Post-trip questions re: tires/wheels/suspension

Since returning from my 3000-mile trip last week, I've thought a lot about my car and how it handled on the trip. After searching the forums a lot I still have a few questions and/or observations... The week before leaving I replaced my wheels (8x18/10x18) Turbo Twists with a set of the 5-spoke lightweights, (same sizes). Tires on the old wheels are P-Zero's (fronts with about 7000 miles, rears under 1000 miles.) One of the rears got a significant but repairable puncture, but since I somehow did not completely trust it for the trip I ended up getting a new set of Sumitomo HTR-ZIII's mainly due to the cost and the fact that I really liked the older HTR-ZII version on my old Audi C4 S4. Tires on both sets are the recommended 225/40 and 285/30 sizes. The first difference is the actual width of the tires. The P-Zero's are significantly wider at the same nominal size. The bulgey out beyond the rim on both sides while the Sumitomo is almost exactly flush with the edge of the rim. (But not stretched, actually the Sumitomo seems to fit the rim well) Initial driving impressions have me believing that the Sumitomo's are quieter by quite a bit. Around town and in most driving they are fine. Even at fast cornering speeds around town they feel fine and progressive enough, no surprises. After 3000 miles they are still very quiet. I keep pressures as recommended by Porsche on both sets of tires and checked them throughout the trip. My biggest problem/issue/questions arose after driving for a while, several times, especially on quick downhill sweeping turns I perceived the car to be quite nervous and not feeling totally securely planted to the point where I found myself slowing and actually in some cases not keeping up with other cars that I really should have no problem keeping up with. Uphill and flat sweepers were fine, but downhill turns especially without much camber not so much leading me to believe it is a handling issue that is somewhat masked by the power of the car on uphill and flat sections that would affect other cars more. Downhill the power issue levels out. I always try to keep the power on at least slightly through turns. As far as I can tell there are 3 main things (besides myself, I can freely admit that on several of the sections that caused me concern I was a bit less than fully fresh) that can be causing this. 1. The tires. Yes I have no problem believing that Michelin Super Sports are superior but many people here seem to dislike the P-Zero as well while the Sumitomo gets mixed reviews. A great tire will possibly mask other issues, no? If nothing else, I suppose a larger contact patch will be better than a smaller one. 2. Track - There seems to be plenty of room to add spacers both front and rear with the lightweights. I've never liked going that route as rotating mass and unsprung weight should be kept as low as possible, correct? But the lightweights look tucked under quite a bit especially with the Sumitomo tires as compared to the Turbo Twists with P-Zeros. A wider track will cause improved cornering, correct? 3. Suspension - Mine is bone stock, 2002, 70k miles on it. I like the way it rides, but am considering at least a set of H&R lowering springs based on what I am reading. Or possibly the ROW M030 package. I think the car could stand to be a bit lower but am not a fan of the slammed look (or even the X74 package, which is NLA anyway) and with my driveway situation can't go too low. I'm pretty sure I don't want to go to the expense of coilovers (or be able to derive all the benefit thereof), but maybe add some swaybars (GT3??). Or is a lot of the stock rubber underneath and even the shocks likely worn out at this point? Anyway, I'm no expert, just looking for some other opinions and maybe "been there, done that" experiences. I'm probably not going to be tracking the car, I do use it on a daily basis, I enjoy a spirited drive and would like to be able to come flying down I-70 into Denver while being more concerned about a reckless driving ticket than about sliding into the guardrail. I've done several DE's back in the day with the quattro club and think I understand the basics of fast,smooth driving so besides being a bit tired do not believe my technique to be seriously flawed. Thanks.

Different brands with the same tire size could and often do have a different "contact patch", hence your differences. As for the nervous feel, some tires on these cars require fine tuning of tire pressures other than stock settings. Try lowering the rears a few psi and see if the feeling improves. There is no hard rule that says you have to stick with stock tire pressures. I've found the 911s to be one of the most finicky when it comes to tire pressures and feel. On the other hand, if you had the same nervous feeling with the Pirellis, you might have some other issues like alignment and such.

My handling problems were cured w/ a swap to the RoW M030 suspension.

