what is a good disc upgrade for fd front? does anyone have something over 310mm to suit factory caliper (relocated of course) that they have used?

 

I think you are confused. It's not the diameter of the stock rotors that causes them to run hot, it's the thickness. The stock rotors are 22mm thick, the 99 spec (and all aftermarket BBK's) are 32mm thick. If you want increased brake "capacity" (which you can think of as ability to absorb and then bleed off heat) you need thicker rotors, not larger diameter rotors.

The stock rotors are 294mm diameter x 22mm thick. The 99 spec calipers (which are for all intents and purposes identically performing) use a 314mm x 32mm rotor. The larger brake diameter increases the leverage that the caliper has on the disc, which (simplified) kinda just translates into brake "feel" i.e. the larger diameter rotor will be more responsive for the same pedal pressure as compared to the 294mm disc. Now does that mean the 294mm disc is unresponsive? No. It just means that you need to add more pedal pressure to achieve the same level of braking vs a larger diameter rotor. Thats it. Hopefully that clears things up for ya.

 

Wouldn't the fact that you get more leverage mean, that to get the same amount of braking force on the rotor, the pad has to exert less force (than the a caliper with stock leverage), therefore less friction, therefore less heat? I always thought that was part of the advantage. And also doesn't the larger size dissipate heat better?

Scroll down to Mandeville Auto Tech Brake Kit:

http://www.rx7.org/Robinette/bigbrake.htm

Uses a 13" rotor (330mm) with Stock Caliper.

 

I think a basic physics lesson is in order...

Brakes are all about converting kinetic energy into thermal energy. Changing brake components doesn't change the amount of kinetic energy you must convert. The ability of a brake rotor to absorb and dissipate thermal energy is directly related to its mass and construction (respectively). I'll let you educate yourself from there.

 

and therefor the larger diameter is the same as adding thickness, from what i can tell, a lot of thickness is in the vented gap between the two faces of the disc not just the thickness of the face material.

And yes, larger diameter give more leverage just like using as strong bar on a socket does.

Basically, I already have calipers and am only going to run light sprint races or one lap time attack time stuff and drifting maybe. some here run factory brakes with good rotors, pads and ducting and out brake a lot of other track cars so all i need are bigger rotors. By all means if I came across a bigger well priced caliper (ie a 2nd hand factory 4pot like the 99 spec caliper) Ide go for it as i have to re mount anyway, but for now as I dont have one, a bigger rotor with some good pads and ducting should see me right

must measure mrs brakes on here car as its an RS with a bigger rotor, are these the 314mm rotors?

 

thanks for th elink there champion

 

Send a note to Coleman Racing. They'll make whatever size rotor you need:

http://www.colemanracing.com/Custom-...ild-It-W9.aspx

A lot of the USA guys used them to make rotors for discontinued brake kits.

http://www.negative-camber.org/crispyrx7/apracing.htm

 

So are the brake upgrades sold by pettit, rx7.com(bonez), etc; which include new rotors, pads, ss lines, not worth the $ & trouble? My car isn't a dedicated track car, but I want to get it on the track eventually, but keep it mostly a street car.