BJ7 Front Brake disc hitting

[RestoreThemAll]

Good day folks. I'm working on what my son calls "the car that would not be restored", '63 AH BJ7. We’re just coming back to the front brakes and hubs. The only new part on the front brakes, other than the caliper rebuild, is the disk. The rest of the parts related to the below problem are all original.

Unfortunately, the inside edge of the disc scrubs on the caliper mount. There is a small bump out just under the bottom rear caliper mount bolt. It hits there. The disc also hits on the outside of the edge of the disc. There is a small bump out on the dust plate.

I included pics of the original disc and the new one. It’s clear that they have been machined and molded differently. I should also note that I read a post about BJ7 and BJ8 disc being slightly different. BJ8 ½” thick and BJ7 3/8’ thick. Both of mine, new and old, are 3/8” thick. Has anyone come across this problem? Can the inside edge of the disc be shaved at a brake shop?

As for the dust plate, it does seem to have a little bit of a curve to it. Just slight. Are they perfectly flat? That may be why it hits? I hope that it didn’t get warped from glass beading. Can the outside edge of the disc be shaved at the brake shop?

Thoughts?

 

[BoyRacer]

You say that it's "clear that they have been machined and molded differently". Sounds to me like you have a defective product.

 

[steveg]

[post was incorrect - unable to delete, so I "disappeared" it.]

 

[RestoreThemAll]

Richard, I'm thinking that you are right about the defective part. There's groove that is cut around only about 1/2 way. It can be seen in the pic. I'll have to pull the receipts. Seems like the disc came from Moss. Maybe they'll work with me, though I've had them for a while.

Steve, I'll check the dust shield tonight. I didn't think to check for orientation. I was thinking that they went on one way only.

Dale

 

[British_Recovery]

Lay the rotors flat and next to each other, and take a photo. If the angle of the center hub mount of the new casting is more vertical than your original, you may have a BJ8 rotor.
Bob

 

[RestoreThemAll]

Bob, thanks for the tip. After studying pic/diagrams on the Moss and AH Spares web sites I did notice that difference in the discs, though I didn't mention it. I'm fairly confident that I have BJ7 discs.
Dale

 

[Griz]

Dale, I too had this same problem on the BJ7 I'm restoring (parts were from Moss). Fortunately it was only a very slight interference between the rotor and the stationary part, so I took a "peanut grinder" and relieved the offending area. BTW I think you have your backing plates on correctly. Griz

 

[steveg]

In previous post, I was mistaken about the backing plates - the edges as shown turn inward toward the rotor, as it should be.

 

[RestoreThemAll]

When I mount the brake caliper it may change the way the sheild sits. I'll have to get past the problem with the inside of the disc first.

 

[RestoreThemAll]

I had both front brake rotors shaved on the inboard inner edge. The left side is perfect now. The right side doesn't hit at all on the inner edge but does hit some on the shield. It's not hitting much. Just a very slight scrape every so often. The only part that's troubling is that it doesn't hit all the way around the rotor. Once every revolution. I'll have to set up something to try and see if the rotor is warped. I'd simply order another rotor but I'd be concerned about getting more defective parts. The vendor says that they aren't having any problems with their rotors. Though we know that isn't the case.

 

[steveg]

If there's a problem with the discs such that you had to shave them down, Moss needs needs to know about it. I've found them to be very responsive to quality-related issues.
Your rotors should be approximately 3/8" thick; late BJ8 rotors will be 1/2" thick.

 

[brianbj7]

I also have problems with new brake discs from MOSS

REQUEST re Rectification -
Could you please confirm that you just had to grind down the inner edge of the new disc to avoid the interference with the caliper bracket.

I purchased a large number of parts at the start of the project through a local MOSS distributer, and I have now passed the MOSS return date. So i am hoping that i can fix the problem by grinding the discs to make clearance.


Many thanks for you help
Regards
Brian

 

[RestoreThemAll]

Brian,

Yes, we ground the inside edges of the new discs. I'd suggest taking off material evenly all the way around. You don't want it out of balance.

Dale