Handling Setup - Oversteer vs. Understeer
 

So here is some background information about my setup:

- stock FR-S suspension, front camber bolts
- camber: (-1.4 FL, -1.5 FR, -1.0 RL, -1.4 RR)
- toe: 0 square
- tires: Nitto NT05 (235/40/17)
- tire pressures cold: 34 F, 32 R

Before my last track weekend, I thought my setup was about as loose as I'd want it. However, I had to rotate my worn front shoulder tires to the rear, which added more oversteer.

And surprisingly I liked the setup even more this way. Turn-in was better. On constant radius turns, I could hear front AND rear tires squealing. A very slight lift would tuck the nose in. Any more throttle would push the nose wide. The car was as balanced as I've ever felt it.

Also track-out rotation under power was very predictable and controllable - just a slight slip angle in the rear. It felt like I could place the car exactly where I was expecting.

So my question is, am I crazy? Some of the fast drivers out there (e.g., Sam Strano, Randy Pobst, etc.) have said the stock FR-S suspension has too much oversteer from the factory. I think Strano even recommends/sells a thicker front swaybar. But all my mods and alignment have been in the direction of adding oversteer. I'm even thinking about slightly upsizing the rear sway. Does anyone else find they prefer more oversteer on stock-ish FR-S suspension?

Well you've got to realize that you've already altered the driving dynamics a lot by making the changes you have. The biggest thing I can see is that you added much stickier tires, which typically tightens the car up a lot (as a rule of thumb in my experience).

Also, when you're talking about drivers like Sam Strano, keep in mind that he may be referring to attitude during autocross, which due to all the quick transitions leads the car to be more tail happy if you're trying to get on the gas asap. (I have the strano front bar FWIW)

Also, as you thouched on, driver preference is huge. It sounds to me that you just found a setup that works great for you. I don't think you're necessarily correct in saying that all your mods are geared towards adding oversteer either. Have you happened to try and toe out in the rear? ;)

Yeah I do agree with you that autocross is a different beast, although if I remember correctly, I think Strano's comments came after he tracked the FR-S at Summit Point. Not sure if he was on stock tires, so that could have been a factor too as you said.

Good points in your post though, especially the suggestion about adding toe-out in the rear. That'd be cheaper than adding a rear sway bar. :) I may try 1/16" toe-out for my next alignment, depending how the car feels on brakes once I match pad compounds front-to-back. Thanks!

If you're hearing the back tires in this platform, it's generally the sound of going slow, even though you may think you're going quite fast.

Interesting - why do you say that? There's one specific section I'm thinking about where I'm always balancing the car on the throttle. Usually I only hear my front tires, but I was definitely getting chirping from both ends after rotating the tires, which was new. My speed through that section was about the same as before, if not a shade faster actually.

Just to be clear, I'm not talking about squealing the rear tires on exit, I'm talking about constant light chirping from both ends mid-corner on maintenance throttle. Hopefully we're talking about the same thing!

Different drivers prefer different things...what might be fast for some may not be fast for others. Driver confidence is huge and for some that means slight understeer. For others that means having the rear super loose.

The best suspension set-up is the one that a driver can get around the course fastest.

You've effectively added front grip and removed a little rear grip. That's a fair trade sometimes, but ideally you would add both front and rear grip (you need more camber front and rear). That will be faster.

- Andrew

Thanks and yeah that's a nice summary - I've basically traded some rear grip for front. And I'll add - found it more intuitive to drive. I guess that surprised me because I thought the car would be a handful, but it wasn't at all.

Also agree on ideally adding more grip to both ends and adding more camber. I plan on doing a full suspension job (possibly using RCE T2's actually), but am pretty happy with how the car is setup. At most, I'll do a few light tweaks to maintain the current balance, then will replace everything down the road when the stock struts start leaking/wear out.

So you took your worn fronts and put them on the back and your slightly better rears and put them on the front and experienced increased frontal grip (better turn in) and a slightly less grip in the rear allowing you to balance the car with throttle?

:bonk:


Everything I've read has pinned the FR-S in stock trim as understeering when driven 100% correctly with a rear end that's slightly over stiff compared to the front and susceptible to any perturbations (either road or driver induced) causing a loss of traction (read: oversteer). I feel that this jives with my personal experience, the front typically goes first unless I make a poor choice or hammer it intentionally to get the rear out, and I realize that I am certainly an amateur, a lot of it is a result of my developing technique.

