Car doesn't feel as stable with new tires & alignment

Went for a DE in my car a few weeks ago. It went great but I shredded one of the rear tires. So it goes in for a new set of rears and an alignment. Got the alignment printout back and found that my fronts were a bit off but the rear was pretty much ok. Well except for one component that is off by 1 degree because the shop tells me that the eccentric bolt is worn out and can't be adjusted to within specs. My problem is when I'm on the highway at speeds around 75 MPH the car begins to feel a little "floaty" and it almost feels like the rear is more unstable now. It's hard to describe but I remember when I had a car with bad wheel bearings that it would pull a bit - almost like that but not as blatant. My bearings were checked before the DE so don't think it's that plus usually there is a noise associated with it and there's nothing here. Is there anything in particular I should check for? The shop that did the alignment is not a Porsche specific shop but they did install my M030 ROW suspension so they should (hopefully) know what they're doing. The fact that it's in spec should be a sign that it was done right, correct? Also how much of a concern is it that the eccentric bolt is worn and it can no longer be adjusted?

How many miles on the new rears? Do the rears match the fronts? I know silly questions.

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Maybe 100 miles on the new tires at this point. Yes both are Bridgestone tires which I've been using now for the past 5+ years or so without incident.

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What are the alignment numbers? A "1 degree" out of spec adjustment is not a good alignment in my opinion. If the adjuster is worn it should be replaced so the setting can be dialed in right on the money. Be sure tire pressures are correct. If uni-directional tires be sure they are mounted correctly. Beyond that the alignment numbers might tell the story.

Need another 300 miles, or so, to scrub off the mold release on the new rear tires. Should improve.

I'm just a simpleton here, but were the new tires balanced? This can cause uneasy vibrations at high speeds. Happened to me in my car when I would go above 70mph. Thought it was the bearings at first, but turns out three tires were severely out of balance.

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This is confusing; how is a bolt "worn out"? It's just a bolt. The only way I can envision it being "worn out" is that threads are stripped or the locknut has lost it's locking-ness. In either case it's simple to just replace those parts, because it would be unsafe to drive around on it if it's not able to be tightened and hold firm. Should not be complicated, or expensive.

the bolt shank is oval and can definitely wear out.

the closer the rear camber is set to neutral, the more floaty the car will feel (until you induce more change of direction input, then it settles). The closer the rear camber to neutral, the longer the tires will last. I do hope they set both sides the same......... Now, take the car to a P car indie who knows what they are doing................... and have the camber discussion with him. Some will set camber at neutral simply because the car STILL handles better than 95% of the cars on the road, ANNNNNNNNNNd the tires last longer than 12k miles.......

Ok I might have found what it is but haven't been able to get up to high speeds to test the theory yet. Someone between the tire shop and the alignment shop filled up the front tire pressure to 50 PSI!!! I lowered it back down to 36 PSI to see if that might be what was causing it. As for the alignment itself, I misspoke before saying it was 1 degree off - it is actually 0.2 degrees off on the right-rear camber. Here are the measurements they printed for me: Is it really that big of a deal to have this off? It's been this way for the last few alignments and even at the dealer they've mentioned it but made it appear as if it wasn't that big of a deal. This shop did take a photo of the eccentric bolt. The mechanic mentioned to me that the bolt and washer itself is not the problem, it's where the adjustment itself takes place is on the body of the car and that area is worn out. He told me I would have to weld a plate there to fix it because it's not something that is part of the suspension itself and can't be replaced. Here is the photo he took: Anyone else encounter this? What have you done about it, if anything?

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I think you need a new shop. 1) 50 PSI, holy cow. 2) I don't think the technician understands how the adjuster works. The photo provided is terrible and it's hard to tell if there's actually a problem, but it looks like it's probably fine. 3) The adjustment is not in the "body", it's in the aluminum subframe. I would not suggest letting them weld a plate to your subframe. 4) The eccentric head/washer on the bolt sits in a fixed pocket on the subframe so as you rotate the bolt, the centerline of the bolt travels laterally across the car, moving the bottom of the tire in or out and adjusting the camber angle. Presumably they're saying that pocket is worn out on your car, but even from that bad picture it looks like the adjuster is sitting in the pocket and everything is fine. It DOES appear to be adjusted almost all the way in, i.e. almost the most positive camber value. You might be able to dial in slightly more positive camber by rotating the bolt slightly clockwise, but you're at about the limit. Welding parts onto the subframe is not going to allow it to be adjusted in further. 5) I would leave it as-is and not let this shop work on the car any more. It's close enough. A few tenths of a degree won't hurt you for street driving, and a little extra negative camber is no bad thing if you drive the car aggressively. 6) This all assumes the nut or bolt aren't broken or stripped or something that we can't see from this angle. If that's the case, just replace the nut and bolt. Again, no welding!!!!

/\ /\ Agree with this, (without any more details pictures / data.) I do think both sides should be set the same, especially for camber. I also think this should be done by a knowledgeable wrench.

whatever GRETCH agree though I can poast my latest alignment spec from a good 996 tech that did mine last summer. He was very detailed about it. Factory specs on alignment ensure proper handling at speed, nice inward bend of between -1 and -2 degrees for rears IIRC plus inward (not +) toe for proper launch characteristics. Really drives the Carrera forward and in a stable manner.

who pissed in your wheaties??????? simple opinion............ that is all I offer. I may be dead wrong. lighten up francis.

Would be great if you could post your settings im just working on my suspension at the moment and it needs setting up afterwards!

Alignment machine seems to think so. The setting graphic is in red. I've had my cars aligned a number of times and at no time did the car ever leave the rack with any setting in the red. Sometimes the tech would have the settings a bit off of "center" but in the same direction and the same amount. If the setting can't be brought into spec this suggests something may be bent or damaged.

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This.

Hmm. 0 camber in the front as well as 50 PSI should be part of the culprit. I recall the fronts need some negative camber as well.

At those specs, your car isn't aligned. There is no other way to slice it. As others have suggested, I think you need second opinion from a better shop.

I missed 50psi. Might as well use the same tires as Fred Flintstone...