Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing brake disc

has any one had there brake discs skimmed on the car with centre wheel nuts watched a video of it being done and the machine used bolts onto wheel studs.

No but Melvyn Rutter has a machine that does it on the car, give him a ring he is very helpful.

I never had any problems on previous Morgans with wider tyres. But when I got my 4/4 in 2014, it was really its only weak point. I don't know if the brake discs are more vulnerable with the very narrow tyres of the 4/4 or what the reason is. I got new brake discs under warranty every 6000 km, replaced four times, so in total five sets of brake discs over 30000km. Unfortunately, the workshop had no prescription except to keep changing them. Before each change, the car was pretty much undriveable. The brake discs were so warped that the sole of my foot hurt from the rattling of the pedal. If I was otherwise happy with my old garage, but they couldn't solve the brake disc problem. In the end they blamed me... something like that only happens when you park the car wet etc.
Then I tried another Morgan workshop in Germany, André Koopmann. He did it exactly as you describe in your post, lez. He took brand new discs. They even were already pulsating slightly. He ground down the new discs and I have had absolute peace and quiet for over 70,000 km. It was like a miracle.

I had a similar problem with my Plus 4 with centre lock wheels. The first pair of discs were replaced under warranty due to warping. The new ones were okay for a while and then went the same way. I then found a garage in Langport in Somerset who skimmed the discs on the car. All has been fine since with no indication of warped discs i.e. no pulsing of the brake pedal. I’ve no idea what the cause of the warping is but the skimming fixed it.
Bob.

I vaguely remember reading somewhere that cast iron discs need to be “weathered” before fitting. If subjected to heat cycles prior to this, they can warp.

If my memory is working OK (it doesn’t always!), could be that skimming on the car is done after the discs have had several heat cycles and they warp no more.

To this end, when I had new discs fitted to my 4/4 in October 2022, I resolved to be very gentle with the brakes for a while. 12 months later, they have yet to warp. It would be lovely to think that I have a fix!

Can any metallurgists confirm or ridicule my hypothesis?

My theory is not so much the burn-in cycle. I suspect that a really flat grinded brake disc has a good chance of always staying flat. But a brake disc with the smallest waviness can become exponentially wavier within a short time. Obviously, the very narrow wheels of the 4/4 can amplify this effect? Maybe because they run less stable round as it is the case with a wider tyre?
Another guess...the brake discs on other Trad models were, I heard, bought in, representing a reliable industrial standard.. Morgan cast the brake discs of the 4/4 themselves for quite a while (so I was told, I don't know). But they weren't really straight in the first place, so grinding them down before first use makes a lot of sense.

Paul, in short yes

Les, Mr Rutter is the only dealer I know who has the proper adaptor to do your hubs, my previous Roadster was the first one it was tested on some years ago and used to be used in his adverts (you can just make out my expensive Bilstein shocks) it completely cured the pulsating brake pedal

https://melvyn-rutter.co.uk/service-repair/morgan-car-service-and-repair/

My break disk were skimmed by Morgan-Park this way. I even got a short video from this work...

Never heard of that before, I get new discs, have them fitted, brakes are fine for many miles...On a variety of cars....fitted by some top mechanics...

Sounds to me like it might have been the mating surface on the stub axle that was at fault rather than the discs themselves?

I can't remember why, but I removed my discs about 15 years ago and when I replaced them I had a dreadful pulsing through the brake pedal as if the discs were warped. Double-checked the mounting and somehow I'd managed to trap a tiny bit of debris between the disc and stub axle mounting faces. Cleaned them up and flatted them off with a bit of emery cloth and some engineer's blue, reassembled and they've been perfect ever since.

I had new disks on my 4/4 last year. The garage warned me to gently bed them in & to slowly build up the heat (harder braking) over a matter of weeks, or they would warp. Apparently for track work, they only use pre bedded in disks.

I was told a long time ago that new discs were heat treated before final grinding, which reduced warp in use. I was also told that this is no longer the norm.

I have access to a Colchester Mastiff lathe.

Can skim a complete brake disc in one operation, without removing it from the hub!

Arwyn

I've replaced my 2011 Plus 4 standard set up (pre industrial revolution Austin Westminster or something similar) with Mulberry brake kit which is all Hi-spec parts, about 8 years ago. The calipers are 4-pot and the discs/bells are 2 piece. The discs are 312mm diameter if I recall, and with Mintex MGB522 pads give a lovely feel under foot and great stopping power. I did buy a spare set of discs for future, which will of course bolt onto the existing bells, but this shouldnt be for a while given summer use and almost sensible driving. After 20k there's no lip on the discs and the pads are bearly worn. I remove the pads, clean and grease every 2 years. After driving my Exige with AP Racing 4-pot set up I didn't feel the standard offering from Morgan was upto spec.