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I'm partially along on making lightweight front dis brakes on RED, my soon to be BP powered drag racer. You can gain quite a bit of horsepower by lightening the reciprocating mass of the front drive train, so I am going with lightweight rotors.
I'm using Aspire knuckles for the bigger bearings and stronger bearing support so I had to source a solid rotor that I could have machined to be lighten. Looking at E-Bay I found Miata rear rotors that were solid and smaller and cheap and looked like they would bolt on to the Aspire hub. So I bought a pair and yes they did fit right on - so time for measurement to see what could be machined off.
The rotor was 9-3/32" in diameter and .385" (3/8") thick. The new Wilwood snow mobile calipers I bought could use a rotor from 6 to 9 inches in diameter and from .160 to .190" thick (up to 3/16" thick - half the original thickness of the Miata disc). I wanted to keep a larger diameter so the brake pads would have something to grab onto and wanted to keep the rotor fairly thick to handle the heat. Remember, it is a non-streetable drag racer so the car only has to stop from speed once every 30 to 60 minutes - plenty of time for the rotors to cool off. Also remember this car has NO rear brakes, so the fronts will get hot.
To lighten the rotors I had them machined down to 8-3/4" od by .188" thick. Compared to the Aspire manual trans vented disc it was a huge weigh savings - 4.6 pounds per rotor! So for the Aspire front brake set up, it was a total weight savings of 9.2 pounds of reciprocating mass for both brake rotors.
To keep with the reduced reciprocating weight up front, I plan on using golf cart aluminum rims in either 6 x 12 or 7" x 12" size with 205/30 x 12" or 215/40 x 12" DOT rated tires. The much smaller tire OD will numerically increase my final drive ratio, meaning I don't have to put in a new ring and pinion gear. The small tires should get me in the 4.90 - 5.0 final drive ratio (still have to do the math) which will be good for both 1/8 and 1/4-mile drag racing.
I still have to make the adapter plates for the new calipers, which will fit in between the existing mounting holes of the big Aspire calipers. Pretty straight forward.
So far, so good. Still having problems putting up pictures, but I've written the webmaster. If you want to see how it all looks at the moment, send me your e-mail and I'll send them off to you.
I'm using Aspire knuckles for the bigger bearings and stronger bearing support so I had to source a solid rotor that I could have machined to be lighten. Looking at E-Bay I found Miata rear rotors that were solid and smaller and cheap and looked like they would bolt on to the Aspire hub. So I bought a pair and yes they did fit right on - so time for measurement to see what could be machined off.
The rotor was 9-3/32" in diameter and .385" (3/8") thick. The new Wilwood snow mobile calipers I bought could use a rotor from 6 to 9 inches in diameter and from .160 to .190" thick (up to 3/16" thick - half the original thickness of the Miata disc). I wanted to keep a larger diameter so the brake pads would have something to grab onto and wanted to keep the rotor fairly thick to handle the heat. Remember, it is a non-streetable drag racer so the car only has to stop from speed once every 30 to 60 minutes - plenty of time for the rotors to cool off. Also remember this car has NO rear brakes, so the fronts will get hot.
To lighten the rotors I had them machined down to 8-3/4" od by .188" thick. Compared to the Aspire manual trans vented disc it was a huge weigh savings - 4.6 pounds per rotor! So for the Aspire front brake set up, it was a total weight savings of 9.2 pounds of reciprocating mass for both brake rotors.
To keep with the reduced reciprocating weight up front, I plan on using golf cart aluminum rims in either 6 x 12 or 7" x 12" size with 205/30 x 12" or 215/40 x 12" DOT rated tires. The much smaller tire OD will numerically increase my final drive ratio, meaning I don't have to put in a new ring and pinion gear. The small tires should get me in the 4.90 - 5.0 final drive ratio (still have to do the math) which will be good for both 1/8 and 1/4-mile drag racing.
I still have to make the adapter plates for the new calipers, which will fit in between the existing mounting holes of the big Aspire calipers. Pretty straight forward.
So far, so good. Still having problems putting up pictures, but I've written the webmaster. If you want to see how it all looks at the moment, send me your e-mail and I'll send them off to you.
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