Changing from front Drum to Disc Brakes

Rickf1985 · May 27, 2016, 11:34 AM

Unless you are driving this thing full time then drum brakes are just fine unless you plan on overloading them. Keep them adjusted and maintained and they work just as well as discs. Even better if you ever lose power.

DaveVA78Chieftain · May 27, 2016, 01:46 PM

Quote from: Jonbbrew on May 27, 2016, 01:27 AM
So are you saying the stock brakes are adequate to not bother with a change to disc since no one else has attempted it?

I do not believe I expressed an opinion either way. I only said I do not recall anyone who had performed this on a M375 chassis so, research around this, determining if parts are interchangeable, and actually performing it would be new ground you would have to invest in.

khantroll · May 31, 2016, 10:08 AM

I have done a great deal of research on this. Jon, you would need to swap the front axle of a 1974 or newer m400 chassis. Technically, you only need from the king pins out, but then you'd also have to re-jigger the steering stabilization on an M375, and it will be a bigger pain to get just those parts. The only parts that can't be bought new are:

Caliper Bracket
Dust Shield
Hub

The cost is high. The only set of the above parts I have been able to locate was close 700 bucks for just those parts, plus shipping. And you still have to buy the calipers, rotors, rims, etc.

I am not saying don't do it, but I'm fighting with myself on it personally. I hate drums, and this has long been one of my two biggest upgrade goals for this rig. At the same time, the expensive in both time and money is much more then I expected.

This is a quick reply as I am currently at work, but if there are specific questions I will do my best to answer them.

jbullet · February 16, 2017, 03:48 PM

I'm the proud owner of a 1973 D-22 (Dodge M375 chassis) and am in the middle of (pretty much all of) the customary fixes involving the chassis. In particular, I'd prefer swapping out in favor of front disc brakes, and read this chain with interest -- thanks to all who contributed. Any ideas on where to find a donor vehicle for the caliper mounting plate, etc.? Comparing brake systems, it appears that the best match to my vehicle (M375) would be front disc brakes from an RM350 or an RM400 in model years ranging 1973-75 or so. As an alternative, is Geoff at Alretta Truck still available to provide these parts?

Thanks for your help, and your patience

Rickf1985 · February 16, 2017, 04:36 PM

I am going to throw in a question here and see if anyone has a real good answer to it.

What exactly is wrong with drum brakes? Keep in mind I am a retired master mechanic so I have worked on both drum and disc brakes extensively on everything from pick up trucks to class 8's.

khantroll · February 16, 2017, 08:26 PM

Hi Rick,

Disc brakes are easier to inspect. Disc brakes take longer to succumb to brake fade. They also don't collect water in the drums. Drums have the advantage of (typically) longer wear, and more friction surface area. The high clamping force of the discs, plus larger calipers can compensate for that advantage.

On the M375, there is also the issue that our parts are more expensive and pain to get right.

I will also fully admit that I have had many bad experiences with drums (both in operation and working on them). So I am somewhat biased against them.

BrandonMc · February 17, 2017, 10:09 AM

Quote from: Jonbbrew on May 27, 2016, 01:27 AM
So are you saying the stock brakes are adequate to not bother with a change to disc since no one else has attempted it?

definitely adequate, and maybe a lot more trouble than it's worth, but up above there he says they're in now and he's very happy. no brake fade.

brians1969 · February 17, 2017, 12:13 PM

I have had more problems with sticking/frozen calipers than with wheel cylinders.

khantroll · February 17, 2017, 09:05 PM

Hi Brian,

I have had the opposite problem. My disc brake vehicles are trouble free, but drums not so much. In fact, tomorrow morning I've got to hammer drums off of my dodge daily driver because the shoes have over extended and stuck. In the past, I've had issues with the locking in the on position, leaking wheel cylinders, etc.

The above being said, if I hadn't gotten the M375 chassis I probably wouldn't bother with it. There are so many pain in the neck issues with that chassis related to the brakes that I'd like to get away from it, and I'm sentimentally attached to my coach.

Rickf1985 · February 18, 2017, 09:03 AM

Quote from: khantroll on February 17, 2017, 09:05 PM
Hi Brian,

I have had the opposite problem. My disc brake vehicles are trouble free, but drums not so much. In fact, tomorrow morning I've got to hammer drums off of my dodge daily driver because the shoes have over extended and stuck. In the past, I've had issues with the locking in the on position, leaking wheel cylinders, etc.

The above being said, if I hadn't gotten the M375 chassis I probably wouldn't bother with it. There are so many pain in the neck issues with that chassis related to the brakes that I'd like to get away from it, and I'm sentimentally attached to my coach.

Ok, There is a good example of why you do not like drums. First off, you should never have to hammer them off. Back off the adjustment and then the drums will come right off. But in any case the problem here is that the drums were not turned as they needed to be at the last brake change. When drum brakes are maintained properly and serviced regularly there are no problems. If the brakes are fading there are a couple things going on, one is that you went into a hill too fast and are riding the brakes and another may be related to what you are experiencing with your drums. They may be worn past the usable limit and at that point they will fade quickly. Also is the fading due to the drum brakes or the fluid boiling? Old fluid will boil pretty quick and even quicker in disc brakes.

