Understeer Issues - Toe Alignment Issues?
 

Hi All,

1) Toe Alignment Spec - Do I Have to much Toe?
2) Is there any other reason I'm understeering

Car - MY14 Toyota GTS.

I've bought some of the TS STI Wheels (17x7.5) and had the tyre shop install 4x brand new Pilot Sport 4 (Not 4s just 4) 225/45/17 as well as align the car.
I didn't ask for any specific alignment specs... See attached.


I've currently running MCA Sport Essentials (Brand New - 2 months been installed by me. Their specification sheet mention it should be 350mm front/rear from of wheel to guard and measuring now, its pretty much even.
Although the driver's side (Right - RHD) was 350 and the Left side was about 345mm....
I've checked tyre pressure after the car had 2 hours to cool down (Also note it's cold outside) and all 4x tyres were about 33-34 PSI. So I'm confident that the pressure isn't the problem.



Now my problem and question.

I've always noticed this with the car, but they had pretty old/worn PS4 on the Stock 17s.

Basically, when going around a corner, when you accelerate the car feels like the front tyres "Slide" and understeers. The steering doesn't feel precise at all. It becomes very light.


There's basically no oversteer at all and just feels crap.

Really you just have to remove throttle input and wait for the car to settle.


The coilovers dampening adjustment (0-12) was 2 from Soft in the front and rear.

I put the rear to 9 and it makes it feel better, but still understeers and "slides" (The front slides - Steering light).


Obviously this feels crap!

It doesn't give me any confidence in the car at all.


This happens with or without traction control on... seems to be better with it off, but still happens.

The TC sometimes come on usually coming out of the corner, not at the start.

Note: I have an NB MX5 and it does not feel or understeer like this.





Question 1) My Alignment.....
Is there too much toe in general?
Everywhere I read has pretty much 0 toe front/rear.
I didn't bother asking for a specific alignment and they just gave me I would assume a standard alignment.

+0.7 front, and +1.2 rear toe-in .. that's in what measurement unit?

If in degrees, way too much.
If in inches, according to this (with 24.62" tire diameter) even worse, +2.65dg front, +5.59dg rear, but i doubt something THAT off may go unnoticed or even set that much.
If in mm, +0.12dg front, +0.22dg rear. A bit too much in front, normal in back.

Understeer or oversteer balance is about which car end has more grip vs other. There are several ways of skinning cat, as in - to add or remove grip to one end of car, to change car grip bias.
For example, to add grip - softer springs, more toe-in, softer rollbars, less air pressure in tires, more negative camber. For less grip - stiffer springs, stiffer rollbar, higher tire pressure, less camber.

Just toe-wise i usually aim/ask to dial on twin for zero front toe, and slight toe-in rear (+0.15dg to +0.25dg total toe in (halve that if per wheel. "+" means toe-in, "-" - toe-out)).

Stock alignment for these cars: at front each wheel 0dg camber, 0.0 toe, rear each wheel -1.2dg camber, +0.2dg toe-in. It's a bit understeer-ish bias.
Most "fix" it by adding front negative camber (which also makes better tire wear on track instead of just ripping outer side as if on stock alignment), extent to how much camber optimal depends on use type (DD only or track), with dialing toe close to "stock" of zero front toe and slight rear toe-in (for some stability under accelerating out of corners, or to ease handling when accelerating in straight if/with wheels spinning (eg. if low grip such as wet/snow/ice)).
Simple to aim camber values for closer to neutral/less understeer-y grip balance might be - by 0.5dg more front camber then rear.

What use your car sees? (just daily driving? pushing a bit more? track driving?)
What camber adjustment means your car has? (twins as stock have only toe adjustment. Aftermarket coilovers may have front camberplates. For rear camber adjustment aftermarket LCA might be needed).

