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.

****
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.
****

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. https://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

Request for careful measurements
If you have one of these trucks and can add to the info please do.

A WMS to WMS measurement for an AD 1 ton dual wheel truck front axle.

For an AD COE in addition to a WMS to WMS measurement also need an accurate width of the axle beam from center of one kingpin lock bolt hole to the other?

Any other trucks/axles you have that might fit into these plans and we don't already have info on?

Thanks,
Grigg

Grigg, If I get some time this next week I will measure the WMS of my '49 3800 DRW. Loving what I am seeing. Fingers crossed that this would become a workable option.

Of course, by swapping out the spindles and hubs, etc., makes using the P-30 a very simple option. Disc brakes, radial tires, man now all I need is A/C and power steering...

Grigg,
For the record I just wanted to take a second to say thanks to you and the rest of the "grandmasters" for posting this kind of info. I am sure I am only one of a ton of people eagerly awaiting for you and them to solve this puzzle so we can all go forward and benefit from your solution. Thanks!

Jon, if you've had a chance to measure please do let us know what you found, and I'll see if we can answer the question about how well this works for AD dual wheel 1 tons.

Thanks,
Grigg

Hey Guys,

Been a long time since I've posted here. But I am still interested in these big bolts and this is the brake/spindle swap I have been thinking about for the last 6 months. I have a question though, who is the actual front axle manufacturer and what is the model for the 5/10 lug P30 front axle? Spicer? Dana? Eaton? I am trying to source the assemblies from a large truck wrecker and he wants to know the manufacturer and model of the axle, I can't seem to get him to look it up by truck application.

Thanx a bunch,
Jaysin

Rockwell.... but I've never seen it listed or referred to by that, I've only noticed the Rockwell logo on some of the parts.
I suspect it is better known as a GM axle which makes a lot of sense because I've never ever seen one under anything else (from the factory).

If you can't get a wrecking yard to find something by application you need to find a real wrecking yard...

Grigg

Here's more info on the single wheel hub and fitting them on P-30 spindles, the inner bearing is the problem.

Here's what I found about bearings....
Already knew outers are the same NAPA 15103-S so we'll just be talking about the inner wheel bearing, the big one.

The single wheel hub to use is NAPA part number 4885580.
It uses inner bearing "Chicago Rawhide BR35" same as "Timken SET45" same as "Timken numbers LM501349 cone and LM501310 cup"
The ID is 1.625" and OD is 2.891"

The stock P30 hub/spindle takes inner bearing
"Timken numbers 26884 cone and 26823 cup"
ID is 1.688" and OD is 3.000"

Ideally there would be a bearing cup with the small 2.891" OD that fits the single wheel hub and a compatible cone with the large ID of 1.688"

It has been suggested that the following bearing may be a partial solution.
"Chicago Rawhide BR50" same as "Timken SET47" same as "Timken numbers LM102949 cone and LM102910 cup"
Has the correct OD of 2.891" and the ID is a larger than needed at 1.781"


So two or four options,
1: The spindle can be turned 0.063" so the stock single wheel inner bearing SET45 fits. If a large radius is kept in the corner strength shouldn't be an issue after removing only 1/32" per side.
2: The bearing SET47 could be used. It has the same 0.770" assembled width as SET45. To fit on the spindle a thin wall bushing would need to be made with 1.688" ID and 1.781" OD... That's only 0.093" difference so 0.0465" wall thickness. One option if just making the sleeve the right size to start with doesn't work is to shrink it on the spindle and then turn/grind the OD to final dimension.
3: find a suitable conversion bearing with 2.891" OD and 1.688" ID (No luck so far)
4: Have that bearing made; which apparently is possible but at what quantity and price?

More on option #2!
Parker shaft wear sleeve number WS1976 with ID of 1.687", OD of 1.813", and 0.625" wide could be a great starting point, still needs to be ground or turned down about 1/32" after installation. (could not find yet a another different bearing that would work without turning the sleeve)

Grigg

Hey guys, I'm the proud new owner of a '54 3800 and am looking to tackle the disc brake conversion problem as well. I've been looking online and over in the 67-72chevytrucks.com forum and found a guy who converted to disc on his 1951 3800 in basically a bolt on fashion. He descibes his final approach at post #22. I'm trying to figure out his front bracket right now and see if I can get one made as a one piece steel water jetted instead of welding two plates together. Below is the link to the post.

http://67-72chevytrucks.com/vboard/showthread.php?t=440043

And for pictures:
He gave me the link, and just got his permission to share. I'm not sure what bearing he used, but I am assuming that they are ball bearings.

https://picasaweb.google.com/mitchell.lmdangerous.rish/1951DiscBrakePhotos?feat=email#

I'm just getting into this project myself, and am looking for guidance as well. Thanks all!

