How to break in new rotors?

[stang5]

I just replaced the warped rotors with a new set on my subaru and kept the same pads cause they still have about 50% left on them. what's the proper way to break them in or heat cycling them? thanks for any help.

 

[SSDude]

You should various stops around 35mph. Do not do high speed driving and sudden stops. Eventually take it up around 55mph and brake until you get it around 35mph. It normally takes 200-500 miles for them to get broken in. Then just drive normally. Avoid sudden high speed sudden stops during the break-in period.

 

[Ken4]

Never use worn pads on a new rotor. It will cause uneven wear on your new rotor. If you examine your old brake pad very closely, it will not be perfectly flat. If you check with a venier caliper some edges wear more than others. And if you old rotor had deep circular grooves, chances are the old brake pad will have them too. Causing your new rotor to wear unevenly right from the start.

 

[JAYCEE]

Definately replace the pads too. Also, avoid splashing through water when the rotors are hot. Cold water on hot metal warps many rotors.

 

[stang5]

I'll go ahead and change the pads too. Their cheap, what was I thinking.

 

[Rick in PA]

The best pad seating technique I've seen: The rotors were scuffed slightly with a Scotchbrite pad on pneumatic drill while the rotor spun on a disk lathe. This gave the rotors a light crosshatch finish, simmilar to a honed cylinder bore. The new pads were installed and the vehicle stopped gently from a low speed a bunch of times. This gave the pads a good chance to seat without developing glazed spots on the pads. It worked well.

 

[Kernel Potter]

Here's an article on heat cycling rotors:

http://www.baer.com/Support/TechTips.aspx?TechTipID=4


And an article on pad bedding:


http://www.baer.com/Support/TechTips.aspx?TechTipID=5


-

 

[tdi-rick]

Ken4 said,

quote:

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Never use worn pads on a new rotor.

---

I strongly disagree.

I bedded race brakes for years, and we religiously stuck to the maxim,

new disc's=old pads,
new pads=old disc's

I've always stuck to it with road brakes, with excellent results.

I pinched these quotes from the Baer site Kernel Potter linked to above.

quote:

---

"Rotor Seasoning for Street or Light Track Applications

The first step in preparing the brake system for duty is to “SEASON” the rotors. The most visible effects are that of burning the machine oils from the surface of the iron and establishing a wear pattern between the pad and rotor. The most complex task it performs is that of relieving the internal stresses within the material."

"Bedding brake pads has a couple of important effects. The friction material in semi-metallic pads is held together by an organic binder, usually a type of phenolic material. As the pads get hot, the binder boils, and burns, from the top surface of the pad. Once this burning or “Bedding” takes place the friction material makes proper contact with the rotor."

"Bedding Metallic or Carbon/Metallic Pads - (NEVER DRAG the brakes)


Note: Never “Bed” pads on rotors which have not first been “Seasoned.” Always allow a substantial coast down zone when bedding pads that will allow you to safely drive the car to a stop in the event of fade."

---

The other reason for avoiding new pads and disc's, is that when you have new pads and disc's, while you are burning the resins and binders out of the pads, at the same time the disc is burning its impurities out and is in a very porous state.
You will end up 'dirtying' the disc surface with garbage that will take a long time to clean out, in the meantime you seriously degrade braking performance. It may not be apparent in day to day driving, but would be in an emergency stop. You also stand the chance of generating too much heat too quickly in both the disc and pad, something that should be avoided for both efficiency and life, at least until the internal stresses in the rotor have stabilised.

Rick.

 

[Ken4]

So what do you do when you buy a new car? You get new pads and new rotors.

 

[tdi-rick]

exactly !

I've never quite got my head around that one.

 

[theguru]

Check with the maunfacturer of the rotor and pads. They will give instructions on bedding them in properly. Different pads/ rotors may require a different process. I found on my last set of performance brakes that I did the full bed-in process myself even though the brake place said they had already done it. Made a big difference. The brakes work as they should, whereas the previous set (same brake pads) I didn't do this and it took a long time for them to bed-in.

These pads are higher performance than standard but I think the same applies. Previously set would not even hold the car when cold until they bedded-in. Bit scary in the morning and the car park after the car sat for a while.

 

[theguru]

Here is the bedding-in procedure for my brakes as an example, however, each type of pad will probably have a different procedure.

BEDDING IN PROCEDURE PECIFIC TO BENDIX PERFORMAX

 

[doitmyself]

It seems that this seasoning/bedding process is always talked about on sites that are dealing with high performance brakes - "Rotors need to be gradually elevated to “race” temperatures before any severe use."

While probably beneficial, are these processes mandatory on street cars with standard brakes???

When was the last time you had a brake job done and the garage or dealer told you how to bed in the pads? Even if they test drive the vehicle, do you think they go through this elaborate process?

Millions of people have decent brake performance without bedding in their brakes.

Labman, what are your thoughts on this one?

 

[theguru]

I think the average brake/ pad combo could probably get away without bedding in. However, you are going to get maximum performance and best wear if you do so rather than let then bed in over 300-600miles of unknown braking applications. Besides you never really know when you will need max brakes.

 

[dickwells]

Having just put a new distributor cap and rotor on my old pickup I read the title and said to myself "geez, I never heard of breaking in a rotor before". When I opened up the thread I had a good laugh to start off my day. Tnx

 

[robbobster]

Green pads/rotors that have not been seasoned will fade quickly with the first extreme usage.

Learned that rather quickly on an autocross course in an Integra I used to own...

 

[mechtech]

If you changed your rotors, I assume there was a good reason. They are grooved, warped, or thin.
Your pads are conformed to them with highs and lows, will have hot spots, and may not be square when retracted back into the calipers.
I'd get new ones and give it the best chance for a long life, but sure, it may work out fine if your's are flat and get seated correctly.
As posted above, racing use has different conditions and requirements.

 

[JayhawkRoy]

Read your owner's manual. Subaru has a specific recommendation about how to do the break in. While I have done the procedure exactly as outlined, and our braking is not the worse for it, if you are concerned, follow the guidelines in the owner's manual.