Just a thought,, Check to see if the caliper piston is metal or plastic.I've been told that the plastic piston distorts with excessive heat and will cause problems.Again just a thought.
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| Outside Brake Pads Wear Faster https://slantsix.org/forum/viewtopic.php?t=51512 |
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| Author: | SpaceFrank [ Mon Mar 25, 2013 8:46 am ] |
| Post subject: | Outside Brake Pads Wear Faster |
I have the 11" front disc brake conversion from an M-body, with sliding rear-mounted calipers. With EBC pads on the front and stock Autozone shoes on the rear drums, the brake performance seemed more than adequate at my first road race. However, when I checked the brake pads afterward, I noticed that the outside brake pads were about halfway worn while the inside pads looked barely used. The calipers themselves are freshly rebuilt units from RockAuto, and we did lubricate the sliding surfaces before installing everything. Is there any other reason for the outside pads to wear faster? This strikes me as odd, because the piston itself is on the inside. I would expect the inside pad to wear faster if the caliper wasn't lubricated properly. |
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| Author: | Sprag [ Fri Mar 29, 2013 6:22 pm ] |
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I'm not familiar with the M Body caliper arrangement, so my guess is that the inboard pad is sticking? Perhaps it goes together fine when cold but once hot (you said road racing), the clearance goes away and the pad hangs. Piston would push on stuck inboard pad and outer would do most of the work right? Just a theory but that's where I would start looking and wonder if inboard pad might show sings of hanging or even bending. I don't recall the application, but I know I've done several where I had to mod (grind/file) the pad plate where it rides on the slide for proper clearance. |
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| Author: | DusterIdiot [ Fri Mar 29, 2013 8:36 pm ] |
| Post subject: | It's... |
Quote: I'm not familiar with the M Body caliper arrangement,
Single piston floating caliper like the 1973-1976 A-body, all FMJ, and R body cars, some late B-body might have this option. FYI. -D.Idiot |
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| Author: | emsvitil [ Fri Mar 29, 2013 11:26 pm ] |
| Post subject: | |
I've always seen the outside pads wear faster with sliding piston calipers........ I think it's because the inside pad is pulled away from the disk more when you release the brake pedal as the piston retracts into the caliper pulling the inner pad with it. |
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| Author: | Greg Ondayko [ Sat Mar 30, 2013 5:17 pm ] |
| Post subject: | |
I had the opposite problem on the truck as the machined ways got so much salt corrosion and rust that it prevented the caliper from moving and the outer pad did not wear at all and the inboard pad was down to the rivets... Greg |
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| Author: | Romeo Furio [ Sun Mar 31, 2013 8:17 am ] |
| Post subject: | |
Just a thought,, Check to see if the caliper piston is metal or plastic.I've been told that the plastic piston distorts with excessive heat and will cause problems.Again just a thought.
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| Author: | DusterIdiot [ Tue Apr 02, 2013 4:39 pm ] |
| Post subject: | Yes... |
Quote: Check to see if the caliper piston is metal or plastic.I've been told that the plastic piston distorts with excessive heat and will cause problems.Again just a thought
This is correct. An FYI also should be out there that if ordering a set of calipers from your local parts store they used to give an option of the phenolic pistons or the metal ones in rebuilt calipers. I notice that the last set I got were plastic with no options for metal pistons when ordering. -D.Idiot |
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| Author: | Romeo Furio [ Wed Apr 03, 2013 6:12 am ] |
| Post subject: | |
The last set from O'Reilly auto parts I got were plastic.The manager was able to find metal thru his warehouse buddy. Also found some rebuild kits in metal. Do some checking and hope you can find some old stock. Also assemble without shoes after taking a file to the caliper bracket and caliper to remove any burs or high spots that can hang the caliper in it's slide.If no binding lube the slide with anti-seze,or if you choose wheel bearing grease.Using a cloth rub the lube into the metal thus removing all excess.The lube will impregnate the metal and should keep rust away for awhile. |
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| Author: | Sprag [ Wed Apr 03, 2013 12:15 pm ] |
| Post subject: | Re: It's... |
Quote: Quote: I'm not familiar with the M Body caliper arrangement,
Single piston floating caliper like the 1973-1976 A-body, all FMJ, and R body cars, some late B-body might have this option. FYI. -D.Idiot  I guess it's time I stop thinking of disc brakes as a 'special option'.
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| Author: | SpaceFrank [ Thu Apr 04, 2013 12:50 pm ] |
| Post subject: | |
It never occurred to me that the pistons might be phenolic. The calipers from the disk brake donor had metal pistons, so I just assumed... I'll have to check this out over the weekend. I don't know if it could be causing the uneven wear issue, but I would want to switch to metal anyway. I'd much rather let the heat flow into my high temperature race fluid than keep it all trapped where the magic happens! I'll order rebuild kits for the junkyard calipers, regardless of what I find. We're going to Eagles Canyon Raceway next month, and I hear the track is hell on brakes. |
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| Author: | SpaceFrank [ Fri Apr 05, 2013 11:28 am ] |
| Post subject: | |
I haven't taken the brakes apart yet, but I just called someone from Raybestos and confirmed that the calipers I ordered (FRC4107 & FRC4108) do in fact have metal pistons. Any other possibilities for why my outside pads would be wearing faster than the inside pads? I will check this weekend to verify that both calipers can slide freely. |
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| Author: | SpaceFrank [ Thu Apr 25, 2013 11:25 am ] |
| Post subject: | |
When we had the car up in the air last, it was apparent that the front brakes are dragging a bit. This is probably the reason why the outside pad is wearing faster. I'm going to be taking a look at the calipers this weekend to make sure the sliding surfaces on the junkyard caliper hanger are smooth, but I'm pretty sure they were fine when installed. What I'm thinking we may have done wrong is overtightening the little brackets that hold each caliper to the hanger. There are two of these on each caliper, front and back, attached with one bolt each. I could see them being tight enough that the caliper wouldn't retract fully, while the pressure of applying the brakes would still be enough to overcome it. Does anyone know what the torque specification is for these bolts? I have a '64 Dart FSM, but these sliding calipers came from an '84 M-body. |
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| Author: | Joshie225 [ Fri Apr 26, 2013 8:26 am ] |
| Post subject: | |
If the caliper stands aren't smooth, if they have grooves or dips in them, the calipers will hang up. The flat spring which holds down the caliper cannot be overtightened and cause the caliper to hang up. The spring is meant to be flat on the caliper stand. The pressure exerted by the spring is not determined by how tight the bolt is torqued (15 ft-lbs) once the spring is flat on the caliper stand. The hardware kits come with rubber bands and small anti-rattle clips. For racing I would throw those away and use only the big spring clips. |
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| Author: | SpaceFrank [ Fri Apr 26, 2013 9:01 am ] |
| Post subject: | |
Roger that, that's one thing I don't have to bother checking. Looks like I'll be removing the calipers and taking some sandpaper to the sliding surfaces. |
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| Author: | Joshie225 [ Fri Apr 26, 2013 3:55 pm ] |
| Post subject: | |
If you have a large file I would use that to make sure the caliper ways are flat. |
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