Stovebolt.com 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

Some questions you might have:
Q)Why not use a 1 or a 1.5 ton axle beam?
A)They are the same (as each other) and appear substantially lighter weight than the 2 ton. They use a 0.921" kingpin that is also much shorter and the thickness of the end of the axle beam is around an inch less, so not a good match for the newer spindles.
Q)What are these axles rated for?
A)A P-30 axle is rated about 5,000 lb, and the 2 ton is rated 4,500-5,000 lb, nice that they are so similar!
Q)What's the difference between a P-30 5/10 lug axle and a 3500HD axle?
A)The main one we'd be concerned with is the steering linkage. The P-30 is setup like our old trucks are with tie rod behind axle under springs, the 3500HD has tie rod on front and above springs, and drag link is there too.
Q)Did they ever make a single wheel P-30 disc brake axle?
A)No, if it has disc brakes it will be a dual wheel type axle


If these disc brake swaps revolve around swapping newer P-30 spindles onto old AD axles there needs to be some similarities, here they are:
The thickness of the I-beam axle end where it fits into the spindle is the same for both P-30 and 2 ton AD axles, About 3.050".
The angle that the kingpin leans in, known as kingpin inclination angle, best I can measure is the same for both axles.
Kingpin length is essentially the same, and the lock pin groove is in the same place.

Now it would be to easy if everything was the same... here is the major difference:
The kingpin diameter on the 2 ton axles is 1.109", and on the P-30 it is 1.179".

Two methods of adapting the P-30 spindles to the old axle:
Use thicker walled bushings, but I've been unable to find any ready made ones. You can order oversize bronze ones and turn and bore them to suit, probably have to mill the grease groves too.
Or you can make thin sleeves to press in the kingpin bores in the spindles to adapt them to the original size smaller OD bushings. So far I like this idea best. I'd use green loctite sleeve retaining compound so they stay put, and in the future new kingpins and bushings are an off the shelf item.

The 1.109" kingpin kit you would use is NAPA # 262-1016. There are other similar kits but this is the best choice from what I can see because it comes with gaskets for the caps on the P-30 spindles, not steel plugs like the old 2 ton had, it has bronze bushings not plastic, and has a ball thrust bearing not a thrust washer. It's also cheaper and easier to get than the other possibly suitable kits.

Grigg

How wide would this new axle be?

Simply put if you swap a 2 ton axle I-beam only to an 8 lug P-30 axle and the result is 9.125" narrower, so WMS to WMS would be 72.5" for a dual wheel 8 lug disc brake front axle.
Is this suitable for a 1 ton AD truck? ...No, the original WMS is 66.25" so it'd still be 6.25" extra wide or tires would be about 3-1/8" further out each side, not fully under the fenders.
Is it suitable for a newer than AD truck? Might be depending on width and adapting the springs to the axle.

How wide would a 5/10 lug P-30 or a 3500HD axle (same spindles and hubs)with an AD 2 ton axle beam end up?
WMS to WMS should be 72.8125 within 1/8" or so.
That's 2.875" wider than an original AD 2 ton front axle, or only 1-7/16" wider per side, I can't see any problems with that.
Or better yet look at it another way, it's only about 1/2" wider than an optional NAPCO front axle!

Grigg

For the single wheel trucks not only would you need to adapt the spindles and caliper brackets from an 8 lug P-30 to the 2 ton axle, but you also need to find a single wheel hub and rotor to fit the spindle and caliper/bracket.

I've searched and searched and the best possible rotor/hub that I can find is a NAPA part number 4885580. It's a GM combined hub and rotor that has the same 12.5"x1.5" rotor that the dual wheel version that comes on the P-30 axle has.
Here are the critical dimensions, look at this sketch for clarity.
https://picasaweb.google.com/lh/photo/WPE6TH44cNiB2d-tiFQ0ptMTjNZETYmyPJy0liipFm0?feat=directlink
Measurements in inches are from rear surface of rotor, from WMS, and from outside faces of installed inner and outer bearing cones

_________________ "A" ____ "B" ____ "C"
P-30 dual hub ___ 7.289 __ 0.955 ___ 3.995
NAPA 4885580 ___ 3.823 __ 0.938 ___ 3.990

As you can see the rotor position in relation to the inner bearing is essentially the same, so the rotor sits where it's supposed to and fits in the caliper.
Also note that the dimension "C" distance between bearings is the same.
The big and expected difference is position of the wheel mounting surface, and in this case it is 3.45" per side, or 6.9" narrower for the whole axle.

Now, don't get to excited because this single wheel hub and rotor won't fit...
It uses a different smaller inner bearing, NAPA LM501349 and won't slide on the spindle.
But luckily enough the outer bearings, NAPA 15103-S are the same!

The P-30 spindle uses a (inner or large) bearing with a 1.688" ID.
The new single wheel hub uses a bearing with a 1.625" ID.
A 0.063" difference.