P.S. Also remember that "hard" to get rear out might not be just because of grip balance .. but also because if tires may have more grip in general. PS4 have much much more grip then stock Primacies. You really have to push them to loose grip .. not so easy when driving within speed limits and not hooning dangerously, just driving together with rest of traffic. Need to push more (eg. on track), or loose grip in other ways (driving in wet, or do driver inputs to overcome available grip). Understeer or oversteer .. it's more about when one pushes to limit, which end of car looses grip first. With grippier tires you have overall grip limits much higher, not just rear but also front.

Power-on understeer is a normal phenomenon. Despite Fast & Furious "physics"... Get on the gas, load up the rears and unload the fronts, the car is going to push. Up to a point anyway, but given 2.0 liters of n.a. fury, for us power-on OVERsteer isn't so much an issue usually...

Proper driving technique is to trail-brake on corner entry, maximum steering input near apex, on the gas at exit while unwinding steering with enough turning already done that you don't have to get OFF the gas to point the car.

That said, your toe numbers look fine (assuming millimeters!), but you could run less. Could run zero toe all around and that would generally reduce understeer a bit, particularly knocking the rear toe down from 2.4mm. Which isn't excessive but from zero to half that is the range I like to be in for rear toe, with zero front toe.

You could run a lot more front camber (assuming coilovers have camber adjustment). Street-only and desiring less understeer I'd try at least -2 degrees front camber, could run more than that and still be streetable, up to, say, -3 degrees.

AS for damping adjustments, go by manufacturer recommendations, but usually you adjust from full *stiff*, not full soft. I.e., the reference point is to screw the adjustment needle all the way in (clockwise), and then count clicks out from that point. Usually the steps between the first clicks out result in bigger changes in damping, towards the soft end you get to a point where more clicks out doesn't do much.

But again, technique is possibly a reason for what you're experiencing. If you're in a corner in anything higher than first gear and just smash the throttle, you're gonna get understeer in general, unless in low-grip conditions.

I assume the measurement is in mm.

So good to know that the toe isn't ridiculous.


Car is a daily, but I still want it to have some fun on some back roads.

Yes, the front coilovers have camber adjustment. Perhaps on my next alignment, I'll get more negative camber and less toe.



I've only experienced the car with Pilot Sport 4 (The older tyres on the stockies were PS4, but obviously much more worn).

I'm not really sure how though that I'm getting to the end of the grip level of the 86 so quickly.

I've been on track twice now (with my other car) and never had this issue, as well as in a honda on back roads.





Yeah, I'm just surprised that the car is able to over grip the front tires and "slide" so easily.
My old honda with a K24A3, never felt like this and it was one Bridgetone Re003s on 225/45/17s.

Obviously different setup and what not, but being FWD the way it understeered during a corner still didn't "slide" out or anything.
Especially seeing as the 86 is a RWD, I just don't really understand why it's doing this.


In my NB MX5 it's a completely different beast. Yes, obviously a lot less power, but it's actually not that far off when you look at power to weight figures.




I might have to meet with some local 86 owners to get them to feel it.

Just something that I thought was quite odd.





And also it just feels weirder then usual understeer. Like the front "slides".

Perhaps I'm overthinking this a bit too much.

Remember that stock alignment is 0 camber front and -1.2 camber rear.
So you do track car. Then i guess worth increasing front camber to ~ -3dg front, rear to -2.5dg. That should both add grip and even out track tire wear and change grip bias to more neutral.
As to why manufacturers usually do stock alignment to more understeer-ish bias in modern cars, because it's supposed to be "safer". People driving cars have very varied skill level, and more often then not lack skill driving on limit, knowing little how to deal with oversteer, but understeer is easier to handle for them, as they can always do usual thing - ease on gas or press brakes "to fix". Countersteer? Hah, if for them car doesn't turn enough due front pushing out, they turn wheel even more :). No manufacturer would want to face any liability or have reputational damage for one of it's cars labeled as death trap just because 9/10 of average drivers have lacking skills.
Remembering MR2.. :rolleyes:

It could just be "new tires", although I just had brand new Conti ECS mounted and they were grip monsters right away...

