyone. also, a bigger front sway bar will help rid the understeer. that's something to think about.

[240 2NR]

I felt like my car had a tendency to understeer. I swapped in the Nismo power brace (and one of the polyurethane steering rack bushings, I think the other is the wrong size) and it really tighened up the front end response in the car. Without changing anything else it feels like the car now rotates around my front tires. I'm not sure if the improvement in steering feel is a result of the brace or the bushing (or both), but it definitely helped firm up the front end and make it more predictable.

I'm running all whiteline bushings up front, koni shocks with whiteline springs (not very stiff), rear subframe bushings, and f/r stb's. To be honest, for $200 I wish I installed the power brace and bushings a long time ago.

[jmauld]

Like tchenku said. Brake in a straight line. When you start turning, you should be easing up on the brakes, which will give the front tires the traction to actually turn. Each tire has a limited amount of traction. A simplified view of this, is that if you're using 90% of the traction to brake, then you only have 10% of the traction to turn. Less brake = more turn.

[nlzmo400r]

yes but if you trailbrake (brake while turning) then its also easier to rotate the car because of all the weight lifted off of the rear tires. What you really need to do is step up to a better tire. Falken makes the azenis rt615 in a 225/45/17. I'd try this first. Also as for aligment specs., with a 225 tire all around, run about 2.5 deg neg. up front, and about 1.7 neg out back. I ran this setup for a while and had great success with it (zero toe all around and caster at 8.0 degrees). Also, as everyone suggessted, to decrease understeer, run stiffer rear (sways, coils, stb, or more tire pressure). If you don't want to run as much camber as suggested (because of tire wear issues). You could step up a 255/40/17 rt615 (as i did) and run about 2 deg neg up front, and 1.3 out back (as I do) and i have excellent balance. The wider the tire is, the less negative camber you have to run to get the same contact patch down during cornering.

[tre]

woah woah woah dont get me wrong.

Normally the best set up for road racing is a stiffer front than rear.

I'm saying stiffing it up a little bit or soften the front a little bit.

Throw your stock sway back on. I plan on only purchasing a rear sway.

You put it soft front stiff rear. You'll be looking for some major oversteering probably, especially if you have power.

Just start wtih a softer front sway bar. See how that works.
If not buy some stiffer rear springs.
Tires are not everything, but are a lot. You could have the grippiest tire in the world and still push due to horrible suspension tuning.

Little cheap things first. Dont upgrade your tires yet. You'll be looking at probably spending double for what I've suggested so far.

[nlzmo400r]

also, ive you've never raced on a decent tire (like an azenis) purchase a used set first, cause you'll flat spot em. You can find em on ebay frequently for about $150-$200

[jmauld]

Also, as everyone suggessted, to decrease understeer, run stiffer rear (sways, coils, stb, or more tire pressure). I don't agree with this! If you have a problem with the front of the car, then fix it at the front of the car, not at the rear.

All of the suggestions you made will reduce the ability to put power down in the corner.

[jmauld]

Just start wtih a softer front sway bar. See how that works.

If you put a softer front sway bar on, will the car not lean more, resulting in less contact patch?

[tre]

If you put a softer front sway bar on, will the car not lean more, resulting in less contact patch?

A stiffer sway bar does cut down on the lean. But at the expensive of putting more load on the outside wheel under hard cornering, and the possibility of lifting the inside tire.

Softer sway bar will tend to even the load out onto both tires better.

He could be pushing for the fact that theres too much load on that outside tire.

So in theory pending on the stiffness of the sway bar. He could really only have one contact patch vs two contact patches (EXTREME THEORY)

[jmauld]

A stiffer sway bar does cut down on the lean. But at the expensive of putting more load on the outside wheel under hard cornering, and the possibility of lifting the inside tire.

Softer sway bar will tend to even the load out onto both tires better.

He could be pushing for the fact that theres too much load on that outside tire.

