1991 - A Hub Oddity (with apologies to Clark and Bowie)

[Adnan]

Hi,

I replaced the front brake rotors and pads on my 1991 535i (after 60k miles!) and noticed something interesting:

The rotors have seven holes, five for wheel lugs and two more. One lines up with the rotor mounting bolt hole; what is the other hole for?

Now here's the funny thing; on my car, the left front hub had a hole that lined up with the other hole on the rotor, not the one it should be. The problem is that this other hole is oversize and just fits the head of the bolt. This means that anti-rotation is ensured but the rotor flops around if the wheel is removed.

I know that this car was involved in some kind of "incident" before I bought it as the left front has been repaired. It appears that the hub was replaced too, but with what part? Did later cars have this different hole pattern? Is this a non-OEM hub?

Finally, is there a bolt I can use that would correctly hold the rotor (hole in rotor is counterbored so it suggests it's possible).

Thanks,
Adnan

[632 Regal]

get some new rotors, I dont think they are very expensive and then you could use the factory style bolt to hold the rotors on.

[Adnan]

Hi,

My hub seems to be non-original. The rotors are OEM and have the holes in the correct place. Since I don't really want to replace the hub to solve this, I was hoping that there was a solution, otherwise.

Regards,
Adnan

[Terry B]

Adnan,

There are 2 different hold down bolts for the rotors. One has a kind of "double lip" while the other looks like a normal hex head bolt.

The double lip one is part number - 34 11 1 123 072
The other one is - 34 21 1 161 806

ETK says that the latter one is for pre 3/91 cars (though I have a 540 that uses this bolt).

Hope that helps - don't know about the rotor holes...

Terry


Hi,

I replaced the front brake rotors and pads on my 1991 535i (after 60k miles!) and noticed something interesting:

The rotors have seven holes, five for wheel lugs and two more. One lines up with the rotor mounting bolt hole; what is the other hole for?

Now here's the funny thing; on my car, the left front hub had a hole that lined up with the other hole on the rotor, not the one it should be. The problem is that this other hole is oversize and just fits the head of the bolt. This means that anti-rotation is ensured but the rotor flops around if the wheel is removed.

I know that this car was involved in some kind of "incident" before I bought it as the left front has been repaired. It appears that the hub was replaced too, but with what part? Did later cars have this different hole pattern? Is this a non-OEM hub?

Finally, is there a bolt I can use that would correctly hold the rotor (hole in rotor is counterbored so it suggests it's possible).

Thanks,
Adnan

[Robin-535im]

There are two rotor layouts (see Bruno's site), as I know from first hand experience: I ordered the "correct" ones for my 1991 535 but they were the wrong part. The difference, IIRC, was in the bolt locations for the rotor hold down bolt. Perhaps either your hubs are the "wrong" part, or the rotors were made to match the other hub bolt pattern.

Look at Bruno's site under wheel bearing replacement and you'll see the difference.

- Robin

[Adnan]

Thanks,

I'll check these things out.

Regards,
Adnan