Changing from front Drum to Disc Brakes

[Slantsixness]

Sent: 1/12/2005 8:07 AM

Does anybody know what it takes to convert over to front disc brakes?

Smurfbago is a '72 and has the front drums. But in looking at it, it seems the spindles come off independently of the kingpins. Can I just swap these over to later model ('74-up) discs/spindles and go with a disc master cylinder and proportioning valve? 

I know where I can obtain the disc setup and even the axle, I just don't want to swap the whole darn front axle.

It looks in the dodge manual to be the same main axle. I don't have the two next to each other to be reasonably sure...

Tom

[Sea Hag]

Sent: 1/12/2005 12:00 PM

What model chassis is under your 72 ? - I can try to check some of the part numbers in the Dodge MH chassis parts manual to see if they are the same or compatable axels , spindles Ect. . Sea Hag 

[Slantsixness]

Sent: 1/12/2005 12:56 PM

Sea Hag,

My winnie is a '72 D20RG with the M300 chassis and a 318-3, front drum brakes with the air filter on the floor (not hydroboost). The Brakes I can get are off a '76 (or 77?) D18RB also with a 318-3 and no hydroboost. The whole axle might not be worth the effort to do the swap, and difficult to transport. Just taking the prop valve, master cylinder and the brakes (tie rods, flex lines,booster too) is what I'm hoping will work.

My drum brake spindle/assembly appears to be held on to the kingpins by 4 bolts. The tie rod ends appear to be the same as the later D18, although I can justify changing them out if necessary, too. What I don't know is if the main axle mounting and length, without the spindles, is the same. I wouldn't want to change the kingpins, for that I'd just swap the whole axle (and hope for good kingpins in the used axle...).

If it's not as eay as it seems, I'll just have to keep adjusting the front drum brakes (ugh!)

Thanks for the help,

Tom

[denisondc]

Sent: 1/12/2005 4:15 PM

Why are you going to the trouble to convert the brakes?
The drum brakes should have self adjusters, and even if those don’t work, they should not need adjusting more often than perhaps oncce each 5000 miles. I assume you arent using your motorhome mostly for stop and go errands. If you need to adjust the brakes more often, I suspect the wheel cylinders are sticking, or the brake shoe return springs are broken, or the shoes are binding against something.

When I got my Winny I had to clean up the threads on the adjusters, along with replacing the leaking wheel cylinders. I cleaned up the self adjusters again 6 years after that, and just did it for the third time this summer, 7 years after I did it the second time. I have never had to adjust my brakes - the self adjusters take care of it. I put the new shoes on when I got it in 1991, at 49k miles, and they arent even 1/3 worn yet, maybe only 1/4th. My rear brake shoes are the originals â€" have 96k miles on them, and have at least that much more left in them. I have had to replace the wheel cylinders a second time though, and I had to replace the parking brake shoe and its actuating cable.

And if you do this conversion, I would save the old parts, or would begin pricing out spare rotors and calipers, or both.

Are your front drums 12.12 by 2. or 12 by 3 ?

[54PrairieSchooner]

 Sent: 1/12/2005 10:32 PM

When I spoke to Geoff at Alretta last summer, he told me the front drums for the M300 are no longer available and haven't been for about 20 years. They probably can be found NOS on E-bay or somewhere, but they are scarce. If its easier to get the disc brake parts, the swap might be good for long term support, but then again, it will probably take a long time to wear out the drums if the shoes are replaced etc. when needed and they don't need to be resurfaced very often.
John

[HeavyHaulTrucker]

Sent: 1/13/2005 2:38 AM

Tom, what you want to do is not really a big deal.  The spindles are the same part for both style of brakes; the only difference in the spindles themselves is that one of the 4 holes on the mounting plate is tapped.

The easiest way to do this is what you have already been thinking -- simply find a donor chassis with disc brakes and swap them over, spindle for spindle.  But if you want to keep your spindles, then the parts swap over perfect -- you just have to tap that one hole on each spindle.  I just got done putting new spindles in mine -- I have disc brakes, but the donor axle had drums.   
John

About the kingpins (not wanting to change them) -- believe me, you want to at least take them out for inspection.  Actually, changing them depends on the amount of wear they show.

It is not really that much more work to change out the kingpins when you get to the stage that you are contemplating -- when you get the brake backing plate off, you are looking at removing 3 more nuts and the kingpin to change them out.  Believe me, if I had the assembly taken down that far, I would change them out while I was at it -- unless they are true and show VERY little wear when you get them out.  While I had to remove mine to change out the spindle, they showed virtually no wear at all -- I ended up putting them back in after I cleaned and rebuilt the thrust bearings.

