Brake rotor - 95 325I

My college-age son (Austin, Texas) needs rotors replaced on his 95 325I, and doesn't want to spend $400. (Pads were replaced a few months ago, and he put off spending on the
rotors.) I'm handy with tools, pretty mechanical, and have tackled water pumps, alternators, starters, etc. on American and Japanese cars, and motorcycles, but haven't done brakes (except on motorcycles). What advice can you offer on replacing rotors on a BMW. I have heard the hard part is a bolt that secures the rotors, and sometimes it must be drilled out. Any advice would be appreciated. Any specialized tools needed?
Clayton In Texas
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It's a cinch. All you need is the hex wrench (comes in any metric set - 3mm or so?), some anti-seize, a screw-driver or clamp to push back the pistons, and a 17mm (IIRC) socket (works on the lug nuts, too) to release the calipers so they will swing off the rotors.
Don't forget to replace the wear sensor (it's about $5) on the side that has it.
FloydR
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You've pretty much got the bit already that can be a pain. Only advice I can give really is to try and undo that rotor to hub bolt (which requires a hex/allen key type head) before removing the pads and calliper. That way someone can stand on the brakes to stop the rotor/hub turning while you are trying to undo it. Which is a whole lot easier than trying to use screwdrivers etc wedged into the rotor vents. Oh, and buy some new bolts before hand so you have them already just in case you need drill them out. Other than that, they are a doddle to do with no special tools required. The calliper mounting bracket bolts are pretty tight too.
Last bit of advice is don't get BMW rotors, buy some after market brands. I use the ATE Power discs, they are much harder wearing than the chocolate BMW ones and cheaper too.
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Rick

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The screw may be a little tight. IME the best way to remove it, is with an impact driver. Apart from that, about all you need is a spanner to remove the two bolts securing the caliper mounting bracket, then slide the whole caliper and mount assy off the disc, or rotor. BTW, when you fit the new disc, the retaining screw only needs to be done up lightly. It doesn't need to be really tight. It's only there to stop the disc moving when changing a wheel etc. Mike.
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That screw doesn't even _need_ to be used, does it? The rotor isn't going to go anywhere when the tires are mounted, so that small screw really has no particular purpose in the grand scheme of things.
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an
remove
whole
done
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Thing is, that on cars with wheel bolts, like BMW's, as opposed to those with wheel studs and nuts, without the screw, there is nothing to stop the disc revolving once the wheel is removed. If it did, it could be enough to prevent the fitting of the wheel bolts when a wheel is replaced. Mike.
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Mike G wrote:

Always has been on my cars, Mike. It's called iron oxide.
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I suppose it could make fitting the wheels back on a pain in the ass, but there is a handy alignment pin in the tool kit that should solve this problem.
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J Strickland wrote:

One word for you Jeff: balance.
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Balance?
The screw we are talking about is 1.) very light, an d 2.) about as close as is possible to the center of the hub as it can be. There is ample weight spinning around near the edge of the tire that can counter this screw without any problem.
We are talking a gram or two here, not ounces.
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Jeff Strickland wrote:

Not a gram or two. They 1/4 oz. (I just weighed one). And yes, a weight that small would seem inconsequential. My thought was that I don't want *any* unbalance in the hub assembly as the would have the effect of adding to any imbalance in the wheels and there is no way to measure or compensate for the hub misbalance other than "on the car" balancing, which is an abomination and should be avoided if at all possible.
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I had to cut one of those screws off once, and I can't tell that it's gone. There is so much weight spinning a great distance from the center of the axle, that this small bit of weight, effectively right on the center, is going to be inconsequential in the grand scheme of things.
PS The lightest wheel weight I can ever remember seeing is 1 ounce, so a quarter ounce isn't going to be a problem.
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J Strickland wrote:

Ahhhh... I can see you don't have any experience with E34's Jeff, do you? ;-)
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Rotors cost in the range of $50 each, and anybody with a sense of mechanics can install them -- all of them -- in about 2 hours. The dealer, or a mechanic with the proper assortment of tools can do it in much less time, but those of us confined to working on the floor of the garage or in the driveway tend to work a bit slower.
If you can do waterpumps, you can do rotors on a BMW.

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It's a metric hex head countersunk setscrew, and yes, they sometimes seize - although they may also have been damaged earlier by someone using an imperial hex tool. However, they're easy to drill out as the hex provides a centre for the drill, and they're fairly soft steel. Once the disc is off, grind the rest of the head off (if needed), and remove the setscrew from the back of the hub with Mole grips.

Use some copper grease on the new setscrew, and don't tighten it till it groans. It's only there to stop the disc falling off when a wheel is removed. ;-)
Also, make sure the mating surfaces on both disc and hub are perfectly clean - any grit etc could cause run out.

Buy a set of metric hex heads for a 3/8 drive socket set.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman (News) wrote:

My experience is that after you drill the head off and get the rotor out of the way, there is plenty of screw shank available to remove it out the front with those "mole grips", which I assume are Vice Grips over here...

Even more to the point, if it is too loose it's not going anywhere with the wheel installed.
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