goin reverse stagger, maybe...

[ZDan]

Originally Posted by adrianj73

Dan, I don’t think we’ve formally met, but I was the guy on a crutch standing there with Roe as you came up on the scales.

Nice to meet you!

Blistering times you set that day, I’ll take any advice you have setting up my FRS for COM next season. New driver, long time wrench, so I have a lot to learn.

PM me any time! I have ideas and not all of them are bad...

Do you think the larger rear circumference matters to the ABS? I assume you have VSC disabled, but it would seem the opposite scenario of what would trigger traction control.

I think the ABS would handle it well enough. But I've been running with the ABS fuse pulled since "the incident" at Watkins Glen last year though...

I've run even more ridiculous tire diameter stagger on my old S2000, 205/45-16 fronts with either 225/50-16 or 245/45-16 rears, and its ABS didn't have a conniption over it, just seemed to maybe have more front brake bias.

That said, I'd probably stick with non-staggered tires, particularly diameter, I only ran non-staggered at NHMS due to fear of stripping the front right wheel studs so didn't want to change the fronts from the 245/40s that were on them.

[CrowsFeast]

Originally Posted by ZDan

I've run even more ridiculous tire diameter stagger on my old S2000, 205/45-16 fronts with either 225/50-16 or 245/45-16 rears, and its ABS didn't have a conniption over it, just seemed to maybe have more front brake bias.

That stagger would give ~7% difference in the lever arm for braking (tire radius). I wonder if that was enough to be noticeable as a change to braking bias.

[ZDan]

Originally Posted by CrowsFeast

That stagger would give ~7% difference in the lever arm for braking (tire radius). I wonder if that was enough to be noticeable as a change to braking bias.

Oh yeah, I noticed more front bias

[TunaNoCrust]

Dan how are your bushings looking?

I added the MCA traction mod to the rear of my car and I get a mid corner push now, which leads me to believe the rear is planting more, giving me more traction, allowing me to get on the gas more and sooner.

Point is, maybe your bushings are worn enough to where they are changing the characteristics of your rear suspension???

[ZDan]

Originally Posted by TunaNoCrust

Dan how are your bushings looking?

Prolly squished! FWIW the bias I mention above is/was braking bias with 7% shorter front tires on the S2000.

I added the MCA traction mod to the rear of my car and I get a mid corner push now, which leads me to believe the rear is planting more, giving me more traction, allowing me to get on the gas more and sooner.

Yeah that mod hasn't tempted me as mid-corner push is a bigger issue for me than drive grip exiting corners.

Point is, maybe your bushings are worn enough to where they are changing the characteristics of your rear suspension???

Yeah, could be. Poly bushings are a zero-point mod but I'm lazy and cheap...

[TunaNoCrust]

When you say mid corner push, are you at the apex and on throttle?

Yeah bushings are pita!

[ZDan]

Originally Posted by TunaNoCrust

When you say mid corner push, are you at the apex and on throttle?
Yeah bushings are pita!

Super-late reply, I missed this! Car is just not as "pointable" as it could be. I'd like to trade some rear lateral grip for front lateral grip. I might try a softer front sway, I'm currently running Eibach tubulars set soft front and stiff rear but that's ~150% stiffer than stock both front and rear. Hmm, akshually I think I'll just try stock front with the Eibach rear and see how that works out next year... But I worry a bit about too much rear roll stiffness overwhelming the Torsen diff's ability to drive both rear wheels out of corners esp. over curbs...

[ZDan]

I was just looking at data from these laps and figured I'd post up, as it's an interesting look into how radically inconsistent my driving is from day to day. Explains a lot, actually! Tires are Yoko A052s, the 245/40-17s were barely used while the 235/45-17s had a few events on them.

Green: 2:14.283, Saturday best, 245/40-17 all around
Brown: 2:14.370, Sunday practice 1, 245/40-17 front, 235/45-17 rear
Purple: 2:14.769, Sunday practice 2, 245/40-17 all around

Conclusions:
At *this* track, the taller 235/45-17s had a gearing advantage.
BUT
The big takeaway is that for some reason on Saturday I was WAY better at getting out of the brakes in Turn 6 and Turn 9 and carried *massively* more speed from turn-in to apex. Why wasn't I doing that on Sunday?!

Originally Posted by ZDan

I ran New Hampshire Motor Speedway South Oval this past weekend, I ran the newer 245/40s all around for Saturday's sessions. 1st practice Sunday was on 245/40 fronts and 235/45 rears... I set similar times as Saturday (1:14.3)... I did 2nd practice on 245/40s all around and did a 1:14.77...

[timurrrr]

Originally Posted by ZDan

I'm currently running Eibach tubulars set soft front and stiff rear but that's ~150% stiffer than stock both front and rear.

Are you assuming "I increased the bars by the same amount of %, so the balance should remain the same"?

This logic fails a simple mental experiment:
Imagine a car with stiff springs, no rear bar, a stiff front bar, and appropriate alignment. Not an uncommon setup among spec Miatas.
Now imagine you want to add overall roll stiffness, while keeping the overall balance.
If you only increase the stiffness of the front bar, the balance will clearly become more pushy.
Obviously, to keep the balance you'd need to increase the rear bar too, but since the baseline for the rear bar is zero, you'll need to increase it by "infinity"%.

