DC,
It's hard to know how much turning the outer ribs to concentric would
improve balance. The rest of the outer drum surface will probably still
run out. It could be trued separately from the ribs if the grinder can
perform such contortions. It would be easy to do on a lathe. I don't
think that completely removing the ribs would be a good idea. They may
add mass in a critical area to prevent vibration (squeal) & or
distortion of the drum. I will chuck one up in my lathe & investigate if
I ever have need to remove a drum. BTW, my drums do not have ribs.
"Why not just buy new drums?" Good question. - They cost $200 or so
apiece. I have no idea about the quality or how many manufacturers of
new drums exist. It would be interesting to know who makes them. Are new
replacement drums more accurately machined than "some" of the old ones.
Maybe they come from Taiwan & are really good.
Even if I bought a couple of new drums & measured concencentricity &
balance, such a small sample wouldn't mean much. Some aftermarket
sources such as Cape, claim to have high quality drums at high prices. I
don't know how good they really are either. I suspect that a lot of
evaluation is subjective. I would want to think that something I spent a
lot of money or time on really was better. Will someone who really knows
the inside story about new drums please clue us in?
I do know that not all original Healey drums were out of true. The ones
on my BN2 have very little runout & no shake complaints. Mowog
originals. Still very good & practically no wear at 85K miles. Plus they
are on all four wheels which should give twice the shake.
Another "tale" that I have wondered about. "The original drums were
surface hardened on the inside & resurfacing would cut through the
original hard surface & leave a softer material". It is certainly
possible to induction harded cast iron but worth the extra cost?
In any event, balancing by welding or grinding is likely to be cheaper
than new drums. How many old drums are really "that" bad. A few, a lot?
Four ounces out at 5.5 inch radius on a drum causes a lot less
commotion than four ounces out at a 12 inch radius on a tire. How good
do they really need to be? We're not talking about 200 mph race cars.
I think that "scuttle shake" is caused more by worn suspension, shocks,
tire balance, & flexible frames due to rust aging, than by brake drum
balance. I drove several fairly new Healeys in the early 60"s & there
was no sign of the "scuttle shake". One even had a small block V8 & was
driven at mind bending speeds. They were tight & solid & didn't need any
reinforcing. Just like a "good" restoration of today.
Dave Russell
BN2
Dave Carpenter wrote:
> Don't know about other drums, but mine have four or so ribs around the
> outside on a wire wheel BJ8. This would make turning the outer side
> difficult. I have a guy with a brake lathe at his house that is willing
> to give it a go. The lathe tool will flip to the outside, so we're
> going to take a look when I can get a drum off and run it over to him. I
> guess if we keep turning until the tool touches all the way round, we
> have the right amount removed. I'll keep you posted. With all the talk
> of balance and turning, one has to wonder why not just buy new drums?
> New ones are cheaper and easier than all this work. Is it a quality
> issue on the new ones, or are we obsessed with keeping it original.
>
> Dave
>
>> it appears that the problem could be mostly eliminated by centering
>> the drum inner locating ring surface & or the inner drum brake contact
>> surface in a lathe & then turning the outer drum surface concentric
>> with the inner.
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