The Ackermann effect / tire judder 20" vs 21"

[ExTesla Driver]

I have 21" spider, too much Tire Judder, very annoying. I read somewhere this can be fixed with software, on full lock there is more power to front wheels less on the back. This way car is pulling not pushing.

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[outie]

Been getting this everyday in the past months and especially recently with the rain and colder temperature it’s getting really frustrating. GTS w/ spyder wheels. Located in SoCal and it’s not even that cold.

 

[f1eng]

The Ackermann effect is actually the fact that a different steering angle is required for each front wheel to go round a curve because the outer front wheel is tracing a bigger arc than the inner.
It is easy to design steering geometry that compensates by turning the inside wheel progressively more as you apply more lock.

The problem is real tyres don't go round corners without a slip angle, which is required to generate the side force, and the optimum slip angle increases with load so with a sports car going quickly round corners having Ackermann steering is wrong to optimise the grip of both front tyres, so less than Ackermann or even anti-Ackermann geometry is used - every Formula 1 car I designed or worked with has anti-Ackermann steering.

This means that at low speed the angle of steer of each front wheel is "wrong" according to Ackermann in pretty well all sports and racing cars optimised to tyre characteristic. The lower profile the tyre the less sidewall flex is available to absorb this difference and it seems between 20" and 21" on the Taycan is the sidewall flexibility which can and which can't.

It is grip dependant whether the tyre skips or not, not temperature, though summer tyres have less grip when cold which is probably where the impression comes from.

The only way out is to have less sporty tyre profiles or drive a limo - it is inherent in good sports car design.

 

[Speedy Gonzales]

Forgot to update this thread;

Loving the “21 inch RS Spyder Design” wheels!

The ackermann effect is only there for me when the temperature is below 6 degrees Celsius so not really an issue for me ??

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