34 replies to this topic

[Jamz14]

Brian,

 

It is part of the proper bedding process to let the pads and rotors cool completely. At least from every manufacture that I have worked with including, Ferrodo, Hawk, Carbo Tech, ETC.

 

People are getting away with bedding outside of reccomneded procedures. That is great, and if they are comfortable doing that, they should and will keep doing that. But proper bedding includes a cool down. People are looking for someone to tell them that what they are doing is ok. But a manufacture is going to tell you to follow their bedding instructions. They will also tell you that their prebedded pads don't need bedding, I mean what else would they tell you?: "Hey customer, our prebedded pads need to be bedded too??!!! Buit what no one has addressed is Dave Wheelers (and mine) that bedding isn't only for the pads!!!! It is for the rotors too! It lays down a layer of material that fills in micro cracks and places a layer that will heat evenly around the rotor preventing warping of the rotor. Exactly how would a prebedded pad accomplish this?

 

This is so simple; either accept the safe advise or feel comfortable buying into marketing, or feel cpomfortable that you can effectively bed the pads outside the reccomended procedures. We don't follow the manufactures reccomendation for timing of the cars do we?

[Danny Steyn]

Danny-

Do you run pre-bedded brakes?  I was under the impression that part of the bedding process was to let them cool off after the initial heat cycle. 

 

Brian

 

Brian

 

No just add new brakes and rotors, go out, gently drag brakes for 20 or 30 seconds to get material transfer, then do some acceleration / deceleration's increasing the intensity and they are good to go.  Remember that our cars are very light and have very little HP so we are carrying lower speeds than most classes, so we are nor nearly asking as much from our pads as some of the other heavier more powerful classes. 

 

However according to my dad's favorite saying,  "man has an infinite ability to justify his actions", so in this case I might just be too lazy to do it the proper way.

 

As I said before, YMMV so find a way that suits your driving. On the other hand you will most definitely have situations where a brake pad comes apart in the last qually session before the main race and you will have no option but to bed your new brakes and/or rotors in on the pace lap, so you might as well get the hang of it to see if it works for you

[FTodaro]

there is the proper way and then the way that you have time to do it. Sometimes you just have to make compromises. sometimes the difference between the proper way and the lazy way is not much or measurable.

[Juan Pineda]

I find that PREBEDDED Carbotech XP8/10's don't need any on-track bedding. Just dragging them a bit on the outlap is sufficient. The first brake application may be a little weak, but after that, they are fine. Occasionally I forget that I'm going out on new pads and don't even realize until I come back in. Hawk Blues were the same way.

 

This is so refreshing vs other pads like Pagid's on my 911 that always had uneven transfer issues. And you wasted one session on bedding. Take-away: only use pre-bedded pads (or pads that don't require bedding.)

[Bruce Wilson]

I'm not really sure what bedding rotors actually means.  The way I see it is, bedding the pads transfers some of the material onto the rotor.  BUT what I do know for sure is you NEVER EVER want to use a different pad compound (even from the same manufacturer) without turning the rotor to remove the old pad compound material.  Tried it twice, once on purpose and once by accident... The first time was annoying, but the second time, my teeth were rattling at the end of a 24 hour race

[Muda]

Learned to bed pads on the pace lap last season.  You don't always have the luxury of wasting a session bedding pads.  And what happens if you have a brake issue in the session before?  Didn't really notice the difference after the first brake zone.

[wheel]

You can also use a DA sander on rotors (rather than turning them) when changing pad compounds.  As Bruce pointed out, you should not change compounds without either changing or cleaning rotors.  

 

wheel

[ChrisA]

And what kind of compound is transferred to the rotors from the sandpapers?

[wheel]

The sandpaper takes off the old brake pad compound and leaves clean rotor.  Sand them with the DA and spray on brake cleaner.  You then can change pad compounds without the issues that Bruce brought up.  

[ChrisA]

^  Found this on the StopTech website. The topic is discussing pad deposits removal, but the cleaning method & caution applies here. 

"The obvious question now is "is there a "cure" for discs with uneven friction material deposits?" The answer is a conditional yes. If the vibration has just started, the chances are that the temperature has never reached the point where cementite begins to form. In this case, simply fitting a set of good "semi-metallic" pads and using them hard (after bedding) may well remove the deposits and restore the system to normal operation but with upgraded pads. If only a small amount of material has been transferred i.e. if the vibration is just starting, vigorous scrubbing with garnet paper may remove the deposit. As many deposits are not visible, scrub the entire friction surfaces thoroughly. Do not use regular sand paper or emery cloth as the aluminum oxide abrasive material will permeate the cast iron surface and make the condition worse."

[Keith Novak]

Last time this topic came up a couple years ago, people had said you could put on some Hawk Blues, and because they're an abrasive pad rather than one that deposits a layer of material to the rotor, it will just scrape off any other pad material.

