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Old 05-24-2020, 07:36 AM   #29
ZDan
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Originally Posted by NutGud View Post
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!

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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.


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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...

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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...

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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...

Last edited by ZDan; 05-24-2020 at 07:54 AM.
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Old 05-24-2020, 08:15 AM   #30
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.. 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?
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Old 05-24-2020, 08:38 AM   #31
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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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Old 05-24-2020, 08:42 AM   #32
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Originally Posted by churchx View Post
@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.

Quote:
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...

Last edited by ZDan; 05-24-2020 at 09:04 AM.
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Old 05-24-2020, 10:12 AM   #33
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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.

Quote:
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.

Last edited by ZDan; 05-24-2020 at 10:25 AM.
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Old 05-25-2020, 01:19 PM   #34
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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...
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Old 05-25-2020, 05:46 PM   #35
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There are a lot of things you can adjust. Just do em one at a time. lol
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Old Yesterday, 02:04 AM   #36
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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?

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There are a lot of things you can adjust. Just do em one at a time. lol
This is good advice ^^^
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