The Stovebolt Site Forums The Parking Lot Big Bolts Disc brakes for 1.5, and 2 ton trucks

Preamble:
This is now an old thread... it has some good ideas and some that didn't measure out to be useful.
Please accept my apology for not following through with a tech tip and clear concise step by instructions with pictures, part numbers and such. I haven't had time and probably won't.
If you're willing to read through it you can figure out how to adapt P-30 brakes to an old big bolt. Several folks have followed through and it works nicely.
It didn't really work for the 3/4 and 1 ton.. kind of but makes for a wide axle, or requires narrowing an axle beam. Not really a success



First, if you have questions about wheels and tires check here for our very own Tech Tip
http://www.stovebolt.com/techtips/wheels/


EDIT: picture links don't work Webshots died then Picasa did too...

This thread is kind of a continuation of this earlier one but different enough to start a new thread in an attempt to not be to confused by the last.
Also check out this tech tip my first method for making a big truck disc brake front axle was to narrow and weld a P-30 or 3500HD axle, this is not simple or quick. The following method I think will be better than the cutting and welding method.

It is my intent to come up with a method of installing disc brakes on AD big trucks 1 ton through 2 ton.
Much if not all of this should also apply to 3/4 tons.
Also consider these methods for 41-46 trucks, possibly even with the original heavy duty 2 ton axle, or an AD (48-54) truck front axle is supposed to be a bolt in swap. AD axles have 26-13/16" spring center bolt to center bolt hole measurement.

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If you're willing to research axles and widths this same method could work for Chevy and GMC trucks from (best I can tell) 1941-1978 Because for all those years an axle was offered with a 1.109" kingpin, and if your truck already has one of those axles the spindle swap described here should work. Or if your truck doesn't have an axle with 1.109" kingpins you can very likely bolt one in from a larger truck of the same body style. again, do your own research and these examples and measurements should be a great start.
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In short the idea is to use an original axle, likely from a 2 ton, and adapt later model spindles and caliper brackets to it.
For a single wheel truck it will also involve adapting single wheel hub/rotors to the new spindles.



First let's get everyone up to speed on what we're talking about:
WMS --- Stands for Wheel Mounting Surface, this is the flat surface on the hub that the wheel bolts against. Likewise a measurement described as WMS to WMS is the width across the axle between those surfaces.
P30 --- Is a model of GM chassis commonly used in the 70's, 80's and 90's (and?) as step vans, bread trucks, and RV's. Many but not all of these have I-beam front axles with either 8 lug or 5/10 lug hubs and disc brakes.
3500HD --- Chevy truck (with pickup style cab)in the 90's that also had a I-beam front axle and shares some but not all of the same parts with the P-30 I-beam axles.
Dual wheel --- Deep offset type wheel, and even when used as a single on the front axle we'll call this style a "dual wheel"
Single wheel --- Wheel with a more or less centered mounting surface.

A few WMS to WMS measurements just for reference on the axles I have here.
AD 1 ton single wheel front axle is 58.25" (If you're curious the rear axle measures 62.625")
AD 1 ton dual wheel front axle 66.25"
AD 2 ton front axle is 69-15/16"
AD 2 ton NAPCO front axle is approximately 72.5" (courtesy of Napco Man)
AD COE 2 ton front axle Approximately 71.25" (can anyone confirm?)
GMC 400 series 3 ton with Clark F466 front axle, about 72.75"
P-30 8 lug front (dual wheel) is 81.625"
P-30 5/10 lug front (dual wheel) is 82.062"
3500HD 5/10 lug front axle (dual wheel) is around 79.5" (still need to get an exact measurement)

How wide are the I-beam axles themselves? It's hard to measure, so a pretty simple and accurate method of at least comparing them is to measure from the centers of the kingpin lock pin holes, I like to insert a 1/2" bar in each and hook the tape measure on one and measure to the inside of the other.
The following are my width measurements from center to center of kingpin lock bolt holes:
48-53 2 ton 52.625"
47-54 AD COE 2 ton 54-54.5" (courtesy of vwlfan)
41-46 2 ton 53.75" with heavy axle (courtesy of Billy Marlow)
GMC 400 series 3 ton with Clark F466 front axle, about 54.75"
P-30 8 lug 61.75"
P-30 5/10 lug about 62" (might turn out to be same as the 8 lug axle)
GM P3500 HD(baby school bus) with 5/10 lugs 62.0625"
3500HD 5/10 lug __.__"?
AD 1 ton single wheel front axle ~49.75"
AD 1 ton dual wheel front axle ~49.75"
(my own previously narrowed 3500HD axle ~49")

How wide is an AD 3/4 ton up to 2 ton front axle from spring center to spring center? Understand that the springs are closer together at the front than the back, they're not parallel as many later axles are.
Center to center of spring center pin holes in the axle is 26-13/16 inches.

keep reading for more details,
Grigg