We are building a well balanced car that will be used for Autocross and Road racing.   I am looking to see if anyone has any data or just knows how hot the brake reservoirs will get in a 30 minute road race event. Our reservoirs are located 24 inches above the master cylinders.  They are currently mounted with a 3d printed plastic that failed in the cold weather. This had us looking at the failure temps for the plastic, resulting in me questioning the plastic at the hot end as well.

 

Hi Scot!

The answer depends on a couple factors. Are you guys running a brake fluid recirculator in the lines?

No Sir we are not.  Also for the group can you post a picture of a brake fluid recirculater. 

No Sir we are not.  Also for the group can you post a picture of a brake fluid recirculater. 

Yes sir.  The recirculator is on the right.


You can see them in my catalog HERE.

----------------------------------------------------------------------------------------------------------------------------------------------------

To answer your original question about reservoir temperatures ...

Without a recirculator, the brake fluid only grows about 10°-20° on road course runs under 1 hour. The heat migration from the calipers all the way back to the reservoir is minor. So we would expect the temps to be ambient temperature + 10° to 20°.  Unfortunately, this is rarely the case, because of other heat sources.

Engine & exhaust heat raise the brake fluid temperature substantially ... think 40°-70° ... if the brake fluid reservoirs are in the engine compartment. It gets 250-300°+ in some engine compartments. It's not uncommon to see ambient temperature, plus 50° to 95° brake fluid in a hot engine bay.  All the more reason to duct the hot air out through side extractors.

Adding a brake fluid recirculator RAISES the temperature at the reservoir. How much depends on how much brake heat is generated from the driver's braking habits. This is a good thing. Whatever the temperature increase at the reservoir (from the recirculator) is a temperature DECREASE at the calipers.  With the reservoirs & recirculator plumbed in the engine compartment, I've personally seen infrared temperature readings on the stainless lines of 190°-250°.  You HAVE TO run good brake fluid & purge it often so it doesn't boil. And, IMHO, you REALLY NEED engine compartment heat extraction to Drop that temperature down.

Another method, if we're running a recirculator, is to use pedals that allow the plastic reservoir to be mounted in the cockpit. Now cockpits get hot too. Especially in the summer. 150° cockpits is not unheard of. But that's minor compared to 250-300° engine compartments.

Circling around to why I think you're asking about temperature & plastic reservoirs ... if the temp is hot enough to damage the plastic ... you need to fix the heat problem, not change reservoirs. That's my 2 cents.

We are using a 3d print to mount the reservoirs. I was just making sure we are not over temp for the plastic used for the mounts. You have answered perfectly and clearly thank you for the quick response. This is also mounted inside. I will post pictures after the car is revealed.