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MG MGA - MGA DISC BRAKE ROTORS

Looking on Ebay I see a huge difference in the cost of brake rotors. Highest priced at over $450.00 and the low at around $100.00. Is there any need for the expensive pair or are the normal $100.00 ones the correct and OK type. The expensive ones have double sided vented rotors and I wonder if they are compatable with the disce brake calipers IE: thickness & diameter. Any help would be appreciated.
The picture below is the 100.00 pair and see my second post for a pic of the Expensive ones.



Gordon Harrison

Here is picture #2 the expensive ones.

Gordon Harrison

Gordon, the expensive ones are not for the MGA. They are way too thick!
Art Pearse

Gordon,

As Art points out the vented disks simply will not fit. The MGA if a fairly light car so unless you are racing the standard disks will be more than adequate. From my recent experience fitting new pads and new disks (Moss parts) resulted in a very snug fit. I had to remove the anti-squeal shims from the pads to get enough clearance. Fortunately I am not having any problems with squealing.

I had also rebuilt the MC and it was holding enough residual pressure to keep the pads lightly engaged with the rotor. Left alone for a few minutes the residual pressure would subside. It took a hundred miles or so to loosen things up.

The attached image shows full assembly with the anti-squeal pads. Since the rotor was not perfectly centered, one of the pads was essentially locked against the rotor. Removing the anti-squeal pads provided enough clearance.

I should add that I have a í59 roadster and the front disk brakes are a retro fit using original parts.

John


jbackman

Gordon:

What finish do you have on your calipers? I like the look - will it stand up?

John
JRS Smith

JRS,

I am assuming that your question was directed to me and not Gordon.

The calipers were broken down and bead blasted. Once I was sure that the passageways were clean of any grit I masked off the mating surfaces and installed bolts in the appropriate holes. They were sprayed with a high temp engine clear coat.

They have been on the car for a year. Not a huge number of miles but not stored in the driest of conditions. So far they still look good.

John
jbackman

John,

Why is your rotor not centered?
The Dunlop disc brakes on the 1600 Deluxe and Twin Cam have shims to center the rotors.
These are shown as item 26 in the attached image, and are mentioned in Section MMM of the Workshop Manual.

Mick

M F Anderson

John,

Following on from the previous message.
The Lockheed disc brakes on the normal 1600 do not show shims to center the disc and they are not mentioned in Section MM of the Workshop Manual.
Why?
My guess is that as the Lockheed brakes went into production later the manufacturing tolerances had been improved.
As your car is a converted 1500 it appears that you need shims.
I would fit them.

Image of Lockheed brake attached.

Mick

M F Anderson

Mick,

I was unaware of the twin-cam shims. None the less I did hand form several shims in an attempt to center up the rotors. In all the shims made the problem worse. On one side without the shims I could fit a brake pad with an anti-squeal pad (barely) and the second pad without the anti-squeal pad. With the shims I could fit both sides, but only without the anti-squeal pads. On the other side of the car adding shims moved the caliper in the wrong direction. I would have had to had the mounting bolt (#13 in second image) turned down to move the caliper inward or remove and shim the rotor where it mounts to the hub.

Making the shims and fitting everything was a real pain. Without the shims and anti-squeal pads everything fit with a bit of working room to spare. In place of the anti-squeal pads I did use a dab of anti-squeal grease. In the end I felt that it did not matter if the rotor was slightly out of center as the caliper pistons will self-adjust to the rotor with use. Please correct me if my logic is incorrect.

Although this was a retro-fit I purchased the calipers, hardware and caliper mounting plates from the same source but donít know if it all came off the same car. As I mentioned both sides had different deviations from the center of the rotor. Since there are probably a half-dozen or more points of possible variation I did not take the time to figure out what was producing the differences.

The OEM pads donít appear to include anti-squeal pads, so if the new pads are made to the same spec but have the anti-squeal pad added as an extra it stands to reason that there may not be sufficient clearance if everything is new and the rotors are not perfectly centered. Using the newer pads on a used rotor is probably not an issue due to rotor wear. It would be interesting to know if others see similar variations on an unadulterated car.

John
jbackman

John,

You are correct. As the brakes are hydraulic you will get the same force on both sides of the rotor by the pads, whether the disc is centered or not.
The two problems that can arise from a disc off center are difficulty in fitting the pads and the possibility (unlikely) that one piston will have it's rear edge come past the pressure seal when the pads are fully worn.
It will be interesting to determine whether other owners of original 1600 MGA cars have their discs centered.
I still tend to believe that the use of non-production line parts causes your off center disc.

Mick
M F Anderson

Mick,

In my case the only non-OEM part that could effect the alignment are the Moss rotors. The steel wheel hubs (unobtainium), bearings, calipers, caliper mounts and mounting bolts are all used OEM. The caliper mounts are not bent.

I can only surmise tolerances were not that great and the fact that I may have some mix and match parts made the mis-alignment worse.

Gordon, sorry if we went off topic here.

John



jbackman

Mick,
Are you taking your Twin Cam to the National Meeting in Toowoomba this Easter?
Mike
Mike Ellsmore

Mike,

I will be attending a family wedding in Adelaide at Easter.

Mick
M F Anderson

That is an awfull lot of info and I thank everyone for their contribution. It is as I assumed and the expensive pads are useless. I will stick to the origional rotors. Thanks everyone.
Gordon Harrison

"The MGA if a fairly light car so unless you are racing the standard disks will be more than adequate."

I'd amend that to say that even if you ARE competing with the cars, the stock discs are more than adequate provided you make a sensible selection of pad material, and possibly attend to basic ducting for brake cooling.

Gordon, the price for MGA Lockheed brake rotors from Moss is $39.95 each. You are apparently looking in all the wrong places.
Bill Spohn

This thread was discussed between 23/03/2013 and 27/03/2013

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