Some time ago there was a concern on the E-type list about sleeves in wheel
calipers being forced out of their housing by hydraulic pressure. The
following is a summary of the test I preformed on some commercially
re-sleeved calipers and some that I did myself. I agree with Bob G. that
the TC type of wheel cylinder cannot have any hydraulic force pushing a
sleeve out of the cylinder. If the sleeve does indeed move it is most
likely due to a poor fit as well as a piston dragging on the sleeve. Also,
since there is no brake booster on the TC, the pressures will be lower than
on the E-type and the "push out" force will be less. The sleeve of the
calipers was about 2" in diameter whereas the bore of the TC master cylinder
is less than 1" hence there will be much less surface area at the end of the
sleeve for the hydraulic pressure to work against.-
---- Original Message -----
From: Jennifer and Hugh Pite <Sent: Wednesday, July 28, 1999 7:38 PM
Subject: [E-Type] Brake Sleeves, Dan Mooney's tested.
> Some time ago I was asked to test some of Dan Mooney's re-sleeved brake
> caliper cylinders. The concern was that hydraulic pressure could act on
> the inner circumference of the sleeve and force it out. There was some
> history of this happening although it appeared that the cause was poor
> quality control and was a rare event. Calculations showed that if a
> reasoneable interference fit was used, there was no way that the sleeve
> would be pushed out. This was due in part to the friction force between
> the cylinder and the sleeve increasing more rapidly than the pushout
> force as hydraulic pressure in the cylinder was increased. I tested
> several of my "home sleeved" cylinders (without using Loktite) could not
> get them to move. I shattered a couple of cylinders at a force on the
> piston of about 6 tons. Note that several months ago I reported in
> error that the force was 7 tons. At any rate a force of 6 tons is
> equivlent to a fluid pressure of 3,400 psi. I do not know what the
> pressure in a E-types brake system is, but I estimate a maximum of 1,500
> psi. Dan Mooney sent me 8 sleeved calipers to test. I have now a pile
> of shattered cast iron and intact sleeves. Before testing I heated them
> to 400 degrees F. for an hour, boiled them in brake fluid for an hour
> and soaked them in brake fluid for a week. I then tested them to a
> minimum of 2,800 psi. In some cases I increased the pressure until the
> cast iron failed, this was at something over 3,000 psi and was variable
> most likely due to differences in the cast iron composition. An
> unsleeved cylinder (one that was going to be used on my car) broke at
> 3,600 psi. Conclusion, I have not been able to make any of the sleeves
> push out by hydraulic pressure. Hugh Pite '69 OTS '69 2+2
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