So in theory pending on the stiffness of the sway bar. He could really only have one contact patch vs two contact patches (EXTREME THEORY)

He could be, but I'm willing to bet that he is bottoming out the outside shock, which results in A LOT more weight transfer to the tire. A smaller swaybar is only going to make that worse. A larger swaybar will help to keep the car off of the bumpstops.

IMO, a ST bar isn't nearly large enough to run into these issues.

[tre]

Probably. But I've never heard of bottoming out a shock, besides a stock one.

I litterally beat the living hell out of my car. Beyond what you guys could imagine. Especially at the track. I come off banks into a flat section completely sideways and still haven't bottomed out a shock, or coil bound my springs yet.

The only time i've ran into coilbind is when I ran into a huge pot hole. Coil binding is the worst noise/feeling i've ever heard/felt in my car.

[jmauld]

here's a pic of my car with 430lb front springs and a front ST bar.
http://i39.photobucket.com/albums/e151/chrishobo3/tn_P1010014.jpg

I don't think I have enough roll resistance. Definitely not enough to warrant going to a smaller swaybar. This was on street tires. I don't have a picture of how much roll I get with my v710s.

[tre]

Also remember there is a weight difference between the s13/s14 chasis

[Wiisass]

are you braking while turning? this also cause understeer. halo's the autocross man! he can elaberate more on this, or anyone. also, a bigger front sway bar will help rid the understeer. that's something to think about.

Bigger front sway = more understeer, bigger rear sway = less understeer.

He could be, but I'm willing to bet that he is bottoming out the outside shock, which results in A LOT more weight transfer to the tire. A smaller swaybar is only going to make that worse. A larger swaybar will help to keep the car off of the bumpstops.

IMO, a ST bar isn't nearly large enough to run into these issues.


I highly doubt that he is bottoming out the shock. The MR Race dampers use a 12k spring in the front right? So unless the MR's have no damper travel or a giant bumpstop, there's no way he's bottoming out.


Alright, now about the problem. You said when braking the car doesn't want to turn. Are you locking up the fronts? Or do you start to turn and then it starts to push? It could be your driving style that's making the car do this. But it could also be the cars setup. Can you clear up exactly when this is turning. Just describe it like a clock, say you enter the turn at around 3:00 heading counterclockwise, where do you stop braking where does it start to push. Assume a straight entry. If you clear that up it will be a lot more apparent as to what the problem is.

Your brake setup is the first thing that comes to mind. But then again, that might not be enough of a brake bias shift to the front to cause issues like this.

I agree with what other people have said about running more static camber in the front, just leave the rear where it is. And unless your braking real far into the turn, then I really doubt that sway bars will have much to do with it. Your shocks on the other hand probably should be adjusted.

The problem with the shocks, is no one knows what they adjust. Does the knob just affect rebound or does it affect rebound and compression? If it just affects rebound then bump up the rear settings a little in order to slow the weight transfer to the front. If it does both, the up both the front and rear settings a little, the rear more than the front, and see what happens, this might be something you have to play with a little before you get it right.

As I said before, unless this is happening later in the turn than I am assuming at this point, you shouldn't have to worry about sway bars at this point. But if you're entering the turn and, using the clock description, it's starting to understeer around 1:30, then it could be the sway bars. But if you say it's neutral during steady state cornering when you aren't hard on the brakes then I would think that the sway bars aren't where you should be looking.

You could mess around with tire pressures, lowering the tire pressure is like softening the spring. If none of this works, you should think about better tires, you could be outdriving them. Oh, does this happen all the time or just when the tires are cold or when they're really hot?

[tre]

I messed around with tire pressure and it helped me out at the track with pushing.

I ran 30psi fronts and 45psi rears.

Came off the track with 35psi front and 52psi rears haha

[jmauld]

I highly doubt that he is bottoming out the shock. The MR Race dampers use a 12k spring in the front right? So unless the MR's have no damper travel or a giant bumpstop, there's no way he's bottoming out.

Well we don't know how low he has his car, so this is difficult for us to say. Easy test though. Push your bumpstop all the way down. If it gets pushed all the way back to the top, then you're bottoming out.