Just a reminder to please keep this thread about front disc brakes only.
Thanks,
Grigg

Just a thought couldn't maybe a 4X4 front hub assy with disk brakes be grafted onto the Big Bolt front axel.The older ones have sort of link pin type set up so without an axel shaft in the way you could run a the pin all the way through.You would then only have to run a bolt through the center of the hub with a Washer or metal disk and gasket to seal it up. There are some tall and not so wide 16 inch tires. These ars close to looking like a 7.50- 20 tire .So they would not change the apperance to much
Or if you know a good welder you could make a nice tube axel also useing pieces of the 4X4 front axel & hub this would be very east to do. The recivers for the front hubs are pressed into the axel tubes and welded so cut them off chuck them up in a lathe turn off the tube and weld .For a jig you would have already figured how long the tube has to be ,so you would bolt your spring pirches to the springs lay your tube accross center it and only tack the perches on.Then level the truck up side to side .Next you would have to a bar turned so it would fit down through the top and bottom pin holes on the hub reciver with enough extra so you could place that magnetic thing that you can check for angle (sorry forgot the word)next you would need your tires on the rims so you can set the height of the truck .Now you can tap the hub recivers into the tubes ,you would have turned them in the lathe so that they are snugg but if you heat them a little to turn them to set the caster once the caster is set tack them good .Now unbolt it from the truck put on a welders table clamp it down good tack a few baces on so it has no chance to move and weld that sucker up .Now you have disk brakes just an idea

Hey All!, After reading about axles, wheels, and tires until my eyes fell out and to be honest I became a bit discouraged I came across an idea that I wanted to bounce off the forum. It may be borderline heresy to say in a place like this but I will brace myself and apologize ahead of time. Keep in mind that my truck means the world to me and is one of my last real connections to my grandfather. However, other than the cab (the exterior), the Cresci dump, and the front axle (which has to go), there is absolutely nothing stock or original about it. My grandfather was all about modifying it to suit his needs and or what he had available at the time. Its a 1954 6100, and it is my understanding that the front axle is just a small hair under 70" wide. So has anyone given any real thought about swapping in a pair of 2.5 ton rockwells with the hubs "flipped"? The width is 69.25 inches with them flipped. The truck would be much more valuable and useful to me as a 4 wheel drive and thus I would have a bit more justification to invest my time and money into it. If 69.25 inches is too narrow I don't think it should be too bad $ to get one side custom shortened and then just cut the tube on that size to the size I need. It looks like I might have a line on some reasonable rockwells, and wheels and parts should be a whole lot easier to come across. My grandfather always wanted a NAPCO truck so this is kind of interesting way of getting my truck close. Thanks.

Rockewlls would make for a very tall truck and just as low gears although I think aftermarket faster gears are now available. Still leaves you figuring out brakes? Mounting the front axle to the springs might be difficult and taller springs are probably required.

Certainly you should look into it, but in my opinion I bet you find it's not a great idea.

Grigg

Grigg I'm looking to put some front and rear discs on my '54 1-1/2 ton truck. What is a good formula on determining the right diameter and thickness of the rotors for safety reasons? I will be using the stock 2 speed rear end and will keep the 235 with the sm-420 4-speed.

Check out this thread again,
This is what I know about swapping disc brakes on an AD 2 ton truck front axle.

I haven't looked at the rears because I think swapping to a whole newer rear with more gear options is a better plan.

Grigg

There are photos on this build link that show the caliper mounts I made and the set up front and rear. Uses F550 calipers. The rotors are from a company that sells disc brake conversions for the 2 1/2 ton Rockweel axles for mud trucks.
http://rides.webshots.com/album/550039908qGswfS

Thanks,
There are countless ways of doing a disc brake conversion.

My intent is to use easy to get parts new and or used and keep the machine work to the bare minimum. So far with the P30 parts that comes down to just a couple bushings.

Grigg

That's what I am using(10 on 7.25") under my '37 GMC. Let me know if you need any measurements.

hi im new here i have a 1947 3/4 ton with the 8 lug bolt pattern i have looked for a disc brake setup for a few years i finally found someone to build a kit for me it was a little bit more than a kit for the 1/2 ton pickups i was the first one to get the kit built the company is called RPM Eng the owner is ron his phone 3 is 760-329-1886 give him a call he should be able to help with a disc brake conversion if you have any ? you can contact me at faynel@prodigy.net for more info

Have you installed the kit yet? How did it work?

yes i installed the kit and it is working fine i had a few things i had to do to make it work but that normal

Any measurement on wms-wms for 1 ton drw front axle?

based on some calculations from taking rear tire center to rear mean difference (wheel offset) and adding that to the front mean (tire position)

i think its ~66"

i wonder if a srw dodge dana 60 front axle at 67.5" would work...

without a spacer i imagine the wheel offset would put it inboard of bearings. i wonder if steering linkage would be ok

i also wonder if wheels inboard of bearings is as bad as outboard.

