[jdstein11]

So I recently noticed feeling bumps as I fully turned the wheel to leave a parking spot. There was nothing on the ground like acorns, etc., so after feeling it for a third time, I brought it in. Turns out this is a known issue by PNA called "Front Tire Scrubbing" that is "normal" and not damaging. They provided me with an explanation in the form of Advanced Technical Information (attached), so I'm just curious whether anyone else ever experienced this.

Temps here in NJ have been as low as upper 30s but mostly 40s and 50s for the past few weeks when I first noticed it. I don't drive much since I mostly work from home and take out the car whenever I'm feeling antsy so the slightly faster-than-normal wear on the dealer review sheet is surprising.

 

[johan]

Yes its a standard thing on 20” at lower temps

 

[Nosmo]

Isn't this called the Ackerman Effect. The is a YouTube video of it here

https://youtu.be/oYMMdjbmQXc

 

[RGM718]

I have experienced it on my 981 on 19" and interestingly less, thus far, on my 718. But it is a known behavior. And, it does not even have to be cold (I live in Florida).

 

[JakiChan]

I think I've felt it on my 19"s on my CS.

 

[Viffermike]

Moved to the Wheels and Tires subforum. As other posters have mentioned, this is typical behavior of a soft-compound summer performance tire at temperatures that approach the low effective operating range of the tire. (I've felt it every morning this week on my Continental ECS 19s.)

 

[Rideguy]

I’ve experienced this a few times on my Cayman with 18” wheels, during a Southern California summer. Winter hasn’t arrived yet so no experience yet with colder temperatures.

 

[GregW]

Yup.
Colder weather and/or reduced traction conditions (water, sand) and on 18" tyres.
Still occasionally scares the sh*t out of me.

 

[718]

My Cayman on 20” Pirelli tyres does it too. Less so when warner bit still enough to make one feel uncomfortable. It’s gets easier with time. I’ve learnt to only apply full lock when absolutely necessary. Small price to pay for the alleged handling benefits.

 

[aeronca65tl]

I notice it Winter and Summer.

 

[timlaw]

yep same here when cold - happened to all of my recent 20" shod sports cars - XKR, F Type, 991 and CGTS

disconcerting but you learn to "filter it out"

 

[ArchiProf]

I experienced this in summer and in winter on my 981 Cayman and also now with my 982 Cayman, both with 19" wheels.

 

[Peter]

OK, so it's normal. But can it affect your tracking/alignment in the longer term? Mine is actually quite embarrassing with onlookers when for example pulling out from a parallel parking spot. It judders along with the front wheels being pushed by the back wheels in a direction they don't want to go.

 

[timlaw]

OK, so it's normal. But can it affect your tracking/alignment in the longer term? Mine is actually quite embarrassing with onlookers when for example pulling out from a parallel parking spot. It judders along with the front wheels being pushed by the back wheels in a direction they don't want to go.

I guess not or else they would push you to have a track check every time they get their hands on the car? or it would be in the handbook?

keep an eye on tread wear?

 

[RGM718]

I have 4 wheel alignment done when I replace tires. My alignment has never been out that much after an average of 2 years in between alignments.

 

[GregW]

OK, so it's normal. But can it affect your tracking/alignment in the longer term? Mine is actually quite embarrassing with onlookers when for example pulling out from a parallel parking spot. It judders along with the front wheels being pushed by the back wheels in a direction they don't want to go.

It's not quite what your last sentence implies--have a look at the "Ackermann Effect" for some details.

IME the jarring is much less than going over any piece of rough pavement, so I don't think it's going to affect the alignment.

 

[Swdea]

Would Porsche Torque Vectoring (PTV) mitigate this?

 

[Nosmo]

PTV only brakes the inside rear wheel when cornering. I am unsure whether this has any correlation to the issue. Please see my above post and you tube vid on Ackerman Effect. It's the geometry.

 

[Peter]

I think my Carerra S came with PTV as standard. It still does a slight juddering sometimes but nowhere near as pronounced as with the 718 Boxster S and the 981 before that. Although I don't remember it with the 987 but could just be my memory fading or it was a car with less torque. Does the 911 have a wider track at rear than at front and could this alleviate the problem. Cos problem it is and should be remedied in design.

 

[GregW]

<snip>Cos problem it is and should be remedied in design.

It's easy to remedy--the remedy just causes overall performance degradation.

Narrower tyres and a change in alignment will solve it--and cause a lack of steering precision and reduced grip at non-parking speeds.