The way to make this fit a good way is to turn that 0.063" off the inner bearing journal on the spindle. Then off the shelf bearings and hubs work in the future.
More/better/different bearing option of a larger bearing and thin adapter sleeve, keep reading or click to skip right to it. http://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=778876#Post778876

An alternative method might be to adapt the hub to fit the larger P-30 bearing cup, this is a 0.109" difference, and I'm not sure about the depth, or if there is enough material in the hub. Not a good plan because you have to modify parts to replace rotor/hub.

The grease seal intended for the new hub fits the P-30 spindle perfectly. It's very common and 1/3 to 1/4 the cost of the P-30 seal, so that's a good thing.
NAPA seal # 21771

Now the big question, is this whole thing narrow enough to fit in an AD truck?
Starting from an 8 lug P-30 axle WMS to WMS of 81.625: the new WMS width could be 9.125" narrower with an AD 2 ton axle beam swap, and 6.9" due to the hubs, for a total of 65.6"
That's 7.35" wider than an original AD 1 ton, and that's disappointing

To start with the original axle could be wider and the tires could still fit, but not that much wider... The limiting factor seems to be the 68" width measured inside the front fender lip at bottom of opening, same both front and back edges.
Some different wheels with a little more inset might work?
I'm still going to see what this all looks like, but not sure how it'll turn out.

One thought is to narrow a 2 ton axle I-beam 5.25" because then half he U-bolt holes could be reused, and a plate made like this to land the springs on and the other two U-bolt holes.
That would leave the resulting axle about 2" wider WMS to WMS than original, which would be fine, 1" per side might not be noticeable to the untrained eye.
Admittedly not a simple or fun solution, but could be a workable one.

Another thought is narrow a P-30 axle beam a lot and still use spring mounting adapter plates like above. Narrowing it 16" results in original single wheel WMS to WMS, but several inches narrower at the kingpins, so less steering angle, and not much (enough?) room for the P-30 steering arm to not hit the springs. Narrowing it about 14" might improve the situation, but then the 2 ton axle narrowed (as above) looks easier/better for same final width.

Grigg

Keep up the great research work Grigg! You may be on to something here! If you figure it all out, you'll have made a lot of folks happy I'm sure!

Looks like a lot of research here. I discovered that the front axel on my 41 1ton had the same parts as the 46 1/2 ton. Both with 6 lug. I compared them all in the master parts list

While it,the 1/2 ton kit, was not listed as fitting a 41 1 ton I took the gamble and it all fitted and worked perfectly.

In 1946 they changed the 1 ton axel so it will not work on that year.

I was sure my 1 ton would never be used to capacity and any disc brake system is better than the old drum system.

I'll add more pictures of the different axles to this post as time goes on

P-30 8 lug dual wheel axle as removed from a step van:
http://rides.webshots.com/photo/2596296970080251109PPqxch

P-30 5/10 lug and an 8 lug side by side
http://rides.webshots.com/photo/2560431160080251109ZUTVYD

P-30 spindles, steering arm, and caliper bracket (for 12.5" rotor) on an AD 2 ton axle
http://rides.webshots.com/photo/2593443670080251109Wpuuin

Here's the condensed info for a 1.5 ton heavy and 2 ton disc brake upgrade.
No need to even remove the axle beam from the truck!

If you have a 1.5 ton with the light axle (thread or press in grease caps) or a 41-46 1.5 or 2 ton also with the light axle then first swapping to an AD 2 ton axle beam would be necessary. (Or consider a 41-46 heavy 2 ton axle and double check all the critical measurements.)

In addition to the info below you'd also need to narrow a tierod, this can be done by using the one that comes with the P-30 axle and cutting it approximately 9-1/8" shorter on one end and rethreading it to fit the tierod end again. Consider choosing the right hand threaded end, taps are more common than left hand taps, but left hand taps are available if need be.

The draglink will also need a solution and it should be reasonably simple to assemble from off the shelf ends (different lengths, threads, and tapered ends are available) and a sleeve to connect them, just as the P-30 used. If you have a ball stud type end on the pitman arm you can remove it and have it reamed for a modern draglink end, or can swap pitman arms for one from a newer truck with the tapered hole already. Like this one from a 52 Chevy 1 ton.

Note that if you want to use the original steering box you want a P-30 axle as the donor, not a 3500HD axle with the different steering setup.



Just for info, I measured 1.5 or 2 ton AD front fenders (on the truck) to be 72" wide inside to inside of the lip at the bottom edge both front and rear of the wheel opening.

hey grigg have you thought about the fwd control chassis on the mini bludbird bus chassis mini school buses that are made by gm?

I don't think I have unless it uses the same axle as a P30. (I'm thinking so??)
what can you tell me about them?

Thanks,
Grigg