No, not yet, do you have one you can measure?

I don't care to speculate what it might be... to be good info to work from we need the real thing to actually lay a pair of straight edges and a tape measure on to accurately measure.

Thanks,
Grigg

I have one but it will probably be a bit before i can pull the wheels.
I agree a direct measurement will be best.

they way i did the calculation was to use the measurements rom the manual. If you take the difference between the center of the outer tires in the back and the mean of both tires int eh back- that should be the offset of a dually wheel. take that and add it to the center of the front tires and thats how much longer they make the axle so the same dual wheel will fit. that came to 66" I'm pretty confident it is correct because I found a measurement by soemone with a 1.5 ton and it was within 1/4" I think all that is different between the trucks front axle is something in the hub accounting for the small difference...

Hopefully I can take a true measurement in the next month or two. This really sucks not having the truck at my place where I can work on it even in any 15 or 30 min stretch I'm "free"

Tj

That's what my P3500HD axles are from.

Hi all!
I am new to the forum, and just purchased a 1938 1-1/2 ton stake truck. My very 1st thought was,"how will I get disc brakes to fit this"? Having read this post, I am wondering, why not find a rotor setup that fits the stock spindles?
This may be a silly question, or something I have missed. Just wondering?

Welcome,

Not a silly question at all, all options are worth considering.

This thread explores the original hub and adding disc option for a 46 Big Bolt, may have something in common with your 38?
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=891012&page=1

I've tried/considered other ways myself, the P30 parts option is the one I like most at this time. With more or less work most of your options will work in the end. The brake capacity, reliability of the system, and availability of parts are all worth considering.

My goal in finding a suitable solution for the mainly AD trucks (but most any year with 1.109" kingpin) is something that is factory for another vehicle (for reliability) and takes very little fabrication or machine work, ideally none. What I've come up with for the dual wheel trucks requires a spare later model (P30)axle for parts and you need to ream or bore the existing P30 bushings out to then press the original size bushings inside them (or turn adapter bushings). The rest is just swapping parts, no disc adapters or caliper brackets to fab.

Grigg

Les, (Roadmarks,) from Raleigh NC, here. I was just rereading your fine article on disc brakes for 3/4T and larger trucks, and now find that the pictures are no longer available. The new service, "SMILE," requires a membership. If there is anything you can do to make the photos publicly available again, it would be greatly appreciated!

beat wishes,

Les

Would it be easier to bore the axle out and use the 1.179 kingpin? You'd have to handle a big heavy piece but you wouldn't have to mess with keeping a .035" wall bushing concentric. Just wondering if any one has actually run the bushing setup yet and whether they cut them themselves or farmed it out?

Edit: Now that I've looked at your wonderful photo collection, Grigg, I see that you likely meant the p30 kingpin is 1.375ish diameter. Now it all makes sense. Looks like something I could whip up at work. How much clearance did you allow from the adapter bushing diameter to the stock bushing?

Sorry, Webshots has gone belly up as far as I'm concerned, it's agrivating...
I have switched over to Picasa but don't have all of my same pictures up there yet, I do have them though somewhere or another. Don't know when I'll ever have time to repair all these dead links.

Here are some and eventually will be all the related pictures.
https://picasaweb.google.com/118082002072608219229/2TonDiscBrakeUpgradeForOldGMTrucks

Grigg

Boring the old axle will change the fit of the kingpin lock bolt/pin and require even more modification. Boring the axle also removes metal from around the kingpin where it's pretty important. Making the bushings fit the spindle and using original 1.109 size kingpins is the safer and I think simpler option.

The bushings aren't all that difficult, it can be as simple as not removing the P-30 bushings and just ream them out to fit the new bushings in.

From my notes, (confirm dimension and fit with your own measuring tools to fit your exact parts)
A P-30 bushing, NAPA part number 262-8273 fits in a about a 1.299" - 1.300" bore.
An old GM 2 ton bushing NAPA part number 262-8081 fits in a 1.229" - 1.230" bore.
So I'd ream the P-30 bushings out to very nearly 1.229" whatever it takes for a proper press fit of the new bushings in. Then ream the new bushings inline to fit the 1.109" kingpin.

Again, I use kingpin kit NAPA 262-1016, it has metal bushings, thrust ball bearings, and is cheaper than other NAPA kits that would also work.

Grigg