Soft brakes

[keith.s]

Just replaced my worn out pads with Bendix CT. The pedal feel is not firm and the braking feels soft and without much bite (no improvement over my 3 year old pads). Any tips on improving pedal feel? Castor / radius rod bushes are shot, and I'm waiting for replacement nolathane's to arrive. Will they improve braking feel significantly?

PS: I tried bedding in the pads after replacement (and rotor refacing).

[Sabbath']

Did you replace the rotors at the same time? Do the rotors have a lip on them? If they have a lip then until the pads wear to the lip, you may experience poor pedal feel.

Edit: Just read the last bit.

Did you let any air into the system at all?

[Not_An_Abba_Fan]

Bedding the brakes in will improve the feel, but replacing pads will make the pedal a bit squishier as when you push the piston back it stretches the seal a bit and the piston moves a bit more than it used to. Give it a day or two and it should come back.

Having said that, if the fluid is old and contaminated, it can reduce pedal feel.

[keith.s]

Not sure about the air part. Installation was done professionally. Lines weren't disconnected. I saw the mechanic use a vice to push in the pistons after removing the assembly from the wheel. The vice was removed and the calipers where left hanging.

It's been a week now, but I only drive a short distance to and from work (10Km each day). For bedding in I took it on the expressway and did a few braking slow downs from 100 to 80, 60 and then a few more firms ones from 100 to 20.

[pau13z]

A few things...

When you say it was done professionally that doesn't really mean much these days. Even pro's often don't do good jobs.

When you say he pushed the pistons in with a vice... you mean like one that's normally mounted to a bench? If that's the case then you've got issues with the piston sticking and have too much moisture in the brake fluid. At that point you probably need to flush out your brake fluid and maybe need the callipers rebuilt. If you mean he just pushed it back then that's fine.

The fact that it was left hanging is never a good thing, they should always be hooked up so there's no pressure on the hose.

Finally.... When it comes to braking systems here's what happens:

When you change brake pads you need to depress the piston into the calliper so the new pads will fit. When you push the piston back the fluid has to go somewhere.... It has 2 options, the bleed nipple or back up into the master cylinder. On vehicles fitted with ABS systems you should NEVER let the brake fluid be pushed back up the hose, it can damage the ABS module. Instead, you need to do it through the bleed nipple. You crack the nipple and push the piston back and the fluid comes out. Often though some air will get sucked back into the system, or if the thread's a little loose some might get in there too. Brake systems are designed to have brake fluid in them... not air. When you have air in the system it essentially compresses and expands, which is why you get a "spongy" feeling to the brake peddle. So when you have fitted the pads in the calliper and put it back onto the car you need to bleed the brake fluid a little for each calliper you've worked on. To do this you need to have someone in the car to push down on the brake peddle as you loosen the bleed nipple. Any air that's in the calliper or hoses should come straight out, and you should see it. Before the person in the car has their foot all the way to the floor you need to close the bleed nipple, so air doesn't get sucked back in.

If you follow that procedure you should be fine.

[Not_An_Abba_Fan]

To bed the brakes in properly you get up to 60, then brake HARD down to 10 without locking the wheels up. Do this 4-5 times, you will start to smell the brakes, when they start smelling, drive around for a few minutes trying not to brake to let them cool down. Brakes will be bed in. If there is no improvement after that, then either the system needs bleeding or flushing, or the pads aren't fitted correctly.

[Munz]

Installation was done professionally - calipers where left hanging.

These words shouldn't be blended.....what a goose

[pau13z]

Also, most Bendix GCT pads now come with a titanium stripe and according to them don't need bedding in, so be careful, you don't want to do damage, but if you are going to do this as Not_An_Abba_Fan said, make sure you drive around and let them cool off. This could take a few mins.

[keith.s]

Hanging is probably wrong usage on my part. They were resting on the hub (but one slipped and I wasn't happy). No it wasn't a bench vice, but a vice that looked like a large hacksaw frame with circular contact areas to push the pistons. Not capable of applying much pressure. Looked like a custom tool built for purpose. These guys do this kind of work from 7 am to 9pm 6 days a week and theres like a 3 hrs wait just to get to the front of one of the 4 lines at the brake shop. If you ever visit the middle east you'll see that car service centres work non stop, and are overloaded (due to the number of cars on the road). Pads where installed correctly and patiently, so were the rotors.

The only thing thats worrying me now is the probabilty of having air in the system. I will try to get it bled asap.