As a more practical example, I just opened the spreadsheet my friend uses to calculate suspension balance for BRZ/86s, took the row with parameters for a stock '17 PP BRZ, increased the front roll bar by +150%. Then I tried to find the % increase for the rear bar that would result in the same front vs rear roll balance as a stock. Turns out the rear bar needs to be +200%.

Things are even more different if you use non-OEM spring rates.

[ZDan]

Originally Posted by timurrrr

Are you assuming "I increased the bars by the same amount of %, so the balance should remain the same"?

No.

[CrowsFeast]

Originally Posted by timurrrr

This logic fails a simple mental experiment:
Imagine a car with stiff springs, no rear bar, a stiff front bar, and appropriate alignment. Not an uncommon setup among spec Miatas.
Now imagine you want to add overall roll stiffness, while keeping the overall balance.
If you only increase the stiffness of the front bar, the balance will clearly become more pushy.
Obviously, to keep the balance you'd need to increase the rear bar too, but since the baseline for the rear bar is zero, you'll need to increase it by "infinity"%.

First of all the increase in the rear bar according to your logic would be 0%, not infinite. Secondly: just because there's no rear bar doesn't mean there's no rear roll stiffness, so your increase would be low/near 0, not actually 0.

Thirdly: if you're going to propose this kind of mathematical problem you would already know that the formula doesn't apply as you approach either 0 or infinity. This neither proves nor disproves the formula for any particular range of numbers.

[CrowsFeast]

Originally Posted by ZDan

I was just looking at data from these laps and figured I'd post up, as it's an interesting look into how radically inconsistent my driving is from day to day. Explains a lot, actually! Tires are Yoko A052s, the 245/40-17s were barely used while the 235/45-17s had a few events on them.

Green: 2:14.283, Saturday best, 245/40-17 all around
Brown: 2:14.370, Sunday practice 1, 245/40-17 front, 235/45-17 rear
Purple: 2:14.769, Sunday practice 2, 245/40-17 all around

Conclusions:
At *this* track, the taller 235/45-17s had a gearing advantage.
BUT
The big takeaway is that for some reason on Saturday I was WAY better at getting out of the brakes in Turn 6 and Turn 9 and carried *massively* more speed from turn-in to apex. Why wasn't I doing that on Sunday?!

Looking at just the overall lap times I would suspect that Saturday you had more grip. Track temp was better suited or simply due to the sticker set of 245's. The drop off in peak grip, combined with experimenting with an 'unknown' reverse stagger set up may have lead you to be more cautious carrying speed into the corners. Was the reverse stagger a little less stable under heavy braking? That may have contributed to your confidence turning in as well. This could have carried over when you switched to 245s simply by muscle memory as you'd already adopted your line for the day.

Based on Sunday's times I think you've proved that the reverse stagger works; maybe you just need to gain some confidence in its grip levels on corner entry to pick that speed back up.

All of this is purely conjecture of course because I wasn't there and I'm by no means an advanced coach.

[TunaNoCrust]

Originally Posted by ZDan

Super-late reply, I missed this! Car is just not as "pointable" as it could be. I'd like to trade some rear lateral grip for front lateral grip. I might try a softer front sway, I'm currently running Eibach tubulars set soft front and stiff rear but that's ~150% stiffer than stock both front and rear. Hmm, akshually I think I'll just try stock front with the Eibach rear and see how that works out next year... But I worry a bit about too much rear roll stiffness overwhelming the Torsen diff's ability to drive both rear wheels out of corners esp. over curbs...

No worries and it sounds like this is in the slower corners? I have noticed it the most in corners such as Palmer CCW Turn 12, Canaan Bowl T8?.


At NHMS I had a similar situation at turn 9 where I was carrying WAY more entry speed, but will have to check my data to see if the difference was Saturday to Sunday or Sunday Morning to Sunday Afternoon. I think I was pretty consistent throughout the weekend in 6.

I'm gonna email yah.

[timurrrr]

Originally Posted by ZDan

No.

Ah, no worries.
Can you tell/remind me what spring rates you're running?

Also, "150% stiffer than stock" — than which stock?
'17 PP or '13-'16?

Originally Posted by CrowsFeast

First of all the increase in the rear bar according to your logic would be 0%, not infinite.

Example: increase from 4 to 5 is 25% because
100 * (5 - 4) / 4 = 25.
Now put 0 instead of 4 and you'll see that it's definitely not a 0% increase.

Originally Posted by CrowsFeast

Secondly: just because there's no rear bar doesn't mean there's no rear roll stiffness, so your increase would be low/near 0, not actually 0.

Well, he said the bar is stiffer by 150%, not overall stiffness.
I know that springs also contribute to the overall stiffness, and mentioned springs twice in my post.

Originally Posted by CrowsFeast

Thirdly: if you're going to propose this kind of mathematical problem you would already know that the formula doesn't apply as you approach either 0 or infinity. This neither proves nor disproves the formula for any particular range of numbers.

Putting on my old "math nerd" hat on, it is indeed not correct to simply divide by zero.
However, if you look at the "% increase" as a function of baseline bar stiffness, the limit of such function at 0+ approaches infinity.
It's not uncommon for people to refer to this as simply "infinity".