What makes a front 3 inch drum not work on the rear?

[MoPar~Man]

Assuming you're set up with 3-inch rear backing plates, what says that a front 3-inch drum won't work / fit ?

Bonus question: Would it really be out of line to have rear 3" and front 2.75" ? Would you do it if your alternative was 2" rear and 2.75" front?

 

[CBODY67]

Last time I looked, the 1x3 drums and linings were the same for front and rear, if the backing plates, f/r, will tolerate the 3" wide drums.

Many Chrysler Corp vehicles and other brands already have an issue of too much rear brake, leading to rear wheel lock-up in panic stops, so why make it worse? Especially when only a driver is in the car. A full load of passengers and luggage should be what they are set up for, as a worst-case scenario.

CBODY67

 

[MoPar~Man]

Someone posted (on FABO) a set of 3" rear brakes (fully assembled backing plates with all hardware) pulled from what they said was a '68 Fury cop car. No drums. After having just driven through PA with my 2" rears, the idea of 3" seemed interesting. I looked quickly through rockauto, I'd have to double-check but I think I was seeing them differentiate front 3" from rear 3".

I guess you think if anything, I'd be much better off holding out for 2.5 inch rear hardware, or maybe even just sticking with the 2" ?

 

[CBODY67]

IF there wre any differences in the frt and rr 11x3 drums, it might be "external fins" on the front and none on the rear, possibly. Nothing related to fitment, just additional cooling for the front drums vs the rear drums.

I would suspect that 11x2.5" rear brakes should be somewhat easy to find as that is what the later front power disc brake C-body cars used, as I understand it. Many more possible donor cars.

Just some thoujghts,
CBODY67

 

[3175375]

@mobileparts - set us straight, please.

 

[Ross Wooldridge]

One has integral hubs (front) and the other does not. That's my guess. @mobileparts - what say you?

 

[MoPar~Man]

The 3-inch drum size is the only size that could be common between the front and rear wheels. I've never heard of 2.5 inch front drums, and they've probably never made 2.75 inch rear backing plates.

The distance from the hub-flange face to the backing plate would have to be the same (front and rear) for a given drum to work in both locations I would think.

 

[3175375]

One has integral hubs (front) and the other does not. That's my guess. @mobileparts - what say you?

Drums are the same, the hub is swaged on, making them front only. That’s my bet.

 

[mobileparts]

I spent HOURS with the O.P. discussing the situation , with time I did not have @ Chryslers @ Carlisle…..

I will give you all the definitive answers next week when I have time….
I am still tieing up loose ends from the show , sending out orders , taking care of other orders that came in during the show , unloading the van of the extra MOPAR by myself , of course , and putting back all the GM and Ford , that has to go back in the van…. I spent yesterday and today , and will Need tomorrow and Sunday to —- hopefully —- complete everything that must be done…..

I already unloaded the U Haul and got rid of it……

I am working 900,000 hours every day….. And what I get done in that time is 50 times more than anyone else could do it….

I will answer it, once I can breathe…. 9 : 30 at night —-
Back to work , on what I can do here at the house , in my wheelchair…..

 

[413]

@mobileparts, your parts shuffle will all happen in time, so take care of yourself, and don't overdo it!

There is a reason that cars have bigger brakes on the front than the rear. So don't get to messing it up and putting more braking surface area on the rear than the front.

You are not special and physics don't change for your whimsical ideas.

 

[mobileparts]

Unfortunately, Scott / 413 , must do the parts shuffle immediately…..
I leave Wednesday night for my next show….
Craig…..
I have 3 orders I have to pull , pack , and address this
weekend , additionally —- to U P S on Monday…..

 

[cudamark]

Both Wagner/Lockheed and Bendix show different part numbers for just the drum, so, something must be different. Maybe the stud hole for slip on vs swedged? Slight difference in offset and/or center thickness? I know there were 2-3 different manufacturers through the years. Some drums were cast iron and some were steel.