'2000 300M: Front rotor thickness?

'2000 300M, 67k km (41.5k miles).

Just put my snow tires on (Alpin's on front, Blizzak's on back), was checking the rotors and pads. Changed front pads about 1.5 years ago because of "groaning/creaking" of original pads, so they're still good. Changed rear pads (probably still 1/2 the pad left but what the hell.) Boy they're small. Still looking for something to cover the center hubs.

Measured the front rotors - both at 1.02". What is the original thickness? (I looked but couldn't find any numbers stamped on them other than a 5 or 6-digit part number.) This is non-PHP. Rear rotors had lots of text stamped on them.

You know, all the stuff about vented rotors is crap. Ever notice how much the outside faces rust to the point where all the venting is jammed up?

Preliminary numbers (based on just over 6k miles) indicates slightly more than 3k miles per 1/32 tread wear on the summer tires (Dunlop Sport 5000 - usually kept at 33 psi). Very rough figure is that these tires are good for 25k miles (if end-point is 2/32 tread). Will probably take another summer's worth of driving to get a better handle on tread wear rate.

I think by federal law the min. thickness has to be on there - but rust does make them hard or impossible to read sometimes.

Front (specs. same regardless of PHP/non-PHP): Original thickness 25.87-26.13 mm (1.019-1.029 in.) Min. allowable thickness 24.4 mm (0.960 in.)

Rear: Original thickness 11.63-12.13 mm (0.458-0.478 in.) Min. allowable thickness 10.4 mm (0.409 in.)

I disagree that that means the stuff about venting is crap. I think what it means is that as rust gets thicker (and forms scales) and clogs up the vent paths that the rotors are more prone to warping. In general, venting aside, I'm not sure if light rusting helps by increasing surface area for cooling or hinders by insulating - maybe offsetting effects. But definitely scaling rust would decrease cooling (especially in the vents).

That's why I don't buy so-called "high performance" tires - a lot less value for the money than a good touring tire IMO.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")