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Need some help from the community here.
My 911.1 C2 (my first 911) is now one year old (as my car). When I bought the car CPO it came with old front tires and brand new rears. All Pirellis. The fronts had lots of tread/life, they were just 3 years old.
So, being this my first ever 911, I quickly learned how easy it was to understeer the car. I was quite surprised, actually. I know the 991 can understeer but to be honest what I experienced was a little too much for a sports car. But hey, with such old tires in the front, I should not expect any better. It was all good. I knew why it was happening.
So I decided to put some miles in the rears before replacing everything with brand new Michelin Pilots (same tire I have in my Audi S4) and I did that 2 months ago. And this is where things got interesting.
Now I have my Audi S4 and the 911/991 both shod with Pilots 4S. And I can easily compare the two. In this match, the 911 still understeers way more than the S4, a car that is famous and criticized for its tendency to understeer.
When I mounted the Michelins I asked my shop to align the 911 for street use. The alignment is attached. They are a well regarded shop with lots of Porsche customers, so I trust them. My S4 is also aligned exactly per factory spec. The suspension on both cars is 100% stock and I run both cars on comfort setting in terms of tire pressure.
So why is the 911, a car that is supposed to be much better dynamically than the S4, understeering so much at 45/55 mph in 60 degree weather in regular city driving?
I see two main possible explanations.
- I still don't know how to drive it properly - always a possibility. Still, even so, even if I'm the culprit, the gap between the two cars is not small. I'm really surprised by this. I'm not a professional driver, but did several years of 125cc go-kart racing so I'm not exactly a green rookie. Or...
- My alignment is bad, really bad, and will always make the car understeer.
So I was wondering if the community here would help me diagnose this.
My car is a C2 with PASM, 20in wheels and the tires are OEM size.
Thanks for any hint.
I’m at a loss how you’re getting under steam driving around town at 40-50mph...never felt it in a stock Porsche especially the 991 cars. I track my car so at the track you can get into,under steam but not at street speeds.
Adjust camber to max front which is going to,be around -1.3-.6....and match the rear with the front. Zero toes front and just a bit toe in...no more than .14 degrees rear.
im using this for my 2017GTS at the track with Michelin Pilot Sport Cup 2 Tires with great success. My GTS has Sport PASM and max camber I. From I could get was -1.6....diledmin same for rear. Works great. In my 997 cars I always ran around -2.5 front and -2 camber rear but the 997 and 991 are very different.
I doubt that the setup is causing your problem. It is more likely it is your driving style. I think that its is possible (under the right conditions) to have understeer at 45-55mph in a turn provided that you are lifting and shifting weight to front into the turn. Try taking the same turn that you are familiar with and add some throttle so that you shifting the weight to the rear a bit. You may find that the understeer disappears. This is a common issue for drivers not used to a rear engine 911. Another area to investigate is the differential in front and rear tire pressures. For the street, I don't like to go more that +3 in rears.
^^^ I thought the opposite was true. Brake to put more weight in the front = less under steer. Go on the gas early lifts the front = more under steer. disclaimer IM NOT A PRO.
There is a definite learning curve. Reading and watching some YouTube videos really helps to understand how to better take advantage of the unique drivetrain layout!
Thank you guys. I do believe I'm the issue here. It is the way I'm driving the car that is causing my troubles. I appreciate all the replies.
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.
^^^ Brake to put more weight in the front = less under steer. Go on the gas early lifts the front = more under steer. disclaimer IM NOT A PRO.
You are correct in your thinking if executed at the right time. Brake too far into turn (with speed) and pushing will result creating understeer. Throttle will assist in correcting.
Can you elaborate on what understeer at 40-50 MPH feels like, and what you're doing when you feel it?
I feel like what I consider understeer differs from what some others do (being that I hear the term thrown around more than I feel it), so I'm curious what I'm missing. Just seems like feeling it at 40-50 MPH is odd. I can pinpoint it better on my Mazda as being FWD I can feel the car *want* to understeer, but even with that I feel like I have to be pushing it quite a bit before I feel like it translates into understeer, or what I consider to be so.
Can you elaborate on what understeer at 40-50 MPH feels like, and what you're doing when you feel it?.
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.
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.
My favorite T-shirt, also one of the most coveted at autocross events, features a 911 in classic hard cornering front wheel in the air pose with the caption: The 911 divided the world. Between those who could drive... and the rest.
No 911 of the last 30 years needs even a touch of the brakes when going a mere 10 over. They do however require the driver to drive the line with smoothness and precision, and using throttle properly to control weight balance. I have been with my wife directly behind a 993 on a wet road and watched his rear end slide out a good 2 feet while we cornered serenely (wife on board, after all) at the same speed in my 911SC. Its not the car. Its the driver.
Your best bet is PCA (or BMWCCA, same course) Driver Skills. Not Driver Ed, which is track. Definitely not track days, lapping days, or anything like that. Emphasis entirely on skills and education is what you want. Speed comes later.
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:
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.
If you do this, all within your boundary of not going more than 10 over on the street, you will have fun and stay safe. There's lots of fun to be had on low speed corners, off ramps and on ramps, while staying at safe and sane speeds.
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.
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How new? Were the tires broken in and mold release chemicals worn off the tires? Brand new tires do not grip out of the box, they have to be driven a couple of hundred miles.
My first 911 (2001 996 C4) under-steered like a pig when I took it to AX. I played with the tire pressures and my driving style and it began to feel much more balanced and at times, tail happy. Moved into a 991 and while it will still under steer, it is far more balanced than the 996 was....and I like to believe I am a better driver now. For me though, a difference of 2 psi makes a huge difference in handling and I am not even close to being considered a good or fast driver.
12-03-2017, 06:28 PM
Too much understeer ?
