I am curious as to what some of you guys are seeing for max Gs when using your iPhone and Harry's lap timer, on street tires? I just used it for the first time over the weekend at an autox and was consistently seeing 1.3 at 2 sections of the course (the two sections I was consistently screwing up and overdriving into an under steer situation). To me this is higher than expected and I wanted to be sure I didn't have an issue with how I set the thing up. But maybe I am wrong and 1.3 isn't all that crazy for the limits of RS3s

 

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I've seen up to 1.2 on old RS-3V2.

My 10hz data logger was a bit less optimistic.

 

1.19g at Roebling on old NT01s. 1:21.1 for lap time.

 

So are we thinking 1.3 is an indicator that my phone isn't accurate? I was at the 1.2/1.3 range quite frequently during that autox. 1.3 seemed to be about when things went to shit

 

From what I have read, 1.5g seems to be around the maximum level of mechanical grip. Anything more is typically a result of aerodynamics.

My data is all GPS based. The best way to measure would be with an accelerometer.

...

Also, sustained G's is a better representation of a tire's grip. Spikes to 1.3 don't seem too far out but sustained 1.3g on RS3s on a non-cambered surface does seem a bit optimistic at autocross speeds unless the car is extremely light...