bouncing down the road in a c4s

i've tried to review the posts to find a solution, but none so far... my 2003 c4s has had vibration problems in the rear since new. P-zero Assym's all around and got a second set of rears and still vibration at 70, bad at 100, horrible at 115+. had dealer balance and index and had independent balance and index. porsche says ??? they don't know, independent tire store says tires are out of round and they show me on the balancer that the tire is bouncing... should i keep demanding new tires until the tread on these is even when spinning????

I've seen new tires come in already out-of-round, until you can rule out that as a problem you can't go much further. I'd hold out for new tires that meet the proper specs and are not out of round. I had an out of round Pirelli once and it was horrible above 70mph... the ride and the noise...

Your tires are probably out round... Pirelli's are notorious for this... see the following thread that has been started recently - go down a few posts... https://rennlist.com/forums/showthre...threadid=93454 cheers Peter

thanks, have any of you experienced wheels becoming out of round from bumps, etc. being aluminum, can't imagine it would take much to know one womperjawed.

What's the common thread......? THE WHEEL(S).....!!!! Brake rotor.....maybe.

I've posted before about a similar problem caused by belt shift. It too defied all usual manner of repair and resolved only with 4 new tires. The culprit tires were Pirelli. AS

FWIW my Asymmetricos were vibrating at 80+ and balancing fixed it right up. Also, I've found that the tires are VERY sensitve to pressure. The proper C4S specs (36 front, 44 rear) allow them to ride smoother than the lower pressure I was formerly running.

get a set of conti sport contact 2's. pirellis suck. their customer service is nonexistent and their quality control is worse!

I lemon lawed a car for that. Keep taking it back and get a service recept each time. At some point, they will have to fix it or eat it... Roy

UPDATE Took C4S to dealer for the 3rd time to resolve rear end vibration at all speeds over 70. The tech agreed that one tire was bad in that it had a "hop". They replaced that tire. Now the vibration is much lessened and only at 86-90 mph, vs. 70 to 130+. Now I figure I just have the imperfect world of balancing to deal with. Techs tell me that you can't balance a tire for 100 mph when the balancing machine doesn't get over something like 55 mph. How do professional race teams keep their tires likely more perfect? Surely at their stiff suspensions, higher temps, etc. etc. an out of balance tire would be unacceptable.

hahah conti sports, and you say assimetricos are junk? those tires have less grip and weigh more than all. Concerning the assimetricos if you drive them hard - heat them up a lot and beat on them through corners they will distort. However if you drive say in a straight line and let them cool down for about 1 mile or so they go back to normal-

the machines today are pretty accurate and sensitive so if you balance a tire for 55 mph it should be balanced for any speed. i also think that the tires you've been getting are out of round and/or not balanced correctly. any decent tire shop should be able to fix it the first time. i had this happen to me, but i called the manager of the shop, and had it fixed the next day. this was in a toyo tire. which, by the way, are excellent all around tires, though not as grippy as i would like, but that's the trade-off you get when you get more mileage out of them.

some tire shops that shave tires, can 'true' tires that are hopelessly out of round, where balancing cant mask the real problem. Yes, having them trued, will take material off, but a round trued tire, should outlast a wobbler, IMHO...

sean with respect, i replaced my p zero assyms with conti 2's. they are much better tires for a daily driver. much better wet traction and much more quiet. p zero's may be better on a dry track but not for daily use. worst of all pirelli customer service is awful. they would not even replace a tire that developed a bleb on the sidewall at 3k mi even though the wheel showed no evidence of damage. my local tire dealer informed me that pirelli is always hard to deal with. they took 10 days to return my call and a week to respond to their authorized dealer. it will be a cold day in hell when i purchase another pirelli!

I'll confirm the report on the Conti's. Mine now have 12,000 street miles on my ttX50, remain quiet, offer good grip, and don't look worn out at all ( I'm guessing about 40% left). The original Pirelli's were far inferior and were junk after 5 hard laps. I did do a full cool down lap (1.8 miles) which clearly did not prevent the problem. The Pirelli's best attribute was surprinsingly good grip in.... SNOW. AS

Hi, I have to say that I'm very happy with my Contis . To be sure, Pirellis (Rossos and Assimetricos) have somewhat more grip in the dry, but for an everyday driver, even with the odd Nuerburgring or other track day thrown in, Contis are a very good compromise in terms of mileage, comfort, dry and wet grip. Cheers, Uwe

I guress you just don't use the tires to the full limits to enjoy the difference in dry traction. The contis are still I believe the heaviest tire you can get other than the so3 which hurts handling with unsprung weight as well as reciprocating inertia.

If you want a comprimise of just a better tire yet still get the new pilot sport sp2's. They are supposed to do it all better than them all-except a cup.

sean i agree pilot sports are great BUT they don't make tires wide enough (295/30-18's) for turbos or c4s's.

