Well, I decided yesterday to crossdrill the front rotors on my TA . The rotors are shot anyway, they are below minimum thickness, one has some minor heat checks, and both have some small cracks in the center of the pad area. I also wanted to check my passenger side spindle and bearing, seems that the face of the bearing eating into the spindle is a common ailment on these cars, every one I see in the junkyard has the same stupid groove cut into the spindle that my car does. So far, the ever so slightly larger bearing I found is doing ok. My objectives were to see if there was any real braking difference, what the weight difference is, and then over time find out how the rotors hold up... I hear alot of stories about crossdrilled rotors cracking, but the few that I machined while I was working in a machine shop were very much in good shape with no cracks at all.

First thing I did is disconnect the battery. Heh. Really! For some reason, it was dead, and I figured I'd throw it on my dad's battery charger for a while. After getting the rotor off, I cleaned it up a little (it was fairly clean anyway) and threw it on the scale. I didnt bother to take out the rear bearing or seal, but the front one was not in there. It weighed in at 18.2 lbs. Yikes, pretty heavy little sucker. Now for the real fun!

To drill them I started by spending about 20 minutes trying to find something to line up the rotor on the mill so I could easily turn the rotor but have it be secure enough to drill into. I wanted the back side facing up, so my marks wouldnt be visible to most when I was done. I finally got it all set up, seemed to be working ok. After that, I marked the centerline of each vent to about 1/8" accuracy. I figured that would be close enough for what I am doing. Then I put a sharp drill in the mill, and turned the rotor to leave a nice scratch to have good circle to line up my holes on. Then it was time to decide what size holes to drill. I started with a 3/16" drill bit, and drilled away. The material really isnt all that hard, I was expecting more problems. After the first hole, I took a look at it... nope, I dont think thats big enough. So, I get a 7/32" drill, and drill that. Yep, that'll work. So I made some rough guesses where to put the holes, and made some felt pen marks on the rotor. I wanted a 3 hole pattern, one near the center, one middle, one top. I was contemplating putting the bottom and top holes in the same vent, and then the middle hole would be by itself in the other vent. Dumb idea. I went at it a little too quickly, and realized the hard way that I should have lined out my holes a little better at first... whoops! So, I came to find out my front rotors have 33 vents. After I drilled most of the holes around the outside path, come to realize its not going to line up right. So, they arent symmetrical. Eh, this is an experiment anyway. So I ended up drilling 50 holes in the rotor. After I drilled all the holes, I chamfered them with a 45 degree chamfer bit. They actually look much better when they are chamfered. Then I had to flip the rotor over and chamfer the other side. Finally, done deal.

Unfortunately (and as it turns out, fortunately ) I only got one done. I cleaned the rotor up, which was a total mess now from all the shavings and cutting oil. Took it inside, and threw it on the scale. 17.7 lbs. Thats a .5lb decrease! Cool deal! So now its time to throw this sucker on the car. I get it mounted on there, and take a couple pics of it. I purposely hid my screwup I'll have pics up soon as they get developed. Install went pretty quickly, no real problems. In putting the tire back on, I bumped the rotor (towards the back of the car) and hear a distinct "thump". WTF? Hmmm. So I grab the shock, and start moving it around... theres the nasty clunk I have been chasing! The strut mount is FUBAR! Oh well. So, tire on, tightened, time for a test drive.

First thing I noticed, was under braking the car now pulls to the left. Why am I not surprised. The loss of braking surface on the right rotor from all the holes DOES make a difference. Its not bad, but it will change lanes if you dont hold the wheel. The harder you brake, the more it pulls. Its not too bad, I can easily keep it in line with my hand on the wheel but there is a definite pull now. Well that sucks. Guess I HAVE to do the other rotor now! So I get home after some seriously hard braking, and get out of the car. I put my hand up to the driver side wheel and its pretty warm, too hot to touch by any means. So, I go over to the passenger side... WOW! The rotor is barely warm! Cant even feel any heat coming off of it! I was expecting it to run cooler, but sheesh... this is rediculous.

So, I think when I do the other side, I will only have one hole in each vent (which will improve the braking slightly I figure) and the rotor will be plenty cool under hard braking. And lighter The long term experiment of cracking I will have to wait and see how they hold up. I figure I have the worst case scenario here, the rotors already have tiny cracks in them, and they are below minimum thickness as well.

Time for a tech article.

 

I did a brake job last year sometime on a guys car, that had home made slotted rotors on it. (This post just reminded me of it)

It looked like the small grooves were made with a dremel tool or something, and were not even close to uniform in shape or length.

He initially brought the car in to have us check why it had a pulsation in the brake pedal. Hmmmm....

Anyways, sounds kinda interesting. I'm curious to hear about how that holds up, and if your pads will wear any faster.

Hellraiser

 

Madmax- check your e-mail. Subject: strut mounts