Dragging disc brakes

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Paul Hollingworth
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Re: Dragging disc brakes

Post by Paul Hollingworth »

Hi Tom - where did you get your anti squeal shims from, I've been trying to get some but cant seem to find them anywhere. I've had to change a perfectly good set of (cheaper) pads for some better quality ones (TRW, I think) and even now after hard use I get a squeal. I went with Pete's recommendation and fitted V8 pads and the discs are clean all the way to the outside diameter. (they were newish anyway). I've found the best lubricant to prevent sticking callipers is engine oil. I wonder if you could find some nearly worn out pads you could force the pistons most of the way out and try cleaning them with wire wool, then oiling and pushing back. That should lubricate the seals. Engine oil shouldn't harm them.
1971 MGB roadster & 2006 MGTF
Ian Fozzard
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Re: Dragging disc brakes

Post by Ian Fozzard »

As far as I know, mineral oils should never be allowed into contact with brake hydraulics, particularly the seals and other "rubber" components.

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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Paul Hollingworth
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Re: Dragging disc brakes

Post by Paul Hollingworth »

Ian - how do you think the oil seals in the engine and gearbox survive then, not to mention stem seals.
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Ian Fozzard
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Re: Dragging disc brakes

Post by Ian Fozzard »

Different "rubber" I suspect. Any other views out there?

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
Ian Fozzard
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Re: Dragging disc brakes

Post by Ian Fozzard »

Mineral Based Brake Fluids (LHM Fluids)
A few vehicles in the past, including Citroen (hence the LHM title, as in Liquide Hydraulique Mineral) and Rolls Royce, used a mineral or petroleum based central hydraulic system for the suspension, which also powers the brakes. To do this the brake system is fitted with special rubber components that are compatible with petroleum products.

LHM is NOT compatible with conventional brake systems, nor are conventional Brake Fluids compatible with systems requiring mineral oil. Failure to use the correct fluid may result in total brake failure.

Taken from:

https://www.mginfo.co.uk/upgrades4mgs/F ... luids.html

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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Paul Hollingworth
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Re: Dragging disc brakes

Post by Paul Hollingworth »

You could be right Ian, so to be on the safe side the original poster should use brake fluid as a lubricant. I wasn't proposing using engine oil in the hydraulics. Having said that SAE 30 mineral oil is recommended for lever arm dampers. It could be down to the type of rubber as you said. I don't pretend to have any knowledge on that.
1971 MGB roadster & 2006 MGTF
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Tom Brearley
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Re: Dragging disc brakes

Post by Tom Brearley »

Hi Paul

I got the anti-squeal shims from Rimmer Bros. "Brake Pad Shim Kit Anti-Squeal GBP242SHIM". These are the aluminium sort. But as a belt and braces approach I was also using stick-on Mintex pads beneath them.

Tom
1973 MGB GT
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Tom Brearley
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Re: Dragging disc brakes

Post by Tom Brearley »

Well, I've exercised the pistons in and out having applied red rubber grease and brake fluid (separately). But the problem is still there. The pads bind up with the shims fitted, and they seem fine without them. The pistons are bright and shiny with no rust anywhere, and the callipers were new last year.

I'm wondering - belatedly - whether there might be a fault further up the system. If the hydraulic brake switch or the master cylinder go 'bad', can they cause the brakes to bind? A small amount of lost movement at the pistons might perhaps be enough to cause binding on my set-up. As mentioned above, I'm using rubber backings plus metal shims.
1973 MGB GT
Mallard Green / Autumn Leaf
Ian Fozzard
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Re: Dragging disc brakes

Post by Ian Fozzard »

Tom, doesn't the solution seem to be straightforward? You are probably using too many backing pieces!
I have only ever used the metal shims, and I'm not convinced they are essential.
If the brakes work fine with less backing then that's how I would use them.
Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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Michael Barclay
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Re: Dragging disc brakes

Post by Michael Barclay »

Hi Tom
When in production at Abingdon, MGB 'S were never fitted with brake pad shims. I change the original brake pads fitted to my MGB last year. After 46 years they were not worn out but seemed to have gone hard. There were no shims behind the pads. I fitted Mintex pads and am very pleased with their effectiveness. So I would suggest fitting the pads without the shims. Just put a small amount of copper grease (As per factory)on the rear of the pads and fit them back in your car and check for any brake squeal.
Best regards
Mike Barclay
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