rdfield1

Have an '04 MT RX-8 (8,000 miles) which has undergone all flashes, recalls, etc. The vehicle used to be very quiet on the highway- until yesterday. Excessive road noise (not engine-related) was noticeable at highway speeds (temp was 60 F so tires were surely warm enough). My first thought was tires (tire pressure monitor indicated pressures were normal) and so I visually inspected same and checked tightness of lug nuts. Nothing out of the ordinary. Alignment was performed 1 month ago so this should not be a problem. But- something is certainly amiss (suspension? rotors? tires?)

The car goes to the dealer service dept on Thursday, but I'm afraid that I'll hear the old "they all do that" refrain. Any ideas out there?

Go48

Funny you should bring this up. I have noticed the very same increase in cabin noise recently. (Same model with 15K miles.)) It sounds like wind noise to me since the amplitude varies when holding a constant speed/RPM. I have attributed the problem to cold temps and stiffer rubber mouldings around the doors, sunroof openings. But it isn't that cold right now so I don't know if that is a valid conclusion.

Could be tire noise, but the increase seems to have started abruptly. Probably not related, but I noticed it right after having the 4206F recall work done. Since the only thing they did was update the PCM, I doubt that this is related. Let us know id the dealer comes up with anything meaningful.

Rhythmic

What tires are you running. Could just be the colder temps. summer tires' performance and ride quality drastically declines with cold weather.
Check tire pressure, and maybe balancing.

rdfield1

Tires are original Bridgestone Potenzas. Temp was 60 F (rather warm for December). Car had an alignment and tire balancing in November. Did not sound like wind noise- more like tire noise. I actually thought that the tread might be separating from the casing but visual inspection showed (to my untrained eye) nothing amiss. Might be suspension related, but the ride quality is unchanged. Might also be that some sound-deadening material came loose (from the heat shield/gas tank fix).

Old Rotor

Same problem I had after rotateing the tires. That was done...right?

rdfield1

Tires were not rotated (rotation is supposed to occur at 15,000 mile service).

Spin9k

It is the tires. OEM Bridgestones are some of the noisiest rubber I've ever had on any car I've owned in 30 years. If you recently got them rotated, they growl and rumble like no tomorrow. As you said it's almost like a tread separation. It fades some after a few thousand miles, but my advice - get some better rubber - you'll hget your peace and quiet back. I got Falkens (RT-615s) and they are so quiet and comfortable it was a real eye (and ear) opener.

TeamRX8

iTrader: (25)

wear has a lot to do with it too, all tires get noiser as the wear down and start to harden

and old rough roads generate more noise then new smooth roads, after winter the snow chains the truckers throw on in the passes tear up the road surfaces down here in the lower altitudes which makes for a rough, noisey ride

we put a set of BFG KDW2's on DKNVs RX-8, which have a reputation for being noisey, but IMO they are quieter than the OE Potenzas we took off, in fact they don't make much noise except on rough road surfaces, we expect them to get noiser over time though as mentioned above