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I bought my c4s with hr springs last year. Then put on a brand new rowm030 kit from Gert. Could not be happier. Compliant, comfortable. Bit floaty if pushed but the car spends 99% as a daily driver. Perfect for my needs.

Walterohl you are welcome to drive my car to see if you like it. I am in Denver.

Find a used set of PSS9s. Often just around $1000, and a set of used ROW sways, see them at times, just $200. You don't have to be a track junkie, or even a super skilled driver to really realize the benefits of the coilovers. They truly earn the "night and day" title. Every time I drive someone elses 986/996/997 (have friends with them) on their stock suspensions, I always think to myself "WTF is WRONG with this car?" I know my friend with the 997 is looking for PSS10s. Hated P-zeros, I tried on a different 996. Had HTRZ-IIs on my car and truly despised them, but never tried the IIIs. The IIs looked very stretched on the rims, and gave no confidence. I have N3 PS2s, and the stance and fit is absolutely perfect on the 5 spoke 18's, and handling is outrageously impressive to me, but totally agree they are rather spendy if your car is a dailey driver. Since I only do around 4k a year, that is a non issue for me. I HOPE to wear them out before they get too hard. I added 7.5mm FVD spacers and have to admit I noticed zero difference in handling. But they look great.

Thank you all for the suggestions, I appreciate it. mrtoro / skiracer - Thanks for the feedback, and mrtoro - I may just take you up on that offer, thank you, I will let you know the next time I head down that way with some spare time! alpine003 - Thanks, I will play around with the pressures and see if I can notice a difference. Thanks! perryinva - Your car is the visual twin to mine! Thanks I will keep en eye out for used PSS9's, maybe put a WTB ad on the classifieds (after paying to be a member) to see what pops up. Do people upgrade from PSS9 to PSS10? Is there a big difference? Good info re: your spacers too, thanks. RE: alignment - My last set of rears wore completely evenly across. Is this normal, I would have thought these cars were more likely to wear on the insides more? What are others seeing with "stock" settings?

I agree with your observations on the HTR Z III. I felt that they were quite narrow compared to the P-Zeros and Pilot Sports. For a variety of reasons that I won't get into here, I'll never buy the Sumis or Pirelllis again. I've never found a tire that compares to the Pilot Sport PS2 on my car. I'll be interested to hear which way you go on the suspension. I'd love to put PSS10s on my C4S, but living in the mountains makes that a challenge for me. I already scrape the ground on a regular basis with my stock C4S suspension.

With the right alignment, you SHOULD see pretty even wear on a dailey driver. No difference between PSS9 and 10s except the 10s have 10 adjustments vs 9 and 1 is stiffest on 9s, and softest on 10s. Got that right from the Bilstein Help line from the PSS expert. I only have 2k miles on the tires now, and even wear. I also have a pretty steep drive, and no problem with normal x74 ride height, which is about where the PSS9s put your car. Driveway pic shows original struts with HTZ-IIs, other pic is PSS9s, spacers and PS2s.

If the new tires are less "bulgey," I'm guessing there is less sidewall, so it's stiffer and therefore bouncing more than your old tires. The slightly lower air pressure may be the trick you need. I had to soften the suspension on my car when I got it - although the lowered stance was amazing, the ride was so rough that PSM was kicking in daily when cornering through a downhill sweeper that's part of my commute home. Softening the suspension slightly was enough to make the car feel like it was tracking properly. I think your inflation may yield the same results. You also mentioned keeping the power down through curves - it sounds like you already realize this, but doing so is essential if you want the car to track properly. Lifting during a downhill sweeper is going to upset the car and in my case ALWAYS triggers PSM.

Cheap tires use cost cutting techniques to enhance profits. Narrower tire means less rubber to make it & less rubber on the road. Check the specs before you buy to see what you are getting. Cheap tires often have less rubber on the road but still heavyer than premium tires made in what is called a premium mold because it is true to size.

If the problem started with the trie/wheel change, I would look there first for issues. All the tires look normal? Wheel bolts all torqued and re-torqued to spec? Tire pressure too low would feel wandering, squirmy. Too high maybe some bounce and skid. Like everyone said check the obvious first. Please post if you find anything. Man, that guy posts some weird responses:

For another datapoint... Let me know if you want to compare my setup. Similar wheels, Michelins, ROW30 79k miles. Glad you're back.

