Brakes do not feel effective

[ggunter]

Hello, I just got my car into go kart stage and it ran great but the brakes scared me when I went to stop as far as pedal pressure to stop the car. It is the Wilwood pedal box with front and rear master cylinders and the FFR supplied brakes. It does stop but I don't think I could lock up the brakes by standing on them. I haven't driven the car more then a few miles and know the pads have to seat. I set up the balance bar with about a quarter inch forward for the front master cylinder and when the brakes are applied the bar is parallel to the firewall. Any thoughts?

[Papa]

Did you bed in the pads yet? If not, I'd try that first. Second thing would be to re-bleed the MC and calipers. Also, use some brake cleaner on the rotors to be sure they are 100% contaminate-free.

[RJD]

I have the same brakes. In my case, bedding the brakes made a big difference. During the bedding process I could feel the brakes become more effective in subsequent stops.

[ggunter]

I figured the pads would need to be seated in and that may be the answer. I have re bled the brakes opening both front and rear calipers at the same time. I have a very good pedal and its not spongy, it just kind of shocked me when I first hit the pedal to stop. I have four miles on the car I will spend some time this weekend trying to bed the pads.

[Nigel Allen]

I put up with the supplied brake pads for a few months. Despite thoroughly cleaning the rotors prior to assembly, bedding the pads in and adjusting the bias to get the most out of them (correct biasing made the most difference for me), they never really improved to a point where I considered the braking to be satisfactory. At least they featured anti-lock capability!
On recommendation of others here, I replaced them with Hawk HP+. Problem solved. Dust is a problem, I felt I was driving in a cloud of brake dust for the first couple of hundred K's. This has settled down, but any decent outing will leave a good coating on the rims. There are other brake pad choices, but this is what I tried.
The Hawks do squeal a bit, but I did neglect to put the supplied grease on the rear of the pads. Perhaps others here can share if the grease does help?

Cheers,

Nigel

[Desert Cobra]

I had the same problem until I readjusted the brake bias bar at the master cylinders. The high pedal effort is because you are trying to generate enough pressure on all four brakes at the very same time. They need to be phased in with about 70% front before the rear start to grab. Play with it until it feels right to you.

[ggunter]

I am going to put more miles on it this weekend and bed the pads after that I will play with the bias on the balance bar.

[NAZ]

ggunter, if your rotors and pads are free of any anti-friction material (oil, grease, silicone, etc.) and you have bed them properly without improvement then you are either not getting sufficient clamping pressure or you need to go to a different brake compound. On street brakes, don't expect bedding to be a night & day difference if this is a new installation but it is certainly one of the steps to take in troubleshooting poor brake performance. And that balance bar is a fine tuning adjustment so if you can't lock up the fronts or rears, don't expect the balance bar to correct this.

Most installations don't have pressure transducers installed so to determine if you have enough system pressure you will need to temporarily install a gauge like this one: https://www.speedwaymotors.com/Longa...SABEgKkv_D_BwE

I can lock up my brakes at 800 PSI on my race car and that's just moderate pedal pressure so if you can't lock yours by really standing on the pedal and you can generate >1,000 PSI you need to look for different pads. When I do a burn out at the track I set my front brake pressure at 600 PSI and hold the line lock button. That's plenty to hold back an 1,100 HP car spinning the slicks at 6,500 RPM. I've had good experience with Hawk's DTC-50 compound, they produce high torque at low temps -- just what you need for a street car.

Good luck.

[ggunter]

Thanks NAZ, I have not run the car enough to bed the pads which I will do this weekend. It took a high amount of pedal force to even stop the car, I don't think I could have locked up the front or rear with the force being applied. I realize these are not power brakes but the car doesn't weigh anything either. The rotors were cleaned with brake clean before install . I may have to check line pressures.

[NAZ]

No need for power brakes in these light cars. You should easily be able to lock all four wheels on dry pavement, if not there is a problem and you'll need to troubleshoot the cause. If you used the parts FFR supplied in your kit with no deviations my guess is pad compound is the most likely issue.

[ggunter]

NAZ can you tell me who sells the Hawk pads. I may just change them out and start fresh after I check line pressures.

[NAZ]

I get mine from Summit Racing. I can recommend the DTC-50 compound and also warn you against getting the race pads or ceramic or other such high temp compounds. Race pads usually don't provide much friction until they build up heat. And yes, Hawk is proud of their pads as the price will reflect but these will last longer than in your daily driver.

[davekp]

I had the same problem until I readjusted the brake bias bar at the master cylinders. The high pedal effort is because you are trying to generate enough pressure on all four brakes at the very same time. They need to be phased in with about 70% front before the rear start to grab. Play with it until it feels right to you.

??????????????????????
This sounds very strange. All wheels need to brake at the same time, not delayed at the rear.
Do you mean the bias should be 70/30?

[Papa]

Silly question: Are you certain you have the proper bore MC for front & back? Not reversed?

A couple of helpful videos for proper setup of the balance bar:

https://www.youtube.com/watch?v=ISLqGf0sMX0

https://www.youtube.com/watch?v=ZYK4VEOae6w

[Desert Cobra]

My comment was poorly worded. You are correct all wheels should lockup at the same time. It is the amount of pressure that is biased to the front. My description was trying to point out that at the balance bar you have to bias it about 70% toward the front. I too tried new pads, followed the bed in per maker, bleed the system, cleaned the rotors, check the master numbers (bore diameter). Only after all that did I monkey with the balance bar by shifting it to move the front master 70% more than the rear. Sorry for the confusion.

[NAZ]

There seems to be some confusion over the balance bar pedal assembly and its relationship to brake bias. The primary balance of braking force from front to rear is accomplished in the design of the brake system (static bias). The rotor diameter, the combined caliper piston area, and the area of the M/C are the primary ways brake balance is designed into a brake system. The balance bar is simply a way of fine tuning that front to rear balance to suit track and or tire conditions.


When setting up your brake system and adjusting the balance bar, keep in mind that maximum braking is only achieved when the front and rear brake torque is at the maximum that traction will allow before lockup. This is what ABS is trying to do under panic stop conditions.


Applying the brakes hard on a car will initiate dynamic weight transfer from the rear to the front as the CG shifts forward, loading the front tires more which increases traction and will have the opposite effect on the rear. Therefore, due to the increased traction the front brakes can be set-up to provide most of the stopping force, as much as 75%. That does not mean that the front brakes see 75% more pressure or that the balance bar is skewed 75% to the front. You can increase or decrease the front pressure with a balance bar (and the front brake bias) to meet track and or tire conditions or help turn in. Dirt cars often have a valve to shut off the right front brake to help turn in. Brake balance is another tool for driver and crew chief to improve handling.




In addition to the set-up videos Papa posted above, here’s some more info on brake systems that use a balance bar: https://www.youtube.com/watch?v=FWxLpVUwEkA
And if you want to make component changes you may be interested in this calculator: Brake Bias Calculator | Brake Cylinder Calculator | Automotive Brake System Calculator | BRAKE POWER

[Duke]

Try sizing down your master cylinders, especially on the front. My front Wilwood 120-10000 calipers with a 3/4" M/C was only generating 620 PSI at the front. Smaller M/C, more pressure. My rear calipers (120-6806) seam to be happy with 3/4" M/C. I just moved the front down to .62. Online calculators help give you an idea of where you should be, but per my conversation with Wilwood techs, it's mostly trial and error. Do yourself a favor though, figure it out BEFORE you get the body on. It's possibly, but a huge PITA to swap out the M/C's after the body goes on. Wiring is usually in the way, especially if you have a coyote like I do.