John

[Slantsixness]

Sent: 1/14/2005 1:03 AM

I'm taking the plunge, and the whole axle, rotor to rotor, or at least I think I am, unless the winds change too much....

Denison's point is well taken, and he's very right, but what he doesn't know is:

I Hate front drum brakes.
I've had 15 or so cars with front drum brakes, and I'm still wishing one of them would have actually stopped when I asked them too! I'm very familiar with all the hints and kinks to maintain them, but I just can't see living with all that maintenance and upkeep for front drums. especially when it's so easy to change them out. (ok, it's really not easy unless you've done it before....)

Whole axle:
16 lugs, 6 bolts, 3 nuts (leave the drag link on, too) 2 brake lines.

What could possibly make it  easier?!!

A 3/4" and 1" drive Breaker bar and socket set.... (yep, those damn lugs and spring u-bolts are darn tight!)

Oh, and the ability to lift about 300 Lbs is pretty much a necessity.... unless you've got a "pick-it-up-and-carry-it-out-for-you-Whatchamacallit", (which I don't!).

Well, I'm off to get an axle.....
(the source of this axle will remain anonymous until I get back, but If you think about it, you'll figure it out....)

Tom

[Sea Hag]

Sent: 1/14/2005 8:52 AM

That sounds like the best way to go . Taking the whole axle . Less time at the donor , and you will be sure you have everything you need .  You might want to grab the front rims too , Not sure if the bolt patterns are the same from 72 to 76 haven't had time to look it up yet . From your discription of the donor chassis  It sounds like a 76 or 77 M300 They still used the single HydroVac booster on the m300 and went to hydroboost on the Larger chassis .

Good move , I don't like front drums either . Let us know how it goes . Sea Hag

[Slantsixness]

Sent: 1/14/2005 9:41 PM

Got 'em!

I didn't take the whole axle. the spindles are the same, and mine are aleady tapped for the one hole. Fantastic!

Smurfbago's getting Disc Brakes for Valentines day.....

Tom

[Cooneytoones]

Sent: 1/14/2005 11:25 PM

SS.......Harbor Freight has 3/4" impact sockets for 29 bucks on sale..reg 39.....the set also includes the Bud wheel nut (square fitting) for the inner wheel removal....They also have very good 1" and 3/4" breaker bars.....none of there tools are expensive....
Timmy           

order.harborfreight.com/EasyAsk/harborfreight/results.jsp
2546-1VGA 
Pittsburgh
    3/4'' SAE DEEP WALL IMPACT SOCKETS  $39.99 

[Slantsixness]

Sent: 1/16/2005 10:10 AM

Timmy,

Already had them, but Harbor Frieght is SOOOOOO cool. There's actually a store about 40 miles away (near where I work). Fun place to shop for CHEEEEEP tools.

And I don't buy expensive tools, ever. If it does the job, I'll take the $2 Chinese crap tool over a $60 snap-on any day. (now that doesn't mean I don't have Snap-on and craftsman and Mac tools either, I just won't buy new ones!)

My 3/4" and 1" set is by MIT, which I've had good luck with their stuff, and this set. I'd recommend it for anyone, but it wasn't real cheap ($100.00) for metric and standard sockets, ratchets, breaker bar, extensions, adapters and breaker extension/t bar. but that's not all! the 3/4" and 1" extensions have a hole in them to use as short tbars or breaker bars. The damn set in the steel case weighs like 70 lbs... so it's not that "portable", but I can't cant live without it!

Tom

[Slantsixness]

Sent: 6/27/2005 10:25 AM

I thought I'd post a discussion on my brake job and conversion.

I would like everybody to know first off that converting to disc brakes from front drums is fairly easy, however if you are not familiar with Brakes, specifically Dana Axle and Dodge Brakes, I would not suggest you dive into it without careful consideration and education. Keep in mind that your brakes are the only thing between your Winnie and that brick wall, and the safety of your family.
I have done similar conversions before on both Dodge pickup trucks and a few other Motorhomes, with great success.

Brake systems themselves are very simple, whether they are disc/drum or drum/drum combinations. It really doesn't matter how many wheel cylinders you have per brake or whether you use a vacuum booster or Hydrovac sungle and dual boosters. (non-booster equipped brakes are bad news in any Winnie)

So... this is how I did it.....
I found (lucked into it...) single piston disc brakes from a donor chassis (a 1975 D19RB on an RM350 chassis..Bob Weaver's "Donorbago") complete and actually still had a firm pedal!

