Warped rotors

[Mayhem_J30]

http://www.stoptech.com/whitep...h.htm

What do you guys think about this article? A guy from carbotech engineering http://www.carbotecheng.com/ pointed me towards this while in another discussion. I've come to agreement with the article myself.

[s13sr20chris]

im sold.

[Eswift]

ive seen warped rotors, quite visibly.

in aluminum.

not on a road car though.

[Mayhem_J30]

Have you heard about the Porsche Ceramic brake systems? There were a lot of problems with them on the track and they only lasted aprox 1500 miles. Then would cost about $17K to replace. I read about it somewhere on http://www.corner-carvers.com I'll look around for the link.

[Q45tech]

Pretty hard to see 0.0028" warp which is out of spec and provides a feelable pulsation. My trained finger tips can feel about 0.005"...........anything finer needs micrometers.

GM now uses a 0.0005" parallelism standard which no vehicle meets after 3000 miles of driving. But they don't cover rotors under warranty after 6k.............by the time the customer notices it, it is too late.

[Eswift]

Have you heard about the Porsche Ceramic brake systems? There were a lot of problems with them on the track and they only lasted aprox 1500 miles. Then would cost about $17K to replace. I read about it somewhere on http://www.corner-carvers.com I'll look around for the link.

heard of them, never knew there were such extensive problems with them (I assume this was on the GT2)

It appears that aluminum metal matrix composite is proving to be a very viable option, except for manufacturing.

we were considering using it on our car because a supplier would give us free materials, until we realized that we would have to use diamond tipped cutters...of which we dont have an extensive supply. Definitley wouldnt be fun to put in our nice cross-drill pattern...

[Mayhem_J30]

While we're talking about rotors. What do you guys think about 2pc rotors? The ones with the replaceable center hub made from aluminum. Doesn't appear that many people have experience with these and not much information can be found. Initially I thought it's a good idea because the rotational mass would be less and replacement discs would be cheaper because of the reuseable center piece. But how much of that center mass is used in heat absorbtion? Is the brake friction heat mostly absorbed in the swept area then vented out or is there a large percentage of heat soaked into the center of the rotor?

[Eswift]

While we're talking about rotors. What do you guys think about 2pc rotors? The ones with the replaceable center hub made from aluminum. Doesn't appear that many people have experience with these and not much information can be found. Initially I thought it's a good idea because the rotational mass would be less and replacement discs would be cheaper because of the reuseable center piece. But how much of that center mass is used in heat absorbtion? Is the brake friction heat mostly absorbed in the swept area then vented out or is there a large percentage of heat soaked into the center of the rotor?

you mean full floating rotors, as on motorcycles and cars set up for race?

I think that the idea is for both reduced unsprung weight and better heat transfer.

The removal of cast iron brake material is more than offset by replacing it with aluminum, which is much more thermally conductive. ( we will neglect any contact resistance between the iron and aluminum interface.)

It is also important to know that the heat created by braking isnt just "absorbed" by the non-friciton surface part of the rotor and removed by airflow, which is very important. A (directionally) vaned floating rotor probably has better airflow and convective heat transfer characteristics as well.

In any case, much of the heat is dissipated through the brake/hub/wheel interface, the aluminum wheel acts as a huge heat sink and fin (pretty inefficient shape for a fin, but it works)

thus, the aluminum (or cast iron) center hubs on any rotor are not a major source of heat dissipation themselves, but are a bridge for the heat through conduction (into the wheels and drivetrain). Thus, they yield better heat dissipation to surrounding heat sinks for high temp/perf applications. {Euro M3 etc.}

also these rotors arent always separatable from the aluminum center to replace the worn rotor (as in euro BMW floaters) because they are integrally cast (guess they cast the Al into the iron rotor piece)

As far as I can tell, the fully floating or 2 piece rotors only fault is cost/ benefit, unless the car is a track vehicle.

[Mayhem_J30]

Here's a picture just to make sure we're talking about the same thing, which I believe we are.These are made by Endless. Supposedly the hat is reusable.

[Eswift]

yeah, we are talking about the same thing. and those definitley have reuseable hats.

this rotor is from a euro BMW M3, it is also a floating rotor design, except the aluminum part is integrally cast into the iron friction surface (no reusable hats)



in any case, either of these rotors provide much better heat transfer characteristics.

[Mayhem_J30]

eswift,that's a crazy swirl pattern grinded into the rotor. is that just machining left overs or does it have some purpose?

[Eswift]

as far as i know it serves no purpose, it could be leftovers from a machining or wire wheel process. to me, it looks similar to the pattern you get on the inner surface of a cylinder when it is honed.

the brembo blanks i put on the back of my car had the same appearance:sorry for the huge pic,

[maxnix]

Huge pictures are good!