? It could be your driving style that's making the car do this. But it could also be the cars setup.
I don't know the guy, so I didn't want to pull that card out. But this is generally the #1 cause of "understeer".

I just noticed this in your list of mods
Stock Tenshion Rods with New Whiteline Bushings

Their's a decent chance that what you're feeling is suspension bind from these bushings.

[Wiisass]

He claims that his car isn't that low compared to most people, so I'm assuming it's lowered just not slammed like a lot of people do. And even if his car was sitting on the ground, you usually need to add a bunch of preload so you can move the whole assembly down further, so there would be no chance of bottoming out there. And if he went the other way and his spring was sitting there loose when the tire was off the ground, he would've had to move up the shock a decent amount to get that to happen, I'm talking like several inches between the upper spring perch and the top of the spring when the car is in the air.

The TC rods could be binding, but there are better things to check first. Maybe after he checks all of them and eliminates them as the problem that would be something to look into.

[tre]

Here's my car. Just as its hitting the flat from the bank. Traveling around 50-60mph. I have 450lb fronts with tokico blues and stock sway

http://img.photobucket.com/albums/v315/SSRtre/caragain068.jpg

[jmauld]

He claims that his car isn't that low compared to most people, so I'm assuming it's lowered just not slammed like a lot of people do. And even if his car was sitting on the ground, you usually need to add a bunch of preload so you can move the whole assembly down further, so there would be no chance of bottoming out there. And if he went the other way and his spring was sitting there loose when the tire was off the ground, he would've had to move up the shock a decent amount to get that to happen, I'm talking like several inches between the upper spring perch and the top of the spring when the car is in the air.
I'll fold on this. I have Koni's and GC's, so my issues with bottoming out are due to using shocks that are the stock length, minus my custom sawzall enabled shock shortening. :eek3: If you say you can adjust those shocks enough to get rid of that problem, then I'll take your word on that. Again, there's an easy test to find out. Just don't hit any pot holes on the test drive.

The TC rods could be binding, but there are better things to check first. Maybe after he checks all of them and eliminates them as the problem that would be something to look into. I'd get rid of those first, just because they are known variable that causes problems. No reason to tune around a bad part.

[sideview_180sx]

If you want a better understanding. Getting some books on handling and suspension setup is your best bet. Everyone here is offering suggestions and tips. However, we all have a different driving style. Where as your setup you experience understeer, another person in your car would experience oversteer or a neutral feeling with a slight hint to push or get loose. "How to make a car handle" is a very good book. Read it and search on it so you can understand it better. Also, as those who you autocross with for suggestions, they usually can help point you in the right direction of what you are trying to achieve. If anything changing out the swaybars and things like that are very big changes, try turning down the damping on the shock if its adjustable up front and go from there, hopefully you will get a good bearing in which way to go from all the input from everyone.

[95zilvia]

Ok so I didnt read anything else after you said what brakes you are running.

Z32 Brakes in just the front and stock in the rear makes the bias mostly in the front, meaning your front brakes lock up faster than the rear. Mixed with your shitty tires, your brakes are definately overpowering ur tires, causing them to lock up.
I'm guessing locking up while turning is what u mean by understeer.

[slider2828]

OK well..... thanks for all the info.... No the car isn't lowered too much at all, I still have about 1.25 inches of clearance all around. I believe the megan racings adjust compression only, hence I would probably soften up the front a little and keep the rear stock. I feel the understeer under braking around 1 o'clock while turning. i used to race motorcycles so I know a LOT about suspension setup... I trail brake into the corners, but the car just doesn't want to respond to that and the front starts to slide. I mean I slowly ease of the gas obviously, but the front definitely feels heavy. I feel the rotation of the car really well when I am not on the brakes as hard (normal street driving), so I really don't think sways do that to a car. In essence I believe heavier sways give you more traction because it plants more traction always on the outside of tire, therefore a bigger front and rear will definitely help you corner better. Yes I think the brake bias is a POS and I think the tires are definitely shitty.... Mid corner stability while off the brakes is fine and exit is great even though shitty tire.... I don't have adjustable tie's, still stock, but that will change soon. But I think possibly its because of the tires, that the front really has crappy grip... What do you guys think about mixing manuf of tires, go with ZRi's in the rear and something more soft in the front like azenis? I think that will help as well......