I also just redid my suspension setup last weekend, re-installed camber plates and went from ~-0.5 to -1ish degrees to -3.3, and during test drive, the difference in over/understeer balance was profound, even driving well below the limit!

You have the adustability, so get you some negative front camber, at least -2 degrees and up to as much as -3 degrees. You might have rear camber bumped up to about -2 degrees as well for general handling balance.
For toe, have them dial front toe to 0.0 and rear toe to zero up to 1.2mm (about 0.1 degrees) total or half that per side. Might be paying for a second alignment if they don't want to redo for free, but IMO it will be worth it to you ;)

My personal experience has been that toe in up front, or positive toe, does cause the car to push pretty badly. 0 toe would probably help out a lot. However, I think more front camber would help you more. These cars need a lot of front camber due to the strut style suspension. 2-3 degrees of negative camber in the front would help a lot. Also, I'd zero out the rear toe as well. I have tried several alignment setups on my car and I have more or less settled for zero toe front and rear to give the car good handling on the street and autocrossing. That's how I like it anyway.

With zero rear toe i find much harder in case of limited grip. Much more mini corrections needed, instead of more or less just driving. Rear toe-in also simplified on track accelerating out of corners. Imho it's worth having some, but to extent when pros outweight cons.
I'm not familiar with auto-x specifics though, maybe there is something to be had from zero also rear toe, did only trackdays + daily driving on different grip surfaces in different seasons. But about some rear toe-in for RWD cars i see suggested by most people, and it's there in even stock alignment for most RWD cars.

That is in line with the differences between track and street/autox in my opinion. I prefer some rear toe in for track driving too but in autox i prefer zero toe to get the car to point faster. You are right you will be making more quick corrections with zero toe but the other side is that it is helping you control rotation rather than having to try to rotate it and then risking over doing it. Again, this is my experience experimenting with alignments on the twins.

OP just follow what this guys said


I would throw in that you want atleast -2dg up front. :party0030:




oh and tires, my PSS understeer like a dog when it was old so i throw that in the dumpster.

Try removing the front swaybar

Lack of negative front camber is what stands out to me.

Also knowing your spring rates and swaybar sizes/settings would be helpful.

Start by adding another degree of neg camber up front and soften the front bar if it isn’t stock

Don't do this, he's joking. I think! It *would* reduce understeer tho...

It will reduce understeer, and there might be applications that may beneficial for this method to add grip (imagining something like rallying on gravel/snow/ice), but why not fix actual issues before trying out hacks not without cons of their own?

Zero front toe, -2 degrees front camber, they shouldn't have to touch the back and you should be able to get a cut rate on the alignment.

The factory alignment on Subarus seems to be universally understeer prone, it's a misery and why I have little interest in ever owning a WRX or STI.

Am I missing something? coming out of a corner, under steer is usually balanced with increased throttle.

I've driven without the front swaybar before, it's really not a joke! They are tuning tools. If it's causing your car to push, you unbolt it. Takes 15 min

If you have to disconnect the front swaybar on a rwd car, something else is bad wrong with yer setup!

You are missing something, because short of power-on oversteer, which isn't much of a thing with these cars, increased throttle induces UNDERsteer, not OVERsteer...

You are. From driver inputs understeer can be reduced by mass/grip transfer to front .. by easing on throttle or light braking, not something opposite that on countrary reduces mass transfer/grip to front and further reduces front grip.
Well, one can reduce rear grip with adding gas even further to level of complete overcoming traction, and go sideways drifting. Skidding tires will certainly have less traction then still having grip fronts. But, it's not norm to drift through every turn on public roads, and drifting is slow way to go around track.

I completely agree with that! Just making sure OP explored all options. I disconnect my rear sway for snow racing

Are you sure that it's increased mass transfer that increases grip? Then how does a larger swaybar work?



The reality is there are more than one possible outcome from applying throttle in a corner with a rwd car.

