Where does wheel contact drum?

[apbright]

Question: Should the wheel contact the drum only in the vicinity of the lug nuts and studs, or also in a circle which is the edge of the cup of the wheel?

In the attached picture, a ring can be seen where the cup of my wheel has been in contact with the drum (this is a front drum), and rubbed the paint off the drum (red arrow). To the best understanding my eyes give me, both front wheels on both of my Model A's contact the drum in this way.

Per another thread, I found a local mechanic to turn one of my drums which was warped. He claims the reason for warpage was that the wheel was in contact with the drum at this ring position, which he says it should not be. He says the wheel should be in contact with the drum only in the area where the studs are. So, is he nuts, or am I?

In case it matters, these are 19" wheels, from a '31.

[BILL WILLIAMSON]

Common sense would tell us that there should be NO CONTACT at the ring area. Sometimes it's caused by paint build up on the drum & wheel.
Bill W.

[31Tudor]

I think the wheel does come in contact with the drum where the circle is. That is the problem when a person puts an early 28 wheel on a non early drum, the wheel leaves a gap there. I don't think any of my wheels have a gap at the point in the drum where the ring is.

[Dave in MN]

All my working wheels make contact at this "ring". All the wheels I have straightened have also made contact in this area. If they don't, I look for damage at the hub mounting/bolt area.
Good Day!

[WestCoast]

it is my opinion that if the wheel contacts the drum any where but where the lug nuts tighten you are lookig at a wobling rim, thats why the lug nuts are tapered and holes in the rim are tapered to hold the rim tight to the hub and in a straight line with no chance of play, thus eliminating any wheel wobble, if the rim is in contact with the drum any where but at the lug nut holes there would be no need for tapers on lug nuts or rim

[bbrocksr]

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Originally Posted by WestCoast

it is my opinion that if the wheel contacts the drum any where but where the lug nuts tighten you are lookig at a wobling rim, thats why the lug nuts are tapered and holes in the rim are tapered to hold the rim tight to the hub and in a straight line with no chance of play, thus eliminating any wheel wobble, if the rim is in contact with the drum any where but at the lug nut holes there would be no need for tapers on lug nuts or rim

The tapers center the wheel , the rim contacting the drum supports the wheel laterally to prevent flexing and eventually cracks.
Bill

[Kurt in NJ]

The wheel contacts the drum, bent wheels can warp the drum--- even too much powder coating where the wheel contacts the drum can distort the drum
When I install a drum I have been checking for distortion caused by the wheel
The drum is part of the strength of the hub, that is why they are swedged together, the multiple contact areas of the wheel make it stronger

[Synchro909]

One of the guys in our club investigated this matter and found that when the wheel centre contacts the drum, there is about 25 thou to go on the nuts before they are tight. Another guy who had ground the wheel centres so they did not contact the drum ended up throwing those wheel away.
In response to the original question, IMHO, the wheel should contact the drum on that ring.

[jw hash]

the wheels are suppose to seat against the drums. like it shows in apbright`s picture. that is part of the structure of the wheels.

[bunnyc]

Glad this question came up. I was wondering if they should.

[Al 29Tudor]

Look at page 328 of the Service Bulletins. The wheel Shell - RIM must contact the drum for support.
Al Leach

[apbright]

Thanks everyone, very good, clear answers. My suspicion was that they should be in contact there, but the mechanic looked at me like I was from Mars and gave a long speech 'in 35 years of working on cars, that goes against everything I know.' Seems 35 years isn't enough for a Model A.

[BILL WILLIAMSON]

I wonder if exacting dimensions are used in machining that area on NEW drums? Maybe Randy Gross will chime in, with his thoughts, Randy, Randy, HELLO, HELLO?
Bill W.

[Mel Gross]

Our cast iron brake drums are 100% machined. They were made to the same exact specs of the Plastometer cast iron drums that were produced many years ago. We have been selling our cast iron brake drums for close to 10 years now and have yet to have a complaint about them (fit or function). When we do change out customer's old drums for ours, most of the old ones have the paint missing from the area that this thread is about.

[Kevin in NJ]

What I have found from taking apart stuff and building my car.

First off Ford machined some drums on the outer area where the larger diameter of the hub section of the wheel touches the drum.

It is likely that Ford engineered the wheel drum system to allow for the use of the cheaper steel drums. Making the drum wheel become a box section creating strength for the wheel and the drum. One can easily see how using a later wheel on the A hub or a later drum with an A wheel can allow for more flex in the unsupported parts.

I powder coated the rims on my car. I did not get an even coat on the edge that mates with the drum. I did a test. I put the drums on a spindle in the vice and set up a dial indicator to check the drums. Without the wheel on the out of round was like .001" on the freshly cut drums. I mounted the wheel and found the drum went out over .020" (from my memory). Took sandpaper and made the edge of the wheel that contacts the drum bare metal (it will get there eventually anyway) and it went back to .001".

As trying to apply modern ideas to the Model A. That is where you get into trouble. The A was designed in a different era and you need to stop and think about what was being Engineered by the very smart guys Ford hired to make his car strong and economical.

[aermotor]

Would like to renew this thread. Before torque, centering the wheel on the hub with the lugs centered I see 3 possible initial contact points on the wheel within a few thousands. 1. the high points between the lug wheel holes and the center 2. the full circle raised area outside the lug holes and 3. the wheel "drum" at the brake drum. Where should the main contact point be after torque (50#)?

John

[C26Pinelake]

Talk about total confusion! Does anyone know the answer for sure. So often on this site thus happens and the person with the question has no idea which answer is right ! Wayne

[oldwoodsman]

I think this picture explains it pretty clearly that they should make contact in both places.

[aermotor]

Thanks oldwoodsman - I'm new to model A's what does AR refer to ?

John

[Tom Wesenberg]

Originally Posted by aermotor

Thanks oldwoodsman - I'm new to model A's what does AR refer to ?

John

Early 1928 wheels had a narrow hub where the spokes are welded to it, so it won't properly fit later A's. Since it will need to be kept in stock for repair parts, it gets the "R" suffix. The "A" means it was the first design of that part. So the next wheel design will get a "B" suffix.