Brake Questions - Cooling related to Rotor Edge to Wheel Clearance
08-30-04, 03:51 PM
#1
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Brake Questions - Cooling related to Rotor Edge to Wheel Clearance
Just got back from an All Mazda track day at Laguna Seca. Tons of fun and lots of RX7s and Miatas.
I have 13" rotors with Wilwood SL-6 front Calipers (with thermolock pistions) and N-tech brake ducts plumbed into the R1 lip brake ducting. This combination can take a lot more heat than my stock brakes did but still doesn't perform quite as well as I like. I still can manage to boil the brake fluid (Motul).
I use the stock 16" rims which BARELY fit over my brakes. There is about 2/3rds on an inch of clearance between the inside of the rim and the edge of the rotor. Do you think this may be causing poor airflow out of the rotor vents? I don't want to blow $$$ on 17" rims but do you think an extra inch of space would help cooling?
Also, I have the RZ rear brakes but feel that the brake balance is still a little off. Anyone have an advise on brake proportioning valves?
-John Magnuson
I have 13" rotors with Wilwood SL-6 front Calipers (with thermolock pistions) and N-tech brake ducts plumbed into the R1 lip brake ducting. This combination can take a lot more heat than my stock brakes did but still doesn't perform quite as well as I like. I still can manage to boil the brake fluid (Motul).
I use the stock 16" rims which BARELY fit over my brakes. There is about 2/3rds on an inch of clearance between the inside of the rim and the edge of the rotor. Do you think this may be causing poor airflow out of the rotor vents? I don't want to blow $$$ on 17" rims but do you think an extra inch of space would help cooling?
Also, I have the RZ rear brakes but feel that the brake balance is still a little off. Anyone have an advise on brake proportioning valves?
-John Magnuson
Last edited by John Magnuson; 08-30-04 at 03:53 PM.
08-31-04, 08:40 AM
#2
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I am not familiar with the brake ducts you mention. What is the diameter of the duct going from the nose of the car to the rotor. Exactly how do the ducts end at the rotor? do they just kind of point at the rotor, or are they directly connected to a shroud that forces all the air to feed the center of the rotor?
If I assume you have a 3" diameter duct going to the center of the rotor, it has a cross sectional flow area of about 7 square inches.
In the 2/3" annulus around the outside of your 13" rotors, you have a flow area of about 28 square inches.
Also, we have the centrifugal pumping action of the spinning vanes in the rotor to push the air out of the rotors.
Therefore, I doubt your problem is not enough air leaving the rotor; I suspect you do not have enough cold air forced into the center of the rotor. If you had a good clear photo of the duct where it attaches to the center of the rotor then I could see for sure.
If I assume you have a 3" diameter duct going to the center of the rotor, it has a cross sectional flow area of about 7 square inches.
In the 2/3" annulus around the outside of your 13" rotors, you have a flow area of about 28 square inches.
Also, we have the centrifugal pumping action of the spinning vanes in the rotor to push the air out of the rotors.
Therefore, I doubt your problem is not enough air leaving the rotor; I suspect you do not have enough cold air forced into the center of the rotor. If you had a good clear photo of the duct where it attaches to the center of the rotor then I could see for sure.
08-31-04, 02:39 PM
#3
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Yeah, a good 3 inch duct doing into a well built custom backing plate that directs the air into the eye of the rotor is what I have. I'll take some pics later today and post them.
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