----- Original Message -----
From: "Earl Kagna" <kags@shaw.ca>
To: "James Lea" <clocks@midcoast.com>
Sent: Saturday, July 02, 2005 1:26 PM
Subject: Re: How much is too much?
James:
Brake shops usually try for 5 thou or less runout on the rotors - the Healey
workshop manual calls for 4 thou or less. If your right rotor is 15 thou
out, you should be able to feel it in the brake pedal - a pulsation when
stopping moderately hard at medium to high speed.
The trick with Healey (and other) wire wheel hubs/rotors is to true the
rotor on a brake lathe while still mounted to the hub - as an assembly. The
hub is centered on the lathe by the bearing races - in precisely the same
orientation as when on the car. In fact, I recall that the dealerships were
instructed to do this as a routine part of an early service on new cars. Oh
for the days when labour was that cheap!
Other things to check first would include front wheel bearing adjustment,
and also insuring that the rotors are properly mounted to the hubs -
stranger things have happened!
If you do remove and service the rotors, do pay attention to the minimum
thickness spec. - .335" on the early rotor - they are nominally .375" when
new, so you would theroretically be able to remove up to 20 thou of material
from each side of the rotor if has never been turned. A competent brake
shop can advise you.
(For any 'lurking' phase II BJ8 owners looking in, the minimum disc
thickness is .450" from a nominal new thickness of .500", giving a total of
50 thou of material that can potentially be removed when turning.)
If you wind up replacing the rotors, I recommend that the hub/rotor trueing
operation be done anyway before mounting to the car, even though the rotors
are new - this could well save you from having to do this later.
Don't know if this will help with the squeak - you could still have it. New
pads would be the only option at that point. There is a section in the
workshop manual that covers the alignment of the caliper to the disc - that
could be a factor. It's worth making sure that the pads and pistons
(calipers) are square with the disc when renewing or servicing any front
brake parts.
Hope this helps.
Earl Kagna
Victoria, B.C.
BT7 tri-carb
BJ8
----- Original Message -----
From: "James Lea" <clocks@midcoast.com>
To: "List Healeys" <healeys@autox.team.net>
Sent: Friday, July 01, 2005 5:50 AM
Subject: How much is too much?
Ever since I bought my BT7 there has been a small squeak in the right front
wheel at speed. I check the pads and installed new bearings, checked the
pistons and everything else I could think of. The squeak would disappear if
I jacked up the front end and spun the wheel by hand so it was very
difficult to hear where it was coming from. Finally I put a machinist's
gauge on the rotor and found it to be 15 thou out. Is this enough to cause
the squeak? If so, can the rotor be trued in a lath or must it be replaced?
What are the tolerances on the rotor being out of flat and perpendicular to
the hub? Thanks for any advice. Cheers, JL
James Lea
PO Box 25
Rockport Maine, 04856
1952 Triumph Mayflower Saloon
1958 Rover P4
1962 Austin Healey 3000 BT7
1967 MGB MkI
1969 MGB GT
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