Brake temps!

[Cupman29]

Thought I'd get some data on brake disc temperatures at a track day as was at yesterday to see how much difference ducts actually make.

I used an infrared laser thermometer and checked as soon as I could when I came off after 2 cool down laps after around 20 fast laps.

Car is a 172 cup with standard calipers, pagid rs4 pads (front) ferodo ds2500 (rear), brembo max discs (front) standard rear discs and motul pbf600 fluid.

Front brake discs = 392degC (R) and 394degC (L)

Rear brake discs = 41degC (R) and 39degC (L)

Also checked my mates M3 CSL with AP 6 pots on the front and 4 pots on the rear.

Front = 395degC (both)

Rear = 265degC (both)

My question is, is the front brake temp normal or high/low compared to anyone else? Also, I know the rear brakes on the cup do very little but the temp on the discs show that they do pretty much nothing at all, is this normal?

I will be fitting brake cooling ducts before my next outing so will be able to compare before and after results but would be interested to know what you guys get.

Cheers,
Steven

 

[Dean.]

I done mine yesterday with an infrared thermometer. 5ish (4mile) laps and one cool down and I only got around 260c. But my brakes are shagged.

 

[Cupman29]

I think knockhill is very heavy on brakes as the track is only 1.3miles and the hairpin and duffas at the end of the main straight you are very hard on the brakes and lap after lap you are not getting alot of time to get the heat out of them again so the heat just builds up.

I know nearly 400deg is hot but not sure how hot.

 

[Fred@BTM]

400deg is just warmed up!

 

[Sam@NP]

You know you're trying when they turn white ey Fred

 

[TheEvilGiraffe]

Ph2 172 cup ? The bias of the rears is almost negligible (you must know this from MOT time?) .. didn't realise it was that pathetic haha !

 

[Tony Hunter]

600 plus is just about getting there.

 

[Cupman29]

Still got some way to go then. With the set up I have (pads/discs/fluid) what would be the temp limit before I should start to worry?

Obviously if the brakes are still good then I can spend more time out on track rather than letting them cool down all the time.

 

[Cupman29]

600 plus is just about getting there.

What do you get on your rears Tony. I guess more than 40deg?

 

[Fred@BTM]

60 tops on Tony's

 

[JamesS]

For the purposes of comparing before and after brake temps. what you've done is fine, but have you confirmed that the emissivity of the IR thermometer is correct for your brake discs?

If not, then the actual temperature reading you're getting could be way out (but at least will be consistently out, so before and after comparisons are fine, but comparisons with other peoples' temps. is not great).

The emissivity correction is very important because for something like a tyre, the emissivity is typically 0.9, whereas for a brake disc it's somewhere in the region of 0.2, so if it's set incorrectly in the thermometer, you'll be getting a fairly inaccurate measurement.

 

[Cupman29]

For the purposes of comparing before and after brake temps. what you've done is fine, but have you confirmed that the emissivity of the IR thermometer is correct for your brake discs?

If not, then the actual temperature reading you're getting could be way out (but at least will be consistently out, so before and after comparisons are fine, but comparisons with other peoples' temps. is not great).

The emissivity correction is very important because for something like a tyre, the emissivity is typically 0.9, whereas for a brake disc it's somewhere in the region of 0.2, so if it's set incorrectly in the thermometer, you'll be getting a fairly inaccurate measurement.

:S

 

[Tony Hunter]

60 tops on Tony's

Just about gets the rust off.

 

[Munson]

Surely that's not your actual peak temperature though if measured in the pits after two cool down laps? I'm no expert but I thought that's why serious people use brake temperature paints?

 

[Cupman29]

I must not be serious person then. :rasp:

It is an indiscation only but fair point.

 

[shiyan]

That seems about right. I've regularly seen 500+ C on the front

After putting in brake ducts they're now usually 300+

But I did put in 2 for each front brake.