I've just replaced the rear shoes on my '67 Dart and ran into some issues fitting one of them (see http://www.moparuk.com/forums/viewtopic.php?t=54883 )
What I need now is some options for the future when the drum will need replacing. Currently it has re-drilled 10" drums, from 5x4" to 5x4.5". From what I can see the drum brake system is original, but it has new shafts. The shoes are 10x1.3/4". Axle is 8.3/4". Wheels 16".
I guess I have a few options, in order of preference..
1. Find a compatible 5x4.5" drum if one exists. I've looked at a few other models (Coronet, Charger etc) but the drum sizes differ. Does anyone know if there is a drum that will fit??
2. Get A-Body drums and have them re-drilled, I'll need to find a fab shop willing and able to do it!
3. Replace the rear brake unit with a later model, options from anyone who knows please.
4. Convert rears to disc, expensive option no doubt. Anyone know what kit would be best?
I would appreciate any help and insight.
Rear drum brake fitment help please
Moderator: Moderators
check out the drums here
http://www.rockauto.com/en/catalog/dodg ... ,drum,1744
each manufacturer lists the spec in the more info
armed with one of your current drums you can get some new ones
pre 73 cars had PCD of 4 inch (mainly) and post 73 cars had PCD of 4.5
so for your post 73 pattern axles you need post 73 drums of correct Inside diameter and depth
next straighten your backing plate
or if you need a new one its going to be axle out time.
you could get rear disks
don't think its necessary
often have a rubbish hand brake
and there would be further expense to correct the brake bias
and in theory you would need a dual circuit master cylinder that was designed for disk brakes
you don't actually have to swap but disks tend to have a bigger reservoir for their circuit.
mind having said all that unless your current drums are worn out I don't see a problem with them having been redrilled for 4.5 PCD provided the holes are centred properly.
the clamping force of wheel on to drum onto flange should be enough to stop any movement
friction between the lot stops wheel studs snapping
loose the friction and you put the studs into shear then they snap
i.e as long as the studs are tensioned properly neither drum or wheel should twist on the flange and the brake drum is fine
Dave
http://www.rockauto.com/en/catalog/dodg ... ,drum,1744
each manufacturer lists the spec in the more info
armed with one of your current drums you can get some new ones
pre 73 cars had PCD of 4 inch (mainly) and post 73 cars had PCD of 4.5
so for your post 73 pattern axles you need post 73 drums of correct Inside diameter and depth
next straighten your backing plate
or if you need a new one its going to be axle out time.
you could get rear disks
don't think its necessary
often have a rubbish hand brake
and there would be further expense to correct the brake bias
and in theory you would need a dual circuit master cylinder that was designed for disk brakes
you don't actually have to swap but disks tend to have a bigger reservoir for their circuit.
mind having said all that unless your current drums are worn out I don't see a problem with them having been redrilled for 4.5 PCD provided the holes are centred properly.
the clamping force of wheel on to drum onto flange should be enough to stop any movement
friction between the lot stops wheel studs snapping
loose the friction and you put the studs into shear then they snap
i.e as long as the studs are tensioned properly neither drum or wheel should twist on the flange and the brake drum is fine
Dave
The Greater Knapweed near the Mugwort by the Buckthorn tree is dying
Thanks Dave,
I think it has the same axle (8-3/4") as original but the drums were re-drilled. They fit ok but only on their respective sides ie. left won't fit right. I guess it was a diy job.
They snug up fine and the foot brake efficiency is fine for the MOT, only the handbrake failed this year. It was suggested I renew the shoes and cables, and that is how I discovered the problems.
Looking at the later drums on RockAuto, they differ in Hub ring size and "height" ( I guess that's from bolt face to back edge?). I'm going to have to investigate a little more as to what's been modified on my drum. If I have later shafts then the hub ring size should match the later drums, and so I would only have to worry about the 'height'. Mine has 1-3/4" shoes and most later ones seem to be 2' or 2-1/2", would later shoes still work with my backing plate and springs etc??
Regards the backing plate, I thought this would be cast ie. difficult to straighten?? I didn't want to whack it, in case I shattered it!
Much head scratching!
I think it has the same axle (8-3/4") as original but the drums were re-drilled. They fit ok but only on their respective sides ie. left won't fit right. I guess it was a diy job.
They snug up fine and the foot brake efficiency is fine for the MOT, only the handbrake failed this year. It was suggested I renew the shoes and cables, and that is how I discovered the problems.
Looking at the later drums on RockAuto, they differ in Hub ring size and "height" ( I guess that's from bolt face to back edge?). I'm going to have to investigate a little more as to what's been modified on my drum. If I have later shafts then the hub ring size should match the later drums, and so I would only have to worry about the 'height'. Mine has 1-3/4" shoes and most later ones seem to be 2' or 2-1/2", would later shoes still work with my backing plate and springs etc??
