Tire recommendation for Carrera 4s

I just acquired a 2005 carrera 4s with worn Michelin Pilot Sport N3s. 295/30 zr18" rear and 225/40 zr18" front. Have been scouring the web for similar brand or others, Conti, Hankook, in all seasons. Even though I won't drive in snow (too low spoiler) temps here will go below freezing. Mich Pilot's summer tires warn their sidewall will be damaged under freezing temps Can't seem to find any in the 295 width in all seasons, seems like 275 are the widest. Any recommendations?

Continental dws06 if you are not going to be aggressive michelins 4s a/s if you are hankooks A/S for anything else

I think OP is concerned that those tires don't come in exactly 295/30/18 But I also believe a 285/35/18 could be stretched to fit the rear wheels. But don't quote me on that I never tried it.

I think most people with the C4S get a set of 10" wide rear wheels for a winter setup and use the appropriate sized tires. I think the widest wheel recommended for the 285/35-18 is 10.5". The 2005 C4S has 11" wide rear wheels.

Thanks for the comments guys. I would like to stay with the 295/40 rears if I can find some. I have been running Hankook Ventus Noble 1s on my 986 through last winter and seemed like a good all around for the buck. Trouble finding the 295 width in 18" anywhere. May bite the bullet and see if I can find A/S Michelins somewhere.

I have a 2004 4S. Be careful if you follow advice to try alternate sizes. Use a calculator to find tire circumferences. The front tires, stock, are very slightly larger than the rears, so they rotate slightly slower, and from what I've read, it needs to stay that way. Apparently the viscous clutch in the front diff will wear out otherwise. That said, I'm just repeating what I've read here, with no first-hand knowledge, so do with that information what you will.

I have a 2003 C4S with 11" x 18" rear wheels. I wish Michelin would make an all-season version of the Pilot Sport AS4 in 295/30-18 but had to settle for 285/35-18 as a winter setup. Tire Rack specs show them fitting on up to 11" rims. I have 235/40-18 front tires to match the diameter fairly well. They do not rub. I have used these in snow several times and was happy with the grip. I now have 14K miles on them and probably will get another 2k or more before the rears are done.

I store mine in the winter so what do I know...🤔

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There are not any all season tires made in 295/30. Your best bet would be get a set of 8 and 10 inch wheels and run the approved winter size 265/35 225/40.

Thanks for the info and good advice on the options!

Just took the advice offered and ordered a set of Michelin all seasons with the 285/35 rears. It'll get down into the teens here in NJ and while she'll be garaged and not out in the snow, I read that the Michelin summer sports shouldn't even be mounted or stored below 32�, yikes! I'll remount with the summers in the spring. I'll report on my experience with the all seasons. Have a toyota 4Runner for the winter.

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What size are you going to use on the front?

Stuck with 225/40 All Seasons in the front. Guess I could have went up to 225/45 to match the sidewall increase in the rear, but hopefully the geometry will work ok.

As someone said, Tire Rack's specs say the 285/35 will run on a 9.5 to 11" rim. Can't afford a grand for a couple of 10 x 18 rims right now or the wife will kill me.

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I run 285s on my factory 18s and the stretch isn't bad. (2003 C4S)

Just to follow up. Did buy the Michelin A/S Pilots in 225/40 front and 285/35 rear. The 285/35s are 10" and tire rack's calculator says 9.5 to 11" rims are ok. I was still a little nervous and started trying to find 10"x18" turbo trims. Would cost a couple grand to order them; couldn't find two used. I called my indie who I trust and does all the track car work for the Schattenbaum PCA region members. He says putting them on my stock 11" rim's will be fine.

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Yes but according to most that post here the AWD system will be compromised with that big of a difference in the front and rear diameters. Rear greater than 3% larger. I don't have a C4 or S so I don't really know if that's correct.

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Tis VERY true !! Porsche has been adamant about this since the release of the C4 .... Back in the day when were Certifying a C4 or C4S for CPO we were required to replace ALL 4 tires with the correct size if only 1 tire was damaged and needed replacing.. If the correct size/circumference differential was not maintained it would case unstable handling in corners and/or viscus clutch damage.. Here is a video that was just posted here on RL last week of a strange noise in the transmission/front drive where the OP's Tech had already replaced the bearings in the front diff, and I diagnosed the noise as a failing viscous clutch and mentioned the possible cause of mismatched tires, of course the OP is MIA now to verify...lol Anyway the viscous clutch is only a few grand so may be not a big deal to most but would be for me... You Tube

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I feel like my posts are invisible sometimes: Well, it's always nice to be confirmed by an expert, @Porschetech3

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I saw your post and it was spot on as most of yours are !! You are not alone my friend, I know the feeling..We are all humans and need to be acknowledged ..Even the little "like" function has meaning and we should all use it more often as it doesn't cost a dime.........

