Squeaky Brakes

[bkz411]

Hello all. I wonder if anyone can advise?
My 411 seems to have (new) very squeaky brakes and I would like to know whether this is simply something I have to put up with (as an owner of a classic car), or whether there is actually something that can be done about it. I have been advised to hit the brakes hard to resolve the issue - but that makes little difference.

[Andy603]

Try copper grease applied to the rear of the pads where they bear on the
pistons.

[Kevin H]

They don't squeal on my 411.

Unless you have kevlar brake pads on your 411, I suspect the "Squeal Deterrent Kit" is missing.

The Girling front calipers used by Bristol included a "Squeal Deterrent Kit" which consisted of a thin metal backing plate behind each brake pad, which were coated with a special grease supplied by Girling. I have read that it is called PBC (Poly-Butyl-Cuppysil), but I suspect there numerous brands of anti squeal grease on the market nowadays - it has to remain thick and sticky at high temperature.

Edit/PS: I should add that I mention kevlar pads only because I experienced terrible brake squeal with kevlar pads on 2 Astons, but that doesn't mean all kevlar pads squeal. They did improve braking performance, but the noise wasn't worth it!

[Rubbond]

Believe me, there is no such subtance as Poly-Butyl-Cuppysil.
It might however be short for some trade name.
I think most disc brakes have shims to prevent brake squeal don't they?
With best regards,
Andrew.

[bkz411]

My 411 brakes are discs all round, with four pot calipers at the front and
two pot at the rear and the suspension is upgraded with adjustable dampers
and a handling pack. Not sure about whether they are kevlar.

However, thank you all for your helpful advice. I did think that accepting
squeaky brakes just because its a classic was a bit strange. Anyway, I now
have plenty of information to take with me to the garage to ensure the
problem is sorted.

Thanks again - very useful.

[Geoff Kingston]

Anti squeal shim kits for the front brakes are available from a seller on eBay motors in the UK, you will find them if you go to classic car parts and enter Bristol.
Geoff.

[Kevin H]

Originally Posted by Rubbond

Believe me, there is no such subtance as Poly-Butyl-Cuppysil.

I'm prepared to believe you, if you tell me what PBC really stands for?

Originally Posted by Rubbond

I think most disc brakes have shims to prevent brake squeal don't they?

They probably do now, but they didn't all have them when the 411s were made. The Girling parts list however, says that the versions of their front caliper used by Bristol did include them, along with anti squeal grease.

They were also three pot calipers, not four pot, which means bkz411 doesn't have the same brakes as originally fitted to the 411.

[bkz411]

My 411 is the series 6 which has had all the latest Blenheim parts 'bolted
on' - so I suspect the brakes are identical to those on the Blenheim S2,
whatever they may be (i.e. 4 pot calipers etc). When I take my 411 to the
Bristol garage soon I shall find out what the brakes are and try to get to
the bottom of this very noisy problem.

Thank you all again.

[GREG]

I imagine that your car is still under Bristol warranty -- No worries !

[Rubbond]

You've got me there Kevin! If Cuppysil is a trade name, it might suggest it
is based on Copper and a Silicone polymer.
I suspect PBC might stand for Pacific Bearing Company, who make high tech
lubricants for the aerospace industry.
I had to revert to the Internet on this one. All I found was a reference to
the US MG club, but couldn't find the relevant text on the site.
A company with website www.traccoatings.com give the following information.
I guess however they are only distributors:
Quote"PBCGR - PBC GREASE Brake Grease

Developed as the optimal grease for braking systems used by many of the
highest rated automobiles. The material is gold in color and is based on an
organo-metallic formulation which does not contain soap greases or
silicones. Can be used up to 1200* C as a torque equalization compound and
anti-seize for studs and threaded components. Also used for roller bearings
and universal joints." Unquote.

To withstand these types of temperatures it couldn't possibly be based on
any hydrocarbon polymer.
With best regards,
Andrew.

[GREG]

If we are into guessing !

PBC If the B is boring, it's easy to guess the rest ! :-)