First is - more speed - more cornering force required from the front - front tires are already at a high slip angle - more understeer results

The other possibility - more rear slip angle due to both acceleration force and additional rear lateral weight transfer - reduced understeer

Third option - wheelspin - much more rear slip angle - reduced understeer. Maybe hard to do in a stock power brz especially with good tires.

However, the first two are both possibilities. Kind of depends on power and how well balanced the car is at steady state. We've setup cars to be fairly biased toward understeer to give the rear tires more ability to accelerate the car out of a corner.

I went for another drive with my partner today with both this and our NB8A MX5.

The lug nuts were loose as soon as we'll took off. So I tighten them up. Lucky we checked as they were all a little looser then I would have thought.

Anyway, we hit a back road and noticed that felt the same as yesterday.
Basically very floaty up front and understeer.
TC light would come on very regularly, even when barely trying to corner fast or anything.

We played with the coilovers, going from stiff (9/12 front/back, then back to soft (2/12) front/back.
Having stiffer helped slightly but not really.

What we both noticed was that turning traction control off completely (left button held down for 10 seconds), that the car would feel a lot better. Not how the mx5 felt but a whole lot better. Much less under steer and much less floaty.
It gave you a lot more confidence.
What the car does still feel is that there is a bit of under steer and when you are putting the power down (even in longer, not sharp corners) that the car would float and push you over in the direction you pointed the wheel. The steering would also be light.
This was still a whole lot better and gave you more confidence then before.

Another reason too we believe the traction control is a part of the issue is that it seems to be very sensitive when driving normally around roundabouts or on high speed corners on bumpy back roads (driving normal to the speed limit not spirited).
With traction control off, you can go much faster around roundabouts without issue. There is more then enough grip in the tyres, and not enough power to blast them off.

So after driving the mx5 back to back, it seems that we have to get an alignment.


So I'm thinking something:

Front:
0 toe
Neg 2.5 degrees of camber (still is a daily)

Rear:
0.5mm toe each side (1mm total toe)
Hopefully 2 degrees of Negative camber (as stock rear control arms)

Also front spring rates are 6kg and rears are 4.5kg. When talking to MCA they recommended the upgraded spring rate.


Long story short:
Car with traction control off, the car feels better but still is slightly floaty and understeery.

Traction Control on, very floaty and under steer prone. No confidence and almost scary.



Pretty sure its just an alignment. Well I'm hoping so.

I appreciate all the replies and will be sure to update as soon as I can get it realigned.

Edit:
Also I don't want to remove any of the sway bars to fix the problem at this stage. I totally get you can use them to tune the car for over/under steer but the car is basically stock with slightly wider tyres (lighter wheels) and coilovers (which are a bit more premium then average).
Currently the car is on stock front and rear sway bars.

Edit 2:
I'm confident that I'm not going into corners with either too much speed or steering angle. Smooth inputs in and slightly more aggressive on the way out once the wheel is going back to straight.
Also I'm still on public roads and I like to make sure that there is a good safety margin and I'm inside the lines.

Yes, increased mass transfer also transfers more grip. Hence why common way to fight with understeer is reduce transfer to rear if you were with under gas with throttle off (to what aswell in addition to opposite when you want reduce that for rear to have more grip, refer as playing with throttle), or with brakes increase transfer to add rotation, maybe less often mid curve, but commonly enough with trail braking on turn-in.
Larger swaybars work increasing effective spring rate for mass transfer from side to side. It results in less roll .. but also in less independent suspension and overloading tires on one side, so at one point of upping swaybar rates it has negative net effect of reducing available grip. Better to rely more on right stiffness springs and damping, but use swaybars more for balancing grip imho. Unless driver was limiting factor and less rolling car was required to bolster one's confidence to push more.
More speed to use up more grip while cornering .. it's not RWD specific, but any car's trait. Google on traction or grip circle. Well illustrates that your tires have limited amount of grip and it's up to you to what to "spend grip budget", and how one may use it most effectively without leaving unused grip on plate (namely - trailbraking and gradual increasing throttle proportional to unwinding steering wheel when accelerating out of corner).
Wheelspin i already mentioned in previous post. Drifting is not fastest way around track. And is easy to do .. if you already have used up lot of grip on something else, eg. cornering at high speed near limit, then many abrupt driver inputs can throw off balance and make car loose grip, including via getting rear sideways and wheelspining.
But! Theory aside, and all those specific ways to loose grip aside, purely from my limited track experience, driving on twins with square tire setup and NA power, i found myself overall much easier to drive/balance grip limit/fight less with car, when i moved grip balance to front, via more front camber then in rear, via less understeer biased then stock setup. It also reduced my mistakes count and upped lap speeds. Also similar alignment seems preferred and suggested alignment setup by many others, that do track their twins.

