Brake Rotors, Safety Wire and bolts.

In the process of developing a brake set for 15″ pin-drive wheels, I was introduced to the world of brake rotors and brake hubs. No more single cast units, no more factory stock units. I chose Wilwood as a supplier and as I got into it, I learned there are a number of little tricks to attaching the rotors to the hats.

  1. The hats (front and rear) use eight 5/16-18 bolts to attach the rotor to the hat. Many are using red Loctite to assemble these and ‘calling it good’. But a recent article in Hot Rod (Jan, 2019; High-Tech Braking Systems) caught my eye and put me onto another path.
  2. Since I track the car occasionally and know how hot the brakes can get, I knew I needed to be at the upper end of performance. Knowing the brakes can get over 800 degrees and Red Loctite loosens at around 525 degrees, the last thing I wanted was rotors or bolts coming loose.
  3. Wilwood has an excellent article about safety wiring rotor bolts(DS386.pdf). I chose to follow this.
  4. Next trick was to come up with the appropriate bolts. Aircraft AN bolts are fine thread, I needed coarse. I’d previously tried to drill bolts for safety wire with less than stellar results. Then I found a little drill jig made by Allstar(ALL10122). Problem solved – almost. It took a few drills to learn I needed cobalt drills to drill the Grade 8 bolts. With a little trial and error, I learned the correct drill speeds (around 500 rpm, regardless of what the internet or drill press label says) and that you need to clear the chips VERY frequently. Also, when you begin to hear the drill chatter as you break thru, back off the feed, let the drill do the work. You will break a few drills till you get the hang of it. Also, don’t scrimp on drills. You get what you pay for and there is a noticeable difference between a cheap and quality drill bit.
  5. Street cars could probably get by with Grade 5 bolts but what the . . . , we’re driving a performance vehicle.

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Posted 03/21/2019 by Paul Proefrock in category "Brakes, Wheels & Tires