drag on rear wheels slowing me down?

mnmike · 08-20-2006, 05:06 PM

Ive added a new master cylinder, and put new front calipers, pads, and had my rotors resurfaced. When the car is jacked up the front wheels spin easily as they should. The rears dont seem to move as easily though and when I drive the car (which i still havent gone more than a few blocks) there is definetely a drag on the car. Its like the brakes are always lightly on. The ebrake is off. Could it be the ebrake or what could cause the drag?

Early_S_Man · 08-20-2006, 05:41 PM

Do you have something in your memory to compare with that was significantly lighter on that car or another 911?

My guess is that it is your imagination at work ... the back wheels have more mass and drag, normally, compared to the fronts, anyway! Fronts only have the mass of the rotors and hubs to move. Rears have the rotors, hubs, stub axle, CV-joints, half-shaft, differential and ring gear, and maybe the viscous drag of the gear oil and turning pinion gear and freewheeling gears inside!

rdrr · 08-20-2006, 05:47 PM

Your rear calipers could be sticking. That was one of the first things I had to fix on my current car when I bought it.

mnmike · 08-20-2006, 06:20 PM

well the car has sat for over 10 years. The rear calipers are old. I just assumed its the rear bc the fronts move very easily when the car is jacked up. And when the car is rolling at say 3 mph, it slows and stops on its own.

rdrr: how did you go about fixing it?

I was hoping I wont have to replace the rear calipers. I replaced the front with rebuilt ones from parts heaven. Id do the rears as well, but they're pretty expensive (i think it was like $400 for the pair).

Early_S_Man · 08-20-2006, 06:27 PM

It helps everyone to give a bit of history on the car along with the problem you are 'presenting' ...

You need to remove, disassemble, and clean the rear calipers to see if they can be rebuilt. The kits are inexpensive, but you need to see if the pistons are pitted before ordering the parts.

rdrr · 08-20-2006, 06:31 PM

The symptoms on my car were similar. There was noticeable resistance that would stop the car when it was rolling, i.e. in a traffic jam I would hardly need to apply the brakes.

My calipers had to be rebuilt as the pistons were corroded. I did not do the work myself and it ended up costing about as much as the rebuilt calipers you mentioned. If you do it yourself it should certainly be cheaper. There is a caliper rebuild kit available from the host. Depending on the condition of the pistons, you might have to replace the pistons. Might be worth trying it first yourself.

mnmike · 08-21-2006, 06:27 AM

well if anything is wrong, im sure the pistons are stuck or badly corroded. Thats why I wouldnt want to rebuild it myself, I figured the caliper would need to be machined and then a new piston put in.