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Setting Brake Bias

Race Driving Fundamentals

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Hi,

Curious what method you use for setting the correct brake bias. Do you have a method you use to get in the ballpark, and then adjust on track?

Bit of background, my new racecar has a pedal box with twin masters and adjustable brake bias. The adjuster mechanism was seized so I've had to lubricate and run it through its whole range of motion a few times. All good now, but unsure where it was previously set (should've marked it). I've set the spherical bearing to be close to the middle for now. We have a test day on Friday, then racing Sat/Sun. Tried to google but just coming up with sim forums. I've heard of people having the car jacked up, applying the brakes until the front is unable to be rotated by hand, but the rear can just rotate as a method of getting in the ballpark before you get on track?

Once you're on track, how do you go about getting it in the ideal location. Obviously I don't want to be flatspotting my tyres while trying to test which locks up first and it may not be completely evident from inside the car without someone watching. Any ideas?

Cheers,

Ryan.

Hi Ryan,

Do you know the F/R weight balance of the vehicle?

If it was correctly sized for the vehicle's weight, brakes, etc, then you'd start at the mid-point, but from there you're really going to have to risk breaking one end loose and skidding the tyres as you slowly increase the braking force to the point where one end or the other locks up. Normally you'd want the front to lock up first because that's easily the most stable condition with the vehicle going straight ahead, where as if the rear locks first you lose stability and greatly increase the probability of spinning out.

A practical demonstation can be done with a supermarket trolley - the front wheels are free to move wherever they want to go, but the rears are fixed and if you give it a shove it will move in a relavively straight line, but if you push it backwards with the fixed wheels to the front of the direction of motion, and the unfixed trailing, it will be almost uncontrollable and veer wildly.