Big Brakes

[pormgb]

I got this figured out!!

My problem is related to rear caliper piston position, GM Metric calipers have this weird adjustment that is related to the parking brake.

For the calipers to function correctly, the pistons have to be adjusted so the pads are close but no obstructing wheel moment. The parking brake also has to be attached.

The rear pistons are sitting so far back there is excessive pedal travel taking up the slack, I moved the pistons up using the parking brake levers and the brakes are now functioning correctly.

[cycleguy55]

Originally Posted by pormgb

I got this figured out!!

My problem is related to rear caliper piston position, GM Metric calipers have this weird adjustment that is related to the parking brake.

For the calipers to function correctly, the pistons have to be adjusted so the pads are close but no obstructing wheel moment. The parking brake also has to be attached.

The rear pistons are sitting so far back there is excessive pedal travel taking up the slack, I moved the pistons up using the parking brake levers and the brakes are now functioning correctly.

I have the larger, non-metric GM calipers on mine, and your comment jogged my memory about those adjusters. Here's the text from the installation manual:

REAR CALIPER ADJUSTMENT
When installing rear disc brakes with calipers that have an internal parking brake you must adjust or set the calipers when installing. Failure to do so will prevent you from getting a firm pedal and you will have no rear brake function. Only do this adjustment with the caliper and rotor installed on the vehicle. You must set the parking brake every time you park to keep the calipers adjusted.

INITIAL ADJUSTMENT
1. remove the spring.
2. crank the lever or turn the retention nut to actuate the lever forward.
3. after cranking the lever forward as far as it will go, rotate it back the other way until you hit the stop. you may need to use a long screwdriver to lever the lever back into place.
4. The rear caliper should now be correctly adjusted.
5. re-install spring

Important: You must use the parking brake mechanism on a regular basis to set the self adjusting calipers. Failure to use the rear parking brake will result in rear brake loss!

Interesting note at the end - obviously important to note!

Sorry I didn't remember this sooner - it sounds like you could have saved some time and frustration had you been armed with this.

BTW, there is another procedure you'll need to know in order to be able to rack the piston back out for brake pad replacement - but hopefully it will be a while before you need to deal with that. You also need to know that procedure should you "crank the lever or turn the retention nut to actuate the lever forward" prior to installation of the calipers." Don't ask why I needed to discover that...

[DanEC]

Well, that's interesting. Good job of tracking it down and correcting. Hope that takes care of everything with the brakes.

[pormgb]

Originally Posted by cycleguy55

I have the larger, non-metric GM calipers on mine, and your comment jogged my memory about those adjusters. Here's the text from the installation manual:

REAR CALIPER ADJUSTMENT
When installing rear disc brakes with calipers that have an internal parking brake you must adjust or set the calipers when installing. Failure to do so will prevent you from getting a firm pedal and you will have no rear brake function. Only do this adjustment with the caliper and rotor installed on the vehicle. You must set the parking brake every time you park to keep the calipers adjusted.

INITIAL ADJUSTMENT
1. remove the spring.
2. crank the lever or turn the retention nut to actuate the lever forward.
3. after cranking the lever forward as far as it will go, rotate it back the other way until you hit the stop. you may need to use a long screwdriver to lever the lever back into place.
4. The rear caliper should now be correctly adjusted.
5. re-install spring

Important: You must use the parking brake mechanism on a regular basis to set the self adjusting calipers. Failure to use the rear parking brake will result in rear brake loss!

Interesting note at the end - obviously important to note!

Sorry I didn't remember this sooner - it sounds like you could have saved some time and frustration had you been armed with this.

BTW, there is another procedure you'll need to know in order to be able to rack the piston back out for brake pad replacement - but hopefully it will be a while before you need to deal with that. You also need to know that procedure should you "crank the lever or turn the retention nut to actuate the lever forward" prior to installation of the calipers." Don't ask why I needed to discover that...

Yea, read this a few times but didn't really think it had such a profound affect on pedal feel.

This write up is actually more detailed, thanks!!

[patrickt]

Originally Posted by pormgb

I got this figured out!!

Nice. Now on to the next issue....