I have had mine on for about a thousand miles now, and yes, they are noisy, but thankfully, the partition really did away with a lot of it. As far as performance goes, I absolutely love them, and have no complaints.
I have them on my '91 Vette and they are not noisy to me.
Maybe you got some older ones that have hardened up.
It's impossible to tell how long they were sitting in a hot warehouse before you got them.
I really like mine. They have great dry traction and great wet traction also.
They are a 'low end' performance tire but they are a LOT better all way around than the Goodyear Eagle GSC's that they replaced.
I have the MX in 275/40-17 on my 87 and they are used for both steet and track and I really don't notice any noise at all (but the lack of mufflers may have something to do with that )
I have them on my '91 Vette and they are not noisy to me.
Maybe you got some older ones that have hardened up.
It's impossible to tell how long they were sitting in a hot warehouse before you got them.
I had them on my care after the GYSC's and found them to be fairly noisy. I found them particularly noisy when they were cold. They handled pretty well in the rain.
I switched to PS2's last spring and I absolutely love them. They were more than the Khumo's but I didn't get the best deal on the Khumo's. Even my wife commented on how much quieter the PS2's were.
Still, for the money, the Khumo is a pretty good tire.
I feel that they are not as loud as Goodyear run flats but not near as quiet as Michelin AS ZPs. I have had all three on either my or my wife's C5. The Kumhos are a good value but if there is a next set they will be Michelin even if I do not like buying French products.