Rear brake size, 10 or 11 inch. How to tell?

[mamatried01]

Where do I take measurements from to tell what size rear brakes I have, 10 or 11 inch?  My self adjuster busted and I need to get a new one. Autozone needs to know what size rear brakes I have.

Thanks

[471_Magnum]

11" drums are fined. 10" inchers are smooth.

The dimension refers to the ID.

If you're dealing with original equipment, they'll be 10" on a non-R/T. R/T front disc cars also came with 10" rear brakes.

[Chatt69chgr]

I am restomodding a 69 charger.  Front brakes will be changed to discs ala A-body spindles with 11-3/4 rotors (need large slider caliper adapters---anybody have any to sell?).  Will be changing rearend to 8-3/4.  The rearend in the car now is a 8-1/4 with 10 inch drums.  I got a set of 11 inch drums and all the rest of the hardware off a 69 New Yorker that I was thinking of using.  Does anyone see any problems using these other than the fact that I will probably need to put an adjustable proportioning valve in the line to the rear.  Seems like the 11 inchers would be a good upgrade.  Also-------I see in the thread that 11 inch refers to the inside diameter of the drum.  When I look up the shoes in Rock Auto, two sizes are referenced.  One is 2-1/2 inch and the other is 2-3/4 inch.  Does this dimension refer to the width of the shoe?.  I think I have the 2-1/2 inch since my rear drums were finned.  Or should I just use the 10 inch drum setup on the car now.  I will need to buy all new parts no matter which way I go.   

[mamatried01]

11" drums are fined. 10" inchers are smooth.

The dimension refers to the ID.

If you're dealing with original equipment, they'll be 10" on a non-R/T. R/T front disc cars also came with 10" rear brakes.

The id of my smooth drum is 11 inches. I don't get it.

[Chryco Psycho]

some 11" drums were smooth , it is not set in stone that all 11" were finned
if the ID is 11" you have 11" brakes , you cabn have different width shoes as well as you mentioned  you need to measure the width of the brake shoes

[Chatt69chgr]

Thanks Chryco Psycho--------Do you think the 11 inch brakes on the back would be a good upgrade since I am upgrading the front to 11-3/4 inch discs?

[is_it_EVER_done?]

Finned or smooth is no indication of diameter as different OEM suppliers provided drums in both configurations for all sizes. The max diameter is cast into the drums on the outside edge so that is the easiest way to tell what size a drum is without having to pull it to measure.

As for shoe width, I would say that 99.999% are 2-1/2 inch. The only wider ones I have ever seen were on Imperials, and once I found some on a Town & Country wagon that had a trailer towing package. You can measure the inside width of the drum across the shoe surface and it should be between a little over 2-3/4 to about 2-7/8 for the drums that take 2-1/2 inch wide shoes.

I'm unclear if you already have 11" drums or not as you state that your drums are finned, but in a previous post you state they are smooth. As I said, that has no bearing on diameter, but I take it to mean that you have two sets of brakes, one from the donor, and the ones that were on your car, and that they are both 11", is that correct?

In any event, upgrading to an adjustable proportioning valve is always a good idea, even with stock brakes, since they are cheap, and you can adjust the proportioning to your specific car, brake lining material, tires etc. Remember that the same stock prop-valve was used in a bunch of different cars - Fords too, so it is only an approximation of what any particular car needs, so it is a worthwhile upgrade, but not necessary if you are happy with the braking performance of the stock valve --- I'm a brake fanatic, but I have a stock prop-valve on my RR vert (12" disks -11" drums), but it just happens to be near perfect for the cars configuration.

As for the caliper adapters you need, you can get them at your local J.Y. from any Cordoba/Magnum, etc. that used slider type calipers.

Other points to consider are if you are going to mount the calipers to the front or rear (I always mount to the rear). If rear mounted, you need to order hoses for a 73 Charger w/disks, as they will fit perfect, and for the rears order complete hardware kits for a 70 Charger RT. The reasons for this is that even though the front hoses were used on other years of cars, there was no changes in 73 so you will get the right hoses, and the rear hardware pack for the adjusters was changed mid year in 69 (improved), so the 70 pack will get you the best hardware.

