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MG MGA - Discs

I've got pulsing on the front brakes (hard and soft braking as the wheel rotates). Annoying, so I'm thinking of renewing the discs, which are 20 yrs old but only done about 6,000 miles and don't look bad> I can't find any runout or thicknes variation. I see that LBC (Moss) has them for only $21 each. I paid about 90 previously.
Has anyone tried the Moss discs lately?
Art Pearse

Don't discount the rear drums being the culprit. My V8 roadster had a violent judder at the front, really pulling at the steering wheel. I checked calipers, changed pads, changed brake fluid, stiffened the rack mounting brackets, checked the TRE's but couldn't get rid of it until I swapped the drums.
The friction surface of the drums was "mottled" , which I assumed were big, polished, rust spots. I think the frictional differences between the rust scars and non rusted were trying to do rear wheel steering as the grip pulsed. But everyone who drove it, like me, thought it was a front end problem.
Allan Reeling

I fitted a new set of Moss discs last year and they have been excellent.

So why not go the whole hog and fit a new set of front discs (rotors) and pads (with a new set of pins and spring clips) at the front. Then do the same at the rear with new drums and new shoes.

It is not a crazy expense and it is not such a big job to do yourself (I did it last year). The only difficulty for me was finding a socket to fit onto the disc mounting nuts as there isn't much space around them on the hub for the socket to fit.

You will be amazed at the improvement in the brake pedal and the braking action.

If funds allow, fit some Mintex M1144 pads, they are brilliant. Don't fit Greenstuff ones, there are far better pads out there for road use than those IMHO.

Colyn Firth

Allan, I will do a handbrake only test to check out the rears.
Colyn, thanks for the report on Moss discs. As you say they are so cheap why not. Its just a PITA to fit them, having to take off the hub, but I'll do it.
I do have the Mintex pads, still loads of meat on them. I agree the other stuff was crap!
The rear drums were always good looking, but I'll see how it is after the discs.
Art Pearse

I found that the brake pedal felt a little spongy even though the brakes were bled properly and correctly adjusted at the rear.
I also noticed that the pedal become very much more solid if I applied the hand brake, which led me to think that there was some free play between the shoes and the drums that I couldn't adjust out with the adjustment screws.

The drums didn't appear to be badly worn but they were quite old.

So I fitted new Moss drums and shoes at the same time as I fitted new pads and drums.
As I said earlier, this has improved the brakes considerably.

Colyn Firth

Check out the Moss website Art, there is a 25% summer sale on brake parts over here in the UK.

Colyn Firth

Colyn, already ordered. 15% off with LBC Co
$20.64 USD each.
Art Pearse

if you get no result from the handbrake test, you 'might' have a seized caliper piston
The pistons will normally move and take up a little bit of rotor runout, but if one is seized the rotor doesn't have to be very far out of true to give a pulsing pedal,,usually would pull to one side under braking as well-
I guess that if you are going to fit new pads you will soon find out if a piston is stuck
William Revit

Art, if you plan to re-use the Mintex pads you may be able to sand paper them flat to get rid of any high spots that remain from the old discs. (They are far too expensive to throw away)
Otherwise it may take a long time before the pads bed in to the new discs. (use a dust mask of you try this)


Colyn Firth

Colyn, just what I plan!
William, you have a good point about the calipers. They are fairly new. Will check.
Art Pearse

OK, changed out the RH disc today.
Both sides sowed a tiny bit of daylight btw pads and disc b4 I started work, shwing there is some retraction.
Caliper off, both pistons retracted easily using a small carpenters G clamp.
Outside face was very slightly scored, inside face was not.
Both pistons have the cut-out closest to the axle. This is how it came from Bob West. I had tried to rotate them but they would not budge, so I figured he knows best.
Pads - Mintex 1144 from Bob, outside pad had worn slightly more than inside pad, but both pads had worn more on the OD than the ID by about .030. Pads are only about 1/4 worn overall.
New disc on, cleaned with acetone. Cleaned pads with acetone - lots of black stuff came off. They were both flat so no sanding, just preserved the slight chamfer.
Back on road for test - brake does not judder any more as it was doing at low speed on RHS.
Hard braking, it is pulling a bit to LHS, so pads probably need a bit more time to re-bed.
There is less of the pulsing overall.
Next report after the LH disc!
Oh, and wheel bearing good - only just perceptible play as I installed close fit bearings on the build. (standard are way too loose!)
Art Pearse

once you have finished both sides, you may have to go through the bedding in procedure again to get the best out of them (especially if you have sanded the surfaces down).

Let me know if you you would like a copy of the Mintex M1144 procedure.

Colyn Firth

Colyn, yes I would like a copy of that!
Art Pearse

OK, just done the LHS disc.
Again, saw daylight between pad and disc before starting the job. Rotating disc indicated about .003 run-out by eyeball as the daylight changed.
Pads had worn pretty evenly this side
Again, the piston cutouts were towards the axle.
Brakes work fine (have not done the Mintex bedding procedure yet)
Front RH still squeals/vibrates a bit sometimes on light braking coming to a stop. But better than it was.
I still have the pulsing, and the handbrake only test seems to indicate the rear drums.
Also have fairly long pedal travel so need to inspect/adjust rears and maybe replace drums.
Had to improvise a hub puller this time as the hub was tight. Used an old spinner, drilled to take an adjustable pointer, and wound the spinner on to pull the hub.
Also made a special tool to pull out the cotter pin, which consists of a 5/16 bolt and nut with a hook cut in the end.
Art Pearse

This thread was discussed between 18/06/2019 and 04/07/2019

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