The Dodge Challenger Message Board

Eddie wrote:Cool, then I would do as Dave suggests.

cheers Eddie, I know you do it to the letter mate. between you all its the world of knowledge no doubt and all very appreciated.

Sorry Bro,,Ive been retired for a while, and with no 2 legged kids, and tend to forget the 'struggle'. Try and remove the crusty outer lip inside the drums, makes re-assembly easier

Could be in luck this week as I might be able to source the parts in the UK, Adrian has a connection so fingers crossed.

Ok managed to whip off the rear drum and cylinders....

Check em

Oh and guys, I very very very annoyed and fit to KILL...

When I whipped off the the rear tyre I found this..........








SCUMBAGS.........

Yea those cylinders are done, and wtf happened in the last pic>?

Somebody tried to torch my challenger mate

How do I get the MS off the firewall

New MS

So you got 11X3 inch drums out front and 10X2.5 inch at the rear? I'll get onto me parts monkey right now Wayne, this 'll surprise him cos it was him who said they'ed be the same all round

The master cyl is attatched to the bulkhead by 4 studs and nuts, or bolts, accessed under the dash mate if I remember rightly

Adrian Worman wrote:So you got 11X3 inch drums out front and 10X2.5 inch at the rear? I'll get onto me parts monkey right now Wayne, this 'll surprise him cos it was him who said they'ed be the same all round

It appear that way mate yes, Im glad we waited until I got the rear drum of to measure eh??

So that 2 front cylinders and 2 rear, two front 2 x 11"x3" shoes and rear 2 x 10" x 2.5" shoes.

Adrian Worman wrote:The master cyl is attatched to the bulkhead by 4 studs and nuts, or bolts, accessed under the dash mate if I remember rightly

Yeah I tried to get a spanner on em and I was like WTF.......Id say your right and Drew said the same, the nuts secure the MS to the bulkhead under the dash so I will need to get under there to whip it off...

Looks like my posts from my mobile last night didn't make it here.

The master cylinder you have there is for a disc brake car. Not drum. However you can still use it as long as either both outlets have residual pressure valves fitted. Or both not fitted. I can't remember which at the moment.

Drum brakes on the standard Challenger measured 10 X 2.5 inches front and rear.
But on the R/T you got 11 X 3 front and 11 X 2.5 rear.

So your car should have 11x2.5" brakes on the rear.

Just to add to the confusion. Cars that came with discs at the front came with the 10" rear drums.

My brain seems to have lost my brake knowlege. I can't remember if the front wheels or the rear have to lock slightly first in order for the car to stop straight?

It is completely gone from my memory. So you will have to look it up. I have probably written about it somewhere on here.

dave-r wrote:Looks like my posts from my mobile last night didn't make it here.

The master cylinder you have there is for a disc brake car. Not drum. However you can still use it as long as either both outlets have residual pressure valves fitted. Or both not fitted. I can't remember which at the moment.

Drum brakes on the standard Challenger measured 10 X 2.5 inches front and rear.
But on the R/T you got 11 X 3 front and 11 X 2.5 rear.

So your car should have 11x2.5" brakes on the rear.

So perhaps the previous owners or the original ower opted for that spec on the build sheet?

No. 11" drums front and 10" drums rear was not an option.

Likely the car was robbed of some parts to build another project, and then some one just had some drums lying around that no one wanted, probably free, and they got used. With these old vehicles any sort of robbery and pillageing has usually been carried out in its dim and murky past, half the fun I'd say

Ideally you should have a bit more braking force at the front rather than the rear anyway (I am remembering now ).
I had to reduce the force to my rear brakes when I fitted discs to the front as the rears were loking up.

I just looked this up;

Maximum braking performance occurs just before brake lockup, as a sliding tire has less grip than a rolling tire, thus tuning brake balance is all about controlling when the brakes lockup. As max performance obviously will occur when all 4 tires (& associated brakes) are doing the maximum work, an ideal brake bias is one that locks the front and rear brakes at the same time. In practice however, locking the rear tires typically result in a rapid spin, and locking all 4 wheels results in a slower spin, especially if the car is trail braking. For this reason, some “extra” front bias is normally used, because when the front brakes lockup the car remains stable (but you lose the ability to steer the car – it just goes straight) and this allows the driver time to recognize the brake lockup and reduce brake pressure to regain max braking performance and control.

I think Ade is right, it seems down through the years it was take what you can to get it running etc.

So do I stick with the 11" and 10" Combo?

Yes. You might find that the fronts brake too well compared to the rears but that is WAY better than the other way around. At least if the fronts do lock up faster than the rears it will still brake straight.

My worry is the new master cylinder for the reasons I already stated.

Well you will have to use the brake booster with that new master cyl, due to the way it mounts, he can rob that off of his 72, it will work, but the front res. is larger than the rear for use with disc brakes in the future

drewcrane wrote:Well you will have to use the brake booster with that new master cyl, due to the way it mounts, he can rob that off of his 72, it will work, but the front res. is larger than the rear for use with disc brakes in the future

Don't understand that Drew.

Why would he need a booster? In fact the booster mounts completely differently. Higher up on the bulkhead and he would need a bell-crank lever on the brake pedal to operate it.

It will be a straight swap on the existing mounts. But someone needs to look up residual valves and sort that issue out.

dave-r wrote:

drewcrane wrote:Well you will have to use the brake booster with that new master cyl, due to the way it mounts, he can rob that off of his 72, it will work, but the front res. is larger than the rear for use with disc brakes in the future

Don't understand that Drew.

Why would he need a booster? In fact the booster mounts completely differently. Higher up on the bulkhead and he would need a bell-crank lever on the brake pedal to operate it.

It will be a straight swap on the existing mounts. But someone needs to look up residual valves and sort that issue out.

The non power unit has the mounting bolts under the dash, the the power assist unit bolts from the engine side,not sure if you can use new bolts but it mounts differently

Also if you use the disk master cly. you will have more volume in the front causing the fronts to lock up prematurely ,

and doing the complete swap of the system requires more work there,

for instance the manuel cars have the plate bolted from the dash side, this has to be removed to install the booster system,

and the studs that hold the non power brake plate on have to be removed, in order to mount the booster plate ,under the dash , you will have to grind these studs off(they are welded to the firewall) and make it smooth for the bolts to hold the power booster on.

you will also have to change the prop.valve

It will be much better to buy a new non power master cylinder , and install that and not have to worry,

I just been speaking to a mate at a local parts store, he said the 11" front drums are listed on his parts manual as a "Police spec brake option , to include 10" rear drums". Also says that the master cylinder is the same part number for drum or disc, manual or power assist, not sure if thats quite right so I'm gonna pop in there tomorrow and have a look, its only 20 minutes away.
Keep you posted .

Adrian Worman wrote:I just been speaking to a mate at a local parts store, he said the 11" front drums are listed on his parts manual as a "Police spec brake option , to include 10" rear drums". Also says that the master cylinder is the same part number for drum or disc, manual or power assist, not sure if thats quite right so I'm gonna pop in there tomorrow and have a look, its only 20 minutes away.
Keep you posted .

All 1970 R/T cars came with 11 inch drums all round. Owned one myself you know.
You only got 10 inch drums on the back of the R/T if you had discs on the front. The parts manual also only lists 11" OR 10" drums front and rear.

The two types of master cylinder. Note the residual pressure valves for the drums. Two in the drum master cylinder and only the one on the disc master cylinder.

I have the complete 1970-71 parts manual on the USB stick around my neck.