 

Can anyone confirm or deny this urban legend?

 

I tested Carbotech's back to back this weekend with Hawk DTC pads and the look of the two rotors was very different.  The DTCs did not leave any visible material on the rotors compared to the Carbos.

[SaulSpeedwell]

Anyone remember when Daniels would just enter a thread and say "10 foot pole"???

 

Brake nerds call the pad/lining-to-rotor/drum interface "the friction couple", and my experience is that some stuff needs no special handling, and some stuff needs symphony music and a 15 minute shoulder rub to get it working the first time, else you are going to have a bad time.

 

"Pre-bedding" ain't really "bedding" at all, it is really what I would call "post-cure" or (I'm about to invent a term here--->) "pre-outgassing" in an attempt to combat all the weird stuff that happens the first time you bring the friction material up to 700, 900, 1100, degrees in REAL USE.  As far as I know, "pre-bedding" is, essentially, a "baking" of the brake pad after the initial manufacturing, curing, cross-linking, whatever-the-hell-else-is-happening-ing during the making of the friction material and joining it to the backing plate.

 

80% of the time I've had "bedding" problems, I'd say it is the rotor's fault - usually by being too polished, or oily, or being coated in something weird (Chinese "galvanizing"?), or by not being flat (i.e. half-inch wide scorched and blued surface on the inner or outer "edge" of the rotors). 

 

The blanchard grinding (orbital swirls) found on some rotors is intended to improve "bed-in" on the street.  I think it causes problems in commuter-car racing, especially if you are running a compound that DOESN'T wear away rotors quickly.  Why?  Because the poor pad is trying to grab only those high spots of the rotors, and it is like you have 10% of the rotor surface working for you until you get the swirls worn away. 

 

My personal #1 brake bedding rule:  Overusing the brakes before they are "bedded" is bad.    Overusing them more isn't helpful, although some compounds (high rotor wear compounds) don't seem to care at all.  If you have scorching and bluing on your rotors after your "bedding" session, you have overused them. I HATE running untested "unbedded" brakes for a race.  Overusing brakes is like overdriving tires.  Once they start to go off, back off and let them come in, especially if they are new.   Just my $0.02 opinion.

 

Disclosure:  Carbotechs were my pads of choice, and I am friends with those people.  If you also like Carbotechs, my experience is that rotors that you get "bedded" to work with Carbotechs will continue working for several sets of pads.  The rotors will work so long that they eventually will get thermal fatigue cracks large enough that pizza slices of rotor will break out (this is known as "Pulling a Murdick" in GLDiv).  Get junkyard Mazda rotors with a zillion heat cycles of "toughening", turn them down to get a fresh flat surface, and you should get several sets of pads out of them.

[SaulSpeedwell]

Last time this topic came up a couple years ago, people had said you could put on some Hawk Blues, and because they're an abrasive pad rather than one that deposits a layer of material to the rotor, it will just scrape off any other pad material.

 

Can anyone confirm or deny this urban legend?

 

I tested Carbotech's back to back this weekend with Hawk DTC pads and the look of the two rotors was very different.  The DTCs did not leave any visible material on the rotors compared to the Carbos.

 

I'll confirm it.  Hawk Blues (and other high temp high rotor wear compounds) remove pretty much anything resembling a "transfer film" (and a fair amount of the rotor itself).  Blues are particularly "abrasive" to the rotor when not up to temp.  For idiots like me who used to run the One Lap Of America back when Hawk Blue seemed to be 80% of the commuter-car track pad market, we would lose more rotor in between tracks than at the track itself.  That's when I first stumbled onto Carbotech (pre-Puskars), and I still put that 1521 compound on all my toy cars - especially if the rotors are expensive. 

 

Many compounds OTHER than Hawk Blue or similar will leave a "smear-y" looking layer of itself on the rotor.  I have seen people occasionally have trouble getting Carbotechs "bedded".  If the rotors are already working with CT's compound, they should "bed" quickly and be fine.  If you rush it, you can get deposits that cause chatter.  See also last line in previous post.

 

I know nothing of the DTCs.  Never ran 'em.

[ChrisA]

Here's a pretty good presentation given at a David Murray track day. Obviously, not everything is transferable over to Spec Miata, but there's some good stuff in there.  http://vimeo.com/88706930

[Bruce Wilson]

I have no doubt Blues will remove everything that needs to be removed, probably better than a DA.  I'm guessing I'm the only idiot who has tried bedding blues on a hot summer night on a country road lined by wheat fields.  The sparks were shooting 10+ feet in the air.  I drove home quickly expecting to hear fire engines roar past me on the way to the grass fire!

 

Btw, the "chatter" we felt on the enduro car at the end of 25 hours ended up being almost an inch of runout (warped rotors due to uneven smear-y stuff).  My foot was bouncing off the brake pedal under heavy braking...  But all ended well, we won the race.  It all goes to show that the lack of braking makes you go faster