NutGud: from your description there imho also another optioon (judging by turned traction control off) - not at right time and right extent interruption of electronic nannies, namely stability control, EBD as in electronic brake distribution and e-diff.
In your case imho it's EBD, and to lesser extent maybe e-diff that worsens things.
(long TC off btw switches only stability control off, EBD and e-diff is still on).
That's why many tracking twins prefer using so called "pedal dance", unofficial procedure, that leaves just basic ABS on, switching all the other nannies off. From my experience in ND miata, it's nannies were way less in way vs prerestyle twin's nannies. Have no own experience in restyle twin though to compare it's nannies. But on older ones PD may help in several cases on track.

Funny you mention the pedal dance, as I was searching on the forums again today and found a couple of post talking about how their Traction Control was sensitive after coilover installation or different wheel/tyre setups, but what's more odd is that this was only for certain people. A shop owner mentioned they installed coilover and wheel/tyres for over 100 86/BRZs and never had these issues.


Regardless, I thought why not give this VSC reset a try.



https://www.ft86club.com/forums/showthread.php?t=121795 - Link to a post specifically about this.



But Basically, you need Techstream, a way to connect and just have the car on a flat ground.
I've just got a Tactrix OpenPort 2.0, so I used this.



I did this and it has helped a lot with the "regular" driving issue I had before, EG, roundabouts you can even safety push it and not have the traction control at all, or if pushing it, it'll only turn on as you begin to straighten up.
So for me, this helped a bit.

It still pushed/floaty/slides the front when pushing it around corners (Only really tried in 2nd/3rd (so above 80kms), but at least with Traction on, it was less serve.


So to summarise, issue is still there, but traction control was very sensitive before the VSC reset and now it operates when you expect it to. So I'm happy about that :).

I'm still under the belief that I need another Alignment to actually eliminate the issue, as with TC off, obviously the issue is still prevalent.



But I thought that was very interesting.



Also I don't really want to be having to do the pedal dance when wanting to drive spirited.

Another factor that can definitely impact the cars balance more than you might think is rake angle. A lot of people find that positive rake helps out and there are reasons that it does depending on your setup. For me, removing the rake to a nearly level, slightly negative rake helped the car balance out immensely. I just couldn't get it to work with positive rake. Just something to consider. I mention it since you said the front feels floaty. Maybe your dampers are blown? Do you have bump stops?

I am rambling at this point because it's almost certain that your lack of front camber is the vast majority of your problem.

I really think your tires for whatever reason are lacking grip. What is the date stamp on them? I had a set of Michelin Pilot Super Sports that "aged out" on me and lost all grip only 18 months after I bought them. Lost all grip, everywhere, it was noticeable even just tooling around city streets at 2-3/10ths!

Repeating what I said earlier, almost all adjustable dampers you adjust OUT from fully stiff setting. You don't adjust IN from full soft. Because at the soft end the clicks do almost nothing anyway, all the way in/full stiff is the correct reference point. Unless instructions for these dampers specifically say otherwise.

But anyway, from what you describe with TC being very active, and turning it off helping a good amount, it seems like a general lack of grip at the front and back of the car. Which suggests tires again. I know Michelin Pilot Sport 4 are *supposed* to have good grip, but maybe they aged out, or bad batch or something. Like I said my supposedly godlike Pilot Super Sports lost all grip, it was very strange... New tires fixed it. Maybe you should contact tire seller and see if you can swap them out.


