abe

Well, my tires are old and dry and it is getting colder in So Cal so I experienced the front tires jumping around as if it was on pebbles or acorns as I was in reverse full turn from driveway to street. I thought it had to do something with the electric power steering and feedback only to learn about the Acorn Effect.
Thanks to this forum I avoided costly and time consuming investigation. I never experienced this in my 997....do not know if it is the tires or the 991, but at least I know it is not a problem.

FYI

Abe

gellie

Andial

I would say the record low CA temps have more of an effect than the size of the rims.

Dewinator

STG

Is this like losing your virginity?

Avalon911

subshooter

It's the 991. Your wheel geometry is designed to solve the problem of wheels on the inside and outside of a turn needing to trace out circles of different radii.

Tires do play a part and can lower the temps at which the acorn noise takes effect. I hate it.

chuck911

Technically its caster not Ackermann. Although it takes a lot of explaining to understand why its the one and not the other. The Engineering Explained guy on YouTube has it covered.

digits

I switched to the winter tires after the acorns arrived in Seattle. I was on a road trip last week and drove through So Cal right around the time that even places as far south as LA saw the frozen water falling from the sky - I really wasn't expecting to need the winter rubber in California, but they were actually perfect for 101 and especially on my run up highway 25 from 198 to Hollister.

Bemo

Yeah, Abe's acorn has been popped!

AdamSanta85

When you guys say 'acorns' you mean like a popping noise when driving slow with the wheel turned and the tires cold?

LexVan

Yup.

AdamSanta85

Thanks, just double checking it wasn't because of how low my car is now, or because of the spacers in the front. I figured as much. Wife the other day "Sounds like your fancy sports car is broken"....

LexVan

Tires?
Temps?
Pressures?

AdamSanta85

After now searching for acorn effect, I am confident this is what it is.

1. P-zerrrrros
2. Ice cold
3. 33