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Rear tires locking on hard braking.(New brakes)
https://slantsix.org/forum/viewtopic.php?t=19171		 Page 1 of 1
Author:  Bren67Cuda904 [ Sun Aug 13, 2006 12:42 pm ]
Post subject:  Rear tires locking on hard braking.(New brakes)
Just did a complete brake job. (new drums X4, hardware, one wheel cylinder and 3 kits, hoses, shoes) Test drove and found it whats to lock the rear wheels under moderate braking. The left rear is the first to lock and the car goes slitely to the right. I have not tried a panic stop yet because I think both rears would lock and the rear would probably come around on me.
My brake adjustment procedger:
All 4 wheels off the ground and in netural. Turn adjusters out until the drum binds then back off a little. Apply brakes and recheck drum turning resistance.
All 4 wheels can be turned with two fingers but not one finger. Test drove and had the above stated problems. Jacked car up again and all wheels turn freely. (3 mile test drive)
Brake pedal feels good to me and is the same level as before.
Are the rears adjusted to tight? Air in the system?
Author:  Bren67Cuda904 [ Mon Aug 14, 2006 8:02 pm ]
Post subject: 
any ideas?
Author:  Avenger2040 [ Mon Aug 14, 2006 8:24 pm ]
Post subject: 
Looks like air in the system to me, last time I remplaced my rear brak cylinders, the same hapenned to me, just purgue the brak system from air and re-calibrate.
Author:  Joshie225 [ Mon Aug 14, 2006 9:23 pm ]
Post subject: 
I doubt it's air. Air is almost always accompanied by a spongy pedal. I would double check and make sure all the long shoes are toward the front of the car. Also, if you really do need to reduce the rear braking there are smaller diameter Dodge Dakota wheel cylinders that will bolt in. Chances are that the front shoes ned to wear in a bit, but I'd double check to make sure everything is assembled properly.

BTW, did the brake bleed normally? Get good fluid flow from all 4 corners?
Author:  Charrlie_S [ Tue Aug 15, 2006 3:17 am ]
Post subject: 
Quote:
I would double check and make sure all the long shoes are toward the front of the car.
?
Josh, I hope that is just a misprint. Short shoe is "primary", and goes to the front, long shoe is "secondary", and goes to the rear.
Author:  Joshie225 [ Tue Aug 15, 2006 4:27 am ]
Post subject: 
Yeah, that was a mistake on my part. I'm working my night shift rotation this week and it's never kind to my mind or body.
Author:  Jeb [ Tue Aug 15, 2006 12:07 pm ]
Post subject: 
Wasn't this a problem with A-body porportioning valves?
Author:  Dart270 [ Wed Aug 16, 2006 8:29 am ]
Post subject: 
This could also be that the shoe material has changed over the years and has different bite characteristics. The easiest way to overcome this is to insert an adjustable prop valve (Summit, $40 or so) in the rear line and dial out some of the rear brakes.

I would bleed them first to make sure, and maybe drive around a while, but it's nice to have an adj valve.

Lou
Author:  argentina-slantsixer [ Wed Aug 16, 2006 11:13 am ]
Post subject: 
hey

don't know if your brake pump is the same (i'm guessing not) but the only way to get them to work properly here by bleeding the air out if you don't have a helper is injecting brake fluid thru the bleed hole on the front wheels. Sometiomes the front brakes never bleeds out completely and then you have "touchy" rear brakes.
Author:  SlantSixDan [ Wed Aug 16, 2006 11:35 am ]
Post subject: 
Remind us, please, what brake system you're working with here: 9" drums all around? 10" drums all around? 10" front and 9" rear? Something else?

Adjustable proportioning valves have their place, but think carefully before choosing to go this route. It is tempting to use them to mask the symptoms of a problem, and sometimes they do that, but without fixing the cause of the problem.
Author:  Bren67Cuda904 [ Thu Aug 17, 2006 2:08 pm ]
Post subject: 
I ve got 9" drums all around. I ve used this bleeding method for year with no problems on late model cars and it lets me do it with no help. First top off master cylinder to the top and watch carefully as not to let it go down very much. Use brake hose clamps to pinch off all three old hoses. Do the brake job completely. Open all bleeders. Change in new hose wheel side and quickly remove and attach new hose to steel line while it drips. Monitor master cylinder level and add fluild to keep it at the top (because if it goes down to far you will then need help with the beeding) untill the fluid drips from the bleeder valve. Close valve. Repeat on the other front. Rear hose to be installed in the same manner. Wait untill both rear beeders are driping at the same time and then close them. Top of master cylinder. Done. This has work so many times for me that I really don't think theres air in there. I am using silicone which is known for holding air in the form of tiny bubbles. I made sure not to shake the bottle or to pour it in to the master cylinder from a distance. I just let it drift in slow from the edge.
I ve always known about one shoe being longer and shorter and i was very careful about matching what was there. I should double check the orientation but the brakes didn't grab before.
One more thing to note: The new rear drums were cleaned on the inside with brake cleaner to remove the shipping oil, the fronts I forgot to clean. Do you think that this may be the only problem. I would think a 3 mile test drive using the brakes very often should burn off this oil.
You thoughts please. :)
Author:  Bren67Cuda904 [ Thu Aug 17, 2006 2:11 pm ]
Post subject: 
Forgot one more thing. Is silcone brake fluid bad for the paint. I got a little below the master cylinder.
Author:  SlantSixDan [ Thu Aug 17, 2006 2:37 pm ]
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Oil will contaminate brake shoes. It does not "burn off" or otherwise go away. You may have identified the problem. Pull the front drums, clean them with brake cleaner and scuff-sand them with sandpaper, then clean them with brake cleaner again. Do the same 3-step process with the front shoes.

Silicone brake fluid does not harm paint.
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