Brake Rotor

[Yuan]

Bro, thanks for your advice.

 

How about e brake situations? Would you feel it?

[Yuan]

I read that in many articles about washing car immediately or soon after long distance or car still warm upon reaching a certain destination or home.

 

So after that, I stopped washing my car.....

[Icetrap]

What are the effects of rotor warp?

 

Don't worry about your rotors warping. It's not that of a common issue in brake rotors. In fact brake discs actually warp or distort rather seldom! Unless you are a regular trackie, or you do skimming on the rotors, this may happen in such rare cases

 

How does a Rotors warps? Go to Sepang and drive likes a mad man. Make sure that your ABS activates at the last corner, go for 100 laps! Or Go down Genting, makes you you jam brake every corner. (Using excessive braking. Usually you find your brake pads fading first). This will cause your rotors to have extreme heat. When the Brake rotors are super overheated, issues may happen!

 

So when overheated when the car is stopped. You pressed on the brake pedal just for fun!

When your keep applying your brakes, the area where the pads contact the disc will cause uneven cooling and lead to warping. Maybe splashing ICE cold water on it on super heated brake rotors when the car stops may also cause it to warp. (But who the hell does that?)

 

Warping will often lead to a thickness variation of the disc. This is the pulsating effect that on bro mentioned that cause you to feel it when the brake pedal is depressed!

 

However, don't be confused with brake jutter and disc warping!

Edited August 19, 2007 by Icetrap

[Ukoh9be]

Any recommedation where to change the rotor disc? The workshop I went quoted me $260 for one and $500 for a pair.

 

I believe $100 plus should be more a realistic price.

[Streetbumpkin]

What is your ride?

[Ukoh9be]

I'm driving a Honda City.

[Elfenstar]

Any bros out there can advise if uneven brake rotors can be filed even without replacing new ones? If so, any workshop to recommend? Thanks.

 

To actually answer your question... resurfacing if the discs have just started to warp will work, but the discs will have to be re-bed-in properly.

[Elfenstar]

You have been spouting a lot of hearsay bro.

 

Warping is mostly a consequence of an improperly bed-in disc. Which has not had the internal stresses released. If you did it properly in the first case, there would have been no problems with the washing.

 

Another thing is that your discs cool fairly evenly if water is thrown in it. Its stopping and holding onto the pedal after a disc is overheated that causes uneven wear in a disc that has been bed-in. Brake discs are designed to cool v.quickly from hot.

 

One piece, two piece makes NO difference. Cooling from 500-600 deg to ambient temps is nothing for the discs considering they are heated to 1350deg then cooled suddenly (think of those knight movies where they heat a sword till glowing bang it while its still glowing then dunking it in the water).

 

Over tightening of the lug nuts also can cause warped discs (and are another main reason), and so can not cleaning the hub surface before putting new discs on as they may not sit flat.

[Icetrap]

you have to pm me then

[Allen]

You have been spouting a lot of hearsay bro.

 

Warping is mostly a consequence of an improperly bed-in disc. Which has not had the internal stresses released. If you did it properly in the first case, there would have been no problems with the washing.

 

Another thing is that your discs cool fairly evenly if water is thrown in it. Its stopping and holding onto the pedal after a disc is overheated that causes uneven wear in a disc that has been bed-in. Brake discs are designed to cool v.quickly from hot.

 

One piece, two piece makes NO difference. Cooling from 500-600 deg to ambient temps is nothing for the discs considering they are heated to 1350deg then cooled suddenly (think of those knight movies where they heat a sword till glowing bang it while its still glowing then dunking it in the water).

 

Over tightening of the lug nuts also can cause warped discs (and are another main reason), and so can not cleaning the hub surface before putting new discs on as they may not sit flat.

 

bro, spouting a lot of hearsay?

i am just sharing the so-call hearsay from my experiences

i maybe not be as knowledgable about technical and production method of the rotors but it is the little habits i have to ensure my rotors does not warp again and to share this is spouting hearsay.

 

then for the benefit of all, can you elaborate:

1) how to properly bed in rotor disc, what is the correct way and not the hearsay way.

and how do we know if the rotor disc has been bedded in correctly?

 

2) so if the rotor disc has been properly bed in, the rotor will never warp, even if u throw water onto it at high temp? then question is what is the correct temp to acheive before we can throw water onto the rotor ie washing.