The ROW M030 Suspension will transform your car into exactly what you are looking for. Just a bit lower with all new factory fresh components to replace a suspension that is 11 years old. Best mod I've made to date.

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Brian - Yeah, I'd like to do that. The ice at Georgetown wasn't the ideal venue! At the latest we'll do it when you move over here - hopefully soon. Did the 40th's comes with the ROW30 or did you (or the PO) change to that? If I like it, that's probably the best setup for me. A tad lower, fresh components all around at a decent price and two sets of summer tires/wheels in the garage to compare back to back. And if I pick up another set of whels for some reason I will try a set of Michelins... Thanks!

All good suggestions. I would start with pressures. I have found my current Conti DWs to be very twitchy unless I keep the right at factory pressure (36f/44r). A poind or two low and the rear feels very loose. My previous Contu Aport Contact 2s were not nearly as sensitive. I would go with the H&R springs myself, but for similar driveway level.

My '03 C2 has 126K miles and still rides on it's original suspension which will be corrected shortly. I have some advice from a local wrench to go with Bilstein HD on all 4 corners combined with Euro spec factory springs. Going this route is going to cost me $1700 in parts alone. I mentioned the ROW M030 kit but was advised that the factory shocks were not great quality and I would be happier with the Bilstein setup. My previous '86 Carrera ran Bilstein HD and I was happy there. Just wondering if anyone can backup the claims or should I save myself $500 and go with the ROW M030 from Suncoast?

My RoW M030 suspension has been installed for about two years and I couldn't be happier. FWIW, the original parts lasted 100K. Also, with the factory kit you get beefier front and rears sways to boot. One thing to think about is the after-installation ride height. Mine changed very little from the stock set up. So if you're looking to lower it, this choice may not be for you.

I'm personally not a fan of Sumitomo tires, including the HTR ZII. They came on my current 996, my past 951, and my past C36 AMG, in each case I swapped them for something different. In tires, like many things, you tend to get what you pay for. Living in CO and driving on summer tires, you also need to watch your temps. Summer tires really aren't designed for under 50 F, cold weather can make them hard and greasy. Your shocks are likely worn out at that mileage, so that might be a contributor as well.

I'd chose ROW30 over mixing springs and struts, or as I mentioned PSS9s, which is an engineered coilover system. I paid around $1000 for a set with only 5k miles on them. But of course you have to wait & find them.

I don't think M030 will change the C4S very much...

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' I've had a lot of various shocks on different cars. In this case, I'd rather get the ROW kit and put the money towards other things that will help improve handling even more(motor mounts, tires, camber plates or LCA's, etc). You just simply cannot beat the value since it comes with sways too(same size as the NLA X74 kit). If you want a slightly firmer ride, the Bilsteins would offer more dampening and better longevity if you wanted to keep the car over 5 years say and not change out the shocks in the future. But otherwise, I see very little value in going this route as this does not include the sway bars. Other more aggressive approach(similiar to x74) would be to get H&R springs, Bilstein Sports, along with H&R sways. That would make more sense if you wanted a more firmer and lower ride. my $.02

Just some thoughts after reading this post: The M030 will improve driving dynamics substantially and lower your front end 10mm. The PSS9/10 will be MUCH better and it is adjustable over a 1.5" range. The M030 will allow a max front tire of 245mm. The PSS9/10 will allow a max front tire of 265mm (thinner coils) Both PSS9 and PSS10 require GT2 drop links, supplied links completely suck. Pirelli PZero Corsa system is PERFECT for the 996 (if you don't mind the cost and low tread wear) Pilot Super Sport is a GREAT compromise (tread wear 300 and low cost) My advice, have a suspension guru drive it and tell you exactly what's wrong.

^^^^ M030 not to be confused with ROW . Also I don't know any sane 996 owner with the least value PZero Corsa's. Ferrari, Lambo, and 991 owners, yes, but not too many 996 owners.

I didn't read the whole thread but the easiest "upgrade" is going for 245 front tires. 245/40 is a bit tall and mine occasionally rubbed the spring perch or fender liner. 245/35 fits better. Of course refreshing the shocks, lower springs, alignment, swaybars all help too. I run 5mm spacers in the front but I don't think they're necessary.