rfn026

Here's my blog on brake rotors. This is Part 1. Part 2 will appear later in the week.

Richard Newton
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X25

Nice write-up. I'll wait for part two before, like a snob, I comment about what else I'd love to see covered :-)

John Shiels

Nice article. Don't take it for granted all two piece rotors are lighter than one piece OEM or others. Modern pads that are decent don't out gas like pads of yesteryear. Personally seat of the pants I did feel slotted rotors are a bit better in stopping on my car.

naschmitz

Grabbing my hammer now ... Great write-up.

2K6Z06

Great write up! Looking forward to part 2

VetteDrmr

Richard,

Nice brake writeup, as well as the rest of your blog!

Thanks for sharing, and have a good one,
Mike

John Shiels

Only thing I find hard to believe is that 20% of the rotors are still made in this country.

John Shiels

Shape of a one piece (cone) makes it more liable to crack than a two piece flat rotor. Personally I have cracked many NAPA premium rotors. Flat rotor is all in one plane unlike a cone.

383 Z06

Great write up...I'll be following that blog from now on

moespeeds

I cracked my Wilwood Spec 37's and the NAPA premiums! What the hell am I doing wrong???

jcsperson

Keep 'em coming!

rfn026

I think a lot of the rotor cracking comes from thermal shock. You really have to carefully break in your rotors. That's in Part 2.

Richard Newton

moespeeds

I'd like to hear it. I break them in as per manufacturer's instructions. Basically do stop and goes from 60-0 until I get brake fade, then drive around to cool them, then repeat. The NAPA premiums usually won't last 2 days before I crack the drivers front, rears last about 4 days, and the Wilwoods got me about 8 days before they cracked off the edge. I've got a set of Spec 37 slotted here so I'm anxious to see how long they last. I always drive around the pits to cool my rotors, and the IR gun says I'm around 400 degrees on the drivers front when I shut down the car.

drivinhard

The Spec37's have lasted longer than any rotor I've run, by far. I started running them at nationals in 2011 and they've been on ever since. 4 wheel to wheel races, 25-30 time trial days, and lots of taxi cab rides. That includes about 3 weekends at CMP and one of those I ran ever lap of every session testing shocks. A weekend at CMP is about like 2-3 weekends at any other track on brakes.

Hard stops is bedding in pads. That's not breaking in rotors. Rotors like to be seasoned, basically street driving, lots of mild temp heat cycles. Season the rotors gently, then bed the pads. I always try to cool them down a lot before parking in the paddock. Pad choice also affects rotor life. Carbotech wins here in my experience.

Bill Dearborn

I break in my rotors and I have cracked them all. Stock, NAPA Premium, front and rear, two piece AFX front that only last a couple more days than stock one piece rotors. The only ones that worked well were my AFX rear brake rotors on the Z. I got 20 track sessions and a bunch of autocrosses out of them before I actually had to toss them because they were to thin. The slots were worn away. Much better than the stock rear rotors which usually cracked after 3 or 4 days with nary a heat check on them. Would really like to find a front rotor that would last as long as those rears did.

Added ducts to the center of the front rotors, added ducting from the fog lights to increase cooling air flow and the rotors don't seem to last any longer.

Bill

moespeeds

My car isn't street legal, so breaking them in on the street isn't an option. I do have DRM cooling ducts on the front. And what about when you have to change rotors at the track? I crack a rotor before lunch, now what do I do to break in the new ones when I only have a few min before I go back out?

drivinhard

Do it where you are doing your 60-0 stops? paddock? access road at a track? Just don't do as many of them in a row, and do it a few more times with cool down time in between.

You don't HAVE to do it, but the rotors/rings typically last a bunch longer if you season them.

Also I try to warm up the rotors before they are used to the max, ie, use the first 1-2 laps to bring them up to temp before you are setting off on a lap record attempt.

moespeeds

Here's what Wilwood recommends:

Go to Rotor Page
Rotor Bedding
All new iron rotors should be bedded-in before being used under racing conditions. Proper bedding-in will prepare the rotor surface, prolong the rotor's life and make it more resistant to thermal checking or cracking under severe braking conditions. The following procedures should be followed when bedding-in rotors:

Thoroughly inspect all brake system components before proceeding to track. Check all bolt connections, make sure mounting bolts and rotor bolts are properly lockwired, that brake pads are properly secured by retaining clips or cotter pins, that master cylinders and brake pedals are working properly, that brakes are properly bled with plenty of fluid, and that proper engagement of brakes occur when pedal is depressed.
Because the bedding process is different for rotors and pads, it is best to bed-in a new rotor (disc) using a used set of pads, preferably ones which will not create heat rapidly. Generating heat too quickly will thermal shock the rotors. Likewise, when bedding-in a new set of brake pads, use a used rotor. This new-used bedding process permits controlled bedding of each individual component.
Make sure that the rotor surfaces are free from oils, grease and brake fluid.
Close air ducts approximately 75% to expedite the bedding-in process.
Run vehicle up to moderate speed and make several medium deceleration stops to heat up the rotor slowly. This will help reduce the chance of thermal shock caused by un-even heating of the rotor.
Pull into the pits and allow the rotor to cool to ambient air temperature.
Do not hold brakes on after performing the bedding-in procedure until cooling is completed. This will avoid “hot spotting” or un-even cooling which can damage the rotor.

Diversified Cryogenics (frozen rotors) recommends 12-24 progressively harder decelerations. Do not exceed 700 deg. Cool, then repeat.

froggy47

Please elaborate.

JRitt@essex

Good basic intro to brake discs.

Here's how I recommend bedding in your pads/discs...shown in my C5 Z06.

Also, here's one I did on swapping from street to track pads and managing your discs.

As others have mentioned, managing your pads and discs properly can make the difference between having your brakes work well, or having vibrations, cracking, etc. In professional racing we have very strict bed-in, or burnishing, procedures depending on the specific disc and pad used. We have computer controlled machines specifically designed for this purpose. You can see one here. We burnish thousands of discs per year for race teams.