Eojj

I'm sure this question may have been asked before...but I still haven't gotten a 100% answer on this lurkin through the board. Hopefully you guru's can chime in.

I recently purchased a set of rotors/brake pads from a vendor here (name intentionally left out as they have been respectful and still answering my questions). The rotors are directional and cross drilled. I dropped off my car to get them installed, and my mechanic noticed both the front rotors both have the same cross drill direction. We looked at the internal vane structure and they both point in the same direction as well. So we thought the vendor gave us two left front rotors by mistake. Note, the rotors are directional vane structured. Here are some pics to help explain this

This is the front rotor leaning against the front left driver side wheel. The blue arrow shows the direction of the internal cooling vane pointing towards the back of the car. This is would be correct..


This picture shows the same front rotor, leaned against the right passenger side wheel. The blue arrow again illustrates the direction of the internal cooling vanes. The red arrow shows the wheels rotation. As you can see here, the internal cooling vanes are pointing towards the front of the car... This basically disregards the whole point of having directional internal vanes for a greater cooling effect. Basically if I were to install this on, it would be "backwards."


After speaking with the vendor, they insisted that this is correct and that our mercedes stock front rotors both are directional left rotors, which is why they gave me two left front rotors... Can anyone confirm this? Will i have issues installing the rotor on "backwards"?

Rudeney

The factory drilled rotors are bidirectional (same left and right). Aftermarket rotors that have the curved drill pattern shown should be opposite, mirror images. I put D+S Frozen Rotors on my CLK and they included an installation instruction sheet showing the directional orientation.

Eojj

Do you happen to know if the factory rotors have directional internal vane structures? Or is it straight? It just doesn't make sense how MB would sell both front rotors going the same direction (unless they are straight vane structured) . Kind of defeats the purpose if one is going the opposite way

A good amount of CLK's are getting old now so I'm sure there's got to be more of you out there with aftermarket rotors. Anyone wearing their rotors backwards? Any issues? 😓

pskdude

I purchased a set of OE rotors and I thought they gave me the wrong ones as well. After contacting the Parts company they insisted that they are the right part numbers. I went through the same process and they insisted that's how they come.

Eojj

Lol man, pretty annoying. Had I known I would've just gotten factory rotors to save money. Forget all the fancy drills and slots - theres no real benefit from aftermarket performance ones if the internal structures don't run with the rotation. I don't track or drive my car too crazy, so I doubt the rotors will go on fire.

Just a FYI for those buying rotors in the future - Ask if the left/right front rotors have different internal vane structures before buying them!

Rudeney

I believe the OEM rotors have perfectly radial vanes, so that makes them unidirectional. It's the aftermarket setup that have curved vanes that would require them to be designated left and right.

lowpost

Yes my 360mm amg front rotors are the same part number both sides.

Eojj

See now that changes everything. Hmm need to go look at my old rotors.. Hope my mechanic didn't throw them away

Eojj

Just an update, checked my OEM rotors. The fronts have curved internal vane structures, and both front rotors are the same (both left side rotors). This is clearly incorrect, and theres no rhyme or reason MB has done this.. Besides cutting down production costs of course.

For anyone out there looking for rotors, make sure you get the correct ones for the front. If they have curved internal cooling vanes, they must be distinct between left/right. Some vendors will continue to sell the same left rotors for both fronts, so make sure to ask before buying..

Rudeney

But OEM rotors have the same part number for left and right, so I guess the vane direction does not matter.

Eojj

Right, that's the thing though. You would think the directions don't matter since they're the same part number but these rotors have directional (curved) vanes. The curves are suppose to point towards the rear to let heat out along with the rotational direction, this can't happen if both rotors are the same. If they were radial (straight) vanes then the directions wouldn't matter. Who knows, maybe theres no real difference performance wise between curved vs straight vane rotors. Probably all a marketing scam 😒

Yidney

But have you confirmed that anybody actually makes left and right rotors? Or that the vanes actually function as you assume? Frankly, my assumption would be the opposite of yours. The vanes facing forward would cool better as air was scooped in.

Eojj

If the vanes faced forward.. No air would be scooped in. It's supposed to face backwards so air could be scooped in along with the wheels rotation (assume we're driving straight).

I can't speak for MB, but all cars I've owned so far have been this way (honda, Toyota, bmw). If it has directional vanes the curves has to point backwards, towards the rear. Unless MB rotors have a missing piece I don't know about, it should be the same in theory as all rotors work the same.

Rudeney

Yes, the curve would point towards the rear. The Frozen Rotors I put on my CLK have curved vanes and the drilled holes and slots are also curved, and they are unidirectional - the curves point to the rear. This is less about airflow than it is to direct any debris (water, dust) "out" of the rotor as opposed to directing it toward the hub.