Looks very good, they won't be able to adjust rear camber but should be fine...

???!!!
Those spring rates are IMO way off. Front springs should not be 33% stiffer than rears. At most front springs should be same rate as rears and if you want to match stiffness to weight distribution the rears should be stiffer.

Thing is that the front strut suspension has a motion ratio nearly 1 (I think it's 0.95ish), while the rear springs are highly leveraged by the multilink rear suspension so motion ratio is ~0.75. The wheel rate is what is important for ride and handling balance, and wheel rate is spring rate * motion ratio squared. What you have:
front wheel rate = 6 kg/mm * 0.95^2 = 5.4 kg/mm
rear wheel rate = 4.5 kg/mm * 0.75^2 = 2.5 kg/mm

Your front suspension is more than twice as stiff as rear! Understeer fo sho... Either get some 6-8 kg springs for rear, or 3.5-4.5 kg springs for the front! Seriously, 6kg front 4.5 kg rear is just wrong...

I think there's more to it than alignment. I think your tires might be "off", and for sure your spring rates are a bit wack...

.. i see several fixes suggested by different people. And indeed, many of them will change grip and grip balance, as there are different ways to skin a cat :).
But suggest to be careful and not do whole lot of suggestions at same time. It's hard to evaluate impact of change if you have done several of those simultaneously.
Imho worth to make some plan of doing changes and testing out impact.
- I'd probably prioritize getting alignment right. And not just because of grip balance, but also to get more out of tires (nobody against spending less on wearables, right? :D), as probably after two track days wear lack of camber in way of ripped outer sides will be obvious. If you go all the way for finding out the ideal alignment for specific track and specific tires, worth considering purchase of pirometer.
- try things that don't require mods at all. For example PD. Or changing tire pressures front vs rear for shifting grip balance. Adjusting driver inputs.
- dial safe baseline damping settings on coilovers. Zdan provided helpful hints how (clicks from full stiff). For initial settings, if nothing else, suggested on forums or in product manual, should do.
- try adjusting damping & rebound on coilovers, increasing & decreasing / try different swaybars / different springs / changing rake. Preferably one change at a time to single out impact of change and hopefully your driving is consistent enough for own mistakes to not affect results instead of changes in suspension.

My wild guess, that better alignment should fix most outstanding handling issues.

@ZDan: but usually all tires in set would have overall drop in grip then, if they had been the culprit, and it wouldn't change grip balance front/rear, just lower overall grip level. As for spring rates .. recalling questions to RCE about why some coilovers have different front/rear springrates, some square and so on .. IIRC response was that can be several ways to reach result that works. Valving of shocks also plays role, and so are bumpstops part of picture, and while motion ratio indeed is different, but imho it's far from something as simple "get square wheel spring rate taking into acount motion ratio", and not as if everything that's not is wrong. Too many possible variables. For example, how about wheel frequency some suspension vendors mention? Available travel? Installed downforce mods? Alignment? Other non springs/dampers mods like swaybars?

Hi Zdan,

The tyres are brand new. Date stamp 1120.

My coilovers MCA: 6kg front and 4.5kg rear
BC Racing is 6kg front 7kg rear
Silvers are 6kg front 7kg rear.

But do note: MCA are the official sponsor for the Australia 86 series.
They certainly know a thing or two about 86s, their motion ratios and both street and race capabilities.
I spoke to the owner who informed for a sporty yet still good ride to get that specific spring rate combo. Their standard spring rate was 5kg front and 4kg rear. He mentioned for a daily and wanted to be sporty that these rates and obviously their specific valving are great.
The main reason I actually selected MCA was because I believed a) they actually know how to design and engineer a good valving system and b) they've been working on 86s since they came out and are the Australian sponsor for the racing series.
As church said, there's a bit more then just the spring rates.

