Hello everyone,

I've been investigating the disc brake situation and all of the pros/cons in staying with SBP vs BBP systems. I really have decided I would rather not change out my rear axle, so I want to stick with SBP. I was talking with someone that makes kits for BBP Mopars and he said it would be no problem to make one for the SBP.

But here's the catch that worried me--he said he'd redrill a BBP rotor for the SBP. I was curious what other people thought of this! Is that really safe? Would that seriously weaken the rotor? Is this early death waiting to happen?

I had never heard anyone else mention re-drilling the rotors, so I was intrigued and scared at the same time. Wilwood brakes are the only ones I've seen with adapters that do both SBP and BBP but their kit for the 62-72 Drum Abody has a radically different rotor setup than the stock stuff.

So give me some thoughts here.

Thanks!

MJ

It is not a big deal to change rear axles. It takes about 4 hours at home. Just buy new U-bolts. You need 10" drums on the rear to balance the disc fronts anyway.
I dont mind redrilling rotors,,,but it is pricy and if you need to change rotors later it is pricy again.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Yeah my problem is locating said axle around here isn't cheap or easy. I also dont have the ability to shorten the driveshaft myself, or find one with the same 3.23 gearing I currently have. I looked at doing it, and its going to run me $400 ($300 for the freakin axle and $100 for the work I can't do) which kind of defeats the whole purpose of a DIY cheaper disc brake conversion! =(

MJ

There are at least a 1/2 dozen axles that can be put under your A-body with the 5x4.5" bolt pattern. Surely not all of them cost $300 to aquire. Do a search of this site and you should find all the options that are available.

Kesteb--

which ones? From what I had looked at on bigblockdart.com none of them had the same dimensions as the 62 Abody. Drum to drum on my current axle is 53", and the only ones that come close are the F body. So perhaps you could clarify for me what exactly "fits" means and what I have to do to make it "fit" The only close fit I see is an F-body (which I'm not even sure what cars are F bodies).

I could pick up a B body axle from 62, but its the 8.25" and thus pretty darn wide.

Also I need to know what cars I could find comparable gearing in. One of the main reasons I wanted to keep my current 7.25 is because it has 3.23 gears in it now

Also, moving the springs inward isn't so great for handling?

I'm totally new to this so specific info would be helpful.

MJ



**image borrowed from www.bigblockdart.com

Nope. 9" rears work fine with front discs. In fact, 10" rears usually need to be force-reduced by means of a cranked-down adjustable proportioning valve or a set of smaller-bore rear wheel cylinders in order not to lock up prematurely with front discs.

I remember when I lived in the Pacific Northwest and A-body parts were widely available in wrecking yards, at swap meets, garage sales, side streets, Nickel Saver classified ads, etc. Here in the rusty "midwest", such is not the case.

So: Cost of rear axle PLUS cost of shipping(!) PLUS cost of shortening driveshaft and making other adaptations PLUS cost of rebuilding rear brakes...is pretty surely going to exceed $300.

I'm also curious: What six rear axles can you think of?

7-1/4" large-bolt...one.
8-1/4"...two.
8-3/4" w/new replacement large-bolt axles...three.

Are you thinking of other-brand axle assemblies, or...?

I just bought 2 new SBP rotors - ordered Raybestos - they substituted
Bendix - They only fit the 4 piston kelsey Hayes setup - But I think if
you want SBP and disc brakes that is what you get. Everything was
pricey for this setup - Probably out to price out the whole deal with
SBP and then with the LBP and a rear swap - see which is more cost effective. But SPB rotors are available under the following PNs:
Expect to pay about 90 dollars each.

Wagner BD60257
Bendix 141054
Raybestos 76739
NAPA 86739

What a crock Dan! What did the factory supply with LBP discs? 10" drums!
I certainly did not need a proportioning valve on my car with bbp discs and a 7.25 10" rear. Try not to give out inaccurate information just to show how smart you are.

