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Agreed with the alignment. One other piece of info....
If I'm on a legit smooth, as in newly paved highway stretch or just a less bumpy one, there is no shake on the wheel. But if there are small imperfections (I'm not talking major potholes, but just an average stretch on a NJ highway) , that's when I get the shake. It's almost as if the steering is ultra sensitive and is giving me too much feedback. Hopefully that makes sense.
How many miles on your car ? What roads in New Jersey? - I get the same thing coming off 78W going onto 24W which has been recently paved. Back in Dec I had a very good road force balance and things seem better, now it seems to be getting worse again. My 2005 car only has 38k on it so is it possible to have worn tie rods from age? Also I do a lot of turn/stop/turn in maneuvering out of my garage and jockeying around other cars in the driveway which may exacerbate wear. I have some new wheels and MPS4's going on in the next week or so, so that will help determination as to if its tire/wheel issue, etc.
If that's the case, you're definitely going to wander. The Porsche factory specs have a LOT of rear toe and a little on the front. You can play around with the specs a bit to address tire wear but you really need to input the correct specs into the machine to know what the acceptable limits are. Just aiming for zero doesn't work on most cars, let alone a rear-engine sports car. Have your buddy use the factory specs and I think you'll find the handling to be much more stable.
Positive rear toe in is added as a safety net to create understeer to save novice drivers from themselves. Porsche does not add toe to make the car roll smoother. Taking toe out will make the car run smoother and track just as well. I run neutral settings as I prefer a car with oversteer and do not want or need a safety net. My cars run and track just fine.
What he mentions seems like a bent rim or bad suspension part. Also, make sure you are getting high speed balancing.
How many miles on your car ? What roads in New Jersey? - I get the same thing coming off 78W going onto 24W which has been recently paved. Back in Dec I had a very good road force balance and things seem better, now it seems to be getting worse again. My 2005 car only has 38k on it so is it possible to have worn tie rods from age? Also I do a lot of turn/stop/turn in maneuvering out of my garage and jockeying around other cars in the driveway which may exacerbate wear. I have some new wheels and MPS4's going on in the next week or so, so that will help determination as to if its tire/wheel issue, etc.
Mostly on the parkway/280. Roughly 71k miles on my car. It's driven fairly often.
Originally Posted by Doug H
Positive rear toe in is added as a safety net to create understeer to save novice drivers from themselves. Porsche does not add toe to make the car roll smoother. Taking toe out will make the car run smoother and track just as well. I run neutral settings as I prefer a car with oversteer and do not want or need a safety net. My cars run and track just fine.
What he mentions seems like a bent rim or bad suspension part. Also, make sure you are getting high speed balancing.
I'd go against rims since it happens with 2 different sets. I'm going to recheck the control arms and tie rods this weekend when I get the chance.
Positive rear toe in is added as a safety net to create understeer to save novice drivers from themselves. Porsche does not add toe to make the car roll smoother. Taking toe out will make the car run smoother and track just as well. I run neutral settings as I prefer a car with oversteer and do not want or need a safety net. My cars run and track just fine.
Porsche factory specs include toe-in on the front wheels, as do the alignment specs of almost all rear wheel drive cars on the road today. Toe-in is needed on cars with flexible bushings to account for suspension deflection when driving, and aids in straight tracking when on the highway, so yes, toe-in does help with smoother, straighter running. Larger adjustments affect under- and over-steer, but even small variations of front toe can result in either darty steering or wander (or both).
While zero toe on the front wheels is used sometimes on sports cars, it usually increases front tire wear and decreases straight line stability, which is why Porsche specifies toe-in for the factory-recommended settings. What people do on the track has no bearing in this discussion.
This may or may not be the issue with the OP’s ‘wandering” steering, but I feel like you’re arguing just to be argumentative, because some of what you’re saying is demonstrably false. And just as an aside, bent wheels vibrate. They don’t cause a car to wander on the road.
Porsche factory specs include toe-in on the front wheels, as do the alignment specs of almost all rear wheel drive cars on the road today. Toe-in is needed on cars with flexible bushings to account for suspension deflection when driving, and aids in straight tracking when on the highway, so yes, toe-in does help with smoother, straighter running. Larger adjustments affect under- and over-steer, but even small variations of front toe can result in either darty steering or wander (or both).
+1
You need some, even if a little front toe. If it's set at totally zero and you have any rubber components in the front suspension (in the LCAs, tie rods, etc) the cornering loads can make the 0 toe go to outward toe and cause a very unstable cornering car. I had a loose suspension component on my 928 that did exactly this and it was such and aggressive and jerky mid corner "crazy Ivan" that it about put me into the concrete highway wall. This happened right after an alignment where the shop didn't notice the loose suspension A-arm bushing and set the alignment very close to neutral, but when things shifted under load in the first medium speed corner it almost got very ugly very quickly.
