Pirelli P Zero - does your GL wander?
12-10-2019, 09:38 PM
#1
Super Member
Thread Starter
Pirelli P Zero - does your GL wander?
I'm wrapping up my first week of ownership on my 2010 GL 550. Overall impression: I'm very happy with my find!
One thing which caught me off guard was that the car likes to wander at any speeds but it becomes really noticeable above 35mph/60kph. It also happens at lower speeds, but it is not as impressionable. This happened when I first got behind the wheel to take the car home from the mechanic. I thought I had a flat front right because the pull to the right was so much, and it happened immediately after leaving the mechanic. The road is not that great and in places has "ruts" on the asphalt from the vehicles traveling on it, while in others it's patched heavily.
The car came equipped with 295/40R21 PZeros which still have decent tread left. At first I thought maybe alignment (side effect of shipping via rail/trailer, which is how I got the car to come to me), or perhaps suspension issues. But after some driving over the past few days, it does this both to the left and right, and when it does not, it goes straight as an arrow w/ hands off the wheel. I think it's the tire with its center strip which makes the car feel like it's on rails (good when the road is in good condition and bad when there are patches or in turns with higher camber). I have had to fight the wheel in the opposite direction to counter for this "rail" effect.
I used to have a tire with a similar design, although not Pirelli, on a hatchback and I recall that the car tended to behave the same, although it was not nearly as pronounced. Probably because its steering was dialed differently and it was less than half the weight of the GL.
The car was inspected by my mechanic before being registered/plated - mandatory for my province. He would not have passed it if there were issues with suspension or steering. That gives me confidence that it's not mechanical/suspension issues. The car is level at all 4 corners.
For those of you who have or had the P Zero, did your GL tend to wander?
Image links courtesy of Tirerack
https://www.tirerack.com/images/tires/pirelli/pi_pzero_pdptrd.jpg
https://www.tirerack.com/images/tires/pirelli/pi_pzero_pdpcrop.jpg
Nik
One thing which caught me off guard was that the car likes to wander at any speeds but it becomes really noticeable above 35mph/60kph. It also happens at lower speeds, but it is not as impressionable. This happened when I first got behind the wheel to take the car home from the mechanic. I thought I had a flat front right because the pull to the right was so much, and it happened immediately after leaving the mechanic. The road is not that great and in places has "ruts" on the asphalt from the vehicles traveling on it, while in others it's patched heavily.
The car came equipped with 295/40R21 PZeros which still have decent tread left. At first I thought maybe alignment (side effect of shipping via rail/trailer, which is how I got the car to come to me), or perhaps suspension issues. But after some driving over the past few days, it does this both to the left and right, and when it does not, it goes straight as an arrow w/ hands off the wheel. I think it's the tire with its center strip which makes the car feel like it's on rails (good when the road is in good condition and bad when there are patches or in turns with higher camber). I have had to fight the wheel in the opposite direction to counter for this "rail" effect.
I used to have a tire with a similar design, although not Pirelli, on a hatchback and I recall that the car tended to behave the same, although it was not nearly as pronounced. Probably because its steering was dialed differently and it was less than half the weight of the GL.
The car was inspected by my mechanic before being registered/plated - mandatory for my province. He would not have passed it if there were issues with suspension or steering. That gives me confidence that it's not mechanical/suspension issues. The car is level at all 4 corners.
For those of you who have or had the P Zero, did your GL tend to wander?
Image links courtesy of Tirerack
https://www.tirerack.com/images/tires/pirelli/pi_pzero_pdptrd.jpg
https://www.tirerack.com/images/tires/pirelli/pi_pzero_pdpcrop.jpg
Nik
Last edited by expl0rer; 12-10-2019 at 09:45 PM. Reason: more info
12-11-2019, 08:51 AM
#3
Super Member
Thread Starter
Good thinking! I didn't consider tire pressure possibly being a problem, but it's an obvious thing to look at! A classic example of "overthinking" the problem. 
