Auto-x, Yoko S-drives, 450/300, FM Bars - questions about how it all went wrong...

I shall start with a paraphrase of the great George Brewer about the Hitachi carbs on my '73 240: "The first thing you have to remember about (Bob's auto-x ability) is that (he) suck(s)."

Or, as my boy said, I'm "Captain Slow". With that out of the way....

First, the S-drives: Before the boy moved out of state, we'd done an auto-x where we did timed and fun runs back to back to back (8 runs ea (4T/4F) x 2, so those tires got a little warm and the rear would let go pretty quickly and unpredictably after that.

This weekend, only me so just the 8 runs again - first 3, not too bad, remaining 5 wiggled pretty good, and the tires didn't feel very warm after the run.

Spring rates: On the street and with the Koni's at full soft, 450/300 is great set up, just a hint of wanting to oversteer on a fun back road slow/medium slow corner.

First 3 runs of auto-x, not terrible, and I'd bump the fronts up a bit, really seemed to make the car settle. Next 5 runs it was all bets off, rear was way loose.

FM bars are stiff at the front, softest at the rear.

So, is it that my auto-x skills are like the Hitachi carbs, have the tires given up, or is my spring/bar combo just too stiff at the rear?

S-drives are worlds away from being autocross tires. That's likely a large part of the problem.

You're way too soft on your shocks, that's a start. Sounds like the tires were starting to suffer as they got hot, too.

What were the pressures doing as the tires heated up?

In reply to Keith Tanner:

By the third run (and best, iirc), fronts were at about a turn towards stiff - car felt pretty good on that run - still too soft?

In reply to mazdeuce:

I didn't monitor pressure on them, but to the touch, a wee-tad warm - nothing like the heat when by boy and I cooked them.

In reply to rslifkin:

For some reason I thought they were decent tires for daily/auto-x. I've got BFG Sportcomp2s on the Focus, seems a better tire for both. Am I wrong there too? It'll be a while before I wear the Yoko's out, I don't drive or auto-x the Miata as often as I should.

OldGray320i wrote: This weekend, only me so just the 8 runs again - first 3, not too bad, remaining 5 wiggled pretty good, and the tires didn't feel very warm after the run.

For all of us up North, allow me to say screw you and your January Autocrosses!
(That was said with a big, jealous smile and absolutely no real malevolence.)

Where did you have the rear shocks on that fast third run? Full soft on the Konis works for stock spring rates, but you're about three times that. I'd want to see your shocks at 1 - 1.5 turns towards firm.

The S.drive is a decent all-around summer tire. It won't take heat as well as a proper autox tire, but it'll do better than the typical "black and round" tire. I wouldn't expect to win an autox on them, but I'd have a good time.

Agree with Pinchvalve.

as to your original topic, your tires are letting you down. There are likely other issues at hand, but the tires are masking the other problems.

Going to a more autocross relevant tire will make enough of a difference on it's own, that its worth doing.

While you are obviously in warmer climate than myself, was it a warm day at the event. What was the outside temp? Was it sunny enough to make the pavement warm?

And pay attention to tire pressures. You don't have to reset them if you don't want, but you do need to get a feel for what they're doing. I would often see tires go up 4-6 psi on a not hot day in a variety of cars. Depending on the car, the tire, and how your initial pressure was set this might not be an issue, but it might. Having a tire act badly because it overheated is a different issue that it being outside it's happy place pressure wise.
It might not matter at all, but paying attention to pressures is free and things you can fix for free are better than things you have to spend money to fix.

I use S-Drives as my regular tires on my Miata and like them for street tires, but wouldn't expect too much out of them for auto-x compared to auto-x specific tires.

OldGray320i wrote: For some reason I thought they were decent tires for daily/auto-x. I've got BFG Sportcomp2s on the Focus, seems a better tire for both. Am I wrong there too? It'll be a while before I wear the Yoko's out, I don't drive or auto-x the Miata as often as I should.

It's hard to say. Most of the autox people I hang out with consider a 200TW tire to be a DD/AutoX tire and expect that dedicated autox tire means Hoosiers. So to them, anything decently streetable is a waste of time for autox. Now to be more realistic, there are more streetable tires that will hold up to autox use and not get too hot/greasy, but those tires won't be winning events.

Keith, rears were at full soft - left that way based on my limited understanding of a little stiffer at one end makes that end slide more. I'll dial them up to your recommended next auto-x.

I'll also pay attention to the psi on the runs, brush up on the whats and wherefores on that.

That said, it was a pretty cold day, temps were probably in the high 40's/low 50s when I ran, but we were about 62 at the end of the day - not terribly warm.

As others have said, my bet would be that the tires got hot and the air pressure went way up, which most likely caused a big percentage of your issues. I have to let a few pounds out of my tires after the first couple of runs to keep them at my intended pressure.

Just for me (and my experience autocrossing a 97 Miata). I'd say go very stiff on the front shocks, middling on the rear shocks, lose the rear bar entirely/at least go back to a factory one, get an alignment done if it's been a while, monitor tire pressures/check corner roll and lower the pressure until you reach that magic point between grip and sidewall rollover.