The rear toe settings are less sensitive from a handling perspective and you can take those almost to 0 to prolong your tire life. Keep a little toe in for the front settings.
I have zero rubber components in my suspension so no wear or bushing deflection in corners and use these settings where the front is almost 0 - similar to what Doug is referring to, but a street car with normal suspension should not from a safety perspective because of the bushing deflection mentioned by Iceter. Both sides of the front should actually be set the same, but one side was maxed out and this is as close as we could get it, but the car drives perfectly.
When I do my next set of tires in about another 5,000 miles, I'll have it done again and have them match the other side to the one that's maxed out. The next tires will be a 245/40 up front and a 325/30 in the rear (12" wide rear wheels) making the rolling diameter 26.7 for both, which will keep the PSM system happy.
Porsche factory specs include toe-in on the front wheels, as do the alignment specs of almost all rear wheel drive cars on the road today. Toe-in is needed on cars with flexible bushings to account for suspension deflection when driving, and aids in straight tracking when on the highway, so yes, toe-in does help with smoother, straighter running. Larger adjustments affect under- and over-steer, but even small variations of front toe can result in either darty steering or wander (or both).
While zero toe on the front wheels is used sometimes on sports cars, it usually increases front tire wear and decreases straight line stability, which is why Porsche specifies toe-in for the factory-recommended settings. What people do on the track has no bearing in this discussion.
This may or may not be the issue with the OP’s ‘wandering” steering, but I feel like you’re arguing just to be argumentative, because some of what you’re saying is demonstrably false. And just as an aside, bent wheels vibrate. They don’t cause a car to wander on the road.
I was actually referring to the steering wheel back and forth "waiving at [him]". I have had that on 2 different 911s. Both times it was a bent rim causing a little shudder.
What I am saying about rear toe is correct and look at Petza's wife's fronts below.
RE: Front Toe
Below shows Petza's wife's car with total toe in of .07. OP's total toe is .05 so are you saying the difference between OP's .05 and Petza's wife's .07 would cause float and shudder on OP's car, but not Petza's wife's 997.1 S?
RE: Rear Toe
On Petza's rears, he still has the safety net, understeer inducing positve rear toe in which he concedes above he could take toe out and Petza says in his post I linked below that "you want very close to zero toe" in the rear. In your post I responded to, you said: "Porsche factory specs have a LOT of rear toe" so I addressed rear toe.
I don't care enough to make stuff up to be argumentative. Just trying to help OP as I had similar shudder caused by bent rims on both occasions. As I and other have said, float is perhaps due to a worn suspension part and definitely not due to a lack of rear toe in.
This picture below is of Petza's wife's alignment from the above link. I run a little less toe in front, neutral toe in rear and factory camber and have no float or shudder.
I was actually referring to the steering wheel back and forth "waiving at [him]". I have had that on 2 different 911s. Both times it was a bent rim causing a little shudder.
What I am saying about rear toe is correct and look at Petza's wife's fronts below.
RE: Front Toe
Below shows Petza's wife's car with total toe in of .07. OP's total toe is .05 so are you saying the difference between OP's .05 and Petza's wife's .07 would cause float and shudder on OP's car, but not Petza's wife's 997.1 S?
RE: Rear Toe
On Petza's rears, he still has the safety net, understeer inducing positve rear toe in which he concedes above he could take toe out and Petza says in his post I linked below that "you want very close to zero toe" in the rear. In your post I responded to, you said: "Porsche factory specs have a LOT of rear toe" so I addressed rear toe.
I don't care enough to make stuff up to be argumentative. Just trying to help OP as I had similar shudder caused by bent rims on both occasions. As I and other have said, float is perhaps due to a worn suspension part and definitely not due to a lack of rear toe in.
This picture below is of Petza's wife's alignment from the above link. I run a little less toe in front, neutral toe in rear and factory camber and have no float or shudder.
Doug, thanks for throwing up that other alignment of mine from my wife's car. She doesn't drive that car the same way some of us guys do, so a focus for her car was to preserve tire life while still making the handling dynamics stable and predictable.
On my car, I had the shop use GT3 alignment settings since I essentially have a GT3 suspension and need the car to remain stable and predictable at much higher speeds and loads than my wife's car. Her alignment is "Safer" in some respects where she has more front toe than I do so her front end never ends up neutral or near 0 no matter the loads. She was wearing rear tires excessively for no real reason so we made her rears run very straight and close to 0. I left a bit more rear toe in mine because of the possibility of breaking the rear loose due to the increased horsepower, higher speeds, and more aggressive driving style. When DDing her car, she puts 3x the mileage on hers that I do on mine so I'm OK with a little faster rear tire wear on mine in the interest of handling.
