how does everybody come up with the "pattern" they use for drilling the holes in the face of the rotor and what size holes, how far to stay away from the edges, how many holes, chamfered holes or not, etc?????

_________________
Just Stand On It!!!!

Chris

Excuse me if this is dumb, but why are buggy rotors drilled?

##,and more #

_________________
If your clutch ain't slippin,, you probably got it adjusted right!!!!!

well evidently it must be better on everything from 4 wheelers, dirt bikes, all the way to nascar so why not a buggy

not to mention the obvious that marty stated,,,,,,,,,,,,, saves weight

_________________
Just Stand On It!!!!

Chris

also they stay cooler if your on them alot

This is gonna be hard to explain, and I'm no expert... but I'll take a stab at it.
A rotary table on a mill is the best way to do this, but you can pull it off on a good drill press with a little patience and layout time. It won't be truely accurate, but it'll work in a cave man kinda way.
First you have to decide how many rows of holes you want. The less rows you have, the bigger you can go on the drill size.
If you don't have access to a rotary table, a vernier caliper will do for laying out your pattern.
Paint the face of your rotor with blue dykem, or color it with a black magic marker...or spray it with flat black primer.
Measure the face of your rotor, take that measurement and divide it by how many rows of holes you
want + 1....For example, say you have a 2" face and you want to lay out 4 rows: (2 / 5 = .400)
A 2" face with 5 rows: (2 / 6 = .3333) , etc.
Now set your caliper to your row width, lock it, and scribe evenly spaced rows on the rotor face.
Now pick a spot on the inner most row and use a sharp center punch to mark your first hole.
Now the hardest part....you have to figure out how you can evenly layout your holes on the circumferance of that inner row. The only way I've found to do this without a rotary table is by trial and error, but you can use some basic math to get a ballpark starting point.
Use your calipers (probably need a 8" or 12" caliper to do it this way) to accurately measure the diameter of your first row. Multiply the diameter X pi (3.14) to get the circumferance of that circle, then divide that by how many holes you want to lay out.....For example, say you have a 7" dia circle: ( 7 X 3.14 = 21.98) and you want to lay out 12 holes ( 21.98 / 12 = 1.8317 )
Problem is, that circumferance is round and all you can do with a caliper is measure straight across. I'm sure there's a better way [somebody chime in here], but what I do is just add .040 or so to the base figure (1.8317 + .040 = 1.8717) set the calipers to that, start with your center punched mark, and scribe around the circumferance of the first row. Ideally you'll end up dead center back on your center punched mark, but it'll take a few times of tweaking the measurement to hit it (save this measurement).
Once you find the magic combination, go ahead and center punch your entire first row.
Now you have to decide what kind of pattern you want and lay out the other rows accordingly.
Say you want the standard radius arc type pattern....remember that measurement you saved?...set you caliper to that dimension and lock it. put one end of the jaw in a center punched hole and use the opposite jaw to scribe a line on your second row. Go to the next centerpunched hole and do the same...continue on around until you have your entire second row layed out...then center punch those, and continue the pattern until you have the entire face layed out and punched.
On your other rotor, you can do the same pattern in the opposite direction...this way you'll have left and right rotors that match.
When your ready to drill.... keep in mind that if you have a double face rotor there will be vanes in between. Alot of your holes will be partially drilling through a vane and this will make the bit want to walk. Start with at least a 1/4" bit (so it doesn't flex as easy) and go slow. The stepped type pilot bits work good for this.
Once you have an entire rotor drilled, check it out...if you want bigger holes just take them up another size or two. When your done use a couple sizes bigger bit to chamfer all the holes.
Your rotors are gonna end up out of balance. On the trails or at moderate speed, or if your running v treads or cut tires you'll never notice...but if your gonna hit the road and see some highway speeds on good tires, you'll probably want to have them balanced.

pros and cons on drilling them
pros, lighter and stay cooler
cons mud packs in the holes and common brake noise
less brake pad life

we put solid rotors on our sport quads because we would burn thru a set of pads every ride ,now we go thru 2 sets a summer

good luck
jason

_________________
Theirs no replacement for displacement !

Such a waste of time. No advantage for what we do.

_________________
Of all the things I've lost, I miss my mind the most.
M
A
G
A

Agreed.

Drilled discs don't stay cooler. You loose more surface area from drilling the hole than you gain unless you use tiny holes, and then they just concentrate the stress and crack instead

Grooves are okay to clear mud and water from the pad surface, but tend to fill up after a while.

If you want some light rotors that keep the pad (not the disc, the disc runs hotter) cooler and push the dirt and water off...



Even better if you're on solid discs because you can get the whole thing knocked out at the laser cutters.