How hot does your brake rotor get?

[Old Can Ride]

Boiling point in Fahrenheit is 212 degrees. Boiling point means water turns into gas. Do a little experiment and spray water to your rotor after a 60 mph stop, you will see smoke(gas) that means is at least 212 degrees. Get it, do not touch the brake rotor!

 

[anglachel]

never been foolish enough to touch the rotor on the motorcycle but after riding my bicycle (also disc brakes) down into the river valley I felt like my brakes weren't working quite right, got off to check them and burn myself on the disc... That was just slowing down 180lbs of me and bicycle (I was lighter back then) never topping 30 mph (though the hill going down the bluff could have gotten me going faster than that the pot holes made heating up the brakes a requirement). I got a blister from that disc.

Can't try it on the motorcycle today (or probably for a few months) but the IR thermometer can tell you exactly how hot it is (great tool if you can find one cheap, ~$10, though I find I use it more in the kitchen than the garage)

 

[HONDABIKEPRO]

Easy 300 degrees, after a couple hard stops. dale

 

[SergeantChuck]

Heat that will one day will be used to charge the battery in everyones car. Eventually we will all have electric. Maybe not my lifetime but its coming. JMO

 

[mdouglas71]

My rotor gets pretty damn hot. I'll ride pretty hard and I'm almost sure you can see it glowing sometimes..

 

[Naked_Duc]

There is a lot of kinetic energy in a moving car or bike. When you brake, you are actually converting the energy to heat (in the brake pads and rotors). Too much heat too fast, then your brake fails. That's why you don't want to ride your brakes down a long steep hill.

But just how much heat is there?

Kinetic energy is calculated as E = 1/2 * Mass * velocity^2

When you brake from 60 miles (or 26.67 m/s) to zero, the mass (214 kg for NCX and 80 kg for rider) would generate about 104,559 joules. So how much energy is that?

It takes 4.18 joules to heat up 1 grams of water 1 degree Celsius. So 104,559 joules can heat up 1 cup of water (236 grams) 105 degrees. That's enough energy to bring a cup of water in room temperature to boiling. Now imagine a car coming to a stop from 80 miles.

 

[anglachel]

Heat that will one day will be used to charge the battery in everyones car. Eventually we will all have electric. Maybe not my lifetime but its coming. JMO

They are here now.

Just still to dang expensive.

Zero and brammo both have regenerative braking.

Sent from my SAMSUNG-SGH-I537 using Tapatalk

 

[danrev]

This is just not that high on my "something I need to do on my NC today" list!

 

[HONDABIKEPRO]

There is a lot of kinetic energy in a moving car or bike. When you brake, you are actually converting the energy to heat (in the brake pads and rotors). Too much heat too fast, then your brake fails. That's why you don't want to ride your brakes down a long steep hill.

But just how much heat is ther
Kinetic energy is calculated as E = 1/2 * Mass * velocity^2

When you brake from 60 miles (or 26.67 m/s) to zero, the mass (214 kg for NCX and 80 kg for rider) would generate about 104,559 joules. So how much energy is that?

It takes 4.18 joules to heat up 1 grams of water 1 degree Celsius. So 104,559 joules can heat up 1 cup of water (236 grams) 105 degrees. That's enough energy to bring a cup of water in room temperature to boiling. Now imagine a car coming to a stop from 80 miles.

WOW thats to many joules for me.. dale

 

[showkey]

Hot rotor:

https://www.google.com/#q=picture+of+glowing+brake+rotor


Click on any picture in the link.............

 

[Mike Cash]

Heat that will one day will be used to charge the battery in everyone's car.

Too much hassle to ride your bike with a cable running to your car, if you ask me....

On a more serious note, though. Consider that instead of using the wasted heat energy of braking to produce and store electricity, railroad locomotives for decades have been using auxiliary braking systems that generate electricity and then covert it into wasted heat energy.

 

[L.B.S.]

Too much hassle to ride your bike with a cable running to your car, if you ask me....

On a more serious note, though. Consider that instead of using the wasted heat energy of braking to produce and store electricity, railroad locomotives for decades have been using auxiliary braking systems that generate electricity and then covert it into wasted heat energy.

Fascinating. I confess I've never had a very good understanding of how all that stuff worked. So basically, the braking is supplemented by channeling the generated electrical energy into resistors, which clog up the works for forward momentum. I wonder how deathly hot the resistors get? Even small ones I have come into contact with have been healthily finger burny, lol. I imagine the size of "braking" resistors would be pretty chunky and in need of some very good insulation or airflow.

 

[SergeantChuck]

I guess what I was really saying is in the future we will all be driving electric cars with regenerative braking. EPA regulations will increase and electric cars will replace fossil fueled vehicles. May not happen before I die but it will happen. And hot brakes started this conversation. LOL

 

[OriginalRocket]

Fascinating. I confess I've never had a very good understanding of how all that stuff worked. So basically, the braking is supplemented by channeling the generated electrical energy into resistors, which clog up the works for forward momentum. I wonder how deathly hot the resistors get? Even small ones I have come into contact with have been healthily finger burny, lol. I imagine the size of "braking" resistors would be pretty chunky and in need of some very good insulation or airflow.

My friend works on those train engines for bnsf railroad. He's had tons of stories about how much heat those electric brakes put out. One that I can remember, a crew pulled a yard loco into a storage shed, without letting it cool down, it melted holes in the metal roof 45 ft above the engine.

 

[L.B.S.]

My friend works on those train engines for bnsf railroad. He's had tons of stories about how much heat those electric brakes put out. One that I can remember, a crew pulled a yard loco into a storage shed, without letting it cool down, it melted holes in the metal roof 45 ft above the engine.

oof!

 

[Mike Cash]

I guess what I was really saying is in the future we will all be driving electric cars with regenerative braking. EPA regulations will increase and electric cars will replace fossil fueled vehicles. May not happen before I die but it will happen. And hot brakes started this conversation. LOL

I was just having a little fun. But it is interesting to consider how much electricity gets intentionally cycled into waste heat instead of the other way around.

I believe you're right about the direction technology is heading, but I also have doubts I'll have any personal experience of it. It might be around before I die, but the cars I get tend to be on the older side. (I like to look at the new stuff on cars so I can get an idea of what I might look forward to ten or fifteen years in the future).