Sharp Turn Scrubbing
01-23-2016, 09:14 PM
#1
Drifting
Thread Starter
Sharp Turn Scrubbing
Hi guys. I don't own a 991, but have had a 2016 Black Edition C4 cab as a loaner for about 10 days while my Macan is being repaired (bad transfer case). I have loved driving the C4, as it is amazingly quick, smooth and compliant (even on the big wheels), and is almost too easy to drive very fast. The driving position is almost identical to my Macan, so it is very easy to transition from the Macan to the 991.
But I find the scrubbing of the front tires when turning sharply out of a driveway etc to be a real problem. I understand they changed the 991 steering geometry so that it doesn't vary the arc between the inside and outside wheels, so the tires have to squirm to make up the difference, and they chatter badly in cold weather. I assume they all do this if it is the way they're all designed. Do you just live with it and get used to it?
Sorry if this has been covered before, but I did do a quick search and didn't want to spend an hour looking.
BTW, the Bose in my Macan sounds much better than in the 991, likely because it is hard to get good sound in small cabins, especially with the added road and wind noise.
But I find the scrubbing of the front tires when turning sharply out of a driveway etc to be a real problem. I understand they changed the 991 steering geometry so that it doesn't vary the arc between the inside and outside wheels, so the tires have to squirm to make up the difference, and they chatter badly in cold weather. I assume they all do this if it is the way they're all designed. Do you just live with it and get used to it?
Sorry if this has been covered before, but I did do a quick search and didn't want to spend an hour looking.
BTW, the Bose in my Macan sounds much better than in the 991, likely because it is hard to get good sound in small cabins, especially with the added road and wind noise.
01-23-2016, 09:22 PM
#2
Three Wheelin'
01-23-2016, 09:43 PM
#3
Drifting
Thread Starter
Thanks Homeles. I hate it when people bring up a topic that has been dealt with to death. I just wasn't sure how it would be described when I did a search. And I still don't know what ACORN means after scanning the threads you provided above. But my question is well answered now.
01-23-2016, 09:52 PM
#5
Banned
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Thanks Homeles. I hate it when people bring up a topic that has been dealt with to death. I just wasn't sure how it would be described when I did a search. And I still don't know what ACORN means after scanning the threads you provided above. But my question is well answered now.
So when people ask, we have a short one word answer. Acorns!
01-23-2016, 10:46 PM
#6
I'm assuming it's a tradeoff that the Porsche engineers were willing to make. Put up with driving on acorns occasionally in order to make the remainder of the steering geometry dead solid perfect at speed (or close to it).
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01-24-2016, 01:22 PM
#9
Drifting
Thread Starter
I just think that for a $100k + car, used primarily as a daily driver and not for racing, I shouldn't have to feel like the whole front end is ready to fall off when turning out of my driveway on cool days (40's here). My previous 997's had a little bit of front tire squirm at cooler temps, especially as the tires wore down so there was less rubber to take up the forces, but it didn't cause the whole front end to kick quite violently like this 991 does.
If whatever handling improvements they created with the geometry change were necessary and useful for me, such as if I was tracking the car regularly and needed that additional handling edge that this design apparently was meant to provide, then the trade-off might be justified.
I have a Macan and a 993 that both handle wonderfully for my needs, and neither one demonstrates this "acorn" effect. Same with my daily driver 997's that I periodically autocrossed. I'm sure none of the Porsches I've owned perform as well, or as easily, as the 991 at very high speeds. But since I seldom exceed 100 mph, but often turn sharp corners.......you get my drift.
I expect with smaller wheels (the Black Edition has 21"), and perhaps winter tires that use rubber that behaves better in cold weather, the acorning would be less severe and easier for me to accommodate.
Bottom line, the 991 is a great car, and this issue is a first world problem.
If whatever handling improvements they created with the geometry change were necessary and useful for me, such as if I was tracking the car regularly and needed that additional handling edge that this design apparently was meant to provide, then the trade-off might be justified.
I have a Macan and a 993 that both handle wonderfully for my needs, and neither one demonstrates this "acorn" effect. Same with my daily driver 997's that I periodically autocrossed. I'm sure none of the Porsches I've owned perform as well, or as easily, as the 991 at very high speeds. But since I seldom exceed 100 mph, but often turn sharp corners.......you get my drift.
I expect with smaller wheels (the Black Edition has 21"), and perhaps winter tires that use rubber that behaves better in cold weather, the acorning would be less severe and easier for me to accommodate.
Bottom line, the 991 is a great car, and this issue is a first world problem.
01-24-2016, 03:13 PM
#11
Drifting
I just think that for a $100k + car, used primarily as a daily driver and not for racing, I shouldn't have to feel like the whole front end is ready to fall off when turning out of my driveway on cool days (40's here). My previous 997's had a little bit of front tire squirm at cooler temps, especially as the tires wore down so there was less rubber to take up the forces, but it didn't cause the whole front end to kick quite violently like this 991 does.
If whatever handling improvements they created with the geometry change were necessary and useful for me, such as if I was tracking the car regularly and needed that additional handling edge that this design apparently was meant to provide, then the trade-off might be justified.
I have a Macan and a 993 that both handle wonderfully for my needs, and neither one demonstrates this "acorn" effect. Same with my daily driver 997's that I periodically autocrossed. I'm sure none of the Porsches I've owned perform as well, or as easily, as the 991 at very high speeds. But since I seldom exceed 100 mph, but often turn sharp corners.......you get my drift.
I expect with smaller wheels (the Black Edition has 21"), and perhaps winter tires that use rubber that behaves better in cold weather, the acorning would be less severe and easier for me to accommodate.
Bottom line, the 991 is a great car, and this issue is a first world problem.
If whatever handling improvements they created with the geometry change were necessary and useful for me, such as if I was tracking the car regularly and needed that additional handling edge that this design apparently was meant to provide, then the trade-off might be justified.
I have a Macan and a 993 that both handle wonderfully for my needs, and neither one demonstrates this "acorn" effect. Same with my daily driver 997's that I periodically autocrossed. I'm sure none of the Porsches I've owned perform as well, or as easily, as the 991 at very high speeds. But since I seldom exceed 100 mph, but often turn sharp corners.......you get my drift.
I expect with smaller wheels (the Black Edition has 21"), and perhaps winter tires that use rubber that behaves better in cold weather, the acorning would be less severe and easier for me to accommodate.
Bottom line, the 991 is a great car, and this issue is a first world problem.
https://leith.porschedealer.com/new/...59215/info.php
01-24-2016, 03:45 PM
#12
Racer
My C2s started doing the "acorn" thing on tight turns out of my driveway or parking places this winter as temperatures dropped below 40 degrees. Never did it in warm weather.
I have PDCC and all four original Pirelli P-Zero tires measure 7/32" tread evenly all the way across at over 13,000 milles, so it is not anything wrong with steering alignment.
I have PDCC and all four original Pirelli P-Zero tires measure 7/32" tread evenly all the way across at over 13,000 milles, so it is not anything wrong with steering alignment.
01-24-2016, 05:23 PM
#13
Rennlist Member
Isn't the OP just describing the Ackerman effect which is a well known phenomenon on sports cars like Porsche and Corvette? Complaining about the Ackerman effect is like complaining at the sound of rocks being kicked up by the high performance car. Not trying to be harsh but a 991 is a true bespoke sports car with luxury features built in... It's going to have carry-over characteristics of race cars.