To make things more complicated, even if you have the correct 8" and 10" rims, it's quite difficult to find a quality winter tire in the correct 265 width with matching front tires.

No, I didn't ignore your posts regarding the awd issues with the tire mismatch. Very much appreciated! Initially I ordered in a rush, and then saw your posts coming in on the size issue. The 225/40 and 285/35 Mich A/Ss are now sitting in my garage while i try and figure out / find suitable replacements.and return the rears or both. It is driving me nuts playing with the 1010 and Tiresize calculators trying A/S combos that are safe. I can't believe I can't find any A/Ss that fully fill the bill! Closest I have in mind now are the 225/40 fronts and thinking 285/30 rear which puts the front .4" larger. Does that sound reasonable? I will still need to buy a set of 10" wide wheels for the rear if I go that way. Is the "less than 3% diff" a solid guideline?

Eventually, we all come to the conclusion that 2 sets of wheels may make sense.

If you've been on the calculator then I'm sure you saw this recommendation with the snowflake next to it. However if you believe that your front tires need to be ~1% larger than your rears to protect your viscous coupling, obviously those top recommendations aren't going to work. You'd have to go to a 255/40 or a 235/45 in the front (if you stuck with the 285/35 rear). I had a similar dilemma on my staggered tire AWD Audi. PITA. Over there it is just the haldex pump instead of the VC.

Thanks for this info! Yes, I already bought the wrong set but will be exchanging for the proper match. So glad I joined the forum and got this critical info before I cooked my viscous clutch!

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Is there any technical information that actually back that? I have read that topic about the wheel differences and the impact in the AWD system. However, never saw any technical details on it. The only difference that I can see is that you can have an slightly difference in the distribution of the par between front and rear. Porsche, in the 997, with the same chassis and AWD system, has different wheels sizes allowed in 18" and 19" for the 4/4S that actually goes against that affirmation.

It has been recommended that they be within 3%, but hasn't been clear if the 3% could be more or less. My impression was that it was 3% either way. That actually opens up more combinations and configurations. I hope I am not perpetuating bad information. Interesting that it may not apply to the 997 as much. Is that true?

Fronts need to turn slower than the rears to keep the viscous coupler ready for use, so the front tire has to be slightly taller. Reversing this leads to very undesirable handling. 997's use a completely different type of center differential, it's electromagnetically operated similar to VW's Haldex and has a different ratio that the 997 rear diff. I would guess that any AWD 996 with 80k+ miles on it has a worn out viscous coupler. Porschetech gave a quick and dirty test for this: jack up one front wheel. Turn that wheel quickly. Within 3 revolutions the force required to turn it should increase dramatically as the VC heats up. I did this check on my 30k mile car and indeed the front wheel became much harder to rotate. I did the test on my 180k mile car and the front wheel continued to rotate easily -> VC worn out, so I did a RWD conversion.

Interesting test! I'll check that next time i get one side up. Have 42k on mine. Btw. Came up with a good combo. Happened to be in my indie's shop today and saw another 996 C4s. He's running 225/45 285/35 Hankooks on 8 and 11" rims. Plugged them into the estimator and the fronts are .4% taller than the rears. Front 777 revs vs 780 for rear. I exchanged my 225/40 for 225/45. Was going to switch to the Hankooks, same model that I run on my Boxster and like them fine., but since I had the Michelin A/S rears, stuck with them. Once again thanks guys for all the good advice and keeping me out of trouble!

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Yes there is LOTS on tech info to back that up. Check the Porsche workshop manual or DrStrangelove has access to TBS's on the subject. Also in the archive here there is plenty of the same info repeated.. Also the post by theperf is spot on.. See the explanation from theprf.... Spot on !! To the OP :: I bet you never thought that asking for a simple tire recommendation would turn so technical !!??? This a "Technical Forum" and is what should happen to keep you from doing harm to your 996 ....good quick technical thread..

Yikes, just listened to the sound in the YouTube posted by Porschetech3 yesterday. I was cruising yesterday and started noticing for the first time a very similar "tinking" sound intermittently coming from the front for the first time. Just bought the car in Dallas with 41k miles on it a few weeks ago and drove it back east, didn't notice it at all until yesterday. It had stock size Michelin summer tire sizes on it and service records saying diff and trans fluids changed 2 years ago. Hope it isn't diff bearings or clutch with such low mileage! I'll keep an ear on it and the thread updated.

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This is not correct. The differential in the 997 is viscous coupled like in the 996. The turbo is multi clutch but also hydraulic operated Also this: "I would guess that any AWD 996 with 80k+ miles on it has a worn out viscous coupler". Why? Where is the technical information that support that? If you change your differential oil you should not have any problem Regarding the wheel size. An slight variation in diameter will only cause only that the distribution under non spinning conditions of the par will be slightly different that is not even considered in the specs when mounting 19" (if you look the par distribution specs in a 997 with 18 or with 19 is the same, despite the different in tire size Front/rear) The 3% ratio that you guys are mentioning is not just for AWD cars. That comes from all European cars in terms of tire size homologation. All manufacturers require that tires sizes are within 3% Again, please show me technical documentation (from porsche) where slightly size tire variation (for instance the 19" setup of the 997) wont work in the 996 or will cause any damage.

