Question for the masses on zinc rotor plating..

[Steve1968LS2]

What do you guys think of this statement:

"If looks are more important than performance, a zinc-washed rotor is fine. Hoever, if max performance is the goal, a zinc-washed rotor can become warped under severe usage as the coating melts and redeposits unevenly on the rotor. Pads can also become loaded up with the unwanted zinc media and alter the pad's coefficient of friction"



Yea, I know that the initial burn in of the new rotors can "stick" zinc to the pads but for me it has always eventually burned off. In one case it didn't and I just replaced the pads..

How true is the rest of this quote? Besides, in most cases by the time you hit the track the zinc in the swept area is but a memory.. I guess that if you put on new zinc rotors and immediatly hit the track there could be issues but I never had any problems "in the real world"

Thoughts?

[Tobey]

I have zinc washed rotors on my daily driver. It quickly wore off in the swept area just from bedding in new pads. Less than a week later, I began autocrossing it on a monthly basis. About 20,000 miles later, still no problems. I do like the fact that they aren't totally rusted.

[Steve1968LS2]

I need more input.. at the end I will tell why.. even though it is too late to fix it..

Thanks Tobey.. that is about my experience with zinc'd rotors..

[CarlC]

No problems here, but I also take it easy on the brakes until the coating is gone.

Pad inspection @ 50% wear showed no embeded particles. No unusual rotor wear was seen.

[MrQuick]

a zinc-washed rotor can become warped under severe usage as the coating melts and redeposits unevenly on the rotor. Pads can also become loaded up with the unwanted zinc media and alter the pad's coefficient of friction

that would be in an extreme situation. Some new rotors come zinc coated and i've seen other techs having squeek problems after bedding them too fast. I buzz the zink off with my die grinder and scotch brite pad. But thats me.

[yody]

Let me guess, it has something to do with tech talk in PHR?? I was thinking about getting my new rotors zinc washed, so i will be interested in seeing what the results of this are.

[MrQuick]

I thought the zink wash was more for the non friction surface rust protection? Friction surface coat wears off after seating.

[67Sally]

I thought the zink wash was more for the non friction surface rust protection? Friction surface coat wears off after seating.

This is my belief too.
W.

[Steve1968LS2]

Let me guess, it has something to do with tech talk in PHR?? I was thinking about getting my new rotors zinc washed, so i will be interested in seeing what the results of this are.

No.. bad guess..

I wrote a story on how the braking story works.. This statement was "edited" into my story. I can't say I agree with how severe it makes it sound. The worse case is the first set of pads is ruined or squeek till the zinc burns off..

When stuff like this gets added it sounds like I said it, so I was curious..

Oh, and to top it off the copy editor f'd up and repeated a paragraph.. it's like deja vu.. lol

[zbugger]

ANY rotor can warp under extreme usage. The fact that there is a zinc wash on it shouldn't matter. If it does embed in the pad and do anything, it may create grooves, but that should be it. Besides, the zinc wash should wear off within the first hundred miles at least if driven normally on the street. I don't know where they got that information from, but it may scare the unknowing.

[MuscleRodz]

I don't know where he got his information but it is not true. I can see this being the case if some idiot tries to use a chrome plated rotor though. I plan on zinc washing mine when the time comes. I have never had any problems with a zinc plated rotor. I would never track a rotors or pads that have never been bedded either.

Mike

[Steve1968LS2]

I don't know where he got his information but it is not true. I can see this being the case if some idiot tries to use a chrome plated rotor though. I plan on zinc washing mine when the time comes. I have never had any problems with a zinc plated rotor. I would never track a rotors or pads that have never been bedded either.

Mike

That was my feeling.. I've never had issues with zinc once it's all bedded in.. I guess it is my fault for not reading the final blue line before it went to press :( (the blue line is what we call the FINAL draft before it goes to press)

Usually when it goes to edit they just tweak minor things and they rarely change or add a complete thought. Oh well, just part of the gig I guess.. they also changed the way I described floating calipers to make it a bit more "positive".. but that was minor.

When I read the part in the story about the zinc wash I was like "huh? That's not right.. "

From now on I a reading every f'ing thing I write right before it goes to print so I can catch stuff like this and look for screw-ups like the double paragraph..

Dammit!

Oh!!!! I know.. I will write myself a tech letter asking about the story and wanting clarification on the zinc comment.. then I can give the correct info.. Or better yet someone can send me a letter sayting "WTF".. So who here wants to send me a letter/email about it when the January issue rolls out? lol

[Steve1968LS2]

I don't know where they got that information from, but it may scare the unknowing.

