Eating Rear Brake Pads

[hollywoodxs11sf]

Hi, all. My '79 Special has been going through rear brake pads faster that I can aquire them.

The rear pads were toasted when I got the bike a year ago. I replaced them, and they lasted about 2500 miles before starting to grind again.

I replaced them again, and they were toasted THE VERY NEXT DAY!!! Simple... rear brake sticking. I disassembled the rear master cylinder, cleaned it and the spooge hole thoroughly, then bled the you-know-what out of it. I ran a whole bottle of brake fluid through to ensure it was clean and flushed.

Less than 500 miles later, I had to replace the pads again, and also the disc. (yesterday). I bought a slotted disc from an '81 Midnight Special.

Would a thinning of the original rear disc (through all of this pad grinding, the rear disc mic'd out at under 4.5) have created enough heat to eat through pads as fast as I am?

What kind of miles are you guys getting from a set of pads?

Am I using too much rear brake?

Are the shop guys selling me inferior pads?

[ratbyk]

Rapid Pad Wear

You made no mention of the condition of your rear caliper. Suggest that you put a kit in it. If it is dragging it wear shorten pad life.
Also, if the push rod that enters the rear master cylinder is adjusted to far in the master cylinder piston assembly cannot return far enough to uncover the master's compensating port (spooge hole) Pressure in the system will build as the fluid heats up and expands causing brake drag.
Ken/Sooke

[xswilly]

ride the bike for 5 or 10 miles then get off
and put it on the center stand
spin the rear tire by hand
does it spin freely or turn hard
is the disk hot

[TopCatGr58]

Hey Hollywood,

Also check your brake pedal for ease of movement. They can get rust and corrosion around the shaft, so that when you depress it, the spring can't pull it effectively back up to full return position. Also, watch your right foot, you may be pressing on it inadvertently when riding?

The pads are the NON -sintered style, meaning NO mixture of metal in the material, otherwise it would wear out the discs too fast.

As for using it too much, if you're mainly or only using your rear brake, then probably yes. You have about 80% of your braking power on the front wheel, hence the 2 brake calipers. So when stopping in a straight line, on good pavement, try using your front brake more in conjunction with your rear...you really shouldn't be using the rear alone!! Also using engine compression to slow you down before you have to apply the brakes can help.
T.C.

[hollywoodxs11sf]

Frightening Discovery

Thanks for the tips, guys. I guess I've got to adjust the rear brake pedal and rebuild the caliper.
I made a frightening discovery today. Around my lower front brake hoses, I noticed little plastic rings which were dated "2/79." My brake hoses are 26 years old. With that much flex in the front lines (because there is so much more rubber hose), I guess most/all of the braking power has been coming from the back wheel. The good news is that I found a local pressure hose shop who can fabricate replacements while I wait. I'll let you guys know if it turns out to be a good deal.

[pathfinder]

Would a thinning of the original rear disc (through all of this pad grinding, the rear disc mic'd out at under 4.5) have created enough heat to eat through pads as fast as I am?

The minimum in my shop manual says 6.5mm if your rotor was 2mm thinner that would mean the piston is comming out way to far and probably not returning when you let off the brake. I think you've about got the problem solved by changing the rotor and the hoses.