I've also driven her car in a more aggressive manner and it drives fine - it's not glued to the road like mine, but is on a stock suspension and different tires, so that's expected.
Doug, thanks for throwing up that other alignment of mine from my wife's car. She doesn't drive that car the same way some of us guys do, so a focus for her car was to preserve tire life while still making the handling dynamics stable and predictable.
On my car, I had the shop use GT3 alignment settings since I essentially have a GT3 suspension and need the car to remain stable and predictable at much higher speeds and loads than my wife's car. Her alignment is "Safer" in some respects where she has more front toe than I do so her front end never ends up neutral or near 0 no matter the loads. She was wearing rear tires excessively for no real reason so we made her rears run very straight and close to 0. I left a bit more rear toe in mine because of the possibility of breaking the rear loose due to the increased horsepower, higher speeds, and more aggressive driving style. When DDing her car, she puts 3x the mileage on hers that I do on mine so I'm OK with a little faster rear tire wear on mine in the interest of handling.
I've also driven her car in a more aggressive manner and it drives fine - it's not glued to the road like mine, but is on a stock suspension and different tires, so that's expected.
Doesn't she actually have less front total toe than you?
The points are: (1) total front toe of 0.00 would still be in range; (2) that you can run neutral rear toe like I do and as you have recommended; and (3) that OP's alignment, in and of itself, should not be causing wheel shudder or a floating feeling.
I only initially responded to Iceter indicating a 997 needed a lot of rear toe and seemingly indicating that neutral rear toe could cause OP's symptoms.
Do you not agree that the positive rear toe in by Porsche is a safety net that can be dialed out to make the car handle and drive better. Those of us that can drive cars at the limits don't want understeer dialed in, especially dialed in with positive rear toe in.
Don't have my alignment sheet, but I believe I run .01ish front toe in per side and pretty much .00 to .01 toe in the rear. My total toe would not be much different than OP's above, but mine is more symmetrical.
Do you not agree that the positive rear toe in by Porsche is a safety net that can be dialed out to make the car handle and drive better. Those of us that can drive cars at the limits don't want understeer dialed in, especially dialed in with positive rear toe in.
l/QUOTE]
Totally agree... handle and drive better, and make the tires last longer, but only for people that understand vehicle dynamics and proper driving technique. Since anyone can plunk down money and buy a Porsche, they need to make the cars have a larger safety margin for driver error and improper techniques so they don't get sued for selling unsafe, unpredictable cars.
Totally agree... handle and drive better, and make the tires last longer, but only for people that understand vehicle dynamics and proper driving technique. Since anyone can plunk down money and buy a Porsche, they need to make the cars have a larger safety margin for driver error and improper techniques so they don't get sued for selling unsafe, unpredictable cars.
Newer 911s without the semi-trailing-arm rear suspension are so nice and stable at or near the limits, but I am sure Porsche got sued a lot back in the day hence the 930s widow maker nickname.
Again, my only reason for commenting was that neutral rear toe is not going to cause floating or steering wheel shudder and neutral or near neutral front toe is actually within spec as well.
You pulling some negative camber out on your wife's car would definitely help with reducing tire wear.
I bet that Ruf of your handles like a dream on the track.
Newer 911s without the semi-trailing-arm rear suspension are so nice and stable at or near the limits, but I am sure Porsche got sued a lot back in the day hence the 930s widow maker nickname.
Again, my only reason for commenting was that neutral rear toe is not going to cause floating or steering wheel shudder and neutral or near neutral front toe is actually within spec as well.
You pulling some negative camber out on your wife's car would definitely help with reducing tire wear.
I bet that Ruf of your handles like a dream on the track.
We got 18,000 miles out of her last set of rears with these settings, so I'm pretty happy with that.
The RUF would if I'd put it on a track, but it's too valuable and I don't want to pay for separate track insurance, so it's track time is limited to some fairly quick parade laps at Road Atlanta, but it doesn't even breath hard to keep up with the pace car on those.
It gets its real workouts in the SC, NC, TN, and GA mountains, which is the reason I have it setup this way.
I'm thinking that since this started after I lowered the car, could this just be a case of bump steer? I didn't see any loose components up front, so I'm thinking my tie rod's geometry is just out of whack. From my experience, a loose arm or bushing would cause a noise or a shake/shimmy more consistently or even at lower speeds. Sounds like a possibility?
Bump steer happens when the car hits a bump and wants to change direction because of the suspension geometry. What you describe with your steering wheel waving back and forth is not that, it's something in the front end that's either out of balance or worn. Have you carefully inspected the tread on the tires from my previous note? The fact that it happens on 2 different sets of wheels and tires says its likely something on the car, and not the wheels or tires.
03-06-2020 | 12:06 PM
