leboeuf

iTrader: (1)

I had a little run in with a tire wall this weekend and I would really like to figure out what happened.

Things I know:
Unexpected and uncontrollable oversteer
Happened with steering pointed fairly straight on pavement
Started to oversteer while in WOT
I tried with all my might to steer into it asap
I probably lifted
There's a slight oil leak on one of the axle seals
It happened fast and I'm confused

Car details:
~200rwhp max
All mechanical steering/bearings/etc <1 year old
Poly bushings all around; Bilstien sports; 550/450 rates (I think...); not slammed
Stock 1992 sway bars
9" jongblooood with 225 rs3v2's (used but still have decent tread)
Kaaz 1.5 way rear differential; Assumed max 100% lockup settings
Basically no aero; just a ricer gv front lip.

Occurred in 3rd gear on a 5spd 4.1 rear end at ~4500 rpm
Here's a sweet mspaint diagram that's accurate to the 0.001" of what happened


Any input would be appreciated! The collective has probably solved this at one point or another...

Savington

iTrader: (31)

550/450 and stock sways is the bulk of your issue. I would start by adding a big tubular FSB and about 200# to the front springs.

Who sold you those springrates?

aidandj

iTrader: (5)

If they are unvalved billies I would take rate out of the rears over adding more to the front.

Savington

iTrader: (31)

You can take 125-150# out of the rear too, but you have to do something.

leboeuf

iTrader: (1)

I probably sold them to myself haha. Really they are SM take-offs I believe and I never re-sprung them. They are indeed stock valved.

I should add that I have ~20 track events on this setup and this has actually happened once before (and I chalked that to cold tires). This was the first day on the turbo setup. It has generally felt pretty good, but I don't have much to compare it to.

That's actually better feedback from a money/time perspective. I was all hot and bothered to dismantle the diff, but from what I've felt/read the diff generally causes a little bit of understeer, which is why I'm confused.

The sage advice is greatly appreciated. It's a little unsettling to not trust your car on a big sweeper with high consequences.

aidandj

iTrader: (5)

A stiff rear end makes for lots of skidmarks.

Savington

iTrader: (31)

SM is 700/325 with a big rear bar, so not SM takeoffs. With stock sways, those rear rates, and those tires you would want something between 900 and 1000lb front springs.

Buy some 325s for the rear, get a big front sway bar, and raise the car to at least 4.5" pinch weld heights.

leboeuf

iTrader: (1)

Golden

Here's the link where I bought these, the springs don't have markings so this is what I'm going on...:
https://www.miataturbo.net/miata-par...t-ready-79853/

Interesting about the SM rates; and great to hear that the setup is so odd. I think I'm at 5" or a little higher for the pinch welds, or whats left of them...
Much appreciation!

aidandj

iTrader: (5)

Those look real thick lol.

Its pretty easy to measure spring rate.

deezums

iTrader: (3)

A stiff rear end could cause unexpected oversteer, wouldn't it, when you are expecting and managing power-on understeer?

dasting

I don't know your driving background, so ignore and tell me I'm wrong if this definitely doesn't apply to you, but

4500rpm on a 1.6 in 3rd coming on power exiting a sweeper... first time on turbo at track...rs3s...blaming diff and suspension...

Your suspension setup needs changes, no doubt, but my guess is that there's some driver error involved in this. If you don't acknowledge that, you're not going to solve the entire problem. You can't just expect to hammer 200ish torques down on a miata coming out of a sweeper at 60mph on street tires and expect it to stay planted.

I've seen newish drivers try and play too much detective on exactly what's causing their unexpected handling conditions when they needed to just focus a little more on their own inputs.

And yeah, work on that suspension, it's not ideal.

leboeuf

iTrader: (1)

I've certainly made many errors at this track and have needed to be pulled out at least once before due to the sand. This is the only one that I don't understand. As mentioned earlier, I've done ~20 track *events on this specific track and I was pointed mostly straight at the time of the oversteer.
Car has a vvt swap, so 4500 rpm on that
I was incrementally pushing the safer zones on the track; this was my third session. I'm a mellow early 30 something... not really on the edge of anything. It broke loose and surprised me.

90 Turbo

iTrader: (3)

Rear alignment bolts in good shape?
I had a worn lower rear bolt. The one at the front on the rear lower arm.

Just an idea. I have never been on a track so take it with a grain of salt.

Double O 86

The tires, although still showing tread, are old and have hardened. Buy some new tires and watch this problem go away.

WMP

iTrader: (1)

One other thing to look at is your rake. The first iteration of my bilstein/ebay/ground control setup had my rear end about .75" higher than the front at the pinch welds and it made the car really snap oversteery. Once I got proper sleeves and was able to lower the rear about half an inch, everything got a lot better.

k24madness

iTrader: (6)

I agree with the above assessment as to why the oversteer but you should also ask yourself what did you do when you hit the point of no return. Did you put two feet in? Normally that will lock the wheels and carry you into a trajectory the keeps you out of harms way.

leboeuf

iTrader: (1)

I should say point of no return for me... I'm not great at saves, the car was dead when the dust settled so I didn't have the where for all to push the clutch in.

I have locked things up on other spin outs (probably too soon) and it made the situation worse.

I'm just a hobby driver and definitely have 0.1% of the experience of some of the commenters here. What do you guys do when you get caught off guard in an oversteer situation?

BarbyCar

iTrader: (1)

Just throwing this out there:

Track condition: any chance there was a fluid spill for your right side tires to get into?

acedeuce802

iTrader: (1)

Is it consistently oversteery, or is this a one-time occurrence? Do you have proper bump travel? If you hit a bump with the rear and your bump stops bottomed out, that could easily cause snap oversteer.

thumpetto007

iTrader: (15)

I cant find the thread, but I remember reading about a condition that is un-saveable no matter the car, or driver. Sudden, uncontrollable oversteer. Like once you realize what's happening, it's too late, and a human's reaction time isn't fast enough to input the proper correction.

The thread was on miataturbo, and someone had linked a video of a formula 1 car that had the condition.

Maybe this type of thing happened?