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Old 10-16-2019, 11:14 PM   #1
ursus
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Default Front Axle Fasteners

I'm in the process of rebuilding a front end on a car that was converted to 1940 Ford hydraulics back in the 1960's, including the use of 1940 Ford spindles. The '40 Ford spindles utilize a tie rod that connects steering arms that project from the lower boss on the spindles. On a Model-A axle, this means that the tie rod actually hangs down below the wishbone and the axle as well. This looks funny and could be a safety issue if a road hazard were to enter the picture and tear away the tie rod.

So, my plan is to re-install stock Model-A spindles and tie rod to effect a more original appearance, with the tie rod passing above the wishbone, but retain the hydraulic brakes using the typical conversion ring and spacers, etc. However, this means replacing the 1/2 inch '40 Ford backing plate bolts with 3/8 inch bolts that are standard for the Model-A. My concern regards the relative strength of the smaller bolts in view of the fasteners available from the usual vendors. Does anybody know what grade of bolts and nuts are currently supplied? The original Ford stuff is usually pretty darn stout, probably SAE grade 5-8.
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Old 10-17-2019, 09:15 AM   #2
Joe K
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Default Re: Front Axle Fasteners

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The original Ford stuff is usually pretty darn stout, probably SAE grade 5-8.
Um. Ford bolting as found is slightly less than Grade 5. Grade 8 bolts are head and shoulders above much else.

Ford used quality materials. Vanadium Steel is common but not universal. The use of "rolled threads" on most fasteners augments what is already there in material quality.

You can probably get away with this, but go to the Grade 8. And be sure to use hardened washers perhaps on BOTH sides. You'll probably have more problem finding the hardened washers than the actual Grade 8 bolts.

Look to available online torque charts for torque requirements for Gr 8.

I went through this conversion of '40 type backing plates - and then backed away when I came to the (correct) thought that the limitation in braking is NOT the mechanical aspect but rather the square inches of rubber on the road and the less effective "presentation" that skinny tires affords. With mechanical brakes properly set up and tuned, hydraulics don't improve stopping - the limitation is in the rubber. And hydraulic conversion might even degrade it since the car "weighting" is different than a later Ford. (2/3rds of braking occurs on the FRONT - a ratio the hydraulic brakes are engineered to in diameter of piston - but the pistons are sized and more importantly "ratio'ed" for the later Ford - not the Model A - once a wheel skids, even one, braking for that wheel is ended.)

In conversion I don't remember exactly the backing plate bolt sizing but 7/16 seems more what I remember. I may have had the earliest hydraulic backing plates - No ratchets/auto-set.

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Last edited by Joe K; 10-17-2019 at 09:22 AM.
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Old 10-17-2019, 09:57 PM   #3
ursus
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Default Re: Front Axle Fasteners

Joe K, thanks much for your sound thoughts regarding '40 Ford hydraulics on a Model-A. The '40 backing plate bolts are indeed 1/2 inch versus 3/8 inch for the "A". Strange that the Model-A rear 7/16 inch bolts are thicker than the fronts which carry a heavier load but Henry must have known what he was doing.

Some of us have acquired cars with hydraulic brakes but our efforts to return to the stock mechanicals are stymied by the relative dearth of decent complete original braking systems available. I have calculated the potential cost to return a car with hydraulics to original might approach $2000 for a fully restored system. The mechanical system does have a lot of bits and pieces and everything must work well in concert. For a safe Model-A "driver" many of us have to dance with the one that brought us, even if the gal drinks brake fluid.
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Old 10-18-2019, 01:53 AM   #4
Randy in ca
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Default Re: Front Axle Fasteners

In case you're not aware, as well as the difference in diameter of the backing plate to spindle bolts, the spacing of the 4 bolts is also different between the Model A spindles and the later hydraulic backing plates. The hydraulic system backing plates must be modified in this regard in order to bolt onto the Model A spindle.
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Old 10-18-2019, 11:17 AM   #5
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Default Re: Front Axle Fasteners

Randy, I am aware of the requirements for the conversion as detailed in Les Andrews "Model A Mechanics Handbook, Vol II".

Of note is an error in Les Andrews directions: he states that the "Long brake shoe goes to the rear". This is WRONG! The '40 Ford (Lockheed type) brake shoes are mounted with the long shoe to the front.
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