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Help - Weak Stopping power after rear disc brake conversion


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Hi all this is my first post so sorry if I’m doing this wrong. 
 

Recently did the rear disc brake conversion using Zcardepot’s kit and I’ve been having issues with the car not fully stopping even when I pull the e-brake up. 
 

I’ve insured to bleed the brakes throughly in the right order (Rear Passenger > Rear Driver > Front passenger > Front Driver). 
 

I’ve also adjusted the e-brake tensioning rod so it fits tightly. 
 

Thank you for the help! 

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Is it possible that the calipers were accidentally installed on the wrong sides?  The bleed valve should be pointing up on both, in order for them to be bled.  If the bleed valve is not at the highest point, you can end up with trapped air inside the calipers.

 

All that aside, how well were your stock brakes functioning before installing the rear disc kit?  Reason I ask is that your stock front discs have plenty of stopping power by themselves when functioning properly.  In a hard-braking scenario, they provide the majority of the stopping power for the vehicle. 

 

Sooooo....even if your new rear disc brakes were not functioning correctly, you should still have plenty of overall stopping power from the stock front discs (again, as long as the fronts are operating properly).  Yet your post seems to indicate that the car has very weak overall stopping power ("car not fully stopping").  Is it possible that you have issues elsewhere in the braking system?  A weak brake booster could cause weak stopping power.  A MC with internal leaks could cause weak stopping power.  Etc, etc.

 

Need some more info on the health and configuration of your overall brake system.

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On 4/18/2020 at 8:00 PM, Cloveland said:

Hi all this is my first post so sorry if I’m doing this wrong. 
 

Recently did the rear disc brake conversion using Zcardepot’s kit and I’ve been having issues with the car not fully stopping even when I pull the e-brake up. 
 

I’ve insured to bleed the brakes throughly in the right order (Rear Passenger > Rear Driver > Front passenger > Front Driver). 
 

I’ve also adjusted the e-brake tensioning rod so it fits tightly. 
 

Thank you for the help! 

 

It's not an E brake.  It's a parking brake.  You're also mixing mechanical performance with hydraulic performance.  The two brake systems work by different mechanisms.

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Providing more detail would really help but I fought what may be a similar issue and that is the brake pedal is soft and doesn't feel like it does a whole lot, but if really pound it to the the floor the car will start to slow down.  In my case it was the reaction disk. If you didn't touch the front brakes and they are not grabbing this could be why, it is a well documented issue that can show many symptoms. 

 

You say you did the rear swap but what else was changed or replaced? did you let the master run out of fluid during the change?

 

If you have a firm pedal and no stopping force then that is a different scenario completely.

 

Air in the lines will result in a soft pedal until you pump it a few times and then it should get firm.

 

Mark your fluid level and pump the brake until your leg falls off, the level should not change. 

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Did you remove the proportioning valve that was intended to be use with the OEM rear drum brakes.  It lives at the end of the line going back from the engine bay through the trans tunnel.

 

https://www.silverminemotors.com/datsun/datsun-240z/brake-upgrades/cancel-out-your-stock-prop-valve-with-double-female-unions-m10-1

Edited by LooseRocks
added link to part for cancelling proportion valve
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Going off what @jhm said; Im going to double check my front brakes to see why those aren't providing enough stopping force. Maybe this is my issue and was so distracted by the rear's. I'll report back once I figure out the issue. Thanks everyone for the help.

@looseRocks; I didnt remove the proportioning valve. Is that something that needs to be done?

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I can't really say for sure as I have not installed my brakes yet.  This was something that was recommended by Silvermine as the OEM valve was meant to balance the OEM front disc with OEM rear drum.  When I do the install I will remove it and add a manual proportioning valve from Wilwood to adjust the balance.

 

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Try pumping the pedal when stopping.  If the pedal gets harder and the car stops faster then there's air in the system,

 

And, to be sure, again, the parking brake adjustment does not come in to play with disc brakes.  The caliper pistons are self-adjusting, each time you apply the brakes.  They're not like the drum brakes.

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