drilled frt brake rotor weight

[jim martin]

has anyone weighed there stock frt disc brake and weighed a drilled version of the same rotor .
just looking at weight after its drilled

[Geoff]

Bruce has and should have that info.

[jim martin]

 speak up Bruce.
i did weigh a original frt disc with studs and bearings = 17 lbs

[Bruce]

I've got a template that fits Type 1 Ghia rotors.  It also fits 914 rear rotors, which are the same as most aftermarket kits.  It has 48 holes that are the same pattern as what the Japanese motorcycle makers use.  It is NOT the silly spiral pattern that everyone uses.  Most of those I've seen are drilled wrong.  Even some OEM rotors.

When drilled with a ¼" drill, the weight reduction is 113g per rotor.  A 3/8" drill gets you 255g.  
For you metric heathens, that's .25lb and .56lb.

Beware, when you drill them, they will make a LOT of noise.  Think about blowing across the top of a bottle, I think that's what makes the noise as the pad swipes over the holes.  The set I drilled with a 3/8" drill were for Larry, and he reported they were so noisy, that he took them off right away.  I've got one pair that are with ¼" holes, and I don't like them.  I remember after I put them on my car, I was in SoCal soon after.  Bill wanted to drive my car to test out the gear ratios I picked for my 5.  As soon as we got over about 20mph, he asked if I had drilled rotors.  He noticed it right away.  If you have solid trans mounts, you're probably going to be ok with the noise.  It will be minor by comparision.

[buddy boy]

what about going the "slotted" route

[owdlvr]

Beware, when you drill them, they will make a LOT of noise.  Think about blowing across the top of a bottle, I think that's what makes the noise as the pad swipes over the holes.  The set I drilled with a 3/8" drill were for Larry, and he reported they were so noisy, that he took them off right away.  I've got one pair that are with ¼" holes, and I don't like them.  I remember after I put them on my car, I was in SoCal soon after.  Bill wanted to drive my car to test out the gear ratios I picked for my 5.  As soon as we got over about 20mph, he asked if I had drilled rotors.  He noticed it right away.  If you have solid trans mounts, you're probably going to be ok with the noise.  It will be minor by comparision.

Chamfer each hole and that should eliminate the noise.

Slotted rotors should have no noise.

-Dave

[Bruce]

Chamfer each hole and that should eliminate the noise.

Nope, didn't work.

I think you're right about the slotted rotors.  I think if one end of the slot was open at all times, they wouldn't make noise.

[jim martin]

thanks for the info good to know ,just doing a little leg work for a friend .i figured it would take away about 1 lb
are the newest aftermarket discs teh same weight as original equipment?
here is what i found when i removed my front discs
17 lbs per disc complete with bearings and grease and frt ATE caliper with fluid and pads 7lbs
quite heavy at 23 lbs per wheel

my new frt and rear brakes are going to sound like a cheese grater.

[owdlvr]

Chamfer each hole and that should eliminate the noise.

Nope, didn't work.

I think you're right about the slotted rotors.  I think if one end of the slot was open at all times, they wouldn't make noise.

Very strange. I've run various brands of cross-drilled, slotted, cross-drilled and slotted and plain rotors all on my Audi Rally car. Never have I heard the noises you mention, but all of my cross-drilled versions have been chamfered. I've got slotted and dimpled rotors on my 4000 quattro currently, no noise. I used to have OE blank rotors slotted for the Rally Car on my friend's CNC mill, and they don't sound any different from blank ones. 

I'd be quite interested to see your pattern actually.

-Dave