Autocross- SCCA EV-X Class vs. SS

[Lindenwood]

The bar has been on for months, since before my last road course track day. At that’s event, I let two instructors drive my car and both remarked specifically at its balance, predictability, and overall lateral grip. I even asked if they had any recommendations to suspension changes that would help reduce the instability under high-speed braking, and the only think they recommended was maybe stiffer bushings / bearings, or aero if I wanted to get real hardcore (hence my wing ).

The only change I have made in 8 months was the FLCABs about 6 months ago (and I could feel the positive benefits), and now last weekend’s swap to the sport set. Perhaps it is a bit over-sprung in the rear with both the sport coils and stiffer rear bar, but I am reticent to blame the bar entirely.

Just verified Toe is 0/0, but camber did go up a bit in the rear.
Front: 3.2 & 3.4
Rear: 2.3 & 2.6

Refined camber to 3.2F and 2.3r and re-zeroed toe.

I set my tire pressures from 42 to 36 as well. Upon reflection it occurred to me that the sport kit might need a bit lower pressures since the heavier coils can’t move against the smaller bumps quite as well.

I also installed the compression rod bearings while I was in there!

 

[tm1v2]

@Lindenwood A few thoughts since you're currently benchmarking with street driving... (vs auto-x where I have no business giving advice, I just open this thread occasionally to live vicariously )

I wouldn't use "nannies kicking in" as a measurement of grip, at least not on this car. I've always felt they were inconsistent in when they'd kick in around sweeping turns. And they can & probably have changed with software updates.

Also, while an inside wheel coming off the ground is probably bad for traction in this car especially with its open diffs (clearly an outside wheel bouncing into the air is no good ever!), the regular driving mode nannies will probably exacerbate it with their braking. They're focused on keeping you from spinning, not maximizing your cornering speed.

All that said I'm not doubting the loss of street cornering speeds is real, I'm just guessing it wouldn't be as drastic if you compared in Track Mode.



For actual causes and fixes, I agree with @dsgerbc, I would revisit that sway bar setup now that you're on stiffer coilovers. I've long said that for street driving I wouldn't want stiffer bars on top of my Redwood "Performance Sport" coilovers, I'd expect stiffer bars to actually slow me down over ill-maintained real world roads.

My guess is you'll arrive at different ideal sway bar setups for track vs street now. With the "Comfort" springs it sounds like the aftermarket sways on full stiff never felt oversprung, which makes sense, but now you've got more baseline spring rate.

Also where are you on compression and rebound settings within the adjustment range? Maybe try backing off one or both of them for bumpy roads. Not sure which to try first, I've no experience with multi-adjustable dampers.



Last and least, *if* street handling were your top priority - yes I realize it's not and this is the autox thread - I'd say go back to your previous height. I'm not saying you were hitting the bump stops on that ramp, this is more a general statement. 0.3" lower than before doesn't sound like much but even a stock M3P feels pretty limited for rear suspension travel. 1.3" lower than stock sounds too low for taking in real world bumps and dips. (Again I recognize that autox and track days are more your priority, so feel free to ignore this part!)

 

[tm1v2]

@Lindenwood One more thing, I remember my coilovers feeling stiffer overall than I expected when brand new, even for "Performance Sport" moniker. At first I was worried I overshot on stiffness for my shared family car. After a few hundred or even a few thousand miles they really seemed to smooth out in their absorption of smaller bumps.

I'm sure some will say I just got used to the new suspension, the change was just in my head. That could be true, I'm only going by my butt shock dyno. But earlier this year I had a stock M3LR AWD loaner for several days and I ended up missing the ride quality of my suspension, not just its handling, so I'm pretty convinced the smoothing out was real. That loaner's suspension was clearly softer but it still transmitted bumps worse and fatigued me more. (It also had like 2x the miles of my car, for what that's worth.)

I've seen a couple other mentions on these forums of brand new aftermarket dampers/coilovers feeling like they softened up (in a good way) after a wear-in period. If I remember right, one person was saying it about their KW(-based) coilovers, with others had Ohlins(-based) dampers like mine. Again, maybe this is all BS and in my head, take these butt shock dyno readings for what they're worth.