Regards the backing plate, I thought this would be cast ie. difficult to straighten?? I didn't want to whack it, in case I shattered it!
Much head scratching!
-
shovelheadrob
- Posts: 959
- Joined: Tue Sep 18, 12 10:27 am
The brake drums should be "hub centric" so the holes for the wheel studs are not critical, as Dave said they are just clamped by the wheel & wheel nuts. The back plates are steel & can be straightened with the application of a hammer, press or even a bit of heat if required without too much worry.
I've got discs on the back of my car, it came with them already fitted, I can only use 15" wheels, the parking brake is absolutely useless, I'm going to have to re-engineer it to get it up to mot standard. Fortunately I have a very understanding tester!
I think that the later (73 up) brakes use a deeper back plate so your choices are stick with what you have, replace with like for like & get the new drums re drilled or do it yourself, or find a complete set of later brakes. I'm not 100% sure if this would work as I can't remember if the axle housing flange to axle shaft face distance is the same between 4" & 4 1/2" axles. Blue might know.
I've got discs on the back of my car, it came with them already fitted, I can only use 15" wheels, the parking brake is absolutely useless, I'm going to have to re-engineer it to get it up to mot standard. Fortunately I have a very understanding tester!
I think that the later (73 up) brakes use a deeper back plate so your choices are stick with what you have, replace with like for like & get the new drums re drilled or do it yourself, or find a complete set of later brakes. I'm not 100% sure if this would work as I can't remember if the axle housing flange to axle shaft face distance is the same between 4" & 4 1/2" axles. Blue might know.
You can't have too much power, only a lack of traction!
An A Body 8.75" axle uses a narrow 1.75" wide shoe and 4" PCD. Other axles with 4.5" PCD use a 2.5" wide shoe. The bearing to hub face distance is different and specific to the shoe width, meaning you can't swap on the wider 2.5" brakes even as a complete assembly to a redrilled A body shaft. The only way you can use the wider brake assembly is either using a shortened and resplined 4.5" PCD shaft or custom aftermarket shafts.
“This ain’t no party, this ain’t no disco, this ain’t no foolin’ around”
ah ha
so you'd need to buy the original style 4 inch pcd drums and get them drilled by a man with a nice accurate machine
other than that the internals are most likley the same as everything else provided you get the correct diameter stuff
eg handbrake strut from a 9 inch drum doesn't work in an 11 inch drum etc
but springs and mounting hardware much the same
i have 60s style aussie made brakes with 73-on pin cup and spring mounting of the shoes and 73 on auto adjuster hardware
running with canadian 9 inch drums and US springs and wheel cylinders
it works
Dave
if stuck
these guys can reline any shoe pad or clutch.
don't be put off by the grotty shed and abysmal working conditions
they do a good job
http://www.autoandindustrial.co.uk/inde ... tactus.php
Dave
so you'd need to buy the original style 4 inch pcd drums and get them drilled by a man with a nice accurate machine
other than that the internals are most likley the same as everything else provided you get the correct diameter stuff
eg handbrake strut from a 9 inch drum doesn't work in an 11 inch drum etc
but springs and mounting hardware much the same
i have 60s style aussie made brakes with 73-on pin cup and spring mounting of the shoes and 73 on auto adjuster hardware
running with canadian 9 inch drums and US springs and wheel cylinders
it works
Dave
if stuck
these guys can reline any shoe pad or clutch.
don't be put off by the grotty shed and abysmal working conditions
they do a good job
http://www.autoandindustrial.co.uk/inde ... tactus.php
Dave
The Greater Knapweed near the Mugwort by the Buckthorn tree is dying
Yes diameter wise the majority of the components will interchange, the handbrake strut is also width specific though. 4" PCD and naarrow rear brakes are such a pain in the arse on A bodies. Why the hell Chrysler tooled up for different parts for these cars is beyond me, they should have just raided the parts bin and cobbled something up like they normally do.
“This ain’t no party, this ain’t no disco, this ain’t no foolin’ around”
Thanks Blue, that's solved that problem! I thought there would be issues with wider drums, I guess re-drilling is the only option for now.Blue wrote:An A Body 8.75" axle uses a narrow 1.75" wide shoe and 4" PCD. Other axles with 4.5" PCD use a 2.5" wide shoe. The bearing to hub face distance is different and specific to the shoe width, meaning you can't swap on the wider 2.5" brakes even as a complete assembly to a redrilled A body shaft. The only way you can use the wider brake assembly is either using a shortened and resplined 4.5" PCD shaft or custom aftermarket shafts.
Dave, thanks for the info, I'll check those guys out. At least I now spare shoes for re-lining in the future .
I'll look into brake upgrades as and when the mot guy looses his sense of humour!
I think this article about sums up the problem, with various solutions http://www.hotrod.com/articles/mopp-991 ... t-pattern/