Brake rotor science for DD

It's about time to do front pads 'n' rotors on my DD.

Setting aside drilled, slotted, etc. rotors for this exercise...

Rock Auto offers rotors from $20-$55

Factory rotors from an online Dealer source are $35

NAPA offers rotors from $38-68

Et cetera.

Isn't a rotor pretty much a hunk of steel, machined to factory specs?

What makes a $20 rotor different from a $68 rotor, and why should I pick any given rotor?

They are all cast iron hunks that get machined to factory spec. After 8 years of managing auto repair shops I have come to this conclusion...

A cast iron hunk is a cast iron hunk. Period. There may be minor differences in porosity, concentricity, and thickness, but for DD duty its all just a hunk of cast iron.

I put cheap chinese parts store rotors on customer cars and never had any of them come back under a lifetime warranty, so I started putting them on my cars. I've never noticed a difference between the cheapest rotors and the few high-end rotors I've had.

Go cheap.

I can't dispute what curtis73 offers but I did have one recent experience with two brand name rotors that were very different. I own a Contour SVT. I have always bought brand name part as much as i could afford. A few years ago when I replaced the front rotors I went with Raybetoes. In less then 2 years they warped. I bought a second set and they also warped! I then bought a set of Wagner rotors. These are way better! The two faces of the rotor are thicker but the air gap is smaller so the rotor is no thicker overall then required. The rotor is a few pounds heavier as well because of this. Two brand name parts but the resulting product and performance is night & day different.

And there is the difference. The Wagner rotors having more cast iron to absorb the heat are the reason for not warping.

also, some better rotors have coated hats. My centric rotors have two Michigan winters on them and have turned brown, but aren't flaking apart in the vanes. Cheaper ones are coming apart and warped really fast in the salt. Better quality iron?

I put cheapo chinese ones on the front of my race car because I had a serious crack in a BMW rotor turn up at the last minute before a track weekend at the Glen. That was at the end of 2010. I did 30 track track days, including 3 full race weekends on them and... they are still OK so they will race at VIR in march. I have another $74 in backups... just in case ;)

Go cheap.

Gearheadotaku wrote: also, some better rotors have coated hats. My centric rotors have two Michigan winters on them and have turned brown, but aren't flaking apart in the vanes. Cheaper ones are coming apart and warped really fast in the salt. Better quality iron?

I do remember such issues during my 20 years in Michigan. Now that I live in Nevada, rust has become far less of an issue. In fact, it's part of the reason I moved here

Only issue I ever ran into with cheap rotors were a set of rears for my Scirocco. The non-machined area were you press the bearing races into were pretty uneven. It just made it look like the race wasn't seated correctly. No actual performance issues.

I'vein always been an advocate for cheap rotors and good pads.

Info taken from a popular auto parts chain website about their rotors

economy brand - "Rotor Material: Primary materials include pig iron & scrap steel"

O.E replacement - "Rotor Material: Iron Alloy"

which one would you choose?

hotrodlarry wrote: Info taken from a popular auto parts chain website about their rotors economy brand - "Rotor Material: Primary materials include pig iron & scrap steel" O.E replacement - "Rotor Material: Iron Alloy" which one would you choose?

Based on the solidity of truth in "a popular auto parts chain website", clearly, the only choice is to spend more money for Iron Alloy. (which is what we call pure iron with E36 M3 in it).

I also buy Axe body spray because in the commercials - the horny bitches go right after the guy as soon as he sprays some on.

I would wager that all rotors are made from recycled steel/ iron. Pig iron and scrap steel is an iron alloy. Sounds like advertising semantics to me.

The only cheap rotors I wouldn't go for are I have seen a few that had the cooling vanes in the middle not right. As long as the whole thing looks like what you're replacing, go cheap.

yeah don't make the assumption all of them are just cheap hunks of iron built to spec.

They're not. Hell Toyota even has put the wrong specs on rotors before and had to be made a fool of in their own plant before they changed it.

Now clarification of what you are buying is complete.

I have used many a cheap Chinese rotor on a DD. Works fine for me. Although on a Ranger they would warp easier but I wasn't exactly driving it like a daily driver.

[\stupidteenager]

Its getting tougher to tell the difference between good and bad now. I look at the centering of the vents, and whether there seems to be the same mass, and go with whats available.

I've cut way down on warping and vibration problems by being a lot more thorough on cleaning, sandblasting and lubing caliper and pad slides, and being sure the mounting surface on the hub and rotor is completely cleaned off.

I tried a couple of sets of slotted rotors on my IT Neon. They cracked at the slots very quickly. I don't approve...

had a cheap rotor on a mk2 golf break off the hub flange years ago. would/could this happen to an oem or big dough part? possibly...

i tend to hit middle of the road for street car stuff that doesn't drive my kids around.