Too much understeer ?
#16
Thank you. When you say PCA are you referring to a program from Porsche Club of American? Care to share more specifics?
#17
The earlier understeer incidents are easily explained by mismatched tires. The chassis is very balanced, so having old worn out tires in front and good tires in the rear is a guaranteed recipe for understeer.
Once it had happened a couple times I think you were probably sensitized to the feeling and are now hyperaware of it. The last incident you describe doesn't sound like much happened, but you were worried about it and it confirmed your concerns. I think your car is probably set up just fine, alignment looks well within bounds, and now it's time to relax and enjoy. Check your tire pressures, that can definitely have an impact, and otherwise learn to drive the car a little differently.
Focus on this:
Good luck!
Once it had happened a couple times I think you were probably sensitized to the feeling and are now hyperaware of it. The last incident you describe doesn't sound like much happened, but you were worried about it and it confirmed your concerns. I think your car is probably set up just fine, alignment looks well within bounds, and now it's time to relax and enjoy. Check your tire pressures, that can definitely have an impact, and otherwise learn to drive the car a little differently.
Focus on this:
- Brake in a straight line, no braking in the corner at all, until you've progressed to the stage at which you can use trail braking at the track. Which basically means you should strive to never use brakes on the street unless your wheel is straight. If you need to brake in a corner it means you entered too fast for conditions, or too fast for your comfort zone.
- Use maintenance throttle in corner entry up until the apex. That means just enough throttle to maintain your speed, no more.
- Once you pass the apex, use the throttle to accelerate and transfer weight to the rear for traction on exit.
Good luck!
#18
#19
pprj, I am going to be more direct... your car should NOT understeer significantly (i.e. enough to make you feel unsafe or ruin your driving experience) at 50 mph regardless of what tires (if in acceptable conditions), pressures (if within a minimally reasonable range) or "driving technique" you apply, provided minimally reasonable adherence conditions (i.e. road not icy or flooded). If it does, something is wrong. Check it. If it may be only your impression, so have someone else that has driving time on a 991.1 drive your car and confirm or reject if it does.
#20
I always suggest track driving...but I tend to believe that doing some autocross events with your local PCA club is better. It’s a lot safer and you can really learn car control. Also sign up for the Porsche Drivng School herald at Barber Motorsports Park. Awesome 2 day learning experience where you drive cars complete stock and you quickly learn...it’s not the car it’s the driver.
I have only had scary understeer twice on the street an both times were due to cold weather + summer tires + too much pre-apex throttle.
Last edited by TheEngineer; 12-04-2017 at 03:27 PM. Reason: Clarification
#21
After going thru this thread I also believe it's your driving style which is making you feel like you are understeering. You cannot drive the RWD Porsche 911 the same way you'd drive an all wheel drive Audi. The weight distribution is very different. Also in the AWD Audi, the front axle is helping to pull you through the corners. You don't have that in your RWD Porsche. With some all wheel drive cars you can just throw your car into a corner and thru brute force the drivetrain will pull you thru the corner. But your 911 won't do that for you.
I think what's happening is... you are probably going into corners very hot and then turning really hard which is probably overwhelming the front axle causing the car to slide forward instead of turning. Not only does your Porsche not have power going to the front axle... but it also is much less weight over the front axle to push the wheels down into the ground. Try changing your driving style and see how that helps.
I came from an AWD car and had to change how I drove to get the most out of the Porsche. Not only because the AWD system functioned differently than the AWD on my Porsche... but because I didn't have as much computers "helping me" push the car anymore.
I think what's happening is... you are probably going into corners very hot and then turning really hard which is probably overwhelming the front axle causing the car to slide forward instead of turning. Not only does your Porsche not have power going to the front axle... but it also is much less weight over the front axle to push the wheels down into the ground. Try changing your driving style and see how that helps.
I came from an AWD car and had to change how I drove to get the most out of the Porsche. Not only because the AWD system functioned differently than the AWD on my Porsche... but because I didn't have as much computers "helping me" push the car anymore.
#22
Happy to.
First time I felt it was with the old Pirellis. I was up in the mountains, temperature at high 40s, and I was on one of my preferred roads, a 55mph speed limit pass.
