Whoever said anything about racing brakes? The focus is the dark rings seen in multiple videos (under engagement - heating) which are exactly like photographed - production, racing, sliding or fixed caliper, single or 4,6, piston, whatever. You may be sure you know everything there is to know, but others aren't. You seem to enjoy talking down to others who do not simply agree with you, leaving no space to acknowledge that you yourself simply cannot explain everything, preferring to brush everything off as cameras playing tricks, eyes playing tricks, etc. "on the surface of the sun we wouldn't see anything but white hot" type BS.

So OEM brakes are horrible and the pads are all screwed... and all those LMP and GT cars with their brakes showing exactly the same thing, on pure race brake systems.. it's just the shadows and light playing tricks, the video cameras and camera exposures and what not all screwing up.. heating is always completely even and there is no temperature and color difference across swept area no matter what. Right. I believe you McGuire, simply because you say so and you're McGuire.. LOL get off your high horse. Getting old just like Phantom.

Sorry, no. Production (floating) and racing (fixed) calipers operate very differently, not least in the manner in which they distribute braking force across the rotor face. You won't learn much if anything about this property in racing brakes by studying production brakes, because that is one of their primary differences. Apples and oranges. Your original inquiry was specifically about racing brakes and I took you at your word.

I have no objection to discussing the same property in production brakes, but it does need to be treated as a different subject, which it is. Important note for the umpteenth time: Production brakes are not capable of sustained operation at incandescent temperatures, which is what you are talking about. If you see production brakes glowing significantly for any length of time, they are failing -- obviously, a non-representative mode of operation. It's hard to imagine anything more stupid or pointless than analyzing their rotor color patterns at that point. Generally, racing brakes can operate at (limited) incandescent temperatures while production brakes can't. Do you copy, is there anyone home in there, do you speak the language, etc.

I don't know what is with the attitude. I have some knowledge in this area and have tried to be helpful but all I get for my trouble is a lot of back sass. If we both don't understand the difference between production brakes and racing brakes or don't think it matters, we can't really have a conversation on this subject. One of us isn't qualified. Sorry, but there it is.

I'm aware of the differences between production and racing brakes.
The topic is not racing brakes, it is 'glowing rotor dark rings'. The examples provided happen to be racing brakes because there are a lot of them around. The rings seen in videos and photos are common to both racing and production brakes.
Your explanation for both types (OEM is horrible, pads are dead, while everything else (racing) is just the mind and cameras playing tricks) seems does not make sense at all, seems more convenient and argumentative than anything, rather than logical. It is just as much (or more of) a guess as anything else mentioned on the thread.
Let those who wonder and seek answers do so, at worst they only waste some of their own time. At best they learn something new and will share it. You can disagree but there's no need to be an ass while you're at it unless you have strong evidence or logic. No point trying to force others to accept that there is nothing going on when you have nothing authoritative. Don't pretend that you care about saving them time, or saving them from their own stupidity. It is very clear when someone is trying to help, or trying to be a cocky smart ass standing on nothing.

You continue to talk down to anyone who does not agree with you. Yah sure we are all stupid, confused, and unqualified. You are smart, qualified, experienced, and you love helping. You're such a great person.

How sure are you it is floating caliper?

This is the Pfadt ST1 racecar. Here are its specs.. http://www.pfadtracing.com/blog/?p=71

Brake system modifications listed as

* StopTech ST-60 fronts
* StopTech ST-40 rears
* Full brake ducting in front
* Tilton 600 series 3 pedal floor mount system
* Cockpit adjustable brake bias spares

Next thing you'll be preaching that StopTech doesn't know how to make brakes or pads.

Here's a screen shot from the video with gamma and contrast turned up in a lit frame. I suppose Pfadt built a high performance corvette in many areas but left the brakes stock, opting to just paint them red. That's not a stoptech caliper.. it's OE sliding rubbish and the pads on the car have been heated to mush.

It's very logical to me, and very conservative. I would say your representation of my remarks here are twisted and slanted. On what are your theories based?

Our disagreement is easy to resolve. I'm not here to argue. You can have the thread to yourself and whoever else cares to participate. Keep me out of it and I will stay out of it. Fair enough?

You've gone too far this time Shaun. What will I do for sport if McGuire leaves?

Thanks to Steve Bryan of AP Racing for replying to my email


The 'banding' visible on the surface of a carbon brake disc is basically the
result of varying contact pressure between the pad and disc surface. When a
new disc runs, the initial contact pressure is even, but there is an energy
gradient across the disc due to the increasing rubbing speed towards the
disc OD. This is combined with a temperature gradient which tends to result
in the disc surface temperature peaking about two-thirds of the way across
the disc face (often resulting in a single glowing band). This hot band will
expand very slightly more than the material around it, resulting in slightly
higher disc wear around this band. As the disc cools before the next braking
event, the wear profile results in a microscopic depression in the disc
surface. The next braking event will then result in two points of higher
pressure/energy input either side of the wear band. Two glowing bands are
the result. The cycle will then tend to repeat itself, with some variation
due to differing energy levels around the circuit.

Phew! That's a relief - well done Cheapy!

+1

Well done Cheapy. There had to be someone out there that knows about this effect. This confirms that high G braking will produce the single central glowing band and low G braking produces the dark band.

Thank you Cheapracer!

So Gruntguru, your theory was in fact the closest to reality hehheh

Oh yeah, I forgot to thank Jezztor and Dosco too, so thanks guys

As a messenger I will neither be shot nor take kudo's.

Messenger yes, however you took the initiative to contact someone in the know.

Thanks for the effort, if nothing else.

+1 on that. With fries.

I thought carbon discs had a 0 coefficient of expansion

Are you trying to bring on a heart attack?

IMHO thermal expansion is not an essential part of the sequence. For the centre ring to get hotter in the first place suggests more pressure there which will cause more wear (pad and disc) at that radius. Of course if expansion occurs (and it could be just pads expanding if the disc coeff' is zero) the effect would be magnified.

Hadn't I read somewhere that C-C rotors actually shrink when hot? Thought I had.

Kevlar has a negative coefficient of thermal expansion (CTE). Carbon, and resin, is +ve.

I'm pretty sure I read it in RCE- specifically the article about Ferodo testing ferrous rotors with Williams for F1 some years back. Unfortunately I threw my old issues away recently in a housecleaning. It may have been negative CTE in only one dimension. C nanotubes and PAT derived carbon matrices also appear to possibly have negative CTE. Here's a link I found anyway:

http://www.springerlink.com/content/l7520856g711p477/

The abstract states that the CTE is negative under 100C, but did not mention CTE at higher temps. It also states that there is a measurable difference between 2D and 3D C-C composites. Not sure I know the difference between 2D and 3D C-C composites ... ...

EDIT: Sorry, usually the entire paper is not available and I did not read the paper. After reading it, the CTE is positive at higher temps (graph shows positive CTE at around 175C).

There is also an explanation of 3D C-C.

I'm not really here, don't want to get involved in another piefight. Just popping in to note that the active factor is not abrasion but adhesion, especially at incandescent temperatures. That's the dynamic issure here -- the pad friction material is interacting not with the rotor surface but with the film of pad friction material adhered to the rotor. I willl now pop right back out again, ciao.