We have often talked of the need for brake bias adjusting. We need for the bias adjuster to be centered when we have the correct amount of braking force in the front verses the rear. There are several ways to do that.
We will not only tell you the different ways to go about that, we’ll now tell you how much your bias is expected to change with each different part. That’s important because if you don’t know the degree of change, you might just end up with the wrong parts, again.
Of course we are talking about a car with a bias adjuster in the pedal assembly. And we are assuming you can change the master cylinders easily. For this discussion, we are also going to assume that making changes to the calipers is more difficult and expensive. So, let’s just leave those alone for now.
We are discussing making changes to the master cylinders and showing you how much each change in size means in overall braking bias change. The percent of change in braking force each size of master cylinder causes could also be applied to the cylinder sizes of the calipers if you so choose to go that route.
Why Change The Brake Bias? – We will need to change the system for bias change if the brake pedal bias adjuster is off center. We might have the bias we need in the system, but it’s never a good idea to have a bias adjuster off center.
An adjuster that is centered is much more consistent and provides the same braking power lap after lap, whereas one that is off center might be a little different each time you apply the brakes. Consistency is important in all of your race car systems.
If you have used up all of your pedal bias adjuster adjustment and are still not where you want to be on brake system bias, then you’ll definitely need to make changes to the master cylinder sizes and the change will be more than if the adjuster were centered to get the adjuster back to center.
Sizes Of Master Cylinders – The most common sizes of master cylinders and their associated areas of bore are: 5/8-, ¾-, 13/16-, 7/8-, 15/16-, 1.0-, and 1 1/8-inch. As we will see, the percent of change from one size to another is most on the ends, from 5/8- to ¾-inch and from 1.0- to 1 1/8-inch.
Another important factor to consider when choosing master cylinder sizes is the amount of brake fluid flow each produces. The smaller the master cylinder, the more the brake pedal will move to move the calipers the same amount.
It takes X amount of fluid to push the brake pads onto the rotors. If the master cylinder was larger, it would move a greater amount of brake fluid per inch of brake pedal movement. So, the pedal will move less with a larger master cylinder. That may be good, or not so good depending on your application.
Note that from 5/8- to ¾-inch and 1- to 1 1/8-inch we have a larger percent of change than we have between ¾-inch and 1-inchsizes. It might be best to stay within the ¾- to 1-inch range for our front and rear master cylinders where we see a more consistent amount of change from one size to another.
Master Cylinder Bias Vs. Caliper Bias – Another important thing to note is that we have two bias’s going on with our brake system in most cases. We have master cylinder bias which we are discussing today, and then we have brake caliper bias, which we might, or might not make changes to.
It is sometimes easier to change a brake master cylinder, or two, than change the calipers. For one, the master cylinders are less expensive, so if you need a size you don’t already have, your cost is less by changing the master cylinder size to achieve a bias change.
If we end up with a master cylinder bias of 50/50, we are still going to have a caliper bias with the front having more braking power than the rear because the front caliper is always larger than the rear caliper.
So, as you think out your bias changes, take into account the difference in caliper sizes, the adjuster position, and what the master cylinder sizes are. Always go larger in size to make changes, no matter which way you go so that your pedal travel will not increase to create a mushy pedal.
That means, if you need more rear braking, you go up on the front master cylinder size, not down on the rear cylinder. And if you want more front braking bias, you go up on the rear master cylinder size, not down on the front. Both of these changes produce less pedal travel, not more.
Sources:
AFCO Racing
www.afcoracing.com
800-632-2320
Hawk Brakes
www.hawkperformance.com
330-722-4295
Performance Friction Brakes – PFC Brakes
www.performancefriction.com
800-521-8874
Wilwood Motorsports
www.wilwood.com
805-388-1188
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