Churchx
I want to play with the height of the coilovers because as I mentioned and checked before the passenger side is like 5-10mm taller then the driver side. Perhaps this was to account for the weight of a driver?
Idk. I'm going to get it levelled first in all 4 corners as MCA recommended it to be 350mm from centre of wheel to guard in all 4 corners. (I also like this ride height as its very practical but looks good).

Then once that is dialed, get the alignment.

I know what you both mean by setting it from stiff to soft and no the other way around, but like at the end of the day, it still has the same amounts of click from stiff.
Also being 2 from soft (or 10 from stiff) was what MCA recommended.
I'll be playing around with this anyway as Its cheap and very easy.

I am thinking of playing with tyre pressure and lowering to 32 psi cold on all 4 after the alignment.
Its easy and simple.



Yes, all along when I've been trying to sort this out with my partner we've both being changing one thing at a time and both driving it to see how it feels.
No doubt there is a lack of grip in the front.
Having 2 drivers feel the same problem as well as comparing it to a baseline (older rwd low power car without electronics and with new tyres (mx5)).


Coolhandmoss
Coilovers are brand new and I'm pretty sure its not riding on the bumpstops. Nothing sounds rough or clunky, and the wheels are very "safe" in terms of offset and size.
Also for the rake, I'll be keeping it level as per my coilover manufacturer recommendations.


Really I just got to wait for the alignment to happen now!
Very excited as I want this car dialed.

Sent from my SM-G930F using Tapatalk

He has lost grip overall. TC is more active for him indicating lost rear grip as well, when it becomes active it conserves rear grip and he gets push. When he turned off TC completely, the handling balance improved as rears were allowed to slip balancing the push. It seems to me like a general lack of grip, front and rear.

For sure a very wide range of spring rates front/rear can work, but there are *limits* to this. Having the front end of the car more than TWICE as stiff as the rear, is IMO exceeding the limits. Having same *spring* rates front and rear is about as front-biased as you want to go. with *even* spring rates, say 6kg/mm square you get 5.4 front and 3.4 rear wheel rates. That is quite front-biased already. Stiffer front springs goes way too far with front bias.

For spring rates, IMO you want the rear springs to be *at least* as stiff as fronts, up to about 1.5x as stiff as fronts.

Front springs 1.33x stiffer than rears? It's a bad place to be. Yeah bumpstops and damping play roles but the basic wheel rates should still bear some resemblance to weight distribution. Front wheel rate >2x stiffer than rear wheel rate is too much front bias. And understeer-inducing...

It would be great if you could swap on a different set of tires just to see if that changes handling behavior.

The problem was noticed after the new tires were installed, it stands to reason that they could be at least partly responsible for the handling issues.

One thing to consider is that brand new tires with full tread depth will squirm around a lot more than worn tires with little tread depth. But you'd think a "max performance" tire like the Michelin Pilot Sport 4 would have pretty good treadblock stability even new. My brand new Contis feel awesome, no issues whatsoever from go.

For sure it can be made to work, might even be better for ultimate track work with track tires if limited to using the stock torsen diff, to limit unloading of the inside rear. It's not where I'd start for a good street-tire setup though...

If understeer is a specific problem, then having front wheel rates more than twice as stiff as rears is something to perhaps reconsider...

Anyway based on your TC being activated a lot, and improved handling balance with TC off but with lower-than-usual grip, IMO it's worth investigating tires.
Again, it'd be great if you could swap on a set from another FT86 known to handle "normally" and see what your car does on them.

Looking at your "before" numbers, you went from a TON of front toe-OUT (7mm or 0.7 degrees!) to a little front toe-IN, and you went from a bit of rear toe-OUT (2mm or 0.2 degrees), to about the same amount of rear toe-IN. That by itself would explain some of the change in handling demeanor towards understeer. But it still seems like the new tires are lacking grip based on TC activity and your description of how it feels...

There are a lot of things you can adjust. Just do em one at a time. lol

I have the same wheels and older MCA X-C coilovers that would be similar spec valving to your street essentials. I have 6kg front and 5kg rears.