(Fyi, I'm the kind of guy that like some spirited drives, but my limit is 10 above. I have profound respect for law enforcement and don't want to put anyone in harms way).
As I approached the turn and hit the brakes the car simply did not turn. You could hear the noise of the front tires pushing, and it took a second for the car to recover grip. It was like the car had too much front brake pressure and nothing in the rear, almost that kind of sensation. At the time I blamed the old dry tires plus the high 40's temperature. That was my explanation and it was good enough for me. I was not worried.
Second time was with the same old front tires on 70 degree weather. I took a 90 degree turn at around 40mph (maybe a little less) and the front pushed so hard I though I was going to hit a pole, I kid you not. The asphalt was good and again, I blamed the old tires. The S4 makes the same turn at 40mph easily by the way.
The third time was with the new set of Michelin Pilots. A slightly downhill left turn, and I felt the car pushing mildly at around 50mph, not as bad as before, but still. That is what got me worried as I could not apply the same explanation as before: these Michelins were brand new tires.
Granted, in all these cases I was braking, transferring weight to the fronts.
This is where I'm now: (a) I'm the sole responsible for this, my driving technique is causing these issues (b) the way to drive the 911 is different from the S4, more than I thought it would be and (c) I need to invest time and be serious about learning the 911.
That will be my journey. It is good to have the S4 to run quick comparisons. Great car, by the way.
Thank you all for your valuable input.
First time I felt it was with the old Pirellis. I was up in the mountains, temperature at high 40s, and I was on one of my preferred roads, a 55mph speed limit pass.
(Fyi, I'm the kind of guy that like some spirited drives, but my limit is 10 above. I have profound respect for law enforcement and don't want to put anyone in harms way).
As I approached the turn and hit the brakes the car simply did not turn. You could hear the noise of the front tires pushing, and it took a second for the car to recover grip. It was like the car had too much front brake pressure and nothing in the rear, almost that kind of sensation. At the time I blamed the old dry tires plus the high 40's temperature. That was my explanation and it was good enough for me. I was not worried.
Second time was with the same old front tires on 70 degree weather. I took a 90 degree turn at around 40mph (maybe a little less) and the front pushed so hard I though I was going to hit a pole, I kid you not. The asphalt was good and again, I blamed the old tires. The S4 makes the same turn at 40mph easily by the way.
The third time was with the new set of Michelin Pilots. A slightly downhill left turn, and I felt the car pushing mildly at around 50mph, not as bad as before, but still. That is what got me worried as I could not apply the same explanation as before: these Michelins were brand new tires.
Granted, in all these cases I was braking, transferring weight to the fronts.
This is where I'm now: (a) I'm the sole responsible for this, my driving technique is causing these issues (b) the way to drive the 911 is different from the S4, more than I thought it would be and (c) I need to invest time and be serious about learning the 911.
That will be my journey. It is good to have the S4 to run quick comparisons. Great car, by the way.
Thank you all for your valuable input.
#23
Driver Skills is a course ideally run on a large runway or parking lot, with exercises marked off with cones. The exercises are designed to focus on braking, cornering and throttle steer, late apex line, looking ahead (proper use of eyes), and often with something like a mini-autocross at the end to tie it all together. Some of the better events will have a truck come out and wet a section so you get wet driving experience. Speeds at these events generally top out around 60-80. Moderate speed plus cones makes it a lot easier to freely push your car to the limit and beyond.
Autocross is a timed competitive event run on a course marked off with cones. The course is different each event and you generally only get three or four runs that count. Because of this autocross places a HUGE emphasis on mental preparation- studying the course, memorizing it, analyzing your performance after each run, studying the other drivers.
Driver Ed events are run on a track, with the emphasis being on technique not speed. Learn to perform all the basic skills- braking, late-apex line, throttle control- and you will go fast. DE is not racing. Passing is cooperative. Speeds vary by track but this is where you get going fast enough to put serious wear and tear on your brakes and tires.
