Understeer Issues - Toe Alignment Issues?

[ZDan]

Originally Posted by NutGud

TC light would come on very regularly, even when barely trying to corner fast or anything.

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!

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.

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.

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)

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

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

???!!!
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...

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

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...

[churchx]

.. 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? ), 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?

[NutGud]

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.

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[ZDan]

Originally Posted by churchx

@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.

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.

As for spring rates .. recalling questions to RCE about why some coilovers have different front/rear springrates, some square and so on

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...

[ZDan]

Originally Posted by NutGud

Hi Zdan,
The tyres are brand new. Date stamp 1120.

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.

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.
...
As church said, there's a bit more then just the spring rates.

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.

[ZDan]

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...

[solidONE]

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

[Turdinator]

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?

Originally Posted by solidONE

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

This is good advice ^^^

[sneaky_pete]

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.

[NutGud]

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.

[jyukumite]

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

[NutGud]

Originally Posted by jyukumite

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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