Wheel imbalance, wheel flange

[Werner]

Hello and a Good Morning.


I would like to balance the wheels of my Model A myself, as there are no more dealers who perform static balancing, and my rims are unfortunately always listless.


Does anyone have a technical drawing of the brake drum's pitch circle?


For my manufacture of the wheel mounting flange, I need the distance between the wheel studs and the radius from the axle center to the stud center.



Measurements with calipers are not reliable enough due to the lack of centering points.


Thank you in advance for any advice!

 

[JayJay]

Werner: I believe the Model A is a 5 on 5-1/2” bolt circle diameter (2-3/4” radius). Since there are five studs, the stud centers are 360/5 = 72 degrees apart and the distance between them is 2*(cos54 * 2.75) = 3.232”, call it a hair under 3-1/4”.

In metric, I believe that converts to a bcd of 139.7 mm (radius 57.15 mm) with a distance between bolt centers of 82.1 mm.

Measure out a hub to be sure I haven’t dropped a decimal point somewhere. Attached is a picture of a fixture I made to hold brake drums to drill out the studs.

Others, please check my math. I don’t use trig too much any more!

 

[katy]

Maybe try balancing on a front wheel hub? Brake slacked off, bearings relieved of grease and lightly oiled to reduce friction.

 

[Werner]

Good evening Jay Jay and Kathy,


thank you for your answers.


Yes, that corresponds to my rough measurement. However, I don't understand <<<bcd of 139.7 mm (radius 57.15 mm)>>>. BCD 139.7 mm is the diameter from the center of the axle, I think.



But what radius means 57.15, please?




Kathy: I tried it on the front axle with warmed-up bearings. But that's very rough. Therefore I use my wood turning lathe, and I want to hang the wheels on it with my home made wooden flange.




Btw: I also tried balancing beads. But that didn't convince me or my car. Perhaps because no one knows exactly how this miracle is supposed to work?

 

[mercman from oz]

 

[JayJay]

Good evening Jay Jay and Kathy,


thank you for your answers.


Yes, that corresponds to my rough measurement. However, I don't understand <<<bcd of 139.7 mm (radius 57.15 mm)>>>. BCD 139.7 mm is the diameter from the center of the axle, I think.



But what radius means 57.15, please?




Kathy: I tried it on the front axle with warmed-up bearings. But that's very rough. Therefore I use my wood turning lathe, and I want to hang the wheels on it with my home made wooden flange.




Btw: I also tried balancing beads. But that didn't convince me or my car. Perhaps because no one knows exactly how this miracle is supposed to work?

Werner - Bolt Circle Diameter (bcd) is the diameter of the circle encompassing all the wheel studs. The radius is half the diameter and is distance from the axle center to the wheel stud. Attached is a drawing that might make it clearer. Or not.

FWIW, I haven't had much luck with balancing beads either.

 

[katy]

But what radius means 57.15, please?

Methinks that is the radius from the center of the axle to the inside circle of the studs.

 

[JayJay]

Methinks that is the radius from the center of the axle to the inside circle of the studs.

Actually, brain or finger error - the radius is 2.75 in * 25.4 mm/in = 69.85 mm. I don’t know where that 57.15 came from. I told you guys to check my math!

And yes, as katy stated, that’s the distance from the center of the axle to the center of the wheel stud.

 

[katy]

Actually, brain or finger error - the radius is 2.75 in * 25.4 mm/in = 69.85 mm. I don’t know where that 57.15 came from. I told you guys to check my math!

And yes, as katy stated, that’s the distance from the center of the axle to the center of the wheel stud.

I DID NOT say "that’s the distance from the center of the axle to the center of the wheel stud"

I said " that is the radius from the center of the axle to the inside circle of the studs." ("Inside circle" not center)

The studs are 1/2" diameter, (12.7mm), subtract 12.7 from 69.85 = 57.15.

 

[JayJay]

I DID NOT say "that’s the distance from the center of the axle to the center of the wheel stud"

I said " that is the radius from the center of the axle to the inside circle of the studs." ("Inside circle" not center)

The studs are 1/2" diameter, (12.7mm), subtract 12.7 from 69.85 = 57.15.

