Drilled disks

I'm upgrading to dual disks on my bike .
Why did Kaw go with this hole pattern and can someone clue me in on how they should be installed relative to each other , the holes don't line up .
Thanks,

JD

I don't believe they need to line up. Ed

I don't think I have seen one drilled like this.

I think they are from a KZ650. Ed

They are as common as a $1.00 bill.

I believe the uneven pattern is to prevent harmonic resonance.

I have wondered the same thing JD. Then it occurred to me that maybe the last stage in the process is riveting the mount to the disc I am pretty sure minimum wage in the US was 2.65 an hour back then and probably that or less per day in Japan just maybe the guy doing the riveting didn't care very much about symmetry

function was its primary goal it was just a bonus the racers drilled their rotors to keep weight and cool the brakes
drilling them saved them tonnage on import taxes. but then again it was the 70's maybe i'm wrong

seriously if someone has the answer I would love to know I fiddled with mine for longer than I want to admit when redoing my front end

Another reason "back in the day" that they drilled discs was due to the resin compounds that were used in the brake pad material itself. The resin when heated would give off a gas. The gas would build up, trying to force the pad away from the disc. This would allow venting of this gas during those times of super hard braking.

Now I think weight savings is the biggest driver of drilled discs currently. As gore the pattern, one idea besides harmonics is that if all the holes would line up, it may cause a weakness in the disc. Kinda like putting two wood screws into a 2x4 on the same line in the grain. Don't know if this is true, but might be why they staggered the pattern.

Cory

I drilled the disc on my KZ900 way back in the 70's with an even pattern and never suffered harmonic vibrations.....

toolmaker wrote: I drilled the disc on my KZ900 way back in the 70's with an even pattern and never suffered harmonic vibrations.....

It was Good, Good, Good vibrations back then.