Join Date: Sep 2011
Location: Aylesbury, , United Kingdom
Make: Honda Goldwing
The purpose of slots on the sides of brake rotors is: to provide an escape path for expanding pad gasses being generated by the braking torque.
In EXTREME situations the outgassing from HOT-HOT pads can physically push the pads off the rotor- despite having your foot or hand buried!
Not a situation encountered in sane street riding, mountain fun maybe, Maaaayyyyybe
On the track, yep
Getting Your Groove On: 2 schools of thought- forward or backwards in relation to direction of travel ~,
Or is that mostly for show- as its not about cooling or dissipating heat- its an escape path
Note: A rotor clearly marked LEFT shouldn't need a directional arrow as well
Just because you all drive on the wrong side of the road over there.........
I've just had another look at my new rotors and laid one on top of the other in the same position they would be on the bike i.e. outside edges facing out. The vent holes exactly match each other, which presumably is intentional to get their direction right, and the holes don't look like they have been drilled through at any angle. There are no vent grooves cut into the rotors. The thickness of each rotor is identical and the mounting holes exactly line up. The service and runout specification is stated as being the same for each side so they do look identical.
Maybe Honda marked one as "left" and had a different part number just for assembly line packaging purposes or maybe just for research purposes on which side sold more replacements if they wore out faster (because of the linked brakes influence). It is though for each person to make their own decision on whether to use them on opposite sides.
And Aloha Tom...you are exactly right, we do need directional arrows here as we do get confused between left and right. You drive on the right which we think is wrong and we drive on the left which we think is right!
Harley Fatboy 2004
Triumph Rocket Touring 2010
Honda Valkyrie 2002 (fantastic!)
Pan European ST1100