8 lug SRW brake backing plates same as 14 bolt six lug axle??

[Burning oil]

Does anyone know where I can buy the 13x2.5" 6 lug complete rear drum brakes? They are hard to find around here.
Next thought is, are the 8 lug SRW backing plates the same as ^^^
if yes I can get the drums and the rest new.

 

[handcannon]

Not sure about that one. Would the backing plate for the 13x2.5" 8 lug brake work on the 6 lug? I know they are different in that the 6 lug is semi-float and the 8 lug is full float, but not sure of any other differences.

I did find out that the backing plate will not interchange between the 1994 SRW 13x2.5" 8 lug full float axle K2500 pickup and the 94 Suburban 13x3.5" 8 lug full float axle. The Sub plate sets deeper on the axle and hits the pickups springs before it will mount onto the pickups axle.

Don

 

[Burning oil]

I understand the 8 lug and 6 lug semi float are both 13x2.5" The 8 lug full float is 13x3.5"
The 8 lug semi would work but they are hard to find. So, Im looking at using the 8lug full float bracking plate and redrilling the 8 lug drum to six lug.
Not sure at this point if it can be done, but I want to find out.
The whole reason is the axle (6 lug) in the burb now only has 10 or 11" brakes and it seems a worth while mod.

 

[tanman_2006]

I did a little searching and according to the 2 parts books at the local parts store the 13x2.5 6 lug never existed.

Wondering if filling 8 lug holes and redrilling on 6x5.5 is the only option.

Stock brakes on a 6 lug SF rear is 11 5/8 x 2 3/4

 

[Burning oil]

I did a little searching and according to the 2 parts books at the local parts store the 13x2.5 6 lug never existed.

Wondering if filling 8 lug holes and redrilling on 6x5.5 is the only option.

Stock brakes on a 6 lug SF rear is 11 5/8 x 2 3/4

Nah, I've seen em. You can still get the shoes at auto parts. I've got alot going right now but this project is on the burners, but on very low heat. Have my TDI in Fiero Im working on then the 6.5 back in the burb.

I did look at my 8 lug axle yesterday and its a 50/50 chance the backing plates are the same because either the 8 lug drum is larger to accomadate the 3.5 wide shoe OR the backing plate is offset. I need to get a 6 lug drum and measure it.

 

[Burning oil]

Correction to above. Tanner I think your right, it just hit me the one I saw was a SF 8 lug w/13x2.5" shoes

 

[tanman_2006]

Yeah, there is another option I forgot to check. Supposedly the 6 lug c2500 ex cab had bigger brakes on the rear.

Might see if anyone is brave enough to convert an 8 lug drum to 6 lug at the machine shop. So far the general concensus is I'm crazy because rear brakes don't do anything anyways. One person told me to unhook the brake line and put a bolt in the end and it will work just as good.

 

[handcannon]

I did look at my 8 lug axle yesterday and its a 50/50 chance the backing plates are the same because either the 8 lug drum is larger to accomadate the 3.5 wide shoe OR the backing plate is offset. I need to get a 6 lug drum and measure it.

OK, I hope I can draw up a good visual picture.

I found a 94 Burb in a pick-n-pull with 3.5" shoes. I grabbed the drums, hubs and backing plates thinking I could make them fit my K2500 rear axle and upgrade from 2.5" to 3.5" shoes. One of those spur of the moment decisions.

Well, the backing plates won't fit my axle. The Burb plates have a deeper offset to them, which means they hit the springs before they will touch the axle mounting surface. If you lay those plates and the plates for my 2.5" brakes on a flat surface, the area where they mount to the axle is offset by somewhere around a half inch (just going by memory).

After doing some thinking about it, I'm thinking the deeper offset is to allow the shoes to set farther inwards, keeping the brake cylinder centered in the width of the shoe. If the cylinder was not centered on the width of the shoe wouldn't they create a twist in the shoe when pressure was applied by the cylinder?

Maybe I'm all wet here, but I do know the backing plates are different between the 2.5" shoe and the 3.5" shoe.

Don

 

[Burning oil]

The is what I was thinking might be the case.
Did you get 8 lug plates off the burb? also full float axle right? (as they are 3.5" wide).
Makes sense that the piston needs to be in the center of the shoe.
Is your K2500 6 lug? 13x2.5"?

Side note: I changed my axle in Burb with one from a K2500 and it fit fine. This tells me the spring perches are the same, but is the 8 lug axle wider from the perch to the lug flange then? What Im getting at is where is the difference that the backing plates need different off sets?

 

[handcannon]

The is what I was thinking might be the case.
Did you get 8 lug plates off the burb? also full float axle right? (as they are 3.5" wide).
Makes sense that the piston needs to be in the center of the shoe.
Is your K2500 6 lug? 13x2.5"?

