Normal for Front Calipers?

[jlsr]

Quick question guys...for the first time after having the car for a year, I was getting ready to check/change the front brake pads and notice a difference in how freely the two rotors spin. The right front rotor turns but takes a moderate amount of pull. The front left rotor can practically spin a full rotation with roughly the same amount of force. Both calipers/pads appear to be touching the rotors and both sets of pads produce some noise as the rotor spins. What has been your experience with your front brakes? What would be normal? Thx in advance.

[rammstein]

Subscribed... I am interested in the answer. Maybe try bleeding the brakes? Perhaps with a bit of air in there, the pads aren't retracting properly? (note that I am not an expert on anything)

[browntown]

So recently I learned that rotors don't actually warp. Apparently it is buildup of pad material. Either way they should spin the same unless a bearing is going out. How old are the rotors? Might consider having them turned at your local parts store like NAPA and with new pads, see if anything changes.

[Atreus]

check your rotors with a caliper if needed, might have to regrind them if you need to.
have your calipers been rebuilt?
if not, how old are the calipers?
what kind of pads/rotors you using
have you bled the system, if not, when was the last time
do the calipers stick at all any other times.

[jlevie]

It sounds like one of the calipers is sticking or you have a bad soft line on the wheel that drags. But it could also be a binding guide bolt. I'd check to see if the caliper moves freely on the guide bolts (with the pads removed) and if that is okay I'd rebuild the calipers and replace the soft lines

[u3b3rg33k]

Rebuilding calipers is stupid easy. I think the parts kit costs $20 at napa. Only other thing you need is a small cylinder hone.
might as well do the lines and calipers at the same time, otherwise you'll end up doing half the job twice.

if you do decide to rebuild, push the piston out using the brake pedal, then take the caliper off. Saves you the headache of trying to do it on the bench.

[jlevie]

Rebuilding calipers is stupid easy. I think the parts kit costs $20 at napa. Only other thing you need is a small cylinder hone.
might as well do the lines and calipers at the same time, otherwise you'll end up doing half the job twice.

if you do decide to rebuild, push the piston out using the brake pedal, then take the caliper off. Saves you the headache of trying to do it on the bench.

I think it abit less messy to push the piston out with compressed air.

[u3b3rg33k]

I think it abit less messy to push the piston out with compressed air.

Sure, if you like breathing in atomized used brake fluid.

I didn't think I needed to list putting a drip pan on the ground.

[Uber E30]

So recently I learned that rotors don't actually warp. Apparently it is buildup of pad material. Either way they should spin the same unless a bearing is going out. How old are the rotors? Might consider having them turned at your local parts store like NAPA and with new pads, see if anything changes.

They do warp its just not that common. Usually has to do with heavy braking over an extended period of time, like going down a steep long road or at the track. Most of the times when people think they are warped its just build up though.

[jlsr]

Thanks for the input everyone. I honestly don't know how old the brake components are, since I got limited history on the car when I bought it. I've had other issues to deal with first (rear diff, starter, timing belt, etc.) that took priority. Was planning on starting with the front pads, but given your comments, I'll plan on including the rear pads, fluid and soft lines. I'll take the suggestion and test the guide bolt without the pads. Depending upon how everything works as it is dismantled, I should be able to determine if the calipers need a rebuild. Was planning on checking the bearings by removing the calipers intact, but that might be easier as the brakes are dismantled. The rotors are probably original, and have some obvious "ridging" that can be felt. So a "turning" would be in line or bite the bullet for new rotors.

When you bleed the calipers, it is standard practice for everyone to bleed the clutch at the same time?

[jlsr]

And as a follow-up, does the entire system have to be drained to replace the brake lines? Or is there a way to retain some of the fluid in the system to avoid introducing more air?

[jlevie]

BMW rotors are too thin to turn and need to be replaced if ridged or worn below minimum thickness.

You will loose some fluid when changing the soft lines and the brake system should be flushed after the repairs. If the calipers have to be rebuilt, plug the lines or all of the fluid will drain out.

Brake and clutch fluid should be changed no less ofter than every other year. Unless there are other problems, it should not be necessary to bleed the brakes or clutch between changes of fluid.

[u3b3rg33k]

And as a follow-up, does the entire system have to be drained to replace the brake lines? Or is there a way to retain some of the fluid in the system to avoid introducing more air?

Leave the cap on the reservoir until you're ready to bleed it / top it off. Then it won't all drain out.

[jlsr]

Quick update and question. I replaced the front right wheel bearing/hub while I was reworking the brakes and calipers. (The bearing wasn't as bad a job as I would have thought.) In retorquing the axle nut back on the axle, I got it up to the required torque but had to torque the nut further on the axle to get the tab on the nut to line up with the groove in the axle, probably another 20/30 lbs to move the tab a few millimeters. There is no noise or play in the hub as it is spun, but it does not spin as freely as the left wheel. Do the bearings take any pressure from torquing the nut or do the races take all the torque? Or does the nut/tab line up properly with the groove if it is started on the axle threads in a certain spot?

[jlevie]

You should always use a new nut when replacing a front wheel bearing (and a new locking plate on a rear wheel bearing). Then torque the nut to the prescribed torque and form a new locking tab.

The bearing doesn't load from the torque. that pressure is carried by the inner races. If very little additional torque was needed your should be okay. A slight stiffness can be just the new bearing and seals.