 

[Lindenwood]

@Lindenwood A few thoughts since you're currently benchmarking with street driving... (vs auto-x where I have no business giving advice, I just open this thread occasionally to live vicariously )

I wouldn't use "nannies kicking in" as a measurement of grip, at least not on this car. I've always felt they were inconsistent in when they'd kick in around sweeping turns. And they can & probably have changed with software updates.

Also, while an inside wheel coming off the ground is probably bad for traction in this car especially with its open diffs (clearly an outside wheel bouncing into the air is no good ever!), the regular driving mode nannies will probably exacerbate it with their braking. They're focused on keeping you from spinning, not maximizing your cornering speed.

All that said I'm not doubting the loss of street cornering speeds is real, I'm just guessing it wouldn't be as drastic if you compared in Track Mode.



For actual causes and fixes, I agree with @dsgerbc, I would revisit that sway bar setup now that you're on stiffer coilovers. I've long said that for street driving I wouldn't want stiffer bars on top of my Redwood "Performance Sport" coilovers, I'd expect stiffer bars to actually slow me down over ill-maintained real world roads.

My guess is you'll arrive at different ideal sway bar setups for track vs street now. With the "Comfort" springs it sounds like the aftermarket sways on full stiff never felt oversprung, which makes sense, but now you've got more baseline spring rate.

Also where are you on compression and rebound settings within the adjustment range? Maybe try backing off one or both of them for bumpy roads. Not sure which to try first, I've no experience with multi-adjustable dampers.



Last and least, *if* street handling were your top priority - yes I realize it's not and this is the autox thread - I'd say go back to your previous height. I'm not saying you were hitting the bump stops on that ramp, this is more a general statement. 0.3" lower than before doesn't sound like much but even a stock M3P feels pretty limited for rear suspension travel. 1.3" lower than stock sounds too low for taking in real world bumps and dips. (Again I recognize that autox and track days are more your priority, so feel free to ignore this part!)

Thanks for the input! Very helpful.

1) I did have a lot of good luck daily driving with minimum compression and minimum+4 rebound. I haven’t driven on it yet, but I did reduce damping from the typical starting settings to I have set my dampers to min compression & min+6 rebound.

2) On the rear anti-sway bar settings, it wasn’t a huge difference with the Comfort coils—I’d still say it affected balance less than +\- 1mm of rear toe, so I don’t think the bar alone is capable of unilaterally causing the effects I have experienced. That said, I wouldn’t be surprised if I end led up backing off the rear bar a bit after a couple of events.

3) You are right that “Nannie’s kicking in” itself isn’t always the best qualitative example of losing traction, because they definitely do kick in early with good tires. But, in this case I truly mean “Id have been skidding or counter-steering without the Nannie’s” .

 

[tm1v2]

@Lindenwood Could you tell what the balance of the car was like before the nannies kicked in? @gearchruncher's point about that was a good one.

Wouldn't surprise me at all if the car's balance was way off, given first pass new setup with questionable alignment!

Or maybe someone leaked oil on your route.

 

[Lindenwood]

@Lindenwood Could you tell what the balance of the car was like before the nannies kicked in? @gearchruncher's point about that was a good one.

Wouldn't surprise me at all if the car's balance was way off, given first pass new setup with questionable alignment!

Or maybe someone leaked oil on your route.

Hrmm. I could tell the car wasn’t directly following my steering input, but Elon was stepping in before I could really get a feel for which end was losing traction first. I do suspect the rear end was breaking loose since standard safety features prioritize avoiding oversteer above anything, and they were stepping in quickly and aggressively. But, I couldn’t really feel it through the steering wheel (or, alternatively, the front end was also breaking loose at the same time and numbing steering feel).

(Sorry about all the typos on my previous post…. I just left a social event )

 

[Lindenwood]

I went a bit too far reducing tire pressure (checked on the way home to see 33psi, hah).

