JCtx

A brief history here. Drove an '03 SC430 once, and thought the tires were noisy, but not as much as they were on my GS400 (bridgestones, in both cases; runflats on the SC, of course). Had the RFs on my corvette (goodyears), and were noisy as hell. Believe it or not, the corvette feels SOFTER than the SC, but that's probably due to the semi-independent suspension and maybe because the front tires on the vette are 245/45s. Yes, this car still has MONOLEAF front AND rear suspensions gentlemen, and GM calls it independent (ha!).

My '04 is amazingly quiet, and since I don't think there were any insulation changes for '04, I can only attribute the change to the tires. If you didn't know, '04 cars now come equipped with Dunlop SP5000 runflats. The car feels as quiet as my ex-LS400 ('98). The tires look too narrow to be 245s, but the narrow wheels are to blame too: only 8" wide; should be 8.5".

Finally, I was surprised dealer inflated my tires (as per 'Lexus') to 40 psi. A runflat is a brick to begin with (can support the car deflated!!), so that number is just plain crazy. Corvettes can run upwards of 170 mph, and the recommended pressure is 30 psi. The door label says 33 psi, so I inflated the tires to that spec; the extra weight of the car might justify that (3200 vs 3800). Even though the extra 12 psi for high speed driving is not warranted on runflat tires, all cars have the computer programmed for this and will sound the alarm if 112 mph is exceeded without the extra pressure. I won't do it. If I ever go over that speed would be only for a moment, so I'd let the darn thing beep.
I remember my dealer saying the same thing about tire pressure when I bought my GS400 with the 17" wheels: 'Lexus recommends 40 psi for the tires to last longer'. I refused to ride a brick, and put the recommended pressure (on the label) of 33 psi, and tires still looked new at 14K miles, when I sold the car. I could feel every pebble on the road, just as this one.
Anyway, car feels firm, just like the GS with the 17" wheels, but not harsh. I like it just fine. I can't see a 40 series tire being soft, so I'll stick with the peace of mind of runflats, especially when being as quiet as these Dunlops. You should look at these as an alternative before dumping the RFs. Test drive an '04 at your dealer to judge by yourselves, but adjust the pressure to 33 (what's called by the manual) to make the comparison fair. This tire seems perfectly suited to a stock SC430; it's a well proven design as well.

Take care guys, and sorry for being so long-winded. Nothing better to do this afternoon.

JC

dsimo

Just to note, I've had Dunlop SP5000s on my BMW 528 for several 10k miles (not run-flats, though). I've been quite pleased with their handling and ride, especially for an all-season tire (I don't think the RFs are all-season, though).

JCtx

Yes, they are buddy, down to the same tread pattern; that's why they're so quiet. The tread design is not aggressive at all, but it's not bad.
I like the SP8000 and 9000 tread pattern better, but THOSE are more performance oriented, and noisier. The SC430 doesn't need any more tire than this IMO, and you seem to concur by your comment, since your BMW might be 'sportier' than our car. I really wanted the car to be quiet, and it really surpassed all my expectations in that department.

My only doubt now is tread life, but as long as it's 20K or better, I'm a happy camper. Some people get 40K out of the corvette runflats, so 20K sounds like a reasonable expectation. I wonder how long do the 'normal' (bridgestone) SC430 runflats last.

Take care.

Doc C

I can't comment on your runflats, but I can say that mine were very quiet as well for the first 5-6K miles (I loved them), and they then became progressively louder and more harsh overall. After 10K miles they might as well have been made of granite. I put some Michelin Pilot Sports on as per Dseag2's advice. It's a completely different car. Quiet and handles great. Granted, they may suck after 10K miles as well, but I haven't heard any complaints. I'm just saying that I would like to hear how your runflats are at 7K+ miles. They seem to not be so great at that point for several members of the forum. I'm glad you like the SC though. My home stereo doesn't sound as good as the ML!!!!

Doc C

golfkwesi

Please do post your opinion after you've driven them for that many miles. I just picked up my "02 SC which has the OEM runflats. Many prior threads have stated that they have replaced them after 5 - 10K so I am wondering which way I will go. The drive from CT to FL was wonderful! No road noise although rough over railroad tracks, etc. They only have under 6K now so the true test may be over the next 5K so hearing how your new runflats perform would be great. I did not check the tire inflation on my tires but I believe that a prior thread stated 38psi was the ideal pressure for an '02?

PS: absolutely love this machine which has already exceeded my expectations. As to the ML ..wow! With it cranked up I haven't heard any door rattle either.

dseag2

By the way ELP_JC, there have been quite a few posts re: tire inflation PSI for the SC430. If you do a search, you'll find that many owners have been informed that 36 PSI is the optimal tire pressure, even though it is different than what is stated in the manual.

Even though you would think a higher PSI would make the car ride rougher, it actually seems to improve the ride. I always kept both my runflats and non-runflats at 36 PSI and found it to be the best.