Brake rotor temps at the track... why would one be >100 degrees hotter?

LeeH · 03-26-2007, 02:30 PM

Why would my right front rotor be more than 100 degrees hotter than the left after a track session? There's no pulling or noise. They've recently been bled and the pads are fairly new.

LF - 126
RF - 237
LR - 147
RR - 163

VFR750 · 03-26-2007, 02:36 PM

How are you measuring the temp?

Is the car corner balanced?

Noah930 · Noah930's Garage

Are you sure the RF caliper's working properly (not sticking)? +1 on how are you measuring the temps? The track isn't all left-hand turns, is it?

NoLift911 · 03-26-2007, 02:48 PM

That is a relatively low difference in temp, you could have one caliper dragging and not notice a pull...to get the difference

Green 912 · 03-26-2007, 03:17 PM

Not to mention that the temps are low all over. 400 is more in the often seen range for rotor temps right off the track.

X 2 check for sticking pistons

Joeaksa · 03-26-2007, 03:46 PM

Another vote for dragging pistons in a caliper.

Pull the pads out of that caliper and measure them. Then measure the pads in the opposite wheel. If your "warm" side is worn more or if one pad in the "warm" side is thinner, then you have found at least part of the problem.

ZOA NOM · ZOA NOM's Garage

FOD in a brake cooling duct?

boba · 03-26-2007, 04:43 PM

Those temps are to low to use to make any kind of interpretation. Set up in hot pit to get temps as soon as you stop coming in from a hot lap. Disks will cool quickly on a cool off lap so come in while on a hot lap.

LeeH · 03-26-2007, 07:21 PM

The temps were taken with an infrared pyrometer after a cool down lap. Would a sticking piston be intermittent - caused by heat?

I just jacked up both side - both front wheels spin freely.

boba · 03-26-2007, 07:35 PM

We have seen disk temps over 1100, 800 is not too high. 200 is cold you need to get temps from a hot lap. Uneven cooling (airflow) on a cool down lap could be the cause. Get some hot temps then you will be able to tell much more. Until you have more data and as long as it is nor pulling or unusual wear I would leave it for now.

LeeH · 03-26-2007, 08:28 PM

Quote:

Originally posted by boba
... I would leave it for now.

Hey! I actually have time to do that! I'll get on it right away!

aigel · aigel's Garage

http://en.wikipedia.org/wiki/IR_thermometer

Cheap hand held IR thermometers do not work well with reflective surfaces. They are not recommended for such an application. They are built assuming an average emissivity. Problem is that the emissivity of a polished iron surface is only half that of any typical non polished, non shiny surface:

http://www.electro-optical.com/bb_rad/emissivity/matlemisivty.htm

On top of that, your emissivity may vary greatly, depending on how much brake dust is on that polished surface ... that will lead to large variations in your readings, making it impossible to even look at the relative "temperatures". I think this is going on here, that's why you have an outlier on one disk.

Also remember that the field of view of these hand held thermometers is rather large. If you get a piece of wheel in your field of view, it will average it into the temperature reading.

All said, the IR thermometers are great on dull surfaces like tires, radiator hoses or even a baby's face. But don't use them on reflective surfaces!

Cheers,

George