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.
- The hats (front and rear) use eight 5/18-18 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.
- Since I track the car occasionally, and know how hot the brakes can get, I new 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.
- Wilwood has an excellent article about safety wiring rotor bolts(DS386.pdf). I chose to follow this.
- 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.
- Street cars could probably get by with Grade 5 bolts but what the . . . , we’re driving a performance vehicle.
Staying with the period correct theme, your selection of wheels is pretty narrow. I chose Trigo wheels, now being produced by SoCal Speedshops. (They’ve purchased the line from Lynn Park)
The system uses an adapter that bolts to various bolt patterns and provides the large center thread for the knock-off.
The pins serve as a lugnut to hold the adapter on but also serve as the drive pin in the wheel. As such, their location must be pretty exact. All five need to line up just right so they will slip into the recesses in the wheel.
Trigo makes a bolt spacer template that helps in this process. While tightening the pins, the template can be slipped over the pins to check that everything lines up just right.The instructions provided to me by Mr. Park call for the pins to be torqued to 60 ft.lbs and no mention of any thread locker. If you are concerned, you might use blue Loctite. I wouldn’t recommend the use of red since the adapters may need to come off and the only way to removed the red is by heating the parts. This could damager the heat treating of the components.
click to view Trigo_Instructions
Tightening the pins isn’t the easiest thing. A tool that slips over an adjoining pin makes it easier but be very careful. If it slips off, you can seriously hurt yourself
The other tools necessary are a 6lb lead hammer and safety-wire pliers. I also learned a trick of tightening the spinner using a piece of 2 x 2 Oak about 24″ long. Hitting it with the hammer and holding it to the spinner makes for an extension and keeps you from hitting the wheel.
Do your own search on which way the knock off should be mounted. It makes for a great controversy. I finally figured out the way to remember correct rotation is the knock-off should spin towards the rear of the car when being tightened.
Need help on how to safety-wire, click here.
Assembled Front wheel bearings and rotor. Mounted first Trigo.