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Old 09-30-2021, 10:36 AM   #348
RT-BRZ
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Quote:
Originally Posted by renfield90 View Post
I've tried. I don't feel like it worked that well, here's my mental model for how they fare.

255s are a bonus on speed maintenance courses that also have a sustained high speed section at around 63mph. You're slightly faster than everyone on 245s there. So, like 10% of courses.

On pure speed maintenance courses (zero digs) with top speed <= 62mph (245s not bothered by the rev limiter) or with top speed > 64mph (everyone deep into third), there is no advantage either way. This is maybe 30-40% of courses.

If there is even one or two big digs (so all other courses), you get destroyed by everyone on 245s. Generally speaking our cars are thrust-limited coming out of digs, not traction-limited, and you are reducing thrust.

Bottom line is wider rubber should help in theory, but the gearing changes add a course dependency factor that is much larger than any extra grip you might get.
Here's a video of a course that's short and tight:


In reviewing the run I felt like the car just didn't stay in the RPM range I would have preferred and that tires causing a taller effective gear ratio is the real problem. I was only about one second off the fastest cars of the day (Supra and '16 M2) but it still didn't feel like I was getting the most out of my setup.

(side note; I know I have a lot of opportunity to improve my driving. I'm just demonstrating what I'm seeing.)
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