05-16-2023, 08:42 AM | #925 | |
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The Following User Says Thank You to kraftyone For This Useful Post: | strat61caster (05-16-2023) |
05-19-2023, 11:49 AM | #926 | |
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05-30-2023, 07:21 PM | #927 | |
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06-28-2023, 01:33 PM | #928 |
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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.
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06-28-2023, 01:58 PM | #929 |
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Did it change the wheel height also?
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06-28-2023, 03:00 PM | #930 |
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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. |
06-28-2023, 03:59 PM | #931 | |
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06-28-2023, 04:24 PM | #932 |
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I'm really confused about what you're asking, I didn't shrink anything, I'm running the OEM wheel size (17x7.5).
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06-28-2023, 05:17 PM | #933 | |
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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. |
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06-29-2023, 06:27 AM | #934 |
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It's more of a curiosity since I don't even compete in SCCA.
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06-29-2023, 09:33 AM | #935 |
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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.
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06-30-2023, 11:24 AM | #936 | |
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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. |
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06-30-2023, 01:17 PM | #937 | |
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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. Last edited by strat61caster; 06-30-2023 at 01:30 PM. |
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06-30-2023, 02:07 PM | #938 | |
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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]
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