I measured this morning: 32psi front, 38psi rear. Seems low for 21s. IIRC they should be 35psi front, 42psi rear. In the winter is 3-5 lbs lower acceptable for the 21s?
32/38 I believe is the pressure for 18-19" tire packages.
I measured this morning: 32psi front, 38psi rear. Seems low for 21s. IIRC they should be 35psi front, 42psi rear. In the winter is 3-5 lbs lower acceptable for the 21s?
32/38 I believe is the pressure for 18-19" tire packages.
12-11-2019, 10:27 AM
#4
Member
Good thinking! I didn't consider tire pressure possibly being a problem, but it's an obvious thing to look at! A classic example of "overthinking" the problem.
I measured this morning: 32psi front, 38psi rear. Seems low for 21s. IIRC they should be 35psi front, 42psi rear. In the winter is 3-5 lbs lower acceptable for the 21s?
32/38 I believe is the pressure for 18-19" tire packages.
I measured this morning: 32psi front, 38psi rear. Seems low for 21s. IIRC they should be 35psi front, 42psi rear. In the winter is 3-5 lbs lower acceptable for the 21s?
32/38 I believe is the pressure for 18-19" tire packages.
Wider tires with low profiles usually do cause wandering and its certain that the 21's fit that description. Run flat construction can add to the problem as well. If the wheels are not original, you could have an issue with scrub radius from as different offset and that would exaggerate the issue. If they are original, then we can rule that out.
Another thing to consider is that the alignment on these things is very dependent on the ride height for the airmatic being dead-on during adjustment and needs to be done with DAS.
12-11-2019, 10:45 AM
#5
MBWorld Fanatic!
How positive are you on the remaining tread depth? I had the same issue about 4 years ago. I think they were Yokahamas, but I really don't think the brand or tread style matters. In my case, it just turned out that the tread was worn enough that it caused the issue (as it didn't happen until the tires got worn enough). As soon as I put new tires on, the vehicle was immediately better - much more of a "planted" feel.
But, maybe you should take the vehicle to a shop that specializes more in suspension/alignment (camber/toe/etc). If those things aren't correct then it seems logical that that could affect things. I don't think that alignment is necessarily something needed for an inspection - unless maybe if it's obviously/way off? If it wasn't/isn't obviously noticeable, he probably would not have picked up on it.
But, maybe you should take the vehicle to a shop that specializes more in suspension/alignment (camber/toe/etc). If those things aren't correct then it seems logical that that could affect things. I don't think that alignment is necessarily something needed for an inspection - unless maybe if it's obviously/way off? If it wasn't/isn't obviously noticeable, he probably would not have picked up on it.
12-11-2019, 12:40 PM
#6
Super Member
Thread Starter
I believe the reason for the higher pressures with the 21's is because the tire has much less sidewall than the 18 or 19" tire so you need more pressure to prevent wheel damage from potholes. Over inflated tires, not under inflated usually cause wandering,
Wider tires with low profiles usually do cause wandering and its certain that the 21's fit that description. Run flat construction can add to the problem as well. If the wheels are not original, you could have an issue with scrub radius from as different offset and that would exaggerate the issue. If they are original, then we can rule that out.
Another thing to consider is that the alignment on these things is very dependent on the ride height for the airmatic being dead-on during adjustment and needs to be done with DAS.
Wider tires with low profiles usually do cause wandering and its certain that the 21's fit that description. Run flat construction can add to the problem as well. If the wheels are not original, you could have an issue with scrub radius from as different offset and that would exaggerate the issue. If they are original, then we can rule that out.
Another thing to consider is that the alignment on these things is very dependent on the ride height for the airmatic being dead-on during adjustment and needs to be done with DAS.
Since they are not winter tires, I wonder if the colder weather changing their characteristics plays some element in this too. I have a dedicated set of winter 255/55R19 on OEM wheels which I was holding off on mounting mainly to get acquainted with the car's handling in its current configuration.
