Whole lot of shakin' goin' on

356 Porsche-related discussions and questions.
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Ron LaDow
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Re: Whole lot of shakin' goin' on

#16 Post by Ron LaDow »

When we ran the F-1, I was amazed that static-balancing tire/wheel was acceptable, even with 16" wide tires. But no one who drove the car ever made comment otherwise. We did balance the rotors prior to fitting as if they were flywheels, and I don't recall any 'balancing' efforts required.
Seems drums are candidates for balancing; they spin at the same rate as the wheels/tires. And they do have axial displacement of any imbalance. And then, not sure that machining one surface concentric to the center bore will guarantee that dynamic balance.
Anyone 'balancing' drums? Any reason they shouldn't be 'balanced'?
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Martin Benade
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Re: Whole lot of shakin' goin' on

#17 Post by Martin Benade »

I think drums are reasonably well in balance to start with, way better than a tire. Much smaller diameter, and they spin pretty slow compared to a flywheel, so we get away with ignoring them. I am pretty sure any shaking caused by drums is related to them dragging while being egg-shaped, hence my test of backing off the adjusters.
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Sebastian Gaeta
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Re: Whole lot of shakin' goin' on

#18 Post by Sebastian Gaeta »

Ron LaDow wrote:And then, not sure that machining one surface concentric to the center bore will guarantee that dynamic balance.
Anyone 'balancing' drums? Any reason they shouldn't be 'balanced'?
To clarify, I am not advocating machining material from the outside of a drum and reusing it. I was saying that if there is enough excess material on the OD of a drum that a lathe will remove it, that is the likely cause of the "cabriolet shimmy" if everything else checks out and is balanced.
Sebastian Gaeta
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Alan Hall
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Re: Whole lot of shakin' goin' on

#19 Post by Alan Hall »

If I recall correctly, back in the day the high end tire shops did a dynamic balance of the tire mounted on the car by using a machine that would spin the tire, brake drum and all by driving the outside of the tire with a spinning rubber drum. As I recall it took a great deal of operator skill to determine the correct amount and location of weights. Supposedly the reason was to balance the wheel/tire/brake drum as an assembly. Don't know if anyone can still do this.

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Greg Bryan
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Re: Whole lot of shakin' goin' on

#20 Post by Greg Bryan »

Perhaps the steering damper has a bit of play at the center of its travel - I've seen that before albeit on VWs. Also, the bushings at either end of the steering damper must be in good condition, bolts tight, etc.
Greg Bryan

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