Sorry, I misread your statement. I was defining the radius.

 

[katy]

Subtract the diameter of the stud, not 1/2 the diameter.
I'm starting to think that you need new glasses.

 

[Werner]

Finally it's right. I've been going around in circles last night because I couldn't understand the 57,15 mm.


Now I'll drilling my bolt holes 69.95 mm from the axle centerpoint and 82.1 mm between the bolts.


Thanks for the help and clarification!



I'll let you know how it goes.

 

[Werner]

Hello and a good day everyone.


Today I turned the flange out of 1 1/4" plywood.

14_IMG_20250418_180311914.jpg


Unfortunately, I still have to wait for the longer wheel studs, which aren't readily available.

14_IMG_20250418_180311914.jpg



The fitting on the brake drum looks good.

05_IMG_20250418_184007881.jpg




I'm optimistic. I'll keep you posted.

 

[JayJay]

Werner - unless I'm confusing how you are going to balance these, could you not use 12"-20 bolts or threaded rod, plus the lug nuts, to fasten your flange to the wheel? These would certainly be close enough in weight, I would think, and probably readily available (as readily available as any SAE hardware would be in Germany!).

 

[katy]

Possibly try 12mm bolts? Maybe you could find 12mm wheel nuts? I don't have a clue what sizes are used in metric.
The studs are 1/2" but the holes in the rim are slightly larger.

 

[Werner]

Good evening, helper friends.




Bar stocks with American fine threads is only occasionally available and expensive.


In Poland, I found suitable original old studs from a Ford FK 1250 [https://en.wikipedia.org/wiki/Ford_Transit#Taunus] and have already pressed them in with epoxy resin through the rim.







The trueness isn't perfect, with 3/10 mm radial runout after mounting on the flange. I don't think it would be much more accurate with wood.


Unfortunately, I still can't balance the wheels. The balancing beads are in the old tubes, and they do not flow out. It's difficult to find a tire dealer in this country who still offers 21" tubes in the correct width. (19" is readily available, however.) The best way to do this is actually through eBay or Amazon.



I'll keep you posted...

 

[JayJay]

Good evening, helper friends.

Bar stocks with American fine threads is only occasionally available and expensive.

In Poland, I found suitable original old studs from a Ford FK 1250 [https://en.wikipedia.org/wiki/Ford_Transit#Taunus] and have already pressed them in with epoxy resin through the rim.



The trueness isn't perfect, with 3/10 mm radial runout after mounting on the flange. I don't think it would be much more accurate with wood.


Unfortunately, I still can't balance the wheels. The balancing beads are in the old tubes, and they do not flow out. It's difficult to find a tire dealer in this country who still offers 21" tubes in the correct width. (19" is readily available, however.) The best way to do this is actually through eBay or Amazon.

I'll keep you posted...

Werner - I put balancing beads in the last time I changed tires, and I'm not happy with them. I ordered and received new tubes.

You might be able to find your 21" tubes at a local motorcycle supply house, or order online from a supplier in Germany. I looked here stateside and Amazon, among others, lists the tube.

 

[katy]

Dunno how balancing beads actually work, but I suspect that the wheel has to rotate at a certain minimum speed before they come into play. Centrifugal force at work, kinda thing.

 

[Werner]

Hello all together.


I took measurements on the lathe today. I can set the speed precisely to 1 revolution per minute. The measurements are not absolute, but subjective, but reproducible.



With the tube hose containing balancing beads:
From 80 rpm, the beads lock into place, and their slight noise is no longer audible.
From 290 rpm, the imbalance begins to vibrate.
From 445 rpm (= 65 km/h), the imbalance is so great that the lathe —which weighs 150 kg— begins to dance.


One revolution corresponds to a distance of 246 cm.


If I do the same experiment in the other direction, it takes a little longer for the beads to lock into place, and the machine also starts dancing a little bit later.
If I repeat this process several times, the result is similar.






The out-of-roundness of the wooden adapter is 0.25 mm.


Next I will repeat this experiment when I have new hoses without beads. Then I can see whether the weight beads are a fairy tale or a fact. Perhaps ...