Your mention of ride height makes me wonder sport or comfort setting on the airmatic or raising the suspension a notch with the dial on the on/offroad package might make a difference. I will give those a test run.
How positive are you on the remaining tread depth? I had the same issue about 4 years ago. I think they were Yokahamas, but I really don't think the brand or tread style matters. In my case, it just turned out that the tread was worn enough that it caused the issue (as it didn't happen until the tires got worn enough). As soon as I put new tires on, the vehicle was immediately better - much more of a "planted" feel.
But, maybe you should take the vehicle to a shop that specializes more in suspension/alignment (camber/toe/etc). If those things aren't correct then it seems logical that that could affect things. I don't think that alignment is necessarily something needed for an inspection - unless maybe if it's obviously/way off? If it wasn't/isn't obviously noticeable, he probably would not have picked up on it.
But, maybe you should take the vehicle to a shop that specializes more in suspension/alignment (camber/toe/etc). If those things aren't correct then it seems logical that that could affect things. I don't think that alignment is necessarily something needed for an inspection - unless maybe if it's obviously/way off? If it wasn't/isn't obviously noticeable, he probably would not have picked up on it.
You are correct that the alignment is not necessarily a reason to fail inspection. I asked my mechanic to give the car a good look over and he did not think anything was amiss. He's not an MB guy, but he is good at his trade. That said, the GL is not your run of the mill car either. I will have to look into a specialized alignment/suspension shop. I might have to take it to the dealer if DAS is necessary for alignment.
Thanks for the suggestions guys! Much appreciated! It's comforting to know that others have had similar experiences and have found ways to rectify them.
12-11-2019, 01:14 PM
#7
MBWorld Fanatic!
I think I have around 6/32" tread. If my assumption that "worn out" is 2/32" tread, I should be roughly about halfway through the tire's usable tread. That doesn't mean that the tires may not need replacing before they could make it to 2/32". Perhaps getting the 255/55R19 winter tires on the car will help isolate the issue to the tire package.
You are correct that the alignment is not necessarily a reason to fail inspection. I asked my mechanic to give the car a good look over and he did not think anything was amiss. He's not an MB guy, but he is good at his trade. That said, the GL is not your run of the mill car either. I will have to look into a specialized alignment/suspension shop. I might have to take it to the dealer if DAS is necessary for alignment.
Thanks for the suggestions guys! Much appreciated! It's comforting to know that others have had similar experiences and have found ways to rectify them.
You are correct that the alignment is not necessarily a reason to fail inspection. I asked my mechanic to give the car a good look over and he did not think anything was amiss. He's not an MB guy, but he is good at his trade. That said, the GL is not your run of the mill car either. I will have to look into a specialized alignment/suspension shop. I might have to take it to the dealer if DAS is necessary for alignment.
Thanks for the suggestions guys! Much appreciated! It's comforting to know that others have had similar experiences and have found ways to rectify them.
Your mechanic probably didn't put it up on an alignment rack to check things. If so, he would have provided a printout of the specs. You don't necessarily need to go to an MB dealer - just someone that knows what they're doing. For example, there's a shop around me that has been doing alignments for many decades and that's a big part of their business. It's the only place I've taken all of my cars (for about 15/20 years, now) as they always seem to get it right the first time. Ask around - I'm sure you can find a shop like that.
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12-11-2019, 02:45 PM
#8
Super Member
Thread Starter
Mine were well under 6/32" when I was having the issue. I'd be surprised if 6/32" is causing the problem - unless the tread is worn uneven.
Your mechanic probably didn't put it up on an alignment rack to check things. If so, he would have provided a printout of the specs. You don't necessarily need to go to an MB dealer - just someone that knows what they're doing. For example, there's a shop around me that has been doing alignments for many decades and that's a big part of their business. It's the only place I've taken all of my cars (for about 15/20 years, now) as they always seem to get it right the first time. Ask around - I'm sure you can find a shop like that.