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This is not correct......The viscous clutch is self contained, changing the differential fluid does not change the fluid in the viscous clutch. The special silicone oil in the viscous clutch cannot be changed... Are you worried about your viscous clutch ? Do you have a 996 c4 or c4S ? What are your current tire sizes?

I had commented yesterday on hearing a similar metallic "tinking" sound in the front similar to that in the video you posted, cruising around for a few hrs and a stretch at 75 - 80 mph, where I first noticed it. I assumed it was mud or sand splatter coming off the tires or chassis, since had been going through a couple of messy construction areas, or something loose. Didn't think too much of it, then happened to play your vid. It's a '05 C4s with 42k on it. Went out yesterday and drove some local roads for 15 mins at speed and didn't hear it then. Hoping it's not a bearing or VC issue that shows itself after a long ride.

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I�m curious about one thing. The winter recommended rear size is 265/35R18, which makes the rear slightly larger than the front. Albeit the difference is less than 1% so well within the 3% tolerance mentioned. What�s more important, staying as close as possible to the original sizes, which the 265/35 tire does, or ensuring the front is slightly larger?

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Whats MOST important on a C4 or C4S is not letting the RPM ( revolutions per mile) get too far apart from front to rear due to tire wear ( starting with the correct size).. The RPM can change as much as 50 RPM from new to worn out....When new the 225/40-295/30 set would have only 7 RPM differential ( out of about 800 rpm) and the 225/40-265/35 set would have only a 4 RPM differential ( out of about 800 rpm) ....as they wear the RPM can increase as much as 50 RPM per tire... That why Porsche recommends this size and also recommends to replace all 4 at the same time....not to mismatch old and new .....

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I understand, I should be ok as I�ve always matched sets all around. Thank you for the clarification. I always appreciate the experts input. Looking forward to upgrading to the UAOS in the not so distant future.

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No worried at all I have a 02 C4S, that has been on Champions RG19 since 2005 (now 67K miles) with absolutely no problems or difference noticeable in behaviour. Tire sizes are the same than the 997.1 (which, again, has the same AWD system than 996s) in 19"s: 235/35/19 front and 305/30/19 in the rear. Actually, if you search the OEM tire sizes, you will find that the 997.1 C4S has 305/30/19 in the rear but the C4 has both, the 305/30/19 and 295/30/19 sizes homologated, what makes for different wheel size.

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With those tires sizes you will be OK as long as you replace them in "sets " of 4 and do not mismatch old and new. Just remember you are already at a 1 mph differential ,and viscous clutch will apply a little torque to the front wheels..It may not be noticeable at 60 mph, but at 180 mph can be a lot different.. Here is an actual dyno type graph showing the torque applied by the viscus clutch at differential speed of 5km/h ( 3 mph) ...( ie..difference between front to rear wheel speed)..

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It occurs to me that I have never thought about how the difference in wheel speeds is communicated to the front differential. Especially given that the two back wheels might be spinning different speeds themselves in a low traction situation. Which wheel ends up being the reference for comparison with front wheel speeds? Or is the front wheel speed just compared to carden shaft speed?

I'm thinking it's got to be the carden shaft speed. Does the front differential compare it to front wheel speed and if it's not keeping up The friction difference causes heating and that results in engagement?

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The viscous clutch acts as a mini torque convertor... The viscous clutch has a set of clutch plates in contact with each other in a special silicone oil that has synthetic viscous modifiers.. Every other clutch plate is connected to either input or output shaft.. If the input and output shafts rotate at the same speed the clutch plates are not sliding against one another... As the input and output shafts speeds start to differentiate, every other clutch plate will slide against each other and the friction will cause rise in temperature of the special silicon oil with viscous modifiers.. As the temperature of the viscous fluid rises, the fluid becomes more viscous and increases the friction, this transfers more torque to the output shaft... So, if the rear wheels spin, this increases the temperature of the fluid and simultaneously the fluid thickens( becomes more viscous) and increases the transfer of torque to the front wheels... ,

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That is so cool. Makes sense... So if the rear wheels are turning too fast the carden shaft turns fast compared to the front differential output, causing heat and engaging torque to the front drive shafts. If the rear tires are smaller diameter or worn down, they will turn faster than the fronts resulting in constant clutch friction , eventually leading to failure. If the front tires are smaller diameter or worn down, the same thing will happen with the front wheels turning faster, heating up the front differential, and trying to turn the carden shaft back through the engine which, of course, goes nowhere.