• Welcome to the new SAOCA website. Already a member? Simply click Log In/Sign Up up and to the right and use your same username and password from the old site. If you've forgotten your password, please send an email to membership@sunbeamalpine.org for assistance.

    If you're new here, click Log In/Sign Up and enter your information. We'll approve your account as quickly as possible, typically in about 24 hours. If it takes longer, you were probably caught in our spam/scam filter.

    Enjoy.

Spongy Brake Pads?

B

Bill Blue

Platinum Level Sponsor
I decided I needed more aggressive brake pads, so we splurged on a set of Akebono ceramic pads as they are supposed to have very good "bite". Got them installed with no unusual problems, did NOT open the hydraulic system. Now the pedal is very spongy. Does not feel like a brake pedal at all, but like a big spring. I can push the pedal to the extent of its movement and the springy feeling never stops. Just gets harder. I bled the system, mostly because that is the only thing I could think of that could be a problem, as there are no leaks. May have made a slight improvement, maybe not.

Any thoughts? Could it be the pads? I don't think I'm going to reinstall the old pads to find out. At least not yet.

Bill
 
sunalp

sunalp

Diamond Level Sponsor
Bill,
Could be the seal in your master cylinder is leaking? I seriously doubt the the pads would cause a spongy pedal.
Steve
 
B

Bill Blue

Platinum Level Sponsor
Steve, so far there has been no drop in fluid level. Of course the fluid could be leaking back into the reservoir. However, the pressure to hold the pedal down remains constant. In the past, when I've had MC leaks, pressure builds then the pedal sinks while the pedal pressure remains constant. Right now, the pedal position/pedal pressure curve is linear with no plateau. But that is today. Who knows what I'll find tomorrow.

Bill
 
belmateo

belmateo

Gold Level Sponsor
You did not break them in properly. You need to get them very hot to "set" them. Check the manufacture instructions. Should work good after that. Good luck.
 
alpine_64

alpine_64

Donation Time
Be careful not to glaze them, as per previous comments, follow the OEM break in procedure, might be a heat cycling procedure for that material
 
B

Bill Blue

Platinum Level Sponsor
belmateo said:
You did not break them in properly. You need to get them very hot to "set" them. Check the manufacture instructions. Should work good after that. Good luck.
Click to expand...
Akebono says "No break in required" for PROACT pads. I cannot find any instructions at their website and certainly none with the product.

Bill
 
B

Bill Blue

Platinum Level Sponsor
I should add that after installing the rear pads I adjusted the parking brake. I could not get the brake lever to feel hard, always felt like it should go a couple more clicks. I should be able to get the car out for test run today or tomorrow as the job is essentially done. Life always interferes.
 
Barry

Barry

Diamond Level Sponsor
Bill,

With your brake setup, 1" of brake pedal movement results in about 0.008" of front caliper piston movement. 4" of brake pedal movement would be about 0.032" of front caliper piston movement. The rear caliper pistons are smaller, so the rear caliper piston movement would be larger.

All material, including brake pads, is compressible to some extent, but I cannot imagine that each of the Akebono pads is compressing / rebounding by something approaching 0.016".

A "springy" brake pedal has to be the result of something "springy" in the system. Probably air, but possibly mechanical. Your comment about not being able to adjust for a hard parking brake could certainly be relevant.

As you noted, Akebono says the Pro-ACT Ceramic Disc Brake Pads do NOT require any break-in.
 
B

Bill Blue

Platinum Level Sponsor
Barry, are you using my most recent brake data?
Front calipers, 2 1/2" (GM metric)
Rear calipers, 38 mm (Miata)
MC, 13/16"
Brake pedal ratio, 6:1

I agree with everything you and George posted. However, I'm to the point I need to get it on the road and see what happens. Just don't know of any valid option.

Bill
 
Barry

Barry

Diamond Level Sponsor
Bill Blue said:
Barry, are you using my most recent brake data?
Front calipers, 2 1/2" (GM metric)
Rear calipers, 38 mm (Miata)
MC, 13/16"
Brake pedal ratio, 6:1

I agree with everything you and George posted. However, I'm to the point I need to get it on the road and see what happens. Just don't know of any valid option.

Bill
Click to expand...

Bill,

I used 2.375" for the GM metric calipers, 0.750" for the MC and 6:1 for the pedal.

Using 2.500" / 0.813" / 6:1 reduces the overall "mechanical advantage" by about 10% and increases the calculated front caliper piston movement by about 10%.

Still thinking about how to calculate the rear caliper piston movement.
 
