# Drum to disc conversion



## Patman (May 7, 2011)

See this thread http://www.cruzetalk.com/forum/12-g...spension/6421-drum-disc-brake-conversion.html


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## NickD (Dec 10, 2011)

Was disheartening when my rear disc calipers on my 2012 2LT quit self adjusting after a season of road salt, were not plated, and essentially a pile of rust. Had my wife work the parking brake while I was holding the caliper in my hand, the piston would just rotate back and forth instead of forwarding like it was suppose to.

Could never learn how these worked, on my 78 Fleetwood, same problem, but they were using a steel binding ring that would dig a groove inside of the piston bore and would just rotate back and forth. Back then, my Caddy dealer wanted 300 bucks each for new calipers, but told me, you are wasting your money, won't last very long. So I had to manually adjust them. Still have that four way caliper socket, but didn't work on the Cruze, just had to change these to two opposite hole in the piston, I made a tool to rotate them rather than buying a way overprice kit.

Pistons are on screws, right turns CW, left turns CCW to reduce that pad rotor gap. Really had a battle to get these calipers replaced, first dealer told me to trade it in for a new one while still under the BB warranty. Second one was more kind call GM tech support, shaking my head, replaces the master cylinder, than the power booster, then the vacuum switch, than the vacuum motor. None of them knew you had to work the parking brake to adjust the rear calipers.

Wife knew I was very frustrated, just said pay 300 bucks to get new ones, but stubborn, went clear to the top with GM, none of these people have any technical knowledge, but finally instructed my dealer to replace them.

You cannot use a C-clamp on the rear calipers to remove them, the reason for torque plates, actually designed by US engineers for Toyota, but with a rim on the rotor preventing you from sliding them off, have to grind that off first. Wouldn't be a problem if the pads were of slightly larger diameter. 

I begged my dealer to have one of the old calipers, refused to give me on, they don't return these, end up in the recycling bin, not worth the shipping charges. I know all this stuff.

88 Supra is really of intelligent US design, uses four conventional calipers, just like the front, are inherently self adjustable to take up that wear, and use much smaller caliper pistons for the rear so no need for proportionally valves, 92 DeVille had those with four wheel disc. Cruze uses the rear two ABS valves to reduce the rear disc calipers, so the ABS pump would also have to be changed.

Did make some improvements over my 78 Fleetwood, no matter how hard you hit that parking brake pedal, would not hold on a hill. Owners manual even said to hit the power service brakes while applying that foot operated parking brake pedal, this didn't work either.

Never looked to see if the wiring for the disc brake ABS is the same as the drums, but also may have to change the wiring harness as well.

Drum brakes need the service brakes applied in reverse to adjust them, people that never back up have a low brake pedal. Major problem with the shoes is the lower anchor plate, it rusts and the shoes cannot self center, so the adjusters do not work. When buying new shoes, do get a credit for your old shoes, pads are throwaway. Want to see those first, some are nicely plated, others are just sand blasted, these will give you lots of problems with binding. Anti-seize works the best for lubrication. With the shoes installed before the drums, should be able with your fingers to move those shoes up and down and sideways. I leave them loose, roll down backwards on my driveway, while tapping on the brake pedal. Each tap, that brake pedal should come up a bit until its at the top. 


Are you sure you want to switch from drums to discs?

While GM did copy the torque plates of the Toyota, did not copy using completely separate drum brakes for the parking, and the rear calipers on the Toyota are much smaller so no proportioning valve or ABS is required. And like the fronts are inherently self adjustable. And since the parking drums are normally only used for parking and are nut adjustable, never have to be adjusted. But also completely independent of the hydraulics and do give you something extra for stopping power.

Had to redo my four calipers on my Supra last summer, mainly because that rubber was 28 year old, total cost for all four was 16 bucks and like new again. And didn't have to touch the drums, were like new yet. Cruze is using a so-called self adjusting parking brake, a little dog grabs the cable, and if that slips or wears, have to replace the entire parking brake assembly. That parking brake lever will go as high as it can go, no brakes. 

If these kids only knew automotive history.


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