... on a w124, the brake discs are held on by one allen bolt, with two "sleeves" 33 degrees away on each side. I assumed these sleeves were basically to correctly position the rotor, with the bolt holding it down, but I'm having an issue getting the rotors on evenly and I'm wondering if those are the culprits. The rotors are on crooked. When you turn one, it passes through the pads very easily on the area of the rotor beside the bolt. It gets completely stuck on the area opposite it ... both wheels (the passenger side to a much lesser degree). I confirmed this by checking runout ... the difference is a 1/20th of an inch on one side and a little less on the other. Technically this could be warped rotors (even though they're new), or a hub problem, but it seems more than coincidence that the part of the rotor that correctly passes through the pads is next to the bolt on both sides. I was going to take the rotors off and give the mating surfaces another clean to make sure it's not some dirt buildup making them crooked. Should I give any thought to the "clamping sleeves"? Do they actually help hold the rotor on evenly, or are they just for positioning?

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

the 201 is very similar.

Measure runout with the rotor clamped down by lugnuts or a similar bolt.

since there is only one allen, it is easy for it to create run-out.

I would re-clean everything like you suggested, including area around the pins and area around the center hub. Use steel wool and sandpaper.

Thanks. I cleaned everything thoroughly and used steel wool to smooth up a couple rough patches on the hubs. It helped a little, but there's still some runout ... it does help to measure it with a spare lugnut opposite the allen screw, then I get pretty much no runout. I guess the wheels hold it even once they're on. It seems like an odd design to me.

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

A wire brush chucked in a drill or grinder will clean the hub very well. If your trying to check for run out you would need even clamping pressure on the rotor so three lug bolts would do that.

In use the rotor is clamped between the wheel and the hub, I suspect the 5 mm Allen screw is just there to keep the rotor from coming free with the caliper off and landing on someones foot in the shop. The torque spec for it is minimal at best with regard to any clamping force. Take a look at the inside of the rotor for anything stuck there or a burr or other manufacturing defect.

I really don't understand the whole allen screw thing either.

The tabs would be enough to keep the rotor in place while you line the wheel up.

Crazy, over-engineering Germans....