If an original drum/drum master cylinder is used, & the residual pressure check valve is left in place, then the discs will not fully release & will drag, but the rear brake part of the master cylinder is the same for both drum/drum & disc/drum versions. Only the front brake section is different, so this is not likely to be the cause of the problem.

mmm master cylinder may be of wrong type, also the m/c has a restrictor in it if you run drum fronts. This needs to be taken out if you wish to run disk brakes. If its still in there you will have heaps more braking in the rear.....

What year model is your ute? Mine is an 84 and came factory with disc fronts drums rear but as far as i have heard only the 84 model ones came out like this

Thanks for the replies. Ok so something is definately wrong. I am getting the manual, so i will have a read. The ute came with discs on it when i bought it about 5 months ago, i assumed that was factory.

I have replaced the master cylinder and the rear slaves....i'll keep investigating.

Thanks

somethin sounds a bit wrong there mate, shudnt need a bias valve on a standard ute

Quote:
Did you change the rear wheel cylinders to the correct size ones for disc brake models when you fitted the discs? 1200 coupes & 120Y's have a smaller bore rear wheel cylinder to help prevent rear wheel lockup as the discs require a higher line pressure to make them work, & of course, the rears see this same pressure, so the smaller bore cylinder actually reduces rear brake efficiency at any nominated line pressure compared to the same rear brake in a drum/drum system.
Are the rear brakes correctly adjusted?
Have the front pads bedded in yet. [I assume that they are new on a flat & smooth disc.]

I often just hose down the brake assembly as the first thing I do. If all is well, then you will wash out all the brake dust & this will help to make it all nice & clean. If there is any leaking brake fluid, then you will get some white foam on the ground as the brake fluid is soluble in water.

If you still have an oily appearance after hosing it down, then you probably have a leaking axle oil seal & a little oil in the linings can sometimes cause this kind of problem. [A lot of oil has the opposite effect.]

Get the manual, then clean, inspect & if necessary, test.

My ute is disc fronts and drums rear and has only locked up once before when breaking and that was in the wet. Mine is an 84 model.

hey all.
My rear brakes (particularly one side) tend to lock really quickly, way before the front wheels. Has anyone else with a ute found this? Its got the standard pissy little calipers on the front.

Is this a design error for the datto, or is somethign not right here? What can make a drum lock up really easy (the shoes look ok and so does the drum). Has anyone put in a bias valve before, and is it a lot of effort?

Thanks all...
ps, great to get it finally back on the road after 4 months. (been busy)