Exactly, on public roads I don't go anywhere near the limits and on the track I'm just willing to compromise. I might try the pilot sports next time. Cheers, Uwe

SPR- guress you just don't use the tires to the full limits to enjoy the difference in dry traction. The contis are still I believe the heaviest tire you can get other than the so3 which hurts handling with unsprung weight as well as reciprocating inertia. For street driving, who can? For track driving, isn't the idea to get the most you can from the car as is? If you want to "enjoy the full limits", I think you'll need way more mods, and true race rubber. The difference between street tires is way less than the difference between drivers. AS

SPR: Ok, a couple things. First off how in the world do you know that the Conti SportContact2 is the heaviest (or second heaviest) tire? I am in the tire business and don't even have this information for Conti, they don't publish their passenger tire weights and the other brands also don't make it known. So unless you went and physically weighed each brand of tire you shouldn't make an assumption. Second, I noticed you have a 1999 C2, I am going to assume your experience with the Continental tires are from the OE fitment from Porsche when you first purchased the car. If that is the case (or even if not) you are probably not thinking of the Conti SportContact2 which came to market in 2001-2002, but the original SportContact. They are two TOTALLY DIFFERENT tires. And I will admit the original Sportcontact wasn't anything special but the SportContact2 is easily one of the better tires on the market and is probably the best tire for the C4S/Turbo sizes. I won't go into any tests because the user experiences above say it all, virtually the same dry grip as the Pirelli, significantly better wet grip and a much quieter tire. If you are able to drive a Porsche so close the the limit on the track that the difference between dry traction on the Pirelli and Conti is significantly noticeable then you are such a good driver that you should be a professional because if you drive the car correctly you will be hard pressed to find a real difference. As for the recently released Michelin C4S/Turbo sized tires, I don�t have personal experience with them but normally Michelins are equal performance wise to all others, they have yet to come out with a tire that is significantly better than the rest and in fact my last set of Michelins were actually quite inferior to my current set of tires. Yes Michelin makes good tires, but for a set of 4 on the C4S you are talking approx $350 premium over ALL other brands. Michelin vs. ALL OTHERS (major brands) is like Rolex Vs. Omega. The Rolex has the name and because of that they charge 2x the competition. Is the Rolex better than an Omega in performance, durability, style...no it is just about the same, but because they put the little crown on it and place it in the green box they are able to charge 2x the competition because their marketing dept. did a great job. Michelin is the same way, their tires are good, no doubt about it but they are not necessarily any better than the Conti, Bridgestone or other brands but they have the name, the French did a great marketing job and what you end up being overcharged is so they can pay for putting a baby in a tire and have the stay puff marshmallow man on the TV every commercial break. So in summation, make sure you are talking about the Sport Contact2, if you don't have personal experience with that exact tread design then you don't know what the tire can do. Read the reviews above, they are all overwhelmingly positive and never be swayed by the �Michelin is the ONLY good tire out there� mantra because it just isn't true. Continental is the #1 seller in Germany, #2 in Europe and #4 worldwide not because they make a substandard ultra high performance tire but because they know what they are doing. A4EP 02 C4S, SG/BLK

Way...Way OT...but could not resist. One point on Rolex vs Omega...underscoring the brand value difference....you might want to check the second hand markets for Rolex vs Omega. It is a rare mechanical device that virtually ignores depreciation....that be the Rolex Oyster series. Only Patek..(and perhaps Lange & Sohne) get close in preserving value.... Now one could also make the comparison in other respects...Porsche vs Corvette...but that would be opening a flame container....

Bill: You are correct on that but also how much does resale have to do with the name recognition? I mean mechanically there isn't anything special about the Rolex, but they are in such high demand...take the Daytona for instance... that the price stays up so high simply because everyone wants one, just like how used Boxsters and 911s were going for the same price as new ones back in the late 90's and 2000. Linking it back to the topic above unfortunatly there isn't a market for ultra high performance casings so its a bit hard to sell a worn out tire, or used tire Of course if you are talking about Semi-Truck tires that is a totally different story, but even there Continental, Bridgestone, Michelin casings are worth the same and are worth significantly more than Goodyear, Yokohama and the other lesser brands. But that's a different story all together BTW: on the weight issue, the Conti SportContact2 in a 295/30R18 (C4S/Turbo rear tire) weighs in at an exact 26.411lbs (I called my warehouse) if anyone has the exact weights of the competitiors we can figure out if the Conti is actually heavier than the rest...I still don't think they are but I could be wrong. A4EP 2002 C4S SG/BLK

Just a couple of data points. Ignacio, the Michelin PS2 is available in 295 18, in fact it is the OEM tire for the 996 GT3 MkII. My GT3 came with them and I am very impressed with their grip. Pirelli Asym tires have been known to slip belts but I thought that issue was resolved years ago. The P 0 Rosso has worked well for me and they have a much nicer ride than the SO2 or S03. Someone asked about how race-car tires are balanced. They use the same machines as everyone else. Rear tires are normally not balanced because the tires rotate on the rim so much that they never stay in balance after a lap. On the other hand a race slick is a very light tire and imbalance is less of an issue that on a much heavier street tire. Lastly, I've had Contis on several Porsches as OEM tires and they were good. I never bought more of them because where I live they are priced far above the top level tires from Michelin, Bridgestone and Pirelli.