The first thing I noticed about your alignment specs is the Castor seems a little low. Mine has been closer to 6deg with every alignment I have ever had. It might be worth checking you have the strut tops at the right orientation. As for toe and camber I have as close to 0 toe all around as they can manage and about 2.5deg front and 2deg rear camber. On a long sweeper the car will understeer but it feels very sharp on transitions and turn in. That is with the recommended damper settings. Is the 2 clicks from soft the recommended setting from MCA?

This is good advice ^^^

I have TRD springs and sways, stock rims with Bridgestone Potenza RE003 (Firestone Firehawks) in the stock size. Threw in 16mm Whiteline Camber bolts in the top mounting hole for the dampers.

I can't adjust caster but have the following specs:
Toe Front +0.1mm
Toe Rear +1.1mm

Camber Front -1.3 degrees
Camber Rear -1.7 degrees

I find I have more front grip after the camber change (didn't measure it before the suspension mods but didn't have much negative camber in it). It still understeers when really pushing it but that is a trait I prefer for street driving. My car is not a daily but I don't track it - weekend warrior only. Suspension guy reckoned not to go with more than -1.5 degrees of negative camber in the front for the street.

Hi All,


Thought I'd update as I'm sure some people are curious about what ended up happening with this car.



I did try cleaning the wheel speed sensors on the fronts (I.E. taking them out of the hub, spraying some contact/electronic cleaner on them and reinstalling), which to my dismay did nothing.




I ended up fixing the issue by uninstalling all of the front suspension I.E hub/control arms/sway bars/speed sensor/end links/brake caliper/disc/etc. (I left the coil overs on via. the top hats, but everything else was removed the car).


I while everything was off the car I wanted to paint the brake calipers and paint the control arms and the sway bar mounts as they had a bit of surface rust on them (which annoyed me seeing as the car only 7ish years old).

See attached photos. I was surprised how much I like the black brakes.



Anyway, after leaving the paint to dry for a day, I put the everything back together and on the first test drive, it finally drove like an 86.


So not 100% sure what actually fixed the issue but the car drives so much better.



That was about a month and a half ago. Just about to take it for an alignment tomorrow to get it dialed in, now that the car is driving right.


Yahoo!


Also, current pic of the car near a Ferry in NSW Sydney
Need to paint the rear brakes, but one day soon.

For anyone else who finds this thread like I did:

2013 86 GTS. New and unsettling understeer mainly on long left sweepers, it seems to jump between two lines, corners like something is loose. On a long left sweeper at ~90kph when the TC light started flashing, it got real*.

Pulling and pushing on the front wheels, really can't feel anything wrong on the pavement. Nothing feels loose when stationary. No codes, doesn't seem like TC/wheel sensors. Mechanic told me the tires were shagged and to lay off the aggressive driving, said there was nothing wrong (I called BS). Tires were over it (18mo and at the indicators), but I switched front to back with no real change. Changed out for four new tires anyway, alignment was about what it was when I got the setup. Problem still there...

Got it home, put it up on jack stands, found that swinging on the front RHS rotor with the suspension unloaded and at full lock is enough to see a tiny amount of slop in the lower ball (not the LHS though).

Aaron Klaver/Import Monster: Have seen it a few times where the castle nut on the ball joint has been tightened with the ball joint not seated properly. Under load it was riding up and the steering geometry was changing mid corner. Straighten up and it plonks back into place. You could feel the toe change mid corner.

Well, I got nearly a whole turn out of the RHS ball nut before it gave any resistance at all. LHS was close to the correct torque already. It tracks properly around corners again! Turns out cars go better when a wheel isn't LOOSE.

Thanks Aaron!

*oversteer scares passengers...understeer scares the driver

Wow. I think that's what fixed my car (undoing and redoing the castle nuts in the ball joints).

I always thought it was odd that taking all of the suspension off and back on fixed this particular issue. I was never sure what the real problem was.

Thanks for the response. It's great to hear back from others who have had the same/similar issues and who has fixed their issue as well.

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