 

3) u mean all rotors are heated to 1350c before dunking into water to cool down, all rotors from japanese made, to korean made to german made? there are different porduction methods thus difference tolerance so cannot assume that all rotors behaves the same way as you have prescribe.

 

4) what do u mean by over tightening of lug nut? how much is over and how much is under?

can elaborate?

 

for the benefit of all in the forum, maybe u can share ur knowledge on this topic.

thanks

Edited August 25, 2007 by Allen

[Nohnemwan]

For the benefit of all those who have no clue about brake disc bedding-in and brake pad bedding-in:

 

Read http://www.apracing.com/car/brakedisc/bedding.htm for disc bedding.

 

Read http://www.apracing.com/car/brakepad/bedding.htm for pad bedding.

 

Of course theses websites are not the only sources of information. But it is a start for those who seem unable to Google the relevant keywords for themselves and instead challenging others for information.

 

I followed the above procedures. My AP rotors have seen moderate track use and everday street use for almost 150,000km. Still going strong. What works for AP rotors should work for normal spec rotors. Of course, such logic may be complete nonsense.

[Apollo]

fwah.. lucky my kachang puteh friend dunno anything abt brake except step on them..

[Megalord]

I actually recalled that there was an article by the book "Brake Design and Safety", 2nd edition, by Rudolf Limpert, that briefly mention about heat stuffs. From the several books i read to date (i hope is the one mentioned earlier), one mentioned about warping of disc with respect to thermal gradient. I do think they provide some informative bedtime story reading.

[Elfenstar]

1) read the instructions that come with the discs and pads. Diff manufacturers have diff instructions. There is general consensus on the repeated, fast to slow braking several times without stopping method. How long to brake, speed to brake and number of repetitions again you have to read the instructions.

 

2) How long is a piece of string? Any street driving will not result in a high enough temp and i'm assuming theres not runout etc from factory (if there's a factory issues it will give some sort of problem regardless of what you do). If you're racing then it can happen, but it would be more likely to crack.

 

3) Nope they have to get to that temp at least as rotors are cast. any cooler and it can't happen. If they are not cooled extremely quickly and left to cool on their own, they'll actually end up more warp resistant so do the math.

 

4)Once again read instructions. The torque figures should be in your owners manual. That being said the real cause of over torquing is using a rattle gun.

 

Btw what do you mean by what you've said comes from your experience when you havent used a 2 piece rotor, and when you attribute the cause of your problem to water when you havent checked to see if any of the other factors was the cause?

[Elfenstar]

There are issues from heat, but we're talking from the 800deg figure ranges upwards, and only if there isnt proper cooling. Temps from hard street driving wont cut it.

[Vtim]

I'm driving a Honda City.

are you looking at stock Honda City rotor or aftermarket rotor? May I ask your City is iDSI or Vtec ?

[Megalord]

The topics i read about, has roughly no relation with proper cooling actually. Like i said, its more related to thermal gradient.

Indeed in that book they talk about elevated operating temp, but with no reference to how high those temps really are. Over there, numerous formulas about cooling, brake torque and even wheel size comes in as a variable. It would be enlightening to us, where the 800 degree threshold came about?

Temp from hard street driving varies alot. I ever used a HH rated pad, that peaks at 0.68u friction coefficient rating on a 240mm ventilated rotor. But again, i did use FG rated pads on 330mm ventilated rotors. The operating temperature are very different for both cases, thus since then i never generalise about operating conditions.

[Elfenstar]

I initially got the figure off one of the Ford GT engineers quite a while back. He was mentioning something abt much increased incidences of "warping" on tracks which "forced" brake temps were 800ish and above. These drivers had 0 incidences of this on tracks that had cooler temps. I'm trying to find the PDF article which found similar results. This article was some study on heat and metallurgy with regards to current and potential brake disc materials. It basically lists the temps for different metals getting soft enough to change the shape of the disc, and it measured the temps across a variety of discs which started at 800+ and going up to 1000+ for some branded ones.

 

Anyways i don't normally generalise but i have yet to hear of brake fade in hard street driving with 600deg pads so i figure there is no way it would get hot enough.

 

To be honest, it isnt easy to damage a properly bedded-in and undamaged disc. On the other hand not bedding-in discs and pads properly are a good recipe to damage the discs, create noise for pads etc.

Edited August 26, 2007 by Elfenstar