[jmauld]

I doubt the shocks adjust compression only. Generally, if they only make one change it will be to rebound not compression.

I just read that you have a welded diff. That's another good cause of the type of problem you describe.

[slider2828]

Yah I think that would make some differences too.... sucks..... would a 2 way be better than a welded in this regard with understeer? Obvious, 1.5 way is best, but I like drifting as well. Thanks!

[95zilvia]

Falken RT-215 in the front, I think they make a 225/40 size
I'm running 215/40/17 in the front of my car on a 17x8 but I think u would want bigger.

[Wiisass]

jmauld, is right about the shocks. Single adjustable shocks usually adjust either rebound only or rebound and compression at the same time.

I don't know if a welded diff would be causing the problems here. I could see corner exit understeer being a result of the diff, but not corner entry.

About sway bars on a race car, I don't lilke to use them for much more than tuning oversteer/understeer balance and not for adding too much additional roll rate. Adding larger sway bars does not always mean more grip. A pair of evenly loaded tires will generate more lateral force than a single tire fully loaded.

Back to your problem, it sounds like you should be messing around with shocks a little to tune out this problem. just try what I suggested earlier and you should be able to tune it out. It also could be the driving style, the last time you were at the track did you mess around with braking points and trying different lines to see if you could avoid this happening. You're using all the tires grip when your braking, and then the steering input just does nothing. So maybe if you try braking a little earlier and not trail braking into the corner, you might be able to avoid the understeer. Take someone with you and have them time your laps or time certain sections of the course so you can compare times with different styles/lines in addition to your feelings in the car.

[s14slide]

I don't know if a welded diff would be causing the problems here. I could see corner exit understeer being a result of the diff, but not corner entry.

I'm not trying to call you out on this, but a welded diff will definately cause understeer unless you are intensionally trying to get sideways. The front tires have to fight the rears. While the fronts are trying to turn the car, the rears being completely locked will try to keep the car straight. In all reality, it lowers the thresh hold of when the fronts will let loose cuz they now not only have to deal with turning and braking, but they also have to fight the rear tires grip now.

It also could be the driving style, .

Now this I agree with. If you've got a welded diff, you just have to learn to drive around it. Try starting a turn and keeping a hair of oversteer till you hit the apex. This will allow you to decide to keep it there and keep you speed up or straighten out, which will all depend on what the car is doing and what the turn looks like. Also, IMO, before you do anything else make all the shocks even at about half the dampening rate, then even up the tire pressures all the way around, drive, record. From there, adjust the shocks till you get close to what you want. Then play with tire pressures. And like said before, more camber up front less out back. Remember, small adjustments.

[Wiisass]

I still can't see the diff contributing much under these conditions. I mena like i said, at corner exit, when your on the car, definitely can cause understeer. But at corner entry and hard on the brakes, with no throttle input, it would be the front tires saturating because they can't handle the turning and braking at the same time and not the effects of the welded diff.

Then again, I've never driven a car with a welded diff, so it may be a little different than I'm thinking it is.

[jmauld]

From what I understand a welded diff is going to cause understeer initially. With the rear tires locked together, it will fight the initial steering input and try to keep the car going straight. Once the inside rear tire starts slipping against the pavement, it should become easier to turn.

I've only autocrossed on a welded diff once, and it was in a car that I wasn't familiar with, so I'm definitely not claiming to be an expert here.

[s14slide]

well, I've never driven on a welded either, but it's got to be at least slightly worse than a car I drove that had a 90+% locking clutch type diff. When I drove that, I had to really rethink my driving techniques. Even though you get hard on the brakes and the fronts are saturated, then the diff still isn't helping. Think about it. There's only 100% that the tires can do, and if a diff is welded, it will always be in a fight with the fronts. So whether it was locked or not, braking and turning can chew up that 100%, but the locked diff fighting it will only lower where all the traction goes, cus now part of that 100% will be used to fight the diff initially. And as we all know, once the tire breaks loose, it can be a handful to get it back. Not to try and play down the welded, but even when drifting I don't like a completely locked diff. I like somewhere in the 70's to 80's locking. To me, it feels like the car is more snap-able at initiation. I don't have to try as hard to get a quick snap to hit lock.

