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Re: Brake drums

To: "Power British Performance Parts, Inc." <britcars@powerbritish.com>, "Triumphs" <triumphs@autox.team.net>
Subject: Re: Brake drums
From: "Karl Vacek" <KVacek@Ameritech.net>
Date: Sun, 9 Jan 2000 20:09:44 -0600
Organization: The Millbridge Companycharset="iso-8859-1"
References: <001801bf5a87$95e71f20$75a2b3c7@gateway> <FFFFFFFF.93471D47@powerbritish.com>
In that case, I'd make bushings to go between the OD of the studs and ID of
the stud holes in the drums.  Those little screws don't have enough shear
strength to rely on them without the studs.  Few cars even have them.

Karl Vacek
'66 TR4A - IRS
'64 Amphicar
'16 Ford T Touring
'46 Piper J-3 Cub

> If the center bore was mis-matched, and so were the wheel stud holes, it
would be
> humanly impossible to properly center the drum upon reinstalling the
wheel.  As you
> say, even slight error would result in pedal pulsation, if not brake
overheating from
> continually dragging for part of each rotation.
>
> Actually, the center bore that fits over the axle nut is the same for both
drums, and
> there is no problem with drums locating on center for either combination.
The
> difference is in the shank of the wheel stud.  While both cars take the
same 7/16 - 20
> lug/stud, the shank on the solid axle cars is stepped to about 9/16 at the
hub and the
> holes in the drum for the studs are correspondingly larger.  With that in
mind, if you
> were to install a TR-4 drum onto a TR-6, the drum would locate properly on
the hub's
> center, but you'd have axial shift about the extra clearance in the stud
holes.  In
> this situation, the only positive location for the drum would be the
retaining
> screws.  True, friction between the drum, hub, and wheel would and should
probably
> keep it from shifting.  But if it doesn't, the drum may slip, especially
in a panic
> stop the forces involved are quite high.  If the drum does slip, all the
panic-braking
> force would be transmitted throught the locating screws and the they might
shear under
> such stresses.  This could result in potential damage to the drum or hub.
>
> Of course, you could run the combo without the screws, and just allow the
drum to
> shift on the clearance around the stud holes, but I sure wouldn't want to
take any
> chances like that with my brakes.
>
>
> Regards,
>
> Brian Schlorff    '61 TR-4     '64 TR-4     '72 TR-6     '79 Spit
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