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YOUR RESEARCHRear Tire and Alignment recos/questions
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Replace 90% of all suspension parts 15,000 miles ago
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Performed · outcome unconfirmed · Original poster
I replaced 90% of all suspension parts 15,000 miles ago.
Leading evidence: 'Replace 90% of all suspension parts 15,000 miles ago' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'bit' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check ride height while you are at it' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
Unfortuantely the shop did not give me the alignment specs but I can ask them when I get the new rear tires swapped on.
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Suspected cause · Original poster
I figured that Porsche has a little camber issue because of the rear engine and also probably a bit so that it corners better.
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Suspected cause · Original poster
I also had a bad wreck 25 years ago that still lives in the back of my mind so I'm probably a lil extra sensitive to the back end washing out.
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Suggestion
To expand the range of toe adjustment you would use these lockout plates that eliminate the factory eccentric washer and then replace the stock fixed length toe arms with an adjustable style that provides for a wider range of adjustability.
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Suggestion · Original poster
By my imagination, if you're running a slight positive camber and thus slightly more on the inner part of the tire, it would make the car follow ruts more and move around in the rear.
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Suggestion
To expand the range of toe adjustment you would use these lockout plates that eliminate the factory eccentric washer and then replace the stock fixed length toe arms with an adjustable style that provides for a wider range of adjustability.
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I drive a 996 carbrio. Purchased it last year and immediately put new tires on. 225/40 18's in front and 285/40 18's on the back. Michelin Pilot Sport 4S's.
I've put ~ 25,000 miles on the car this year and the rears are already due to be replaced. After the fact, I read,
"30,000 Miles warranty -
Half mileage for rear if different size than front
"
I have 2 questions:
1) What rear tire would be a good recommendation that does not need to be replaced every 20,000 miles? I don't drive crazy, just a lot. No track days, just street driving.
2) alignment - I feel like the car drifts in the back, rides in the ruts of the road a bit. I had the car aligned when I put the new tires on, and like all porsches the insides of the rear tires are wearing slightly faster than the outside.
Does anyone have other alignment specs that help the car to not feel so tail happy in bad weather?
The continental dsw4+ is a great driving tire. I tjinknit has a treadwear in the 350 range so it should last but 20k out of a sports car tire is pretty good.
Fot the alignment just go with the factory spec. The alignment shop should have the numbers. I would guess the rear toe or camber is a little too high
Yup, that's correct. Apparently they are factory widebody specs. I bought the car from Cali (I live in MN) with 15 year old tires. I ordered the tires kinda on short notice with not as much research as I would like to have done.
They fit fine. 35 psi. Unfortuantely the shop did not give me the alignment specs but I can ask them when I get the new rear tires swapped on.
Thanks for this. I figured that Porsche has a little camber issue because of the rear engine and also probably a bit so that it corners better. By my imagination, if you're running a slight positive camber and thus slightly more on the inner part of the tire, it would make the car follow ruts more and move around in the rear. Plus wider tires tend to wander more, don't they?
These are all anecdotal thoughts, which is why I wanted to make the post so I can get others opinions.
Honestly, the car is scary sometimes how it wanders in the back. But... I also had a bad wreck 25 years ago that still lives in the back of my mind so I'm probably a lil extra sensitive to the back end washing out.
I dont' see any signs of the bolt slipping. One of them is new, I know that. I'm hoping to get a bit more insight so next time I go into the shop I can be more specific with what I want...
Is the car on stock suspension or lowered? If it is lowered it may be beyond the factory range of adjustability for toe in the rear.
I had this same/similar problem with my car. It has KW coilovers and the PO had it dropped as low as it could go and the car would burn through a set of rears in like 5000 miles wearing almost exclusively on the inside edge.
The solution people here pointed me to was to install aftermarket adjustable rear toe arms and the Tarrett kit that locks out the adjustment of the eccentric bolt, RAISE the cart to GT3 ride height and align to stock specs. The results were great.
For tires, I love my Michelin PS4S's.
C4S OE is 295/30. Your initial post didn�t specify a C4S. Your current tire size is 5 cm taller than the 295/30 spec. This results in a 7.5% difference in rolling circumference front to rear. ROT is no more than 3% to protect the AWD and not cause any handling anomalies.
It's a Carerra 4 Cabrio. So yes, AWD. If my fronts are 225/40 R18's, what size should I be looking at for my rears ideally? So the circumference difference could potentially cause increased wear and drivability differences, correct?
It's all stock suspension. I replaced 90% of all suspension parts 15,000 miles ago. Do you think any of those other parts would be needed with stock suspension?
If it is all stock/OE bits, then no, you shouldn't need the parts that I mentioned.
Lowering the car causes the suspension to change enough where you exceed the limits of the stock toe adjustment via the eccentric bolt and washer. To expand the range of toe adjustment you would use these lockout plates that eliminate the factory eccentric washer and then replace the stock fixed length toe arms with an adjustable style that provides for a wider range of adjustability.
I believe it will tell you your recommended tire sizes in your users manual. I have a 4S and my sizes are 225/40R-18 front and 295/30R-18 in the rear. The "40" and "30" are not set dimension but a ratio. The different circumference will cause the front and rears to travel at different speeds, which if it is too great a difference can be really hard on your front dif and I would imagine cause driveability and tire wear issues.
OP - Your car is a narrow body. Any idea what wheels you have? Standard narrow body rear wheel is 18x10et65. Standard OE spec tires that work are 285/30, 265/35 and 275/35.
I could look tomorrow to double check. Photo below if that helps...
Tire Rack shows a 285/30 (I believe). Now that I think of it... When I ordered the tires originally I ordered what was specified, but they were out of the rear tire size. Tire Rack called me while I was on my way home from driving the car back cross country and told me the 285/40's would fit. Not the best timing for me to make an educated decision. Yeah, they did. But like you said, they're the wrong circumference now that I've looked that up.
I think I'll just order some 285/30's and talk to the shop about the alignment specs before I have them mounted. I may try 275/35's also. I feel the wider tire tracks in the road ruts more. This is one of the two things I'm trying to minimize...
Rear end looseness and tire wear.
285/30 is going to feel real nice and tight compared to a 40 series. Going to be quicker too. Those look like solid or hollow twists and should be et65 if they are 10 in. You can put a 265/35 on there. Either way That ought to feel good. Tram lining is a different topic and associated with alignment geometry. Check your ride height While you are at it.
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