Brake Rotor Questions

[Keith M.]

So continuing the tear down of my 69 L46. Plan for the front rotors and trailing arms is to bring to Bair's to do their thing. As far as I know rotors are all the originals. I put a brake caliper to check some measurements and getting some readings below 1.215. I will let the Bair's folks be the ultimate judge of reusability..but in the event they are trash what are thoughts on sourcing for the most originality?? The usual suspects such as Zip and Paragon would seem to have them but is there a better way to go?

[Duke W.]

Re: Brake Rotor Questions

I assume you are taking about rotor thickness and I recall new was nominally 1.25". In '68 or '69 a FMVSS went into effect that required minimum rotor thickness (and drum ID) to be placarded either in the casting or die stamped, but it might have been later. Check the parts and also check the CSM, COM, and AMA specs.

If they have no runout and are above minimum thickness, I recommend leaving them alone. Brake shops love to turn rotors because new pads will break-in quickly. Used rotors take a couple of hundred miles of light to moderate braking - normal around town driving usually does the job - for new pads to break in

Over somewhere between 5000 and 8000 miles in about 15 years I ran my Cosworth Vega in track time events at Riverside and Willow Springs. I upgraded the OE solid rotor front brakes to '76-up Monza spec which are 0.880" thick vented rotors with larger piston calipers. I swapped the entire front knuckle assemblies from a junkyard Monza with only 5000 miles, but to be safe I overhauled them and did a precision turn taking 10 thou off each side.

I went through six sets of OE semi-metallic pads, never turned the rotors and made sure new pads were well broken in prior to the next track events. When I retired it from track events the rotors were scored silly, but measured 0.845" with zero runout, comfortably above the 0.815" minimum. Any brake shop would have call them junk. I called them fantastic as nothing on street tires could out brake me. They essentially ran the 24 hours of LeMans, TWICE, with nothing, but a handful of pad changes, and I drove the Porsche and Ferrari guys nuts because I could brake later and pass them going into corners.

Bottom line is that those old parts may be better than whatever you can buy today. Save them, which is likely quite possible


Duke

[Keith M.]

Re: Brake Rotor Questions

YEs rotor thickness. My understanding is 1.25" is new...1.215" is minimum and at or below that should be trashed. I am aware of the fact that 1) they do not make them like they used to, and 2) in many modern vehicles rotors are a disposable item...made to be replaced, not turned like the old days. That said...I am getting a variety of thickness readings on each rotor with some readings below 1.215". Not sure where this will lead but anticipating the possibility of needing replacements am seeking guidance on sourcing of those closest to original. As I said I will let Bairs guide me on this based on their assessment on what I have and prefer to salvage original if at all possible. But not sure if this is a case of just replace them and be done with it. Replace them for me would mean getting closest possible to original and have them riveted in. Also, for whatever reason the lug studs on the rear do not have the headmarks of original..the fronts both do. Not sure what if anything to make of that. Probably nothing than they were replaced at some point...for some reason. Easy to replace with headmarked ones.

[James W.]

Re: Brake Rotor Questions

I had my 1965 trailing arms rebuilt by Gary Ramadei. He sourced my rotors from NAPA for the restoration. Notice the run-out data on the each rotor. Gary does excellent work.

James

[Keith M.]

Re: Brake Rotor Questions

I had my 1965 trailing arms rebuilt by Gary Ramadei. He sourced my rotors from NAPA for the restoration. Notice the run-out data on the each rotor. Gary does excellent work.

James

Dang those are purty. Bringing Gary my steering box soon. Maybe have him do the arms too. Two questions...do you recall ballpark of what the arms cost with new rotors? and do you happen to know if he redoes front rotors...replace bearings etc?
Thanks james. Very helpful.

[James W.]

Re: Brake Rotor Questions

Keith,

He has a flat rate fee plus parts. I elected to replace my trailing arm bodies due to some corrosion issues along with the stub axles because the splines where twisted and the rotors. He found all of this during his disassembly inspection and sent photos of everything. You won't get that from Bairs. I'm not sure about the front rotors. I know that is something he could do based on his skills. Give him a call.



James

Dang those are purty. Bringing Gary my steering box soon. Maybe have him do the arms too. Two questions...do you recall ballpark of what the arms cost with new rotors? and do you happen to know if he redoes front rotors...replace bearings etc?
Thanks james. Very helpful.

[Keith M.]

Re: Brake Rotor Questions

Thank you!! Was already planning to have him do my steering box and now probably trailing arms and possibly front rotors. Grateful for the recommendation.