SCCA Solo D Street discussion

[kraftyone]

Originally Posted by strat61caster

ProParts Megans, there’s also Shaftworks and Redshift for similar money, they all come with camber plates. Monotube, built by autoxers who understand the sport and the locations you run at, closing in on 40k miles on my Megan’s and they’re still great. You might run into Shenefield at an event where you’re at, ask how he would advise your setup. They’re all single adjustable rebound which is where the handling changes come from, while they’re 20-30 clicks you don’t really feel 1 click so put in 2-4 which effectively narrows you down to a ~10 adjustment damper. Once you get compression set right for the surface odds are you don’t change it.



I don’t like the KW stuff, twin tubes, useless support (KW NA that is, RCE is clearly better) but they can take you to the front. MCS cars ride great but a lot of people local to me are switching to shaftworks, their support is great and local to us.

I did the Shaftworks route this winter. Well worth the money all the way around. Car actually rides better as a daily driver, and performed great at the first event of the year.

Sent from my SM-G986U using Tapatalk

[RacingredGR86]

Originally Posted by cmiovino

I was today years old when I realized SSC PAX is 0.807 and DS is 0.808. AKA, with Konis, Ebach springs, camber bolts up front, ~2.5 degrees up front, adjustable lower control arms AND 8" wide wheels, you need to go actually slower to get the same PAX score.

Again, all on a 225/45/17 RT660, but that's what I was on last year. Fucking christ the 1st gen is boned in DS.

Going to STX the PAX is only 0.817, meaning you need to go exactly 1.1% quicker to maintain the same PAX position. This equates to exactly 0.5 sec faster on a 45 second course or 0.33 seconds quicker on a 30 second course.

Given I'm on a 225 on stock wheels, moving to a 245 on a 9" wheel, plus coilovers offering ~4 degrees of camber up front and 2.5 in the rear with LCAs... I think ANYONE could go half a second quicker just from that. Let alone adding a header and tune to top it all off eventually.

(This is just me convincing myself to go to STX.)

What you just laid out is exactly why I decided to not pursue DS and just did a STR "lite" set up (coilovers/ camber plate, front sway bar, and RLCA, 17x9 wheels, and 245 tires). I've only taken it out to a handful of events and definitely no regrets.

[Locust]

Originally Posted by cmiovino

Do you know what coilovers those are for $2k?

I haven't made the jump to STX because I keep thinking I need at least ~$3k RCE Tarmac 2's with camber plates, if not something like MCS and up in the $4-5k range.

I've been thinking about it and something like $1800 RCE SS-1's or something similar with good valving, but less adjustable might be better. I don't want to get totally lost adjusting 2-way dampers, or having 30+ adjustment clicks to play with.

My car was highly competitive in STX (in the hands of other drivers...) with just some Fortune Auto 500s and a whiteline 20mm front bar for suspension. You don't have to go all in to be competitive if you can get your settings dialed in right and learn the car you'll be fine.

[otter]

For shits 'n giggles I took a pic of mounted and unmounted 255s side by size to see just how much they get squeezed down on the class-legal wheels.

[dragoontwo]

Originally Posted by otter

For shits 'n giggles I took a pic of mounted and unmounted 255s side by size to see just how much they get squeezed down on the class-legal wheels.

Did it change the wheel height also?

[otter]

Originally Posted by dragoontwo

Did it change the wheel height also?

Wheels are 17". Did you mean tire diameter? If so, here's the diameters of common BRZ autox sizes on the Stones from TR:
OEM 215/45/17 - 24.7"
225/45/17 - 25"
235/45/17 - 25.4"
245/40/17 - 24.7"
255/40/17 - 25"

There's also a 245/45/17 tire that's 25.7" but I've not seen anybody on this tire.

[dragoontwo]

Originally Posted by otter

Wheels are 17". Did you mean tire diameter? If so, here's the diameters of common BRZ autox sizes on the Stones from TR:
OEM 215/45/17 - 24.7"
225/45/17 - 25"
235/45/17 - 25.4"
245/40/17 - 24.7"
255/40/17 - 25"

There's also a 245/45/17 tire that's 25.7" but I've not seen anybody on this tire.