Alpine 1789

Alpine 1789

SAOCA President
Diamond Level Sponsor
Bill Blue said:
Got them installed with no unusual problems, did NOT open the hydraulic system.
Click to expand...
Bill, just a random thought: to replace the pads without opening the system, did you force the old pads back into the calipers a bit? I know doing that pushes fluid back into the master. If you did do this, I wonder if that might have damaged the seals?
 
belmateo

belmateo

Gold Level Sponsor
I found this on the web about the pads you are using (i.e.) Ceramic.

They scorch the surface of their OEM pads on new cars for that already broken in feel. The reason for bedding/breaking in is the organic materials in the pads such as rubber, cork or walnut hulls. These are considered noise deadeners but put off gas as well as the binding agent that holds it all together. The ProAct pads do not get the same pre-scorching in their process so the bedding is definitely recommended.
 
belmateo

belmateo

Gold Level Sponsor
I also found this on Tirerack.com
The last sentence contradicts what others are saying.

All brake pads must be bedded-in with the rotor they will be used against to maximize brake performance. The bedding-in process involves a gradual build up of heat in the rotors and pad compound. This process will lay down a thin layer of transfer film on to the rotor surface. Following the bed-in procedures provided by the manufacturer will assure a smooth, even layer of transfer film on the rotor and will minimize brake judder. Here are a few things to keep in mind when installing new rotors and pads:

When installing new pads, the rotors should be new or at least resurfaced to remove any transfer film from the previous set of brake pads.

It is critical that the installer clean any rust, scale, or debris from the hub mounting surface thoroughly and check it for excessive run-out with a dial indicator gauge before installing the rotor.

The new rotor should also be checked for excessive run-out using a dial indicator gauge before the caliper and pads are installed. If a rotor has excessive run-out of over .004" (.10mm) it should be replaced.

If your new rotor has excessive run-out, please contact our customer service department for a replacement rotor. Do not install and drive using the rotor! Rotor manufacturers will not warranty a used rotor for excessive run-out. Running with excessive run-out on the hub or rotor will cause vibration issues.

"Bedding-in new pads and rotors should be done carefully and slowly...Most brake pad compounds will take up to 300-400 miles to fully develop an even transfer film on the rotors."

Failure to follow these procedures may result in brake judder, excessive noise, or other difficulties in bedding-in the new brake pads. The pads need a fresh surface to lay down an even transfer film. Residue from the previous pad compound on the surface or an irregular surface on a used rotor will cause the pads to grip-slip-grip-slip as they pass over the rotor surface under pressure. The resulting vibration will cause noise and telegraph vibrations through the suspension and steering wheel. This vibration is known as brake judder or brake shimmy. This is typically caused by an uneven transfer film on the rotor surface or an uneven surface on the rotor not allowing that transfer film to develop evenly. This is often misdiagnosed as a warped rotor.

Bedding-in new pads and rotors should be done carefully and slowly. Rapid heat build up in the brake system can lead to warped rotors and or glazed brake pads. Most brake pad compounds will take up to 300-400 miles to fully develop an even transfer film on the rotors. Following are the recommended bed-in procedures from each manufacturer:

AKEBONO
400 to 500 miles of moderate driving is recommended. Consumer should avoid heavy braking during this period.
 
B

Bill Blue

Platinum Level Sponsor
Well, I guess the "problem" is squishy pads. Just got back from a relatively low speed drive of about 15 miles and the brakes are just fine. They feel a bit strange, but the results are linear with input. One rapid stop from about 50 made the tires complain, the car got a bit skittish and out of alignment with the rest of the world. That is something that never happened before unless the road was bad. This road is way above average for a county road. I may have to back off the pressure going to the rear.

It will be interesting to see what happens during the next 500 miles.

Bill
 
Barry

Barry

Diamond Level Sponsor
Compressible brake pads does not compute for me, but a Google search for "spongy brake pedal with Akebono pads" suggests that it is a common issue.
 
B

Bill Blue

Platinum Level Sponsor
Forty five miles and the pedal is getting harder. Still does not have that "line" in the pedal that you cannot pass. I'm pretty sure its going to be fine. The pads are aggressive enough that I do not notice the absence of traditional brake feel. Very quiet, smooth and powerful.

Bill
 
B

Bill Blue

Platinum Level Sponsor
belmateo said:
Glad things worked out. sounds like more miles will make it right.
Click to expand...
They did. The brakes are fine. At times like this when I am not in the car, I think I will take note of how the pads feel/perform. But when I'm driving, I forget about the brakes. It stops just fine with no pedal strangeness and braking is better than it ever has been, regardless of brake temp. I have yet to really tax them, such as coming down from Pikes Peak. That day will probably never happen.

I think that pretty well describes a superior product.

Bill
 
belmateo

belmateo

Gold Level Sponsor
Bill,
Glad to hear that worked out for you. Pikes Peak, no? What about Putnam Park or Winchester Speedway?
 
You must log in or register to reply here.
Top