Brakes, linings, AL factor, and other musings

[allan5oh]

I didn't realize how much variety of brakes are out there. For example my trailer takes 4707 shoes, which are 16.5" x 7", Q plus. Meritor sells about 13 different versions of this exact same shoe!

I understand AL factor (area x length). What I don't understand is how you go from a 20,000 shoe to a 23,000 shoe with the same AL factor and coefficient of friction (FF)? I guess within the "range" of FF you move up a bit.

Do higher brake force shoes generally not last as long? Are they harder or softer? I can understand a higher quality shoe is more expensive. Why is it that everyone just goes for the cheapest shoe they can find?

http://meritor.com/products/aftermar..._friction.aspx

[allan5oh]

If you google the various friction models, you can get technical data on them. Wear increases exponentially to braking power. This is not good for us due to the new braking requirements. I think long life brake shoes are going to be a thing of the past. Disc brakes here we come.

R301, MA310, and MA312 all look interesting. R301 and MA312 are comparable, MA310 has slightly better braking power but more wear. MA310 is more for vocational.

Quite the difference compared to the standard linings.

[allan5oh]

And the plot thickens....

On a somewhat standard 4707 shoe there's no less than 35 meritor part numbers. It's a combination of new vs remanufactured, 12 shoe materials, "MG" or meritor production, and a few that are coated thrown in as well.

This is crazy.

[YerDaddy]

Funny I was just researching this for my trailer. I ended up with what my closest dealer stocked. Usually parts places will stock only one or two types of linings. You want something else you gotta special order it.

I think the faster they wear the better so they get replaced more often. They always develop cracks or rust jack before they wear too low anyway.

[Windwalker]

I understand they've had disk brakes in Europe for some time. I know that back in the days when I drove a school bus, the buses were equiped with disk brakes. No matter how hard you stood on the brakes, they would not lock up, But, the braking was extremely effective, and going down a hill, they did not fade. I don't know why, but you could get them hot enough to warp the disks, and they still did not fade. I'm actually surprised they have not started introducing them here. I had heard of them being used in Europe something like 10 years ago.

[allan5oh]

Peterbilt uses them standard for all wheel ends now.

[YerDaddy]

Brakes 101

Not fading is inherent to the design of disc brakes. The disc gets hot and expands thus they become even more effective. Eventually you will smoke the pads or light the hub oil on fire though if the hill is long enough! The disc would be cherry red.

The opposite with drums; the drum expands with heat, moving away from the shoes.

[allan5oh]

I've talked to a few drivers that have used disc brakes. Hands down they love them. They feel much better, more passenger car like. They're also harder to lock up apparently.