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Discussion Starter #1 (Edited)
Time for new front brakes, nbd, routine. At the parts counter when selecting pads I'm asked "with 2.5in rears or with 3.5in rears". I assumed 3.5in rears because in the past there have been instances where catolog asks 7200gvw or 8600gvw and I ended up needing the later. Knowing this, I figured the 2.5" vs 3.5" related respectively. An example would be I required 8600gvw rotors that are sandwhiched in hub, rather than 7200gvw rotors which clearly don't.

So when the time came to do the deed, and not owning a lathe, I obviously was replacing rotors as well. Lots of other things got tended to while it was on jack stands (hub bearings, ball joints and control arm bushings) but when it was time for new pads in caliper to slide over new rotors, there wasn't enough clearance. The pads where to big!

Having an appointment first thing the next morning for alignment, I just put in the new inner pads, and had no choice but to assemble back using the old outter pad. The inner's that I took off where worn all the way to the back plate, so the decision was pretty clear which half to use to limp the 0.3mi to tire shop.

I leave a note in the truck explaining the brake scenario, the consensus was I must have gotten the wrong pads, because there is no way they are fitting as is. Also, they weren't able to complete alignment because something about the control arm bushing mount needing to be adjusted which they didn't have time for that day. :mad:
This was a Friday, just last Friday actually, the day before the Sebring Endurance Race, of which I haven't missed since I knew it existed haha. Knowing this year was going to be a struggle I had spent a huge amount of effort creating the freedom to fall off the grid for a weekend only to not have a vehicle. CensoredCensoredCensored

Let's get back on topic shall we? So pads, and other parts I just installed:

Wheel hub bearing
Rotors
Pads that DID fit
Pads that DIDN'T FIT

So finally all buttoned up with new brakes, hubs, etc. and braking performance is seriously lacking. Knowing the rears at minimum need adjusting, I begin to do so. Left side, I could tighten down without much resistance, right side, quite the opposite. I hit up my buddy at earlier mentioned tire shop and thankfully was a slow day for him. Get there, get drums off, right side wheel cylinder has visible leak :shake:
Further inspection showed the shoes where beginning to crack; I just so happened to already have new shoes because I had a coupon a while back that needed redeeming. I choose the 3.5" because of all of my accumulated knowledge, but this was months ago. So I'm sweatin they are even the right ones, but bring 'em out the box and sure as sh!t, 13x3.5" rear brakes.
My buddy having the available time aided me in replacing everything, hardware, adjuster screws and all. He ordered the wheel cylinders from Napa, but I don't know which version he got (I'll confirm tomorrow and update). Between these two I would assume he got the one's specified "For 13" brakes" because they are a 13" brake, and the other one only specifies 7200gvw. Neither defining 13x2.5" vs 13x3.5" or 7200 vs 8600 I don't even know what to think anymore. Napa has always had (in my experience at least) very clear specifications, or special notes in descriptions when an option or detail of vehicle determined replacement part. This one slipped though the cracks I guess.:confuzeld


Any thoughts?
I would be extremely surprised if some how my [alleged] 8600gvw truck at some point in it's life before me got calipers that came from a 7200gvw. Because that would mean the knuckles would have to be 7200gvw as well, (right?) and my knuckles are the ones that fit the rotor/hub/bearing combo which designates 8600gvw....right??:think:
I'm only getting more confused the more I try to apply my limited knowledge here.
 

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Have you checked the rpo codes in the glove box? Maybe someone changed out one of the axles at some point.
 

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The suburbans for some reason seem to be completely complicated when it comes to the brake systems used compared to the trucks. One thing, I don't believe the SRW trucks ever got a 3.5" shoe on the rear, except maybe the 3500 SRW, but not the burbans. You should measure the old shoes to be sure.

7200GVW 11-5/32" x 2.75" rear shoes. Semi-float 14 bolt with 6 lug axles. SRW
8600GVW 13" x 2.5" rear shoes. Full-float and Semi-float with 8 lug axles. SRW
10,000GVW 13" x 3.5" rear shoes. Full-float with 8 lug and DRW.

I believe the suburbans follow the same setups for the most part.
 

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There is also the variant of having the 3.5" wide drums with 2.5" shoes. First time I ran into that I figured someone just got lazy and made things work so I tried to make it 'right'. I was unable to find a combo that made things match even by changing wheel cylinders. My first time was a 87 V20 and the second was my 96 Burb. Both were the 9.5 rears so that may have something to do with the weirdness.
 

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It should go by which brake package your truck or burb was ordered with. A vin decoder site or a GM dealer should be able to tell you which it should have if the RPO code is not visible in the glove box. Here is the spec page from the 95 GM service manual. Something tells me it's not 100% correct either because it doesn't list the 13 x 2 1/2 rear drums.
 

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It should go by which brake package your truck or burb was ordered with. A vin decoder site or a GM dealer should be able to tell you which it should have if the RPO code is not visible in the glove box. Here is the spec page from the 95 GM service manual. Something tells me it's not 100% correct either because it doesn't list the 13 x 2 1/2 rear drums.
That's weird that it doesn't even mention the 13x2.5" rear brakes as an option?

EDIT: I wonder if that's the drum measurement and not the shoes?
 

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That's weird that it doesn't even mention the 13x2.5" rear brakes as an option?

EDIT: I wonder if that's the drum measurement and not the shoes?
:confuzeldAny of my K2500 HDs[8600gvw] that I have worked on the rear brakes have had the 13 x 2 1/2. From what I read somewhere, the 13 x 3 1/2 were available as a option on a K2500. All 3 of my K2500 [8600gvw] burbs have the 13 x 3 1/2 drums.
 

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:confuzeldAny of my K2500 HDs[8600gvw] that I have worked on the rear brakes have had the 13 x 2 1/2. From what I read somewhere, the 13 x 3 1/2 were available as a option on a K2500. All 3 of my K2500 [8600gvw] burbs have the 13 x 3 1/2 drums.
That's strange, burbs are just a different breed I guess. I kinda wish I would have done the 3 1/2" as an "upgrade" when I just did my brakes a few weeks ago.
 

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My burban has a 7600 gvw, but the very large rear drums.... everything on it is 3/4 or 1 ton, but the badge... and the 9.5" axle...
 

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My 6.5 scared a prius
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C6P : GVW RATING, 8600 LBS / 3900KG
 
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