The cross-drilling on front and rear rotors have a definite direction - either flowing outward following a counter-clockwise spin (make sense?) or flowing following a clockwise spin.
My front rotors were installed following a different direction of spin than the rear cross-drilled rotors.
Which one is correct?

I've heard a few opinions from front-yard mechanics, now I'm wondering what gives?

 

Are they solid or vented rotors?

 

vented in front, not vented in back.

 

Straight Vane or curved?

Straight Vane is not directional



Curved Vane is directional. This is how the Left front would look.

 

When I had Zimmerman cross drilled rotors the directions were different for right and left sides but same direction for front (vented) and rear (solid rotor).

Here is a JCW brake with cross drilled pattern

Shows the holes start moving outward in a clockwise direction.

This JCW brake picture seems to suggest that both right and left JCW rotors show the same cross drill hole pattern.

Or is the pattern different right and left? Can anyone check.

 

The drilled and slotted JCW rotors have the "direction" different on each side. I have them on my car. There is only one part # for the rotors; there is not a "left" and "right". So they face "backward" on the driver's side (as shown in the on-the-car pic) and "forward" on the passenger's side.

 

That's because it's a straight vane rotors as gnatster showed above.

Only a true directional casting has any direction to it. Slots, holes, dimples, etc all mean nothing in the air flow. Most directional rotors do look like the "off car" pic (RF) shown as this is how the hole patterns develop when you do the drilling. You could however have a swept back appearance also if you were to drill three holes per air slot for example but that's often many, many more holes than one would want in a rotor....at least me anyhow.

Oddly Chevrolet did the same thing on the Vette some years ago. But they got it all wrong! They had A true directional casting. But used that ONE on each side! At lower speeds it's doesn't mean much though.

 

Well, I have the Wilwood rotors on the front so I'm not sure if they are directional vanes or not.

AND - good to know, it doesn't mater what direction the cross drilling takes because they are non-directional in function.
Some have told me they actually lessen the braking ability of a rotor but I'm not exactly sure why.

Thanks guys.

 

Base Wilwood kits are non DV. (Directional Vane)
The drilled and slotted rotors are also non DV.

The 'race' kits and those with "GT" rotors are DV.
All TCE/Wilwood kits (except solid rear rotors) are also DV.

Yet for the average street enthusiast it's not really that big a deal, clearly not for the daily driver at least.