Those are diameters given on the manufacturers width wheel. What is the difference on your wheel? You shrunk the wheels. What effect did that have on diameter?

[otter]

I'm really confused about what you're asking, I didn't shrink anything, I'm running the OEM wheel size (17x7.5).

[strat61caster]

Originally Posted by otter

I'm really confused about what you're asking, I didn't shrink anything, I'm running the OEM wheel size (17x7.5).

With the tires squeezed beyond an inch of their life do they still measure in spec for circumference/diameter or did they balloon out due to the pinch?

This could affect a small gearing change worth arguing about because you have too much free time in a weekend only getting 5 minutes of seat time.

[dragoontwo]

It's more of a curiosity since I don't even compete in SCCA.

[cmiovino]

Originally Posted by dragoontwo

It's more of a curiosity since I don't even compete in SCCA.

Basically per SCCA rules, street class cars have to stick to OEM wheel widths. For the twins here, that's usually 7.5" now for 2022 and first gen PP models. So everyone jams on 245 or 255 tires, but what actually happens is the actual tread that's touching the ground is usually pinched heavily, leading to less of a contact patch than you'd think. It also has less support for the tire, so when cornering, it deflects more.

It's not to say everyone should quit running 255's. There's still apparently benefits and more grip. But it does mean that limiting wheel width REALLY effects the tire's ability to do it's job.

Back to your picture, unmounted tires are usually fully expanded and just chilling there, but when you mount them on any wheel, the stack will shrink. Even more so on something like a 7.5" wheel.

[renfield90]

Originally Posted by strat61caster

With the tires squeezed beyond an inch of their life do they still measure in spec for circumference/diameter or did they balloon out due to the pinch?

This could affect a small gearing change worth arguing about because you have too much free time in a weekend only getting 5 minutes of seat time.

I might be dating myself here. Were you around back when Integra Type R owners in DS were mounting 275 Hoosiers onto 6" wheels? If it's compliant to the rules and it's faster, send it...

FWIW, back in my CS days I ran 245s, but it was definitely a compromised setup and I don't think it was any faster except for the first 60' of a ProSolo start. I've probably made this exact comment more than once, and probably in this specific thread, but it's worth repeating. With most modern 200tw tires I think you are just lighting money on fire. As always, please don't rely on vibes or theory, go test! The clock never lies.

[strat61caster]

Originally Posted by renfield90

I might be dating myself here. Were you around back when Integra Type R owners in DS were mounting 275 Hoosiers onto 6" wheels? If it's compliant to the rules and it's faster, send it...

FWIW, back in my CS days I ran 245s, but it was definitely a compromised setup and I don't think it was any faster except for the first 60' of a ProSolo start. I've probably made this exact comment more than once, and probably in this specific thread, but it's worth repeating. With most modern 200tw tires I think you are just lighting money on fire. As always, please don't rely on vibes or theory, go test! The clock never lies.

No I only started paying attention to autocross after 200tw Street class came into effect and stock was dead. I’ve heard stories, like those Integras would kill a pair of Hoosiers in 6 runs at a pro and you needed fresh tires if you were in the challenge. And I’ve put 225 A7’s that are as wide as my 245’s on 7.5” wheels and they feel alright.

Hoosiers were and are a different animal from the 200tw we’ve had since the re71r came out. Meanwhile tirerack is turning faster laps with a 225 on a 9 than a 245. We’re in a new era and I don’t think much tire wisdom from the 2000’s is carrying over into the 2020’s. If stx isn’t disrupted next year the next tire I’m buying is a 225 re71rs, not a 265 even though we’re allowed it and that much tire has already been successful.

[cmiovino]

Originally Posted by strat61caster

If stx isn’t disrupted next year the next tire I’m buying is a 225 re71rs, not a 265 even though we’re allowed it and that much tire has already been successful.

Isn't something like a 245 on 9" going to be quicker and properly fit the wheel? Because I get the idea here is you want a tire that fits the wheel width you're running, but not totally overly balloon it (although people seem to still do this). 265's on a 9" are getting there.

I guess my question is 225 on a 9" is going to be start actually pinching, so what are you trying to achieve here?

[Yes, I have watched the TireRack video]