Still, a quick jaunt indicates the lower pressures substantially increased grip. I suspect the comfort coils 1) allowed more body roll with the all seasons for a flatter contact patch on the outer tires, and 2) had a bit more compliance over small bumps, resulting in more available traction on the all-season tires. Reducing camber a bit and reducing tire pressures might be the ticket when running lower-traction tires.

 

[Lindenwood]

(To be clear, I am not surprised at the concept that lower pressures tend to increase grip. I was just surprised that a simple coil change had so many cascading affects on handling).

In summary, my hypotheses:

Comforts: Even with my lower traction daily tires, the softer coils allowed enough body roll upon turn initiation to flatten the contact patches against the ground despite the high camber. Additionally, the softer coils allowed more bump compliance over minor irregularities to maintain more even tire contact with the ground.

Conversely,

Sports: The stiffer coils plus higher baseline damper settings reduced body roll such that the contact patches couldn’t flatten against the ground without reducing camber. Additionally, the same stiffness required reduced tire pressure to increase bump compliance and maintain more even contact with the ground.

All that said, I definitely do enjoy how it feels. Especially at the lighter damper settings, it doesn’t feel too different over bumps and road undulations. However, it definitely stays flatter during cornering and feels a lot more…crisp.

One note, this definitely does make me re-think going down to 18s from the current 19s. Not only does it allow a bit more bump compliance for simple comfort, but if I’ll need to run a bit lower daily pressures, the extra inch of rubber does give a bit more flexibility to do so.

 

[Lindenwood]

Whew. Passed the wife test on the new Sport coils + compression rod bearings!

She asked if she could take my car to go grab lunch for us. I didn’t actively ask for her opinion when she got back (I’m not an idiot), but she didn’t offer any comments so I’d say I’m in the clear .

 

[dsgerbc]

So, after last three events I returned home with a bit skewed steering, after aligning it fine beforehand. I though the first one might've been suspension settling. The second got me concerned to check most suspension things for loose bolts etc, w/o anything major. Had a two-fer of events today/yesterday and it happened again both days.
Returned yesterday with maybe steering required to go straight at 1-2 degrees CCW, and today with 2-3 degrees CW.

Checked everything again. The only thing remotely relevant - maybe not too tight coilover lock ring on one side. Ride heights are fine though. Cambers too. Even toe is very close to where I set it last.

So, any ideas of what to check other than sub-frame bolts coming loose?

 

[gearchruncher]

Adjustable caster bushings? Shock towers loose and moved?

 

[dsgerbc]

Adjustable caster bushings? Shock towers loose and moved?

Nah, solid whiteline ones.
Checked the towers.

Checked all main subframe bolts' torque. Added less than 1/4 of a turn to a couple and even less for others.
Maybe the steering rack or steering wheel-to-rack bolt is loose?

Today we were running pretty much the same course as yesterday backwards, so it's kinda indicative that the steering wheel shift is in the other direction today...

 

[The Other Dan]

Quick non-autox question, but this is probably the best group to ask...
What video editing software are people using for their autox vids, and what system are you using for the data overlays? Video is from Gopro 11.

 

[SK360]

Quick non-autox question, but this is probably the best group to ask...
What video editing software are people using for their autox vids, and what system are you using for the data overlays? Video is from Gopro 11.

RaceRender with Tesla Track Mode data.

I had shared my template years back that I know a few people are using or used as a base, I can always post an updated one.

 

[The Other Dan]

Thanks, that looks like it will do the trick.

And it's been 45min since Nats opened for general registration. 4 of us are in so far. 840 registered in total. Aside from me, anyone else from the forum signed up or will be signing up?

 

[dsgerbc]

4 of us

5 already + a guy from Texas in SSP

 

[The Other Dan]

7 now in EVX. 1 in SSP. 1 in SS. I don't see the husband/wife duo that normally run in SS yet.
The guy in SSP ran ASP last year. The classes got merged.

 

[dsgerbc]

The guy in SSP ran ASP last year. The classes got merged.

He runs in EVX in the Dallas region tho. The 3 was an uncompetitive ASP car, I'm sure it still is in SSP.

 

[The Other Dan]

Looks like one Mr. Gearcruncher decided to join the fun too.

 

[dsgerbc]

Only 60 spots left....