I am not using you as an example, just what you presented so that it makes it easier for others to see what I am saying. Yes, drum brakes are much more labor intensive to work on but they are every bit as effective as disc brakes. As far as stopping power it takes a lot more hydraulic pressure to stop disc brakes. Drum brakes are self applying. If you lose power to the power brakes I can assure you that you will wish you had drums every time. Water on the shoes is only an issues when you run in water deep enough to get it there. That is not often for most people and if you apply the brakes lightly for a half mile or so they dry off very quick. Pads get wet also, it is only because of the extreme pressure that they dry faster.

My only point here is that it is not really worth the money to try to convert to disc brakes unless the parts are readily available. If you have to spend thousands of dollars and end up with a vehicle that is next to impossible to get parts for on the road it simply was not worth it.

M & J · February 18, 2017, 10:58 AM

I mostly agree with Rick. Our classic VW has drums and there are plenty of aftermarket disc kits for it. But I put in a rebuilt OG master cylinder and wheel cylinders, cleaned the springs and shoe hardware, replaced the fluid, bled and adjusted the shoes. Stops on a dime with no fade.
I wanted to retain the originality of the car and didnt want to spend $1000 on a conversion kit. Before anyone says theres no comparison, the systems are proportional to the weight and size. Once set its very easy to maintain and no hard to find parts.
Our woods buggy does have discs but its in mud, water and are abused and self cleaning and drying are a must off road.
My thought is if its not broke dont fix it.

khantroll · February 18, 2017, 04:10 PM

Hi Rick,

I mostly agree with you. On my dodge, the issue is that they are over extended to the point that you cannot reach the adjuster to retract them. I have seen this happen in both situations in which the brakes were used way past their service life, and I have seen it happen when the adjusters have failed. I'll be perfectly honest, my current situation is probably the former. Either way .. it's hammer time, and I will say that most people I know who put a lot o miles on a non-fleet vehicle with disc drums wind up banging them off at some point.

Here is the problem with the M375 though: repairing the drum system will cost nearly as much as the disc conversion, and there are two other benefits to switching to disc brakes: better parts availability, and no more budd rims. I am also much more comfortable working on the disc brake systems. The parts to the disc brake system are available from most parts houses, where as the M375 drum parts are a royal pain. You more or less have to find a NAPA, and the part numbers may not match (as was recently discovered by another user). And the drums and boosters are only handled by two companies (who are kind of expensive).

As for losing power, I can't say I've ever had that issue in a vehicle equipped with power drum brakes.

PipefitterGuy · April 16, 2017, 01:34 PM

I have a m500 chassis 27' Winne. I have completely renovated her, so some weight was added. I am also thinking of changing the axles with modernized axles from a larger truck. Has anyone ever done this? If so, what did you use?

Thanks, Curt.

Oz · May 07, 2017, 10:54 PM

Any1?

Rickf1985 · May 08, 2017, 08:21 AM

I would suggest keeping an eye on this thread, He seems to have done a lot of research between himself and Dave.

http://www.classicwinnebagos.com/forum/index.php/topic,13764.0.html

Ronnybass · August 28, 2019, 02:29 PM

Tom, Dave or anyone,
Doing some home work on a drum to disc brake swap.
I have a 1972 M300 chassis

Ronnybass · August 28, 2019, 02:33 PM

Sorry I hit the wrong button and sent the wrong info.
Hat would be the disc brake info for the parts I have D:oH!

Ronnybass · August 28, 2019, 02:55 PM

Here is what I have.
Rick pointed out the GVW differences and he has a great point( will the disc brake set up on the 75 M300 be heavy enough?
It also has 17.5 8 lug (not split) rims.
Looking over all the posts on this topic it appears that this disc brake set up will work but would like to hear from all of you and your experience, thank you.

Swapping out the PV instructions would be great!
DoesnÃ¢â,¬â,,¢t look like they just mount right up.

DaveVA78Chieftain · August 28, 2019, 08:15 PM

Your best starting place is to get the Service and Parts manuals. They contain most of the reference information you are looking for. I am almost certain the brake boosters are different model. Master cylinder is definitely different (drum vs disk). I think there may be issues with the steering linkage.
Sorry for slow response. I am in the middle of moving to a new house.

Ronnybass · August 29, 2019, 02:44 PM

ThatÃ¢â,¬â,,¢s ok, I understand.
I have the M 300-375 Chassis manual in print(came with the coach when I bought it)I also bought a couple from the your store and gonna get the new one also that covers the 75Ã¢â,¬â,,¢. And IÃ¢â,¬â,,¢ll start diggin and dig in to the posts again and make notes

On the booster/MC set up:
Thanks IÃ¢â,¬â,,¢ll take a closer look;
they look just like my 72 and what you show on your page, Bendix Master-Vac same set up and mounted the same way.
All these parts are free and IÃ¢â,¬â,,¢m gonna go back and grab the whole set up so at least I can get part numbers.
The MC and PV are different for sure.
Hope Tom can weigh in with details with what he did on the PV plumbing.

Steering linkage:
Good point, IÃ¢â,¬â,,¢ll dig in the manuals and measure and eyeball things.
The spindle measures the same and from what I have read in the past posts will interchange; or I can Tap the one hole for the caliper mounting bracket.

I think IÃ¢â,¬â,,¢ll run back down and grab all that is relevant before it gets crushed🙁
Thank You Dave for all you and everybody do!
Any more thoughts or advice would be appreciated.