hornet

This is an interesting video. It makes total sense to me. Rotors are cheap enough to just replace.....Brakes are something you shouldn't cheap out on....

http://www.oeqf.com/techinfo/index.htm

DTN

I've heard that before. When a manufacturer specifies a tollerance and puts a bevel on the edge of the rotor to show that it can still be resurfaced, I will resurface it. By specifying tollerances, the manufacturer is certifying that the product will be usable at that spec. A bit of warpage is perfectly curable by resurfacing. When the warpage becomes too bad, you do not want to resurface. Usually, you can get 2 semi-metalic brake pad changes out of a single rotor. At $40 for resurfacing versus $100 for replacement, it makes financial sense to resurface the rotor.

Of course, if the manufacturer has specified that the rotor not be resurfaced, or if the rotor is aftermarket, you should never resurface.

LM80

Interesting video, but I can't believe that 130+ feet is what most people would expect from a 30mph stop with .020 finish rotors.
I'd agree it may be detrimental to overall performance initially, but a cheap organic pad would wear into those rotor grooves (which are extremely small) almost instantly. The test was replicated with a new set every time, which did minimize contact area, but I bet after a day of driving the pad shape would mold to compensate for any rotor irregularity.

DTN

Yeah, lathing is not resurfacing, that is lathing. You must flatten the lathe grooves with a good non-directional sanding first so that you do not reduce contact area.

Stocker

1) LOL @ the car falling off a cliff

2) Remember that this video is from people who stand to profit from your desire for NEW brake rotors.

3) They kept the brake effort the same throughout the testing. Admirable consistency as far as it goes, but then, if YOUR car is not stopping well, do YOU keep the pedal effort the same or will you stand on the pedal?

4) Using NEW pads on OLD rotors was "shown" to NOT increase stopping distance. This is why I have NEVER had a set of rotors turned.

5) The test they can't really do effectively/repeatably, is with old wornout and glazed pads and glazed rotors . . . which would have got them more than 70 feet stopping distances!

6) All this vedeo shows is that you shouldn't turn your rotors without smoothing them out again. Aside from some pretty graphics, I fail to see how this adds to the current body of knowledge.

7) The REAL reason that you should turn rotors 100% of the time is if they are GLAZED. Glazing affects the ability of the pads to get a grip, and it goes pretty deep sometimes. If you turn rotors but don't cut through the metal affected by the glazing, you might get pulsing and degraded performance again even if you smoothed it out after turning . . . not that you would notice (see point 3 above)

HotBlue02

I repair brake lathes for a living along with lots of other types of automotive equipment. There is nothing wrong with turning rotors as long as its still above the minimum spec for thickness. And if you have a high quality lathe like an accu-turn lathe there is no reason for a bidirectional finish on the rotor. I will say that a new rotor has more mass to absorb heat created from braking vs. a rotor down to the minimum spec, not a problem for daily drivers, but I would want new rotors on a race car.

Stocker

"no reason" because you don't think so, or because you didn't watch the video?

HotBlue02

Depends on the lathe your using, if i were to turn a rotor on a ammco lathe then I would do a bidirectional finish. Ammco uses whats called negative rake cutting bits, in other words they scrape the metal of the rotor vs an accu-turn lathe that uses a positive rake to cut, like a real metal lathe would use. The fact that u didnt need a bidirectional finish on the accu lathe was one of many selling points they used over ammco along with the fact that you can turn a rotor in one pass vs taking 2 passes on the ammco.

HotBlue02

So many things wrong with that video. First off why are they even bothering to show you braking distance with a course cut rotor, no tech that has any pride would not put a course cut rotor on a car so that argument is a moot point. The rotor they show that is fine cut doesnt look right, they need to repair the lathe they cut that rotor on. That FMC lathe they show in the video is not a great lathe to begin with. " A customer with badly refinished rotors" as they say, well of course a badly refinished rotor is not gunna stop as well, duh! This video is made by a aftermarket rotor company so that basically sums it up.