Welded blocks on brake drums - what are they?

2007 Base w/2.7

When I was replacing the rear brakes today I flipped the drum over so the open side kind of 'slapped' down onto the concrete. I always do that with drums to knock out any nasty black-soot brake dust. But this time a small steel block about 1/4" thick and maybe 5/8" by 1 1/4" long popped off the exterior side of the drum. The 'block' had a pressed dimple in the center - as does it's previous place on the drum. I imagine it was spot-welded in place originally. I checked the other side and found the mark for where it had apparently been - but that one has obviously been gone for some time.

What are these brake-drum blocks?
Why are they there in the first place?
What harm can come from them being missing?

"Balancing Weights" seems like the obvious answer - but the drums are cast and then machined symmetrical, they are very close to their rotating centers, and both weights appear to have been the exact same size. And how likely it is that both drums needed the exact same sized weight to balance them. <g>

So? Anybody really Know what they are?

 

Balance weights

 

This^^^for sure. Some aftermarket like the Centric Premium have them too and Centric confirmed they are balance weights.

 

The OP does not and will not believe it.

 

They are there to cause turbulence in the wheel to help spread chemtrails making them more effective.

Or, they are indeed balance weights.

You pick.

 

I'm kind of leaning towards the chemtrails.

Steve........

 

I always thought the accepted and recommended way of cleaning brake dust was to use brake cleaner spray??

 

My thought being that there's only so much duct that can collect. So even if I made it all spotless - in a month it's back to the same level of dust. So just knock it off / out of the drum and call it good enough.

PHM
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So? How did you reach this conclusion? <g>

PHM
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So I guess now I need new drums, eh?

PHM
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Don't worry about them, I lost mine around 60K and kept the drums till 125K. I actually glued the first one back on with JB weld, the second I didn't bother. Crappy, over-priced drums! They're $110 each, even after market, so make them last!

 

I'm going to run from Philadelphia to Tampa in about twelve hours soon - so if the brake drum balance is a factor I will soon know it. <g>

If I get new brake drums I guess an answer would be to paint them and prevent the weights from corroding off the drums. That seems to be what happened with mine.

PHM
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Could be balance weights, but being a machinist with machining of cast iron parts experience, I am
leaning more to it being there to eliminate the harmonics /brake chatter in the thin cast iron drums .
Have you ever seen them re-machine the drums? They wrap a rubber bungee cord around the drum to stop the harmonics during the machining process.
Just my guess though

 

My first street bike was a 1937 Indian Chief. Or; what was left of it by then. <g>

Thinking of it from a machining perspective: where could any imbalance large enough to require that large heavy steel balancing weight come from? It's a concentric casting, concentrically turned, and then five evenly spaced holes are drilled in to the face. What weirdness would they be balancing against?

And from looking up brake drums for sale it seems that every one has the same sized single weight attached to it. How likely is it that the imbalance that is being corrected is always exactly the same? <g>

PHM
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I don't know if they are balancing weights and/or for harmonics.

Being in the investment casting industry for 29 years has taught me a few things about castings...they have variability.

Concentric machining of the ID bore to the OD cast surface will not remove the casting variability.

Castings in the machining industry are known as "snowflakes"...

Good question though OP...I've seen these for years. My vote is balancing weights.

 

Yes it was a 1981 FXB (First duel belt drive & 80" (1340cc motor) it now has been lowered & 16" wheels makes it look like a FAT BOY.
Not fast but fun to ride

 

spread out two equal dollops of JBweld

jbweld the weight back on

put a blob of equal jbweld opposite the weight