FWIW, I run no rear bar at all. Stock, FM, Eibach all net me terminal oversteer. Good for drifting, bad for dodging cones.

Consider selling those tires and getting something with a 200 TW rating. If you don't drive it a lot you should get a couple of years out of them. Miatai are sensitive to tires and what seems fine on the street will just suck autocrossing.

In my experience our 94 likes full stiff front and 2/3rds stiff in the rear. That with koni yellows, flying miata springs and falken azenis on stock 14s

for your shocks id agree with keith, you really NEED more dampening to keep the car under control. id get your dampening rates right-ish first before you decide to loosen your dampening.

this is a decent 'ok guide' on how to fix your cornering problems. http://speed.academy/how-to-fix-understeer-or-oversteer-suspension-handling-setup-tuning/

as far as the tires go, i remember driving on those with your car. they are good tires, but when they got hot the grip was there and then let go; my neo gens often suffered the same fate but were more predictable in the same condition.

imho its all 3 of the issues you described, but mostly the tires if the first 3 were ok. the dampening would be something easy to adjust on the go and lastly the biggest improvement is you just going out there and learning + having fun.

My experience with s-drives is that they get hot and greasy fast. A--- would not buy again.

I do tend to the excessive aggressiveness, though.

Man, I thought I'd get more out of pinchvalve and sachilles with my "it was a pretty cold day" response...

Ok, so plan for next auto-x will be to firm up the damping as recommended here and watch tire pressures as the car starts to wiggle and/or tires heat up.

If it weren't for the gratuitous sliding rear end, I probably could've wiggled my way closer to the back of the STR pack, and on 195's when the other guys were all running 205s. I still have to work on my driving, so less than stellar auto-x tires will help me learn, I'm ok with that.

If you find yourself oversteering much at the next event. You can remove one side of the rear sway with two 14 mm wrenches. Just tape that endlink up to the bar, I suspect you'll like the change.

Addressing the driving part.

Was it loose on Transitions? Sweepers? On entry or exit?

Are you a pitch and catch kind of driver or slow in fast out?

Smooth or abrupt off the brakes?

Hammer the throttle or feed it in on the way out?

Are you aiming for the back side of the cones?

Right or Left foot braking?

All of those things affect how the car behaves. Recognizing how your inputs affect how the car handles will allow you to adapt to changing conditions on the course.

Don't worry about the tires and tighten the loose nut behind the wheel

Nick (Bo) Comstock wrote: Are you a pitch and catch kind of driver or slow in fast out?

This is a dichotomy? My personal driving style is both. Pitch it in slowly so you can power it out. (Yes, I'm speaking of autocrossing, not just playing on dirt)

(Hey, I autocross every now and then!)

In reply to Knurled:

I was looking for the right term but came up empty handed... Or headed. Your preference

KyAllroad wrote: If you find yourself oversteering much at the next event. You can remove one side of the rear sway with two 14 mm wrenches. Just tape that endlink up to the bar, I suspect you'll like the change.

I also have yanked the rear bar from my car entirely, although it can still be a tail-happy machine when the conditions aren't great. Part of that may have had to do with the whipped ZII Star Specs I ran the tail end of last year, but any time I let someone take my Miata for a fun run they looped it at least once.

Nick (Bo) Comstock wrote: Addressing the driving part. Was it loose on Transitions? Sweepers? On entry or exit? Are you a pitch and catch kind of driver or slow in fast out? Smooth or abrupt off the brakes? Hammer the throttle or feed it in on the way out? Are you aiming for the back side of the cones? Right or Left foot braking? All of those things affect how the car behaves. Recognizing how your inputs affect how the car handles will allow you to adapt to changing conditions on the course. Don't worry about the tires and tighten the loose nut behind the wheel

Was it loose on Transitions? Sweepers? On entry or exit?

• Both. On Sweepers, the front had great grip, no hint of understeer - and then the back would let go. On transitions (i.e. slalom cones) same thing.

Are you a pitch and catch kind of driver or slow in fast out?

• Slow all the time, as the boy would say, but I generally favor smoothness in and out. I tried a little pitch and catch, but I could feel the car getting skittish and would back off. Interestingly, the boy attacks, and is always faster than I am, but I'm trying to overcome my 5ish years of driving on back mountain roads where an attack approach could have you attacking rocks or a cliff. My driving style probably indicates why my time only runs are always faster....

Smooth or abrupt off the brakes?

• smooth, usually.

Hammer the throttle or feed it in on the way out?

• it's a Miata, is there a difference? . That said, I'm usually a gas pedal masher coming out.

Are you aiming for the back side of the cones?

• as I think about it now, I was mid-cone aiming usually, back side depending on where the next gate was.

Right or Left foot braking?

• right; I don't see that changing, especially at autocross, it would be really hard to modulate with the left foot at this point.

The nut behind the wheel fell off and was lost long ago...