A few more specifics:
The 1972 Brave M300 (mine) had 12X3" front drum brakes on 8 lug coined hubs. The conversion here that I describe is specific to this brake system. To convert 5 and 6 lug budd type, the process is similar, but the donor vehicle would obviously have to have the same weight axles and wheel types. The single piston Calipers won't work on systems with the Hydrovac boosters or M400's with 4 piston rear brakes.
Also, the larger dual piston calipers and brake parts are MUCH more expensive. Not that even this "cheap" conversion was cheap  (about $1000...to date)

here's the process:
Remove the hub/disc assemblies and the adaptor/caliper/dust shield assemblies. Keep ALL hardware, bearings, cups, caps, nuts and bolts...
Remove the master cylinder and booster as a unit (I did this just as a spare, since it's the same as the 1972 original booster....)
Remove the flexible brake lines and brackets that hold them to the frame (these are rare, but more on them later...)
Remove the disc brake propotioning valve (this is important!) (behind the battery box on a '75 D19, not where you expect it...On the '72 it's right next to the starter relay on the left inboard frame rail...)
So, now we have everything we need....except for replacement parts... so a phone call to Geoff at Alretta, and you can get pretty much everything you need.....except those dang-blasted front flex hoses....obsolete and no replacement... what to do?

I did both front and rear brakes at the same time, along with the conversion, so I had a "Hefty-Bonded 3ply" parts bill, but That was because my rear brakes were in pretty sad shape (well, my front drums were shabby too, but getting rid of them altogether is the focus here!)

I'll take some liberty here, and assume that the front drum brakes and backing plates have been removed from the Front axles..

Reassembly.... yeah, it's time for that!

go buy a 9/16"-18 tap.
There are two bolt hole that must be tapped out. One each, right and left.
On the left side, tap out the upper left hole in the spindle backing plate (knuckle assembly)
On the right side, tap out the upper right hole in the spindle backing plate (knuckle assembly)
Attach the dust shield  and adapters to the spindle, using the bolts and nuts saved from the donor chassis. The 9/16"-18 short bolt goes in the tapped out hole, and you must use the 1/8" washer from the hardware you saved on this bolt!
Assemble the hub (preferrably with new bearings, races, seals and a new rotor...) onto the spindle.
Attach the caliper mounting adapter to the spindle adapter (two bolts)
Attach the caliper and brake pads to the mounting adapter. (please note that the 4 caliper spring clips are important to put on right. On the larger one, the nubs go up! The little one, the wider bar goes down! (this is a common mistake, and the brakes will chatter, or even dislodge the caliper!)
And there they are.... almost! Well, they look like they'll work.....What? no brake lines?!!

The brake lines exposed!!!!!

The original flexible brake lines can be used, if they are in good condition, if not, then you can't even imagine them into existence. I mean REALLY..they don't exist ANYWHERE. So, what do you do.....? Making the steel brake lines fit the original brackets isn't that hard, but..... there's a better way!!!!

You will notice that the original brake lines enter the frame and are bolted onto a 5/16" brake line, and bolted to the frame with a nut, not a clamp. The later version of brake line had brackets that mounted to the frame, and the steel brake line made a 90° bend and came through the frame....

Well, with a little digging, I found that the Brake lines for a 1975 B250 van (I can supply you a part number) replace the original drum brake line and attach to the caliper correctly, too! And they were reasonable cost, too! The original 5/16" steel line just bolted right in! The length of this line is within 1/16" of the original line, so there is no sag or flexible line issue with suspension or turning clearances. There is a small metal clamp bracket on them that needs to be removed but that's simple enough.

So, I have disc brakes now, right?....

NOT EXACTLY.

The last steps:

Remove the old master cylinder.
Remove the original proportioning block
Install a new master cylinder (don't re-use an old one!)
Install the disc brake proportioning block (you could get a new one of these, but there's really not much to one...)
Bleed your brakes. Now bleed them again tomorrow.

Be prepared to smash your face into the front windshield when you hit the brakes the first time with the discs!

I would like to thank Geoff at Alretta Truck Parts for putting up with my wierd and quirky requests and actually delivering me all the right parts, in record time! Not to mention that he had all this stuff in stock!

I can go into even more details about this, but this turned out to be a fairly long post, so I'll save it for later. Pictures coming folks!

SurelyStoppingTom 

[Oz]

Sent: 6/27/2005 11:18 AM

Fabulous description and instructions, Tom! 

This would certainly be a worthwhile up-grade for folks with front drum brakes. 

