Hi Magnus,
The main reason I've found for rear brakes locking is that most modern
rear brake shoes are relined across the entire shoe.
Standard Healey shoes in the era were never relined over the entire
metal shoe surface. NEVER.
Hence more rear braking capacity.
If we take a "perfect" Healey BJ8 braking system, from the factory...
The first wheel to lock should always be the passengers front,
assuming driver only in the car. Because that is the least laden tyre.
That's an issue because production cars aren't race cars. More info if
you google something like "corner weighting cars" or "corner balancing
racecar". Or something like that.
That's why we corner weight cars, and move batteries etc in Rhd healeys.
Anyway.... Back to the issue..
The problem is that the lining is covering the entire metal shoe. The
brake system was never designed for that much rear shoe grip.
Rear brake shoe lining size adjustment is the way that many race car
drivers have adjusted rear brake bias long before adjustable bias
systems came along. And still do in classes of racing that prevent the
adjustment of things that weren't adjustable. Like we have in most
historic race classes in Australia. It's not about buying stuff.
It just takes time.
If I get up to my mothers place soon, I'll take some pics to show
everyone.
Conceptually. Just use a hacksaw to cut the lining to reduce the
surface contact area, until the rear brakes no longer lock first. i.e.
Just reduce the lining surface area!!!
Brake balance adjustment front to rear, without modern stuff, on a
perfect reco'd Healey is all about time. Just reduce the lining area.
It's Not about money or adding stuff.
The process:
Break really hard like your kid ran out in front of your Healey, IN A
SAFE PLACE - well away from other people/ cars/ children. Full
emergency brake. Just test to see if you have rear lock up.
If you do...
Jack up and cut 1/8 in off both rear linings.
Start at the trailing edge.
Retest. Repeat.
Retest. Repeat.
Retest. Repeat.
Etc
Until it no longer locks at the rear.
In many classes of historic racing with rear drum brakes it isn't
unusual to adjust brake bias this way for the entire first practice
session, and carry 6 or 10 sets of rear shoes. To save time.
It's not rocket surgery.
But it is time consuming.
Chris
Sent from my iPhone
On 18/10/2010, at 5:16 PM, Magnus Karlsson <magnuskarlsson@bornet.net>
wrote:
> It can be very dangerous if the rear wheels lock up before the front.
> Unfortunately fixing the servo won4t cure that condition.
>
> If you assemble a Healey brake system today, correctly and with all
> new parts,
> you will find that in most cases the rear brakes lock before the front
> ones.
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