Side note: I changed my axle in Burb with one from a K2500 and it fit fine. This tells me the spring perches are the same, but is the 8 lug axle wider from the perch to the lug flange then? What Im getting at is where is the difference that the backing plates need different off sets?

The axle on the Burb was an 8 lug full float. In retrospect, I wish I had got the full axle housing. The gears and axle shafts were already gone when I first found the Burb, meaning if I used it I would have had to have somebody take the gears out of my axle and swap them into the Burb housing. A short time later when I went back to the pick-n-pull the Burb was still there, but the axle housing was gone.

My pickup is an 8 lug 8600 GVW. I don't know for sure where the difference in axle housing length was at. I had done some measuring and as I remember it the spring perches were close between the Burb and my pickup. However, because of having the pumpkin in the way of accurate measuring I wasn't absolutely convinced at the time that the axle housing would be a drop in replacement. Hindsight is 20/20, right?

Going by my experience and yours I can only conclude that the difference between the two housings would be between the spring perch and backing plate mounting surface. I wish I knew if the axle shafts were different between the two. That would add more info about where to look for the actual difference.

I know the hub is different between the two axles. Brake drum inside the rim mounting flange vs brake drum outside the rim mounting flange. Maybe the difference is made up in how the hub is laid out. I vaguely remember trying the Burb hub on my axle spindle and it not working. Seems like the Burb hub went on too far and the back of the hub hit somewhere in the backing plate area before the inner wheel bearing came to rest in the proper location. At the time I was disappointed enough that I didn't spend any extra time checking out any possible solutions to being able to use the Burbs' brakes.

Since I already have the complete 3.5" brake assembly, drums turned and new shoes, I've been spending some time pondering how I might be able to utilize them with my axle. I'm thinking I might be able to use my pickups current hub, remove the 2.5" drum, and place the 3.5" drum over the outside. Then use the Burbs' backing plate and have a spacer machined to put between the axle mounting flange and the Burbs' backing plate. When I figure I have the time I'm just going to have to tear apart my pickup to see what can be done.

The biggest problem is that we are in our rainy, nasty wind, winter weather now and I'd have to do this out in the weather. I grew up doing farm work after school and weekends no matter what the weather was like and I have a hard time with choosing to work out in the winter weather. I've been collecting parts for one of these 10' X 20' metal frame canopies like you find at Costco, and am almost able to put it together now, so that I would at least have a dry, even if not so warm, place to work in.

Please keep me posted on what you find with your brake project, and let me know of any good or bad things you see about my possible project. Maybe my limited experience may be of some use to you.

Don

ps: I wish we lived close to each other. I'd enjoy being able to see what you are doing, pick your brain, and even lend a hand helping. I love doing these kind of projects where you do something a bit out of the ordinary, have to do a bit of research, and figure out how to make things work. That's why I spent fifteen years installing cabinets, the last few years working in some very fancy and expensive homes with lots of specialty cabinets and wood trim.

 

[Burning oil]

Well your talking about 8 lug to 8 lug differences. Me 8 lug to 6 lug differences, so it can be a confusing thread.
Like you when I get time I going to dig into it more.

 

[tanman_2006]

I'm heading to the auto salvage today. If they will let me look around I'll report back. We dont have many pull it yourself yards and the only local yard is owned by some worthless guy that only crushes cars usually.

 

[Burning oil]

Found some time to get some rough messurements. Looks like Im very close to the same boat as Don, but this is using 3.5" backing plate off a FF axle. A 1/4" spacer between axle and backing plate "should give" the clearence, but I have not thought through if the spacing affects anything else yet. Might need another spacer between axle shaft lug flange and inside of drum.
If this is doable it give me back my 13x3.5" brakes.
Also, the distance from spring perch to backing plate mount is more (appox 2.5") on the FF. On the 6 lug SF it was 1.75" roughly.
I bet the 8 lug SF axle backing plate is perfect and I'd be happy with 13x2.5" shoes too.

So Don, is your K2500 P/U an SF axle?
Tanner did you see any thing?
I'd like to know the distance from the backing plate mounting (where 4 bolts hold it to axle) to the leaf spring or the spring pearch on the 8 lug SF.

 

[tanman_2006]

Didnt make it today, plans got changed. I need to go by and get a couple wheels soon so I will have to make a trip by soon no matter what.

 

[handcannon]

So Don, is your K2500 P/U an SF axle?

No, it's a FF axle.

All this talk about front brakes (another thread) and rear brakes has got me feeling antsy to try something more with them. Hopefully in the next few days I can finagle some time to finish getting the weather canopy set up and start doing some more with the brakes.

Don

 

[Burning oil]

Didnt make it today, plans got changed.

Happens to me daily it seems.

No, it's a FF axle.

All this talk about front brakes (another thread) and rear brakes has got me feeling antsy to try something more with them. Hopefully in the next few days I can finagle some time to finish getting the weather canopy set up and start doing some more with the brakes.

Don

I know what you mean.