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Thread: downgrading brakes to fit 15" wheels for rallycross

  1. #1
    Registered Member

    Join Date
    Sep 2019

    downgrading brakes to fit 15" wheels for rallycross

    I am prepping my car 2004 2.3L for rallycross. Though I'm starting in the stock class, long term I might move up to Prepared or Modified. In those classes, you can run rally tires. Problem is, most rally tires are only available in 15" and smaller sizes. According to all the threads, the brakes on my 2.3L car will not allow for 15" rim.

    So I've been thinking if it would be possible to downgrade the brakes to 2.0L brakes. I know that is the opposite of what most people do, but it would really open up possibilities for rally tires. Of course, the idea of smaller brakes is obviously going to affect stopping power. Some might even say it would be dangerous. But all those rally cars with 15" wheels have WAY more power than my 3. There must be a way to have sufficient stopping power with smaller brakes that accommodate 15" wheels. Any ideas?

  2. #2
    Registered Member concept's Avatar

    2014 Mazda3 S GT auto, 2008 MX5 6-speed

    Join Date
    Mar 2009
    San Diego
    Compare the weight of the average rally car vs your car's weight. Are they the same? If not close, then you are asking for problems with smaller brakes unless you can remove non-safety-related parts (seats, etc) from your car to bring your car's weight down to rallying shape, assuming your brake pads are already appropriate. Brake pads can make a big difference in stopping power but can also wear down the rotors very quickly. There is a company that can apply a very hard layer of metal on rotors to allow them to resist wear against sintered metal/racing pads, but having one set done may be very expensive if they accept the order.
    2014 3S GT, Deep Crystal Blue, Eibach Pro-Kit, Enkei PF01s, Koni Sports, Pirelli P ZERO ALL SEASON PLUS tires, 225/45/18
    2008 MX-5 Touring (Mazdaspeed CAI, HIDs, Progress/Koni Sports/Racing Beat sways, SST Magnaflow muffler and tips)

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