I am changing out the diff on my 52 M3 to a Dana 60, primarily because the diff I have ( the origional Timken) and every other one I have looked at to replace it are toast. The truck had 12"x 2" linings all around, I have kept these on the fronts but now the rears are 12"x 2-1/2"with more lining length than the fronts; therefore I will be running a good 35% more lining area on the back than the front. Both front and rear have one leading and one trailing shoe so when energized the rear brakes will probably do 35% more work? Where I live in central Alberta we have 6 months of winter (and sometimes 9) with the ugly streets that go along with it. As I remember with these trucks they were dynamite with rear wheel lockup unless you had a large load on the back end even with factory brakes. So do I grind 35% off the rear linings, use a proportioning valve, drive only when it is dry or throw 1500lbs in the back? Many of you have made this swap so I would love to here your thoughts on this. Thanks Don (no power brakes, standard master and wheel cylinders, linings do not appear to be metallic)

 

The proportioning valve would be quick and easy. I've used the Summit Racing branded ones as they are inexpensive and work well. Packaging had Wilwood on it.


Worked great on my front disc swaps on early Mustangs. Never tried it on our trucks. Easy to take out if you don't like it, you won't have to grind your shoes or carry a bunch of weight.

 

While some peace of mind....lining or pad size has little impact. It's pressure.

The same input pressure on a larger pad or lining makes the same torque. Only more surface area.

Not sure...? Put some bigger pads in a caliper and see if you stop shorter. If it were that simple you can be certain the Internet would be flooded with suppliers!

 

Hello and thanks for your comment Todd. I completely agree with you on your argument for equal pressure creating equal torque regardless of pad or shoe size, however when we are speaking of break shoes we must consider the "self energizing effect" caused by rotating of the break drum; the leading edge of the shoe is drawn into the drum which ads considerable force to the stopping action. A example of this are electric breaks on a trailer, i believe they only work well when the wheel is turning, do almost zip when stopped, and zero when moving backwards. There is very little pressure put on the shoes by the magnet on the actuating arm, the stopping power comes from this "self energizing effect" . Pads in a disc break are completely different animal. Thanks for your thoughts Don

 

Hi

Actually Todd is absolutley right.....

Look at this link and chapter 28.4.1 and also more precis 28.4.2 and the formula stating TB= my x Nr (unit Nm)

Brake Shoe and Pad Fundamentals (Automobile)

This says that the brakeing torque is direct equivalent to the friction coefficient between lining and drum and the radial force N between lining and drum (Unit N)

However in on this page they dont show you exactly how you can calculate the Radial force as that is a quite complex formula but it is still not dependent on any of the factor related to the drum and brake lining dimensions other than the drum radius......

The formula is close to the same but I cant find it online so this formula for a double pivot shoe brake is good enough

Frictional brake with two pivoted shoes diametrically positioned about rotating drum - MATLAB - MathWorks Nordic
The Tls and Tts says the same thing as above but in a more complicated way my(friction coefficient) times pb or pa (Maximum linear preassure at leading or trailing shoe) times rD drum radius........

The only thing the width and lineing length will effect is the energy (torque over time) the brake system can be subjected to without fadeing.

....... so ......the science says its no problem at all.......just keep the drum size (radius or diameter) the same as stock and also keep in mind to keep the wheelcylinder the same size as stock...... and you are home free

 

BRAKE, it's not broken.

 

Since you are not sure about the critical lining material I would try this on a slippery streets and going down hilly roads at various speeds before I would start grinding on anything.

 

Thanks for the reply's , the links to the info sites are great, just need time to digest the data. Special thanks to Grey Beard for the spelling lesson, the problem started when I was in grade 1.

 

For what it's worth, I swapped to a 9" rear with 2.5"-wide shoes from the stock Dana 44 with 2"-wide shoes. No real difference in braking, in fact seems less prone to lock-up. I do notice the e-brake is a little less effective tho, but that could be a number of other things.