If you notice a progression, that is not by accident. Having instructed hundreds over years I can say without a doubt the absolute best approach is to do at least one Driver Skills, then autocross for a year or so, then progress to the track. If ever. Do the first two, you will be head and shoulders above almost anyone at the track.
#24
Hope this doesn't confuse things further but here it goes. I also previous to my current 991.2 c2 had a sweet 991.1 c2 cpo with old tires. I experienced everything you have stated here. However in every situation and temperature the bad handling went away if I warmed the tires thoroughly. Thoroughly meaning you could smell the tires melting. When the tires were really hot these problems disappeared, even in cold temps. I have not experienced any of these habits in the 991.2 c2. I also had a chipped audi avant and if I drive the 991.2 through a curve like I did the Audi I get the power cut and rear end hop. Driving a c4s like an Audi through a curve and it seems not to care. I think you would love a 991.2 c4s, however I believe you will become a better driver mastering your current ride. We are all blessed to be driving any 911. They are all special and beautiful.
#25
The two day school at Barber is awesome. One topic they cover very clearly is the connection between your right foot and under/over steer.
I have only had scary understeer twice on the street an both times were due to cold weather + summer tires + too much pre-apex throttle.
I have only had scary understeer twice on the street an both times were due to cold weather + summer tires + too much pre-apex throttle.
Actually, since you went to Barber then you know what's in the Going Faster video, which is even more advanced (and risky, and scary) the notorious trail braking, which if I remember correctly he refers to as the only really new development in driving technique in something like 50 years. Which that video was made decades ago. And nothing new since! So its not like any of this is rocket science. Yet people just aren't taught it. Go figure.
#26
Hope this doesn't confuse things further but here it goes. I also previous to my current 991.2 c2 had a sweet 991.1 c2 cpo with old tires. I experienced everything you have stated here. However in every situation and temperature the bad handling went away if I warmed the tires thoroughly. Thoroughly meaning you could smell the tires melting. When the tires were really hot these problems disappeared, even in cold temps. I have not experienced any of these habits in the 991.2 c2. I also had a chipped audi avant and if I drive the 991.2 through a curve like I did the Audi I get the power cut and rear end hop. Driving a c4s like an Audi through a curve and it seems not to care. I think you would love a 991.2 c4s, however I believe you will become a better driver mastering your current ride. We are all blessed to be driving any 911. They are all special and beautiful.
#27
Yes all the standard ideas will work and will affect handling to some degree. Tire pressure, camber, wider tires and wheels, springs and anti-roll bars, spoilers and wings, all these things matter. Except for when they don't. Which is the instant you push gas or brake. Because all these things together, they might add up to 10% or maybe even 20% more traction. But throttle and brake, not even full-on they transfer the weight of the car to the tune of well over 1,000 lbs, probably more like 2,000 lbs, which affects traction a whole lot more. Way more. Not even close more.
Want proof? Porsche has gone to great lengths to tame the oversteer inherent in their rear-engine design. Yet even with all their best efforts and sending the car out the door biased towards understeer people still manage to spin the darn things. Which, if you look it up, is called oversteer. Which, read the thread "track day spinout" https://rennlist.com/forums/991/1037...questions.html can happen even with a 4!
Despite the understeer bias the cars are still close enough to neutral that while one driver complains about understeer another driver is spinning out in oversteer.
They should make a refrigerator magnet, or stencil on rear view mirror or maybe a T-shirt with Bart Simpson writing a 100 times: Its the driver. Not the car.
#28
#29
One thing I haven't seen mentioned is the 1/32" toe-in I see on the front wheels (positive being toe-in). This converts to close to 0 degrees 5 minutes, which is which is near the middle of the Porsche recommended range of 0 minutes to 10 minutes. Porsche is known to prefer understeer on its street cars. Toe-in increases understeer and is often used for street alignments since understeer is considered safer. You'll probably see some improvement if you drop the front toe down to zero; the bottom end of the recommend range. As a side effect you'll get slightly better front tire life too
http://winhpde.com/car-setup/track-alignment/
http://winhpde.com/car-setup/track-alignment/
#30
Here's another interesting reference I forgot to mention: http://www.morpca.org/drivers-educat...eer-oversteer/