Clear, Consise Brake Upgrade Instructions, please.

[markinnh]

Thank you smilesafari excellent post I cut and pasted the list onto my works documents

[Astro-SS-V8]

Does anyone have the part numbers for the 11" backing plates .....there are none in this area at the salvage yards...so I'll have to go with new ones.

[Cobra]

everyone i've phoned about the new backing plates say they are discontinued and not available if you find someone who has them you MUST tell me

[markinnh]

try autozone, & advanced auto. they are the only stores that could get me calipers for my ford e150 and I called 7 different autopart stores.

[Mr_Roboto]

I got 11" drums when I did my axle swap. Well worth it. If you have RWABS up until 89 or 90 I think) there is another trick you can do, even though I would likely consider it a safety hazard at times. You take the ABS valve and you remove the accumulator spring then put the cap back on it. What this does it it will push that piston out and it will totally bypass the RWABS system. My van always had "soft" rear brakes until I did this. I actually got rear ended between this and the 11" drums IMO. Well that and the dumb kid behind the Excursion's wheel. Nother story nother day.

[1Gary]

This link might resolve the issue if someone wants to buy new parts for their rear end brake 11" conversion.

http://www.mpbrakes.com/uploads/documents/discdrum.pdf

[Smiliesafari]

Good find, Gary. This clears up some questions that the newbes might have.

[Astro-SS-V8]

Does anyone know the bolt spacing on the backing plates and the axle housing diameter . MPBRAKES.com has 11 rear brake kits for 10 and 12 bolt rears but do not have 5 on 5 drums. Just exploring the possibilities.

[Smiliesafari]

The 5 on 5 drums can be had in the aftewrmarket. Here locally they are less than $40.00 each. I have the bolt spacing dimensions as I kept a log on the 12 bolt conversion I did on my Safari. If I remember I'll post those dimensions tomorrow. I keep the log at the shop.

[Smiliesafari]

Here's the dimensions you ask about. These are center to center of the bolt holes.
Top: Horizontal- 3 1/8"
Bottom: Horizontal- 2 11/16"
Top to bottom: Verticle - 2 7/16"
Holes are 3/8"
Center hole for the axle tube: Stock Astro/Safari: 1.95"
Center hole for the axle tube: 12 bolt: 2 3/4"
I don't think it's all that important to have the center hole exact for centering the backing plates. The bolt holes will do that well enough. The shoes are floating on a pivot. They'll center themselves.
These dimensions were the same on the Safari (1996) and the mid 90's Buick Roadmaster that I got my backing plates from. It made the conversion a no brainer swap.

[markinnh]

Well apparently some of these donor vehicles have a different backing plate as the parts I grabbed , the backing plates are totally different and will not work. So if anyone knows a part number and a parts place that may carry them I would appreciate the info. Mark

[MountainManJoe]

This link might resolve the issue if someone wants to buy new parts for their rear end brake 11" conversion.
http://www.mpbrakes.com/uploads/documents/discdrum.pdf

That's a good find Gary. It raises questions about doing brake upgrades, and whether the master cylinder has enough stroke to accommodate the larger calipers people are using.

Don't semi-trailer trucks use drum brakes because they have more surface area?

[1Gary]

The testimonies by members who have done this upgrade is more than enough proof that the upgrade does substantially improve the brakes.Guess work over was a long time ago.Skip has on his van untold miles on his van as well with him traveling across the country to balloon events with at the very least 800lbs of equipment.This site has old timers that has done everything that you can think of on these vans.So if you looking up ref's to do a mod,that's one thing.But if your looking up threads to open a discussion that are ref's,that is something else where train has left the station on that long ago.Beyond what I just said,really not much more can be added.

[MountainManJoe]

Not all of us are on the same train as you, Gary. I hope I don't have more replies like this to look forward to from you.

[Cobra]

This link might resolve the issue if someone wants to buy new parts for their rear end brake 11" conversion.
http://www.mpbrakes.com/uploads/documents/discdrum.pdf

That's a good find Gary. It raises questions about doing brake upgrades, and whether the master cylinder has enough stroke to accommodate the larger calipers people are using.

Don't semi-trailer trucks use drum brakes because they have more surface area?

One of the members posted about the correct Wheel cylinder to use since 2 different bores are listed they found the 1" to not work well with their system but the 7/8" to work perfectly (probable cause is exactly what you mentioned since the original Wheel cylinders are 7/8"). Balance is important and it appears that 1 ton front calipers (larger bore piston) and the 11" rear drums appear to be within the limits of the master cylinders of our vans. I can think of a couple reason why transport trucks use drums but i don't have any facts on that so i'll keep my mouth shut I'm sure someone on here can give a good answer though