cayenneturbo

According the the directions we are not to confuse the L and R side rotors. I have not pulled the tires yet to compare, but I am looking at my new rotors on the floor and they are exactly the same and marked the same. I did not by Zimms, instead I bought rotors from Cquence and they are stamped M1396 on both.

So before I pull the tires and calipers off , I just wanted to make sure that there is or is not a difference.

SCOTITUDE

yes there are different rotors for l and r sides. they are not identical.

yeldogt

Interesting -- I do not remember seeing any differences - but I see the parts from Sunset on my invoice listing 955-351-401-51 and 402-51 ??

What is the difference?

CarreraCup03

From what I know about other front Pcar rotors .. the difference is the direction the cooling vanes on the outside are pointed. They do not cool as well if they are on the wrong side. Probably not a huge problem for road going Cayenne. Take a look ... I think you should see the difference.

Renn 951

I would describe the difference more as the vents you see on the edge of the rotor - between the outside and inside surfaces. They are designed so that they help cool the rotor (I can't remember if they draw cool air in or expel heated air out.) So if both the replacement rotors are identical then one of them will be rotating in the wrong direction and you won't get the cooling. As you say, probably not a big issue for a car in normal use on the street but it could make a difference under heavy use - for example, towing a trailer and driving down a mountain road. And it would certainly make a difference on the track.

IMHO, it's not worth it buying non-OEM rotors just to save a few bucks. On Porsche rotors the center hats are painted. On all non-OEM rotors I've seen (including non-OEM Zimmermans for my 951) the hats aren't painted and they end up with a rust coating that looks shabby. OEM rotors from Sunset Porsche (in Oregon) or Suncoast Porsche (in Florida) can be bought on the internet for a very reasonable price, and the parts guys there know there's a difference between left and right.

CarreraCup03

yes ren 951 thats pretty much it.

Bob Rouleau

Are your replacement rotors slotted or ventilated? If yes to either or both, there is a left and right. If they are solid discs without ventiliation in the middle (turbine vanes) then they are the same on both sides. Google and you'll find a diagram which shows which way slotted and or ventilated rotors should rotate.

Best,

SCOTITUDE

the difference is vane directiion on the fronts. rears are identical due to straight vanes (little pic).

yeldogt

My heart missed a beat for a second !

I always get a set -- recently from Sunset - at $123 each for the CS.

My mind never gave it a thought that the disc had to be different -- but I always point the veins to the rear.