Personally I like it loose, I know true neutral is fastest but the result is if you've overdone it all four wheels are sliding and all you can do is back off and hope the grip returns before you're screwed, when one end is sliding you can compensate and bring it back, or at least that's how I always felt. A slide with the rear fixed with some steering and throttle modulation, a slide with the front fixed with a lift or touch of brake easy.

We are in similar positions right now @DarkSunrise I spent the last three months fighting understeer and a feeling of a lack of grip at the local autoX.
Camber: -1.1 Front, ~-1.7 Rear (camber bolts)
Toe: 0 Front, slight toe in rear
Tires: Dunlop Direzza ZII SS (215/45/17)

My last development was that I'm now starting at 25 psi cold, dropping the rear pressures definitely reduces any oversteer but I never felt like it was buying me any additional speed, I would think that bumping up your rears to match the fronts would help you bring the car a bit more 'balance'. I broke down and bought camber plates to try and get the front to hook better, I'll know how well it works this weekend...

Edit, fun thread from long ago

http://www.ft86club.com/forums/showthread.php?t=23166

Haha sort of. I basically took a stock suspension FR-S (which certain drivers I respect like Pobst and Strano claim oversteers too much for their liking) and added more front grip using front camber bolts and a zero-toe alignment. I thought I was happy with the setup, but unintentionally took some rear grip away and added it to the front and found I liked it even better. It's not that I couldn't balance the car with throttle before, but this just made it even easier to do without any of the drawbacks I was expecting (like twitchiness or snap oversteer).

That's exactly how I felt before this experiment, but I've now reconsidered. What I found is when all four tires are chirping in a steady state corner under maintenance throttle, the balance is actually easier to control. Even the slightest change in throttle position produces an instantaneous response from the chassis. If you're running wide, lift slightly and the nose tucks back immediately. And vice-versa. As long as you're smooth with your throttle inputs, it never feels like the car will bite you. It just responds quicker.

Thanks good suggestion on bumping the rear pressures. I'll probably do that to keep the current balance after switching to fresh tires.

Take a look at Strano's quote from that thread, makes me question everything I think I know about setting this car up lol:

Oh yeah I was definitely going to go stiffer rear than front if you asked me yesterday, found that thread while I was typing up a response. I've only heard his name in passing on here so no idea about his rep outside of that (he would be a vendor in my dealings with him and a XX Champion second, in my experience Champions are repeat champions because they protect their innovations) but I totally understand his preference, it's going to be interesting to see where the trend goes, generally speaking most people converge in a general direction but it will take some time, we're only 3 years in after all, even NA Miata setup is still hotly debated 25+ years later.

And yes, for anybody trying to correct me I appreciate CSG's perspective on stiffer rear and HPDE vs. AutoX setups as well.

I still feel the car wants to understeer, or I should say I think there is more front grip to be found, and I think a stiffer front is a part of that equation unquestionably, where the rear goes I have no idea.

Makes me miss my racing days when you could pick up a box of used springs from a guy retiring for a couple hundred bucks and try out a 6 combinations on a Sunday at the local club for no money (cause you volunteered to clean up the track) and just the cost of gas for the car and pickup truck (no need for a trailer) and an old set of tires.
:sigh:

In any case I really need to fix the nut behind the wheel before I choose a suspension setup. I plan on doing lower control arms in the rear (I have an imbalance like you do) this winter and after that no more unless it's consumed or faulty until I can really drive the wheels off it.
:bonk:

Edit: and I'll take your comments about a neutral 86 to heart, my past experience is probably clouded by time.

The stock set-up is a little wonky for direct comparisons...soft front springs, very bumpstop active, and front geometry challenged. Most people just end up looking at spring rates and that is not the full story.

IMO it can both understeer and oversteer depending on how you drive the car. Stickier tires changes things too.

- Andrew

how come your driver-side rear wheel is half-degree off camber from the rest?

Apparently a lot of these cars come from the factory with rear camber that's lopsided by up to 0.5 degrees. I haven't installed an adjustable camber kit for the rear yet, but planning to once I replace my suspension.

Strano has a different background, which is where his preference comes from.

Randy has a preference for cars that are easy to drive and are forgiving to large, harsh inputs.

You've discovered that you actually like having more slip angle. Keep exploring deeper in that direction; you'll discover that at some point, there's TOO much slip and it'll start slowing you down. Until then, the only way to figure that out is to keep experimenting.

You're starting to see the light as to my particular driving preferences :D

@sw20kosh can elaborate on a few tricks I've shown him that are used to intentionally induce controlled rotation which result in significantly faster lap times.