Rear Drum Upgrade

[67malibu]

It's been several years back but I remember seeing an upgrade kit for full size trucks that was a bolt in replacement for stock rear drum wheel cylinders. It was still a drum brake but with beefier parts and a supposedly better grabbing ability. I'll looking for better stopping power when doing moderate towing but I'm not going to put out the cash for a rear disc coversion kit. Anybody seen/used such an upgrade?

[ChevyWonTon]

First of all, disk brakes do NOT have greater stopping ability despite the fact that all cars went to front disks in the mid '60s. They have other benefits like more consistent output over the life of the linings (no adjusters), better cooling properties (not generating heat in an enclosed "box"), and lower cost (due to less moving parts).

However, properly adjusted and maintained drum brakes actually generate a reasonable amount of braking output. In your case, I'd worry about two things...

First, if you generate more output at the rear wheels when your truck is running empty, you run the risk of causing them to lockup much more often. This can be dangerous and is the reason most trucks have less rear brake output than you might want otherwise.

Secondly, changing the wheel cylinder size is not a trivial matter, as the wheel cylinder size is carefully matched to the master cylinder output characteristics. If you put in a larger wheel cylinder (greater diameter), you might get greater force on the linings but you also need more fluid displacement at the master cylinder and risk running out of master cylinder capacity.

You're better off looking at more aggressive lining materials instead of messing with the hydraulic components of the brake system. You might end up with brake noise due to the increased friction properties, but I think you'd accept that extra inconvenience.

Also, if you're towing enough weight to worry about the brake output, I hope you're towing a trailer that has brakes that can help out. If you're flat towing another vehicle, consider adding a brake-assist device that is designed for use with motorcoaches (RV's) that flat tow a "toad" by actually applying the brakes when the motorcoach brakes are applied.

Hope the added insight helps.

[Blue Bowtie]

[quote=ChevyWonTon]... disk brakes do NOT have greater stopping ability despite the fact that all cars went to front disks in the mid '60s. /QUOTE]

All good information, except that all cars did not use front discs since the mid '60s. Many cars started getting discs in the mid '60's, and most had discs by the mid-70s.

Another thing to investigate is an adjustable proportioning valve.

[ChevyWonTon]

OK, I don't know which ones took so long to convert over, but most of the GM, Ford, & Chrysler vehicles went about the same time. I suspect the lagging vehicles were niche vehicles instead of primary-selling models, but the point is still the same.

Related to these comments is the switch to Rear Disc on GM trucks around '99-'00 (depending on model). This was a marketing move rather than an attempt to get more braking output at the rear wheels. The brake output from a caliper is more linear and predictable. Surprisingly, GM switched the lighter full-size trucks back to drums a couple years ago.