[ms!3]

are your front and rear brakes the sames keichi was saying in the drift bible if your front brakes are bigger than your rear that can cause understeer.

[s14slide]

that may be true, but you got to remember that the most important part of a car is the driver. Now don't get me wrong ya'll, I'm not saying that this guy doesn't have the potential to be a good driver, but parts mean crap if the guy behind the wheel doesn't know how to till the wheel and dance on the pedals. Front biased brakes can be driven around, which in all reality doesn't fix the problem, but I don't know enough about the setup of the car or what he's driving on (surface) and I have no experience with his tires. All I can say is what I've already said (see previous posts for this).

[go240]

i had my first track driving experience this weekend and found i had terrible understeering issues as well. i think it's mostly because i suck at driving lol. raising the front tires to 45psi helped a lot - the sidewalls were just buckling before (i'm on fuzions as well. 195/50/15. the hri's though, not the zri's). car has a welded diff, mr track coils, hawk hp plus pads, goodrich ss lines.

i'm going to get tension rods, maybe the nismo power brace (my oem one is kind of fucked up lol), and a rear sway bar, possibly tie rods too since mine are shot. then it's just time to work on driving technique

[s13coupedrfter]

It's really easy, NEVER BREAK WHILE TURING. Try this new technique and if you still feel the car understeers to much play with tire pressure (since it wont cost you a dime). Remember, this more about driver technique/skill than throwing parts at a car. You can change spring rates, sways, and camber/toe but in the end this won't change bad technique

[slider2828]

ok there is a reason why you trail brake and not do ALL the braking in a straight line. You do most of your braking in a straight line then less pressure as you turn the wheel. That is how it works, the later you can brake the faster track times you usually get.... You go fast in the slow stuff, that is how it is. Trail braking almost eliminates suspension oscillation when done correctly and that is the hey to being smooth and fast. I am trying to reduce understeer during braking, maybe it is driving style, but I cannot attribute all of it to that.

Yes HRI's really are horrible. I have them on my TL Type S, and I can feel the walls flex, its not all the great... but awesome for cruisin, but really bad in rain.

I really wanna thank everyone on contributing to this thread and hopefully it keeps coming.... I am going to replace my inner ties with OEM, because I can't afford the whole splparts tierod combo, so oh wellz.... But I will increase tow in and I think that will help. Tires and all else can wait right now and need to fix brake bias...... will update as I get all of that fixed

[HyperTek]

remove the front strut tower bar.. try with just a rear strut tower bar.. these things make a night and day difference..

[EchoOfSilence]

I don't understand why running without a strut tower bar (which should only keep the towers in place and not allow for any alignment change when installed) in the front would have any positive benefits

[slider2828]

I seen some japanese S13's running without a front upper stb, it allows the front to flex therefore basically the same idea of getting the front end to follow the initial steering input. I seen people do that... such as in a AE86 N1 battle, basically the driver just took the front end stb to decrease understeer... dunno if it made a lotta difference, but he definitely knew what he was doing...

BTW I did lower the compression/dampening of the front to about 4 click above 0 (soft setting). These are MR tracks and it did make some difference. Noticeable difference in braking distance and less understeer but you definitely feel a little loss in intial turn in. Basically car turns slower initially, but the car does follow. I also reduced the dampening force in the rear as well, but I think I will raise both fronts and rears a little, by 4 in front and 2 in rear, should be close.

In regards to Keiichi Tsuchiya's drift bible, I think definitely pads and rotor will help a little with the brake bias.... but dun have that much money right now, and trying to sort out some sorta wheel hop issue in the rear.... But dampening and compression did play a noticeable part in understeer issue.... Thanks everyone.... Thinking about playing with a little toe in and see if that helps will update...