- Sob

[mightybooboo]

Sent: 6/27/2005 1:20 PM

WTG! Sounds like a great upgrade.Nothing outranks good brakes in my opinion.

BooBoo

[Cooneytoones]

Sent: 6/27/2005 10:38 PM

BRAVO.......

   Nothing like gitten' er done.....Great discription....

Looking forward to the pictures..... nothing better than looking at a work of art......  from a master......

Timmy

[Slantsixness]

Sent: 7/26/2005 8:37 AM

update: !!

215 mile trip. up and down mountains, in and out of traffic...105° day....


STOPS ON A DIME! (well it's just a saying...)

NO BRAKE FADE!


WELL WORTH THE EFFORT IT HAS BEEN TO CONVERT.

Tom

[John Robinson]

HI, well I am new here.  My story, I got a clean '73 D20T 318 to fix up with no rv stuff in it and only 68,000 miles. It was used as a job site office and bed for security guard. Then as it goes when ur not looking u find what ur looking for. On craigslist (while searching for parts) I found a D20T 318 116,000  for sale in St Louis from the orginal owner. They drove it to Alaska in summer and Colorado in winter. really nice shape and clean and complete. I flew right out and drove it home. It already has disk brakes, (a upgrade that I wanted to do to the first one). Inbetween the the D20t's I bought a '75 indian m400 D23 for parts. Runs great 440-3 with headders. roof leak that never got taken care of. chassis is clean and good with only 67,000 miles.

I noticed that it has bigger disk brake calipers. I was told (Mike on Goodoldrvs.com) that I could change the complete axel from the 75 (really '74 chassis) to my '73 RM300 D20T. The axel is a bolt on and is also 4" or so widder per side. This would make it more stable for cross winds with a wider track. I thought the twin pistion calipers would be better) (also note that the '75 had 16" wheels that cleared the calipers on it)   

Anyway, a lot of info and everybody is probley confused.  also all 3 motorhomes have 8 lug wheels. 1st one has new 16" the st louis one and the '75 have 17.5 wheels. (when I bought the '75 the owner kept the 16" chevy wheels and put the orginal 17.5 wheels back on)   

That's my background on my question>> what do you guys think of changing the front axle, and would the twin pistions and axle be a good upgrade?     

I don't know what the rear brakes are (drums I know) and what master/boosters I have. the '73 r under the driver attached to master cylinder (pain to put fulid in) and the m44 '75 has 2 boosers mid way on the chassis.      tha't for ur time and have a great safe day. John

[DaveVA78Chieftain]

As far as "is upgrading to front disks a good thing to to do?" I think Tom's post 11 above says it all.  However:

1.  Reread Tom's post 11 above.  Especially the "A few more specifics" section.  Not sure if your donor stuff is compatible.

2.  Review the configuration data in the Dodge MH Service manual to better understand piece part combinations.  I have a lot of that info assembled here: http://dave78chieftain.zxq.net/DodgeRBrake.html

Dave

[John Robinson]

Thanks, My '73 has single disk brakes, I wanted to know if the 2 pistion system would be a good upgrade.or not really worth the work.

[DaveVA78Chieftain]

I do not feel it would gain you anything.  Your 20' rig does not have the same GVW my 27' M400 has.  These single piston caliber units should be more than adequate for your GVW.

Dave

[Jonbbrew]

I want to do this but not sure how to start to get a donor. Not many options around here. Do you donor searchers just contact every wrecking yard in the phone book one by one until someone says they have a....? Mine has been changed to or had originally 5 lug but they are 19.5 already. M400 (M375)

[M & J]

Many larger yards have a parts network. If they don't have what you want they can enter the request on the parts search and any yard that has it can ship it.

[Jonbbrew]

Many larger yards have a parts network. If they don't have what you want they can enter the request on the parts search and any yard that has it can ship it.

Thanks. Well, not exactly what I should be asking for. Do you know when there was a option for front disk for a M400 (M375) for 1973? Seems like it wasn't until later, but still not sure what year or what model will fit my earlier year...and with 5 lugs.

[DaveVA78Chieftain]

I do not recall anyone who did this sort of change out on a M375 chassis.   
From the size perspective, that would be the M400 (also known as RM350).  It had dual piston disc up front with 13"x3" in the rear.

The M375 was produced until early 1973.   It was replaced by the RM350 chassis in late 1973 which was then renamed to M400.

So, you would be treading into new ground.

[Jonbbrew]

So are you saying the stock brakes are adequate to not bother with a change to disc since no one else has attempted it?