Disc Brake Pads, Part II; A Sequel

Grumpy's Garage; A Sunny Thursday in November! --

In the last segment, I told the readers about the noise (let's call it a "groan" or a "moan") emanating obviously from one or both of the front disc brakes on Grumpy's Red Rocket. Today, the Grumpy One took matters into his own hand and decided (and acted!!) to do something about this annoying moan. Not because it portended anything catastrophic or potentially damaging, but simply because -- well, Grumpy just got tired hearing the noise everytime he touched the brakes, or made a slow turn to the left. 

Besides, it is embarassing that any "strange" noise should come from a car proudly maintained by the Eminent Engineer of Mechanical things. The noise must be eliminated or fully explained with something other than a bloviated theory.

Grumpy removed the wheels and found that the disc brakes on this Honda are the easiest of all to work on! Two bolts hold the caliper assembly (right) to the fixed part of the suspension. By loosening the top bolt a half turn and removing the bottom bolt, the caliper assembly can be swung upward and laid to rest on the top of the wheel suspension. The brake pads are now fully accessible to examine, replace, or, as Grumpy planned to do this time, to clean the non-braking contact surfaces (above, left and right) and apply some hi-temp grease to these contact areas so that these parts can be free to move relative to each other and thus not vibrate like a bass fiddle when light brake pressure is applied.

The picture at left shows the fine, thick condition of the left front brake pad, thus confirming what was reported in the previous post on disc brakes. Yes, after nearly 86,000 miles these original brake pads are showing very little wear -- perhaps the Grand Mother would prefer that they showed much more wear!!

But, I digress! The non-braking contact points on the brake pad backing are shown on the right with grease applied. Grumpy used a wheel bearing grease containing Molybdenum di-Sulfide. This grease is especially designed for use in high temperature applications, which is the case with disc brakes. The Molybdenum di-Sulfide is a solid lubricant (similar to Graphite) so that, even if the grease is disappated by the heat generated by the disc brakes, the coating of Molybdenum di-Sulfide will still function to prevent friction and/or binding between these contact points. It is when these parts stick together (held by friction) that the caliper unit vibrates to create the moan that has annoyed Grumpy and his passengers.

A critical caveat: Be careful to not get any grease on the brake pad friction surfaces or on the brake disc surface!!

Viva a Red Rocket!! Viva o mal-humorado Um!! Graças a Deus pelo silêncio!!

Disc Brake Pads

From the Liar's Lair; 8 October 2010 --

The other day my Son-in-Law was helping me with a job that needed two good men. Well, the Son-in-Law was one good man and we got the job done despite the obvious deficiency. But this isn't about the job -- or even the Son-inLaw. This is about the disc brakes on the "Red Rocket".

As we rolled down the road, a strange noise appeared whenever Grumpy applied a long, light pressure on the brakes. Son-in-Law opined that it was the right front brake. Grumpy's faulty hearing was just able to confirm that there was, indeed a strange new sound emanating from the proud Red Rocket but Grumpy sure couldn't tell where it was coming from. But for sure, it was happening everytime the brakes were applied ever so lightly for more than a few seconds.



Left Front Disc Brake
(Looking Forward)



Right Front Disc Brake
(Looking Forward)



So tonight, Grumpy dismounted all four wheels on the Red Rocket and examined the disc brake pads on each hub. Here are the results: 

Notice, just above the hub in either photo, and next to the polished disc rotor, the 3/16" thick brake pad. Looking very carefully you can see the springy metal "tell-tale" extending toward the disc from on top of the pad backing. This "tell-tale" is placed such that it will contact the disc rotor when the pad is less than about 1/16" thick; the idea is to alert the driver of the need to replace the pads before the metal backing comes into contact with the rotor, causing a disgusting grinding sound and much damage to the rotor disc. The right front shows a similarly thick brake pad remaining; with about 85,000 miles onthe odometer, Grumpy estimates that these pads are "good" for at least another 40,000 miles before needing change. Of course Grumpy will plan to spot check them again every 10,000 miles (when he swaps the front tires, left to right). This very long brake pad life is predicated on conservative braking -- using engine compression as much as possible, by downshifting on long down-hill stretches, and by letting up on the gas early upon noticing a red-light or STOP sign up ahead, or traffic slowing down.



Right Rear Disc Brake
(Looking Aft)



Left Rear Disc Brake
(Looking Aft)

 The rear disc brake pads are apparently about half as thick as the fronts; either that or they have undergone more wear than the fronts. The emergency brake on this Honda Accord is applied to the rear disc brakes by a mechanism of which Grumpy is not sure. But the fact that the rear brake pads get wear due to the emergency brake application could explain more wear here. Even assuming that the rear brake pads were originally the same thickness as the fronts, Grumpy estimates that these should also be good for another 40,000 miles. However, since Grumpy plans to rotate the rear tires to the front at about 107,000 (after 40,000 miles on this set of tires), he will reassess the expected life of the rear pads at that time.

Unless the little "Tell-Tale" squeakers alert him before that!