Allen Heffner wrote:
>I would suggest that you replace the rotor
>bolts, especially if you don't know how old they are. They should last a
>long time, but if they are the original ones, they may have been removed and
>re-used several times. You don't want stressed out bolts on your brakes.
>Safety Fast!
Hi guys,
I'd like to weigh in on this rotor bolt replacement bit. Read on for some
interesting info, some dry!
The bolts used on the Spridget hub to caliper application are a special one,
known
as place bolts. They are an old but very effective design that acts as a spring
and a shock absorber. (Shock absorbers as we refer to them are really dampers
of
spring motion.)
These bolts are easy to identify as they have on the head a counter bore in the
center of it and a cross of 6 cuts, similar to pie cuts. For the Spridget they
are 3/8-24X3/4" grade 8 Place bolts. THESE ARE NOT THE SAME AS NORMAL GRADE 8
BOLTS.
Quoting from Carroll Smith's Nuts, Bolts, fasteners and Plumbing Handbook:
>From page 92. Edited somewhat-Pa
------As nearly as I can determine, it was developed to enhance the resistance
to
shock loads in the reciprocating steam engine. The head of the bolt is shaped
so
that, when the bolt is shock loaded in tension, the head acts somewhat like a
spring in compression--a shock absorber in the classic sense of the term.-----
The place bolt has a counter bored bearing surface and a slightly hollowed
and/or
slotted head. The bolt is dimensioned so that it is stronger than the shank and
proportioned to act as a spring. When the shock load arrives, the head
compresses
and absorbs the shock. Clever!
Now, these are not the cheapest bolt in my inventory at $1.75 each. I use these
on all Disc brake conversions that I install on Morris Minors. They are
originally supplied with Spridgets, BMC part # BTA370. Ford flywheel bolts are
the same type, but I'm uncertain of the length or diameter. Ford part number is
B8AZ-6379A, Bolt, Fly/whl. Travel there at your own risk!
Regards, Paul A
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