New Lancer Man: The most effective simple setup is a BBP front (Uni-cast) with a 7.25 rear with 10" drums. It will stop your car like you cant imagine. Look for a complete A body parts car for under $300. You can put your 3.23 gears in any 7.25 rear. I put my 3.23 gears from my 65 7.25 into a 76 7.25 with 10" brakes in about an hour and a half. You wont have to shorten your driveshaft or modify the axle in any way.
You will get all the parts you need.

7.25, 8.25, Ford 8" from early mustang or Mavrick, 9" from 57-59 Ford, Jeep Cherokee 89-97?, or if you want to get fancy : Jeep Grand Cherokee with Dana 35 Aluminum Carrier 3.23 gears , rear discs , limited slip,,,,,or Ford 8.8 from Explorer with discs, 3.23.,,,,,all of these except the Dana 35 are available for less than $300. www.spalding.com

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Yeah I priced the entire setup assuming I bought everything new except the spindles and I'm approaching $700. Its certainly more than i'd like to spend =)

Sandy: Ok, I'll bite. You know the odds of me finding a parts car here is pretty low in that most stuff is 80s or newer in yards around here. Tell me what I'm looking for in a 73-76 A body car (models). And how do I deal with the 1" shorter on each end vs. my existing axle?

And why do you mention all those other axles! LOL You know I'm not going to have the skills or tools to adapt that crap to my car =/

PS--anyone have thoughts on the redrilling of the 4.5" rotors down to 4" like the guy building kits suggested??? IF this was doable it might make life a lot easier.

MJ

I think the lug holes are only part of the issue here - The wheel
centering part of the hub/rotor assembly is a different size between
the LBP and SBP if I remember correctly. So I think there also
would need to be enough meat in the hub area to turn it down to
the correct size for SBP to center the wheels properly.

One of the disc conversion kits that fit on the 9" drum spindles
has a 4 or 4.5 bolt circle option. It looked to me that the rotors
were drilled with both patterns. I am not remembering what vendor
made that kit now (Wilwood, SSBC, ???) Also may have been a drag
race only kit - not streetable - I dismissed this option as too pricey
when I started my KH setup - Now that I have all the KH parts I see
it is very comparable in cost.

Hey new Lancer man , I have a friend who is contemplating the same swap-- he has found a vendor that also will produce a small bolt pattern disc. I'll check today & see if I can provide a link. Why not upgrade to 10" drums& dual master cylinder & call it good? L

Relic: Is this the kit you were thinking of? The Wilwood looks so radically different than stock (uses the drum spindles even) that I wasn't thinking there is anyway to get the rotor and adapter plate to work with anything else stock:




The rotors the guy was talking about using jeep rotors and chevy calipers iirc. I have it written down at home. If you guys do have a source on the rotors, please share

And yes, I might just change to 9" finned drums for now in the front or 10" like you suggest. I was hoping that a KH swap wasn't going to be the same price as these $900-$1100 kits but its looking as though its close!

MJ

I went to their web site and read about it again -
It has very large rotors - 11 3/4 inch jobs and
so you get to use 15 inch wheels

Im currently doing a K-H disc upgrade on my wifes 63 Dart and have about 400$ invested in it including the $50 purchase price of the used setup.I was lucky as all of the bearings were good as were the lower balljoints,but the calipers were toast from sitting and they cost $144 from Autozone for the pair loaded with new pads and your cores.I also needed the rotors at $85 apeice.The reason I stayed with sbp is that I already have new set of sbp Cragars with tires and really like the 3.55 gear tht is in the car now.I still need an adjustable prop valve and master cyl. and a few odds and ends.
In my case it was more economical to use the the K-H setup as my wife really wants the Cragars onthe car and we already had them(4 new wheels and tires bought for $250) but I would suggest finding a donar car with the bbp and swapping everything onto your car. A 3.23 rear in bbp should not be hard to find.
HyperValiant

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1960 Hyper-Pac Valiant(rolling test-bed)
1963 Valiant V2OO(Son's summer project,- he just turned 15 )
1972 Valiant 4dr(Daughter Kelly's repair in progress)
1974 Valiant (v8) daughter Kelly's work in progress