[סּ_סּ]

I recently got new "quiet" brake pads. I drove them for 10minutes and they were squeaky and were weak when I pressed on the brakes.

I took them back to where I got them installed - They sprayed some pink stuff on the brake pads and "adjusted" the brake sensitivity. Now its heaps better

[pau13z]

Not sure how the "sensitivity" thing works.... brakes are brakes lol you push your foot down and the piston pushes out....

As for the pink stuff, it's essentially glue which holds the pads on the piston side to the piston so it sits flush on the rotor when the brakes are applied. You can get some stuff from repco called CRC Disk Brake Quiet, or the stuff a lot of mechanics use is Wurth Anti Squeal Spray.

[ivabiggen]

In my opinion VZ commodores in standard form have brakes that are crap and once pads have been changed no matter what you do the brakes will be soft.

[RiCeY]

A few things...

When you say it was done professionally that doesn't really mean much these days. Even pro's often don't do good jobs.

When you say he pushed the pistons in with a vice... you mean like one that's normally mounted to a bench? If that's the case then you've got issues with the piston sticking and have too much moisture in the brake fluid. At that point you probably need to flush out your brake fluid and maybe need the callipers rebuilt. If you mean he just pushed it back then that's fine.

The fact that it was left hanging is never a good thing, they should always be hooked up so there's no pressure on the hose.

Finally.... When it comes to braking systems here's what happens:

When you change brake pads you need to depress the piston into the calliper so the new pads will fit. When you push the piston back the fluid has to go somewhere.... It has 2 options, the bleed nipple or back up into the master cylinder. On vehicles fitted with ABS systems you should NEVER let the brake fluid be pushed back up the hose, it can damage the ABS module. Instead, you need to do it through the bleed nipple. You crack the nipple and push the piston back and the fluid comes out. Often though some air will get sucked back into the system, or if the thread's a little loose some might get in there too. Brake systems are designed to have brake fluid in them... not air. When you have air in the system it essentially compresses and expands, which is why you get a "spongy" feeling to the brake peddle. So when you have fitted the pads in the calliper and put it back onto the car you need to bleed the brake fluid a little for each calliper you've worked on. To do this you need to have someone in the car to push down on the brake peddle as you loosen the bleed nipple. Any air that's in the calliper or hoses should come straight out, and you should see it. Before the person in the car has their foot all the way to the floor you need to close the bleed nipple, so air doesn't get sucked back in.

If you follow that procedure you should be fine.

Its not necessary to open the nipple when pushing the piston back. I never have and have never had an issue. Simply have the cap of the reservoir so it doesn't pressurise.

The official Holden procedure says the same thing.

You simply suck fluid out of the reservoir to account for the new pads.

[RiCeY]

In my opinion VZ commodores in standard form have brakes that are crap and once pads have been changed no matter what you do the brakes will be soft.

Not true at all, I have excellent pedal feel and performance from my stock brakes with genuine pads. If your pads are soft either the system hasnt been bled correctly, the pads are crap, rotor face is poor or the master cylinder needs replacing.

[pau13z]

Its not necessary to open the nipple when pushing the piston back. I never have and have never had an issue. Simply have the cap of the reservoir so it doesn't pressurise.

Just because that's the way a lot of people do it doesn't mean that's the right way to do it... Now I know they're working on a Ford, but I'm pretty sure the guys from DBA should know a bit about brakes....

[stick3]

when i replaced rotors and pads over 2years ago on the vz ,i followed the same procedure as dba vid shows and i had no dramas ,this was my first car i own with abs and i done a lot of research as i didnt want to waste money unneserary repairs

[keith.s]

Its not necessary to open the nipple when pushing the piston back. I never have and have never had an issue. Simply have the cap of the reservoir so it doesn't pressurise.

The official Holden procedure says the same thing.

You simply suck fluid out of the reservoir to account for the new pads.

This is exactly what the mechanic said today when I went back to bleed the brakes. I'm inclined not to agree, and if I knew better I'd have seen to it that they bled the fluid while pushing the pistons last time around.

The supervisor said it might not improve a lot and the problem is mostly with the master cylinder. Anyway, to cut a long story short, the brakes feel much better now after bleeding. Initial feel on pushing is firmer. Also, I didn't get charged for it (returning customer). Just spent $8 on a bottle of ACDelco brake fluid.

The fluid was horribly dark (pic attached). The guy who did the job stuck his finger in the reservoir and smelt the fluid. At one point I thought we was gonna taste it, LOL!