Rotor/Brake Pad Wear Opinions - Page 2

Raptor · 03-11-2005

If you cut them to true up the rotor and it is off enough, it will cause an out of balance condition. Then you get to buy new rotors anyway.

Matt D. · 03-11-2005

JET's advice is spot on. EclipseTurbo and Rapor bring up good points as well that you should keep in mind.

Carlos, stop posting in tech threads already...

LightningGSX · 03-12-2005

I've found in most cases, they warp so quickly after being turned, that is not even worth it.It could be my driving though too, I'm hard on brakes

Raptor · 03-12-2005

Drive a lighter car Eric.

TheBlizzard · 03-12-2005

From what I have seen and read in my opinion there is no such thing as a warped brake rotor. If there is it is very rare and more often than not it is merely mis-diagnosed "run-out". This may be way off but I think that in most cases whether on a racing car or a street car, rotors end up failing due to the friction pad material being unevenly transfered to the surface of the rotor. This uneven deposition results in a thickness variation or "run out" due to hot spotting that occured at elevated temperatures.

Getting them turned is not a good idea because the more material you take away, the less material there is for heat dissipation. You may get away with it here and there but what is your time worth? Who wants to keep pulling rotors off and putting them back on when they are fairly cheap to just by new ones.

I think it should also be stressed that your wheel and rotating assembly be balanced and not be uneven. An uneven wheel or a wheel thats mounting surface is uneven with cause undesireable stress on your braking system. A wheel that is not tightened properly could also cause your brake rotors to wear unevenly.

This is just my opinion. Take from it what you want.

CRAIG

Khadgar · 03-12-2005

I don't want o hijack any threads or go off topic but since the original question has been answered I just want to ask a quick question and don't want to start a new thread about it.

Besides the obvious slotting/drilling, is there any difference between rotors or will cheap ones from napa work fine?

Jakey · 03-12-2005

I'd also like to know rotor differences since you can purchase solid, slotted, drilled, dimpled, and a combination of those. I've seen that people have had problems with the slotted rotors cracking but what about drilled or dimpled? Plus the vast number of different brands out there: OEM, Napa, Brembo,AEM, Powerslot, Rotora, etc always makes decision making fun.

LightningGSX · 03-12-2005

I believe its the drilled rotors that crack, not the slotted.Could be wrong though

Jakey · 03-12-2005

Yep, you're right. I stand corrected.
http://www.acquiredperformance.com/C...s/Dscn6151.jpg

LightningGSX · 03-12-2005

Quote:

Originally Posted by CRAIG

From what I have seen and read in my opinion there is no such thing as a warped brake rotor. If there is it is very rare and more often than not it is merely mis-diagnosed "run-out". This may be way off but I think that in most cases whether on a racing car or a street car, rotors end up failing due to the friction pad material being unevenly transfered to the surface of the rotor. This uneven deposition results in a thickness variation or "run out" due to hot spotting that occured at elevated temperatures.

So you're saying the run out is cause by the pads' friction material accumulating on the rotor itself?

LightningGSX · 03-12-2005

Quote:

Originally Posted by Jakey

Yep, you're right. I stand corrected.
http://www.acquiredperformance.com/C...s/Dscn6151.jpg

I think if the drilled holes are chamfered, the cracking should be a non-issue

Jakey · 03-12-2005

Quote:

Originally Posted by LightningGSX

I think if the drilled holes are chamfered, the cracking should be a non-issue

I guess I don't understand how chamfering the holes would be of benefit? Granted I'll probably understand it when I take a materials class next fall but anyways.

LightningGSX · 03-12-2005

Quote:

Originally Posted by Jakey

I guess I don't understand how chamfering the holes would be of benefit? Granted I'll probably understand it when I take a materials class next fall but anyways.

It was just a guess, in my head it seems to make sense though

TheBlizzard · 03-12-2005

Quote:

Originally Posted by LightningGSX

So you're saying the run out is cause by the pads' friction material accumulating on the rotor itself?

I am not saying that it is the only reason but it is a contributing factor. Here is why:

Regardless of pad composition, if both disc and pad are not properly broken in, material transfer between the two materials can take place in a random fashion resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken in and when they are very hot or following a single long stop from high speed or if the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a unique deposit behind that looks like the outline of a pad. This kind of deposit is called pad imprinting and looks like the pad was inked for printing like a stamp and then set on the disc face.

Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake rotor, any uneven deposits standing on top of the disc surface become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad the temperature increases. When this temperature reaches around 1200 or 1300 degrees farenheit the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral the amount and depth of the cementite increases with increasing temperature and so does the brake roughness.

But I would say all of this is a direct reflection of the rotating assmebly being out of balance, combine that with a hard driving style, long stops from high speeds and you will have obvious problems. The choice of brake pads and rotors you chose will also affect how quickly they reach the failing temperature I stated above.

Again this is just my opinion, take from it what you want.

CRAIG

TheBlizzard · 03-12-2005

Thread renamed and moved. This has turned into more of a tech thread than anything. Some good points have been brought up, I would like to hear some more opinions on this.

CRAIG

Jakey · 03-12-2005

Quote:

Originally Posted by CRAIG

I am not saying that it is the only reason but it is a contributing factor. Here is why:

Regardless of pad composition, if both disc and pad are not properly broken in, material transfer between the two materials can take place in a random fashion resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken in and when they are very hot or following a single long stop from high speed or if the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a unique deposit behind that looks like the outline of a pad. This kind of deposit is called pad imprinting and looks like the pad was inked for printing like a stamp and then set on the disc face.

Cast iron is an alloy of iron and silicon in solution interspersed with particles of carbon. At elevated temperatures, inclusions of carbides begin to form in the matrix. In the case of the brake rotor, any uneven deposits standing on top of the disc surface become hotter than the surrounding metal. Every time that the leading edge of one of the deposits rotates into contact with the pad the temperature increases. When this temperature reaches around 1200 or 1300 degrees farenheit the cast iron under the deposit begins to transform into cementite (an iron carbide in which three atoms of iron combine with one atom of carbon). Cementite is very hard, very abrasive and is a poor heat sink. If severe use continues the system will enter a self-defeating spiral the amount and depth of the cementite increases with increasing temperature and so does the brake roughness.

But I would say all of this is a direct reflection of the rotating assmebly being out of balance, combine that with a hard driving style, long stops from high speeds and you will have obvious problems. The choice of brake pads and rotors you chose will also affect how quickly they reach the failing temperature I stated above.

Again this is just my opinion, take from it what you want.

CRAIG

Do you have the source for your middle paragraph?

TheBlizzard · 03-12-2005

Can't remember off hand. I found that information while researching brake pads and rotor characteristics.

CRAIG

unreal808 · 03-12-2005

I have tried to cut a lot of rotors with severe lateral-runout or what I call a warped rotor. Lateral runout is caused by over-tightened or unevenly tightened lug nuts. Extreme heat or rapid temperature variations also cause runout. Rotors with a lack of parallelism is a variation in the thickness when it is measured at several pleases around the circumference and is caused by soft spots and I see it every day . IMOP rotor refinishing is gay. I have wasted so much time checking & cutting rotors only to have to replace them anyway.