[bollybib]

NOTE: This thread was written before I started my Project thread. It forms part of the BRAKES section (Posts #6 thru #12) in that thread.

I have a 1969 C20 with rear coil springs and an Eaton H052 rear end. The rear brake drums appear to be original equipment and are the nondemountable type. They operate with 11 5/32 x 2 ¾ shoes. They are heavily scored and at the wear limit.

The replacement drums that I purchased appear to be identical to the originals except for the bolt holes. The replacement drum bolt hole diameter is approximately .627 in. The bolt holes have been countersunk on the inside face of the drum. So have the drain holes.

The original drum bolt hole diameter is approximately .550 in. The splines of the wheel bolts fully engage the drum holes. There is no bolt-to-hole play. if you have access to one, Figure 52 in Section 4 of the 1969 service manual shows the hub and drum details.

The engagement of the wheel bolts with the replacement drum (I am reusing the original bolts) doesn't seem right to me. The bolt is loose in the hole and the splines are not engaged. The drum could potentially move relative to the hub within the constraints of the hole diameter unless the oil deflector (mounted inside the drum and secured by the wheel bolts) is deformed by the head of the wheel bolt into the countersink. Deforming the oil deflector with the wheel bolt heads into a countersunk hole is not mentioned in the service manual nor does it seem a secure fastening method.

I haven’t yet contacted the vendor (Centric part no. 122.66024). I’ve found and used a lot of good info from this forum so I thought I’d run this issue by y’all to see what you have to say.