You will also have to make sure your MC does not have a residual pressure valve in the reservoir for the front brakes when you switch to disks, and if you buy new wheel cylinders for the back, you will have to make sure the RPV is removed (or is not there to begin with) from the reservoir for the rears..

[Chatt69chgr]

Thanks for the excellent information "Is it ever done".  I am sorry I wasn't more specific about my drum sizes.  My charger as it came from the factory (and as it now exists) has the 10 inch smooth drums on the rear.  The 11 inch finned drums and backing plate assemblys came off the 69 New Yorker that I dismantled to get my 440 engine from.  It had an 8-3/4 rear (which is what I am changing to in my restoration--not the one out of the New Yorker but another I got from a 69 B-body).  I understood that the 10 inch brake assemblys currently on my car were the same as used on the 8-3/4 rearend, thus the question, should I go with the 10 incher's I have on the car now or 11 incher's from the New Yorker.  Based on your response, I will plan on using the 11 inch units on the rear and will plumb in the adjustable proportioning valve toward the rear for fine tuning front/back brake action. 

I am converting the front to 11-3/4 inch discs and the hardest parts to find have been the bellcrank used between the power booster rod and the brake pedal and the proper caliper adapters (brackets).  I scored the bellcrank last friday.  I still have not found a 76-79 B body or 79-up R body to get a set of large slider caliper adapters from.  You can find the small slider adapters all day no problem.  Which brings up a good question and since you are a brake afficionado I will pose it to you.  Should I go with pin type or slider type calipers?  I know both will work but I wonder which is considered superior.  Richard Ehrenburg in his "famous" disc-o-tech" article championed the pin type-----claimed the sliders required more maintenance.

Finally, I had planned on mounting the calipers to the rear due to sway bar interference.

[Chryco Psycho]

in most cases the rear brakes need to be limited with a propotionng valve to reduce the braking of the rear brakes so using a larger 11" brake seems pointless Except that thet will have less tendency to over heat on multiply hard stops

[is_it_EVER_done?]

Since you have the 11" drum Assemblies you might as well use them but you could use your 10" setup if you want as you won't notice any difference in general driving around, but if you race your car, or drive/brake hard while dicing through traffic on a regular basis, the 11's will be a more resistant to fade, and offer more modulation before lock-up, of course the same thing is true for the different disk sizes for the front. In other words, the bigger brakes don't necessarily offer "more" braking than the smaller ones, but do offer more potential due to increased modulation and heat handling ability.

As far as slider vs. pin calipers, I used to prefer the pin type because they seemed to release, after being applied, a bit better than the sliders would, but I only use the sliders now days because all the really good pads for the pin type have been discontinued. You can still get pads for them, but not the excellent ones that are available for the sliders (Bendix Fleet Met-Lock pads). Also, it's pretty effortless to maintain the sliders for max performance (maybe 10 minutes per year).

What area of the country are you in? I find it amazing that you are having trouble finding the big caliper adapters, but I guess all parts are getting harder to find anymore. I'm sure I have a few in my storage unit and I'll see if I can find some this weekend (they would be slider type), but I can't promise anything, as it is generally easier to find the Holly Grail than it is to locate anything in my storage unit, but send me a PM with your e-mail or number, and I'll see what I can do.

[Chatt69chgr]

Thanks to Is it ever done and Chryco Psycho for the replys.

Looks like I might as well go with the 10 inch brakes on the rear since I will not be racing the car at all.

I would like to discuss further my plans for the front brakes.  I will be going with the 11.75 inch rotors since I have already bought them.  And your information about the pad availability convinces me that I need to go with the large sliders.  I live in Chattanooga, TN (actually a suburb named Hixson) and have scoured this place pretty good and have not found the requisite adapters (Is it ever done---I will e-mail you my contact information).

As I mentioned, I will be rear mounting the calipers and will use the sliders.  You mentioned that the perfect hose to use was one for a 73 Charger.  Was this when one was using rear mounted sliders?  And which slider caliper do you ask for at the parts store, ie, car make/year. ( Is it a 2.75 inch diameter piston unit?)

