Car Pulls to Left when Accelerating, Tire Losing Pressure

History: I recently put a new set of rims on my 00 996. Initially the new rear left tire would lose air pressure fairly rapidly, especially when I travelled at high speeds. I assumed this to be a problem with the new rims and tires I put on, so I had the wheel dealer replace the rear left wheel AND tire. Now the new tire and wheel exhibit the same pressure loss as the first!?! I know that there are no leaks in the tire. Symptoms: 1. Tire is losing pressure when travelling at highway speeds. 2. Car pulls to the left when accelerating, goes back to center when I let off. I'm taking a stab that this is this an rear-end alignment problem, with the rear left being terribly out of whack. Any ideas of what this could be so I can be somewhat educated when I go to the dealer or my local shop would be appreciated. This car is certified, with 1 year remaining on warranty... so I'm thinking of just taking it to the dealer, paying a premium and if there's something major in the suspension that's under warranty, they can fix it during the same visit.

You could swap the two rear wheels and see if the pulling moves to the right side. Even if the tires are "directional" that would still tell you if the problem is with the wheel. I take it the pulling didn't occur with your old wheels? If your car is certified, I don't think you need to say to the dealer: "I'm here for an alignment". I'd just say "my car pulls to the left" and let them figure it out. Are these the 20" wheels from your previous posts? You could be inviting the dealer to say: the suspension wasn't designed for those. I don't think losing pressure has anything to do with alignment.

Same pressure loss is so unlikely! Keep us posted!

Lower pressure on one side will make the car pull to one side acceleration. Two wheels nd tires losing air is more of a puzzle. Are you SURE they changed them?

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+1

Check your wheels/tires for a bead leak. Some of the aftermarket wheels, esp with chrome outers have bead leak issues with very low profile tires.

Just went through the same saga...... I have a 15" wide(yea wide) rear wheel with 335's PS2's on them. I had new ones mounted and went through the same experience. Don't know the width of your rim but in my case the tech had to remount the tire three times and use a bit of bead sealer to get the rim sealed. Depending on the wheel, you may want ot spot check the bead area and hit it with some cleaner or thinner. Also check to make sure that the mold tabs are removed from the edges where the tire mold release is. Good luck....

Are they one, two or three piece wheels?

Thanks for all the great ideas fellow Rennlisters. I ended up dropping it to the dealer late yesterday. They called and told me the could only find that the pressure was low on the rear left (which I just equalized earlier in the day no less)... and said that everything checked out. I'm picking it up later, so we'll see if the car still pulls after they checked and fixed all the pressures. I may take the rim/tire in again to have it dismounted/remounted. Guess I'm just unlucky with that particular side of the car! To answer Bob's question: Yes I'm sure it was a new wheel and tire. I brought the old one in by itself, then handed me the replacement and took the old one. Jim: One piece

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did they check the valve?

After taking it to the dealer, the tire continued to lose air! Turns out that my mystery problem turned out to be plain ole bad luck. I had a screw in the brand new tire!! Since patched. Go figure. I had it aligned too.. what's weird is that the car still PULLS to the left when hard accelerating and when I back off it goes back to center. So when I'm in 2nd, floor it, and keep the steering wheel perfectly straight... the car wants to veer left, albeit pretty slightly... when I let off it goes back to the right/center. Could this be a differential issue? I asked the dealer to investigate. Their response: "COULD NOT DUPLICATE PROBLEM" Bull****.

Pull to one side during hard acceleration is usually a thrust angle problem (unequal rear toe relative to the vehicle centerline). But since your alignment apparently checks out, I'd be looking for wear in a rear suspension component, allowing toe change under acceleration. You might want to find a different shop and have them take a better look.

Doug - thanks for your very insightful and technical input - I printed your response and will take it to the dealer with me. I intend to give the dealer one more crack at it (car is certified) and do a test drive with them so they can actually see the issue. If they don't/can't fix it, I know of a very highly recommended shop nearby which I will go to next. Thanks again.

Who is the dealer? You're close to AutoGallery, but they are usually pretty good.

Yeah, Auto Gallery... I think they hate me because my car: a.) wasn't bought there b.) is certified I deal with Don (who's a real courteous and nice guy) at the service manager level, who knows who actually does the work. On my writeup it says verbatim: CUST STATES WHEN ACCELERATING HARD THE CAR WILL PULL TO LEFT SEE DON 46 UNABLE TO DUPLICATE CUST CONCERN AT THIS TIME Fooey!

I'm surprised - Don has always been very helpful to me (Dave too, the new guy), and my car is CPO too. If you're around the Calabasas area in the daytime, PM me if you'd like to try a non-pulling-to-the-left 996 to compare.

An update. Today I traded from 20x11s to 20x10s wheels in the rear, but kept the same tires. Unfortunately I didn't see which tires went on what wheel (should have looked - doh!) .. read on. The weird part: Now my car pulls right upon acceleration and goes left/center when I let off (opposite of what was happening before where I would accelerate and the car would push left and go back to the right/center when I let off). Can I conclude that one of the tires in the rear is screwy? Something's definitely rotten in Denmark.