Your mechanic probably didn't put it up on an alignment rack to check things. If so, he would have provided a printout of the specs. You don't necessarily need to go to an MB dealer - just someone that knows what they're doing. For example, there's a shop around me that has been doing alignments for many decades and that's a big part of their business. It's the only place I've taken all of my cars (for about 15/20 years, now) as they always seem to get it right the first time. Ask around - I'm sure you can find a shop like that.
12-11-2019, 04:18 PM
#9
Super Member
Thread Starter
I drove around town for a little while this afternoon (at or below 35mph/60kph) and set different ride heights. First for baseline I used Comf/Sport off (I will call this base), which is the setting I have been using in town - I have a good feel for what the car would do, since this was my preferred setting for city driving so far.
Next came Sport - and the wandering was worse. The ride height is lowered by about .6 inches, IIRC along with a myriad of other changes, one of which is the steering. I am not surprised that I would feel the wander more.
Next came Comfort (ride height is raised .06 over base IIRC) - wandering improved (lessened) over Sport, but I would not say it was noticeably better than "base"
Next came the manual dial. I raised the Airmatic one notch (of available three; the second and third I believe can be set with the car either in offroad modes, i.e. locked diffs, or stationary) - marginally less wander, but still present quite a bit.
Winter tires are going on the car Monday. We shall see if the smaller contact patch and higher sidewall will mitigate this. In the interim, I'll see if I have a specialized alignment shop close by.
Next came Sport - and the wandering was worse. The ride height is lowered by about .6 inches, IIRC along with a myriad of other changes, one of which is the steering. I am not surprised that I would feel the wander more.
Next came Comfort (ride height is raised .06 over base IIRC) - wandering improved (lessened) over Sport, but I would not say it was noticeably better than "base"
Next came the manual dial. I raised the Airmatic one notch (of available three; the second and third I believe can be set with the car either in offroad modes, i.e. locked diffs, or stationary) - marginally less wander, but still present quite a bit.
Winter tires are going on the car Monday. We shall see if the smaller contact patch and higher sidewall will mitigate this. In the interim, I'll see if I have a specialized alignment shop close by.
12-11-2019, 06:41 PM
#10
MBWorld Fanatic!
Good luck!
I meant to add that I certainly don't want to lead you to believe that your alignment is out and that's DEFINITELY the cause - just that it is a possible/logical explanation.
I meant to add that I certainly don't want to lead you to believe that your alignment is out and that's DEFINITELY the cause - just that it is a possible/logical explanation.
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expl0rer (12-11-2019)
12-11-2019, 07:23 PM
#11
Super Member
Thread Starter
The information you guys have shared is great! Thanks for that.I'll wait till the winters are mounted and drive on them for a few days. Like you said, it makes sense that it could be the suspect soon or alignment. It would be good to have a shop on hand if this wandering continues.
12-13-2019, 10:33 AM
#13
Super Member
Thread Starter
Good idea, thanks for thinking of this. Worn suspension components would have been one of the items to look for during the inspection which was required for the car to be registered/plated. Nothing stood out to my mechanic.
12-16-2019, 06:02 PM
#15
Super Member
Thread Starter
Winter tires went on this afternoon. After the car leveled itself (more on this later) which took maybe about half a km of driving it has been driving as straight as can be. No pulling or pushing. It feels well planted and responsive to my steering input. Road imperfections don't unsettle its direction like before with the 21 inch wheels/tires. Maybe those summer tires will need changing sooner than I thought. Next year I'll rotate them and if the problem is still there, will consider seriously a replacement.
About the leveling. I noticed thile they were torquing the wheels on the garage floor that she was leaning towards the front right. 1.5 inches diference as my mechanic measured. Perhaps the car being up in the air might have affected the shocks? I will check it tomorrow am to see if there is any difference between the corners.
About the leveling. I noticed thile they were torquing the wheels on the garage floor that she was leaning towards the front right. 1.5 inches diference as my mechanic measured. Perhaps the car being up in the air might have affected the shocks? I will check it tomorrow am to see if there is any difference between the corners.