My plans for the power booster is to use the Cardone 5473603 which is what is called for use in a 69 Charger. The illustration of it appears to be a rebuilt Bendix dual diaphram unit.  I plan on using a Cardone 101474 master which is a power brake master with 1-1/8 inch bore and lines coming out on engine side which is supposed to be correct for 69.  Cardone also makes the same unit with lines coming out on fender side as a 101404.  I would paint both of these gloss black including the master cover to make them appear correct for 69.

I have two brass combination valves from 70 b-bodys which I cleaned up.  They appear to be reusable but do have rubber parts inside that are 35+ years old.  I was thinking of using the combination valve sold by Pirate Jack (website is www.piratejack.net).  Specifically, the PV2.  It's brass and it's new.  What are your thoughts on combination valves?  I would still plumb in the adjustable valve toward the rear.

I hope I havn't worn everybody out with my questions.  Thanks again to everyone.

[is_it_EVER_done?]

Chatt,  First of all, in re-reading what I posted, I discovered a mistake in that I said the correct front hoses for rear mounted sliders were for a 72 Charger. I meant 1973 Charger. I corrected my post, and would appreciate it if you would also edit your last post so that no gets led astray by my mistake (of all the things I've lost in my life I miss my mind the most).

Make sure you understand that using the big rotors requires 15" wheels. If you have 15's fine, otherwise go with the smaller rotors.

The 73 Charger front hoses are the best ones to use but only for REAR mounted slider calipers on either small or big rotors. I can't offer any help on front mounted since I never front mount them, and can't see ANY reason to do so. The hoses I use are the Raybestos PG plus hoses, part #BH36828. These run roughly $20.00 each. Raybestos makes a cheaper version of this same hose in their Raymold line, but the PG plus version is worth the few extra dollars in my opinion. The Bendix hose is twice as much and I have never been able to tell any difference between the Bendix, and raybestos PG plus, so I use the Raybestos. --- These aren't essential, as they are within a 1/4" of the ones for say a 79 Cordoba, but the later lines have huge ends on them, and cold possibly require a bit of filing to sit flat on some calipers. In fact the 73 Charger lines are listed as alternative replacements for a Cordoba, but the reverse isn't true, so I just use the 73 Charger ones as they will fit on any slider caliper you may end up with.

As for calipers, I always use the Cardone #184102 & 184103 rebuilds (right and left). These are less than $20 each without a core, and I have never had one fail in many years. These are "unloaded" meaning that they don't have pads. Plus they have Phenolic pistons (far superior to metal). If the parts store insists on a year/model, order for a 79 Cordoba (thats the year I use even though they are the same for many years and models). I honestly have no idea what the piston size is, but they are the HD/Police/Taxi ones.

For pads I only use Bendix "Fleet MetLok" pads, part #MKD84FM (use a 79 Cordoba if a make/model is needed). These pads are the best available bar none. This isn't just my opinion, they have been tested against all others, and come out ahead for Police/Fire, and other HD use. You can do a web search if you want to find/read some tests. They cost about $55 bucks, but are excellent in both braking and minimal wear.

I can offer no input on "correct" style parts or numbers for the M/C or booster as I usually go manual with the drum M/C, or use the stock booster (or whatever one I have laying around or can pull at the JY), And I honestly couldn't care less if the brake lines exit to the engine or firewall side of a car. -- Sorry, but I'm not a numbers or originality type of guy. I will say that if you have an aftermarket cam that "sounds radical", you should ditch the power booster due to the lack of vacuum to operate it properly. If you have a stock or very mild cam, you can use the booster with no problem if you want, but the dual chambered boosters tend to over assist the brakes. so I like the A body, or drum boosters, or any single chamber (thin) booster even if it's from a Ford.

Lastly, I'm sure the combo valve you linked to will work fine, but I personally prefer to use a stock distribution valve with an adjustable proportioning valve, due to the fact that if you don't like the proportioning that a combo valve provides, too bad, you are stuck with it. You can always disassemble your stock 69 distribution valve so that you can clean the insides, then add an adjustable (or even a stock) proportioning valve in line to the rear, plus it will cost much less than a new combo valve, but since you aren't looking for Max performance braking, I'm sure whatever