Yea.. me neither.. and isn't it great that people will read it and think I said it.. :rolleyes5

Thanks guys for helping me determine that I'm not nuts.. lol

[Steve1968LS2]

I bent the ear of a product engineer at Wilwood.. this is what he had to say..

"Regarding the issue of zinc washing, or most other corrosion inhibiting coatings, there is no correlation between the coating and a rotor's resistance to warpage. The ability to resist warpage is based on the overall mass (weight), material (differences in thermal expansion rates of various materials), and cooling surface area of the rotor. If a zinc-washed rotor becomes structurally warped, the rotor weight and brake cooling efficiency should be re-evaluated.
There can be adverse affects with zinc washing if it is applied too heavily(thick), or if a new zinc washed rotor is run with high metallic compound pads in a high temperature competition application. The problems that arise however are usually not due to warpage. If the pads become embedded with zinc and the friction is compromised, it can usually be corrected by scuffing or sanding the pad surface clean and reinstalling the pads. Uneven build-up on the rotor faces is more often an uneven layer of pad material or "pad smear" that occurs when proper bed-in procedures are overlooked. It is highly unlikely that the zinc would ever be melted and rebonded to the rotor face. The zinc wash layer is usually worn away long before the faces would reach a temperature that would melt the zinc. If the driver is feeling chatter from the pedal, and the rotors have a "smeared" look on the surfaces as opposed to a smooth appearance, the rotor surfaces will need to be restored. This can usually be accomplished by sanding away the pad build-up or resurfacing the rotors until they are smooth again, and then re-bed the pads. It is often a good rule of thumb to bed new rotors with used pads. This can prevent unseasoned pad material from building on the rotor faces. It can also prevent the zinc from clogging the faces of the new pads. In order to simplify and expedite the bedding process, Wilwood rotors intended for high temperature, race-only applications are usually not zinc washed. But, for any real competition or high temperature application, the primary consideration for rotor selection should be on weight and cooling capacity, and mot necessarily the surface treatment."

I'm going to run this in the Tech Letters section so people have the right info on the concept..

[David Pozzi]

Steve,
My thinking on rotor warping is you can't warp a rotor by overheating it unless you got to the point of almost melting it.
The warping would come from improperly cooling it. Let's say you run on a racetrack and come in with the rotors way too hot, you then just let the car sit and cool, the calipers cover one part of the rotor, this part does not cool as rapidly as the rest of the rotor and causes it to warp.

In my reading of brake books, I've seen warnings to carefully cool the brakes on the cool-down lap. I haven't seen warping as a result of simple overheating.

[Steve1968LS2]

Steve,
My thinking on rotor warping is you can't warp a rotor by overheating it unless you got to the point of almost melting it.
The warping would come from improperly cooling it. Let's say you run on a racetrack and come in with the rotors way too hot, you then just let the car sit and cool, the calipers cover one part of the rotor, this part does not cool as rapidly as the rest of the rotor and causes it to warp.

In my reading of brake books, I've seen warnings to carefully cool the brakes on the cool-down lap. I haven't seen warping as a result of simple overheating.

I would agree.. warping is caused by the uneven heating and cooling of the metal as it expands and contracts unevenly..

Can I tell you how I see people come off a hot lap then park and set the e-brake

No biggie.. I got the good info in the tech letter section thanks to an email from a reader so people will have the correct info.. don't fear the zinc!!

[protour_chevelle]

Steve,
My thinking on rotor warping is you can't warp a rotor by overheating it unless you got to the point of almost melting it.
The warping would come from improperly cooling it. Let's say you run on a racetrack and come in with the rotors way too hot, you then just let the car sit and cool, the calipers cover one part of the rotor, this part does not cool as rapidly as the rest of the rotor and causes it to warp.

In my reading of brake books, I've seen warnings to carefully cool the brakes on the cool-down lap. I haven't seen warping as a result of simple overheating.

I have a question regarding this statement. Come summer time when my car is running and I'm competing in Solo II... Some times we do back to back runs with at most 7 minutes in between runs(up to 5 runs each) What would be the best way to cool the brakes, or is the 7 minutes slowly rolling in the lanes good enough?

-Matt

[vanzuuk1]

Matt off topic, but You and I must face off on the autocross circuit next summer.

Its on!

[protour_chevelle]

Matt off topic, but You and I must face off on the autocross circuit next summer.

Its on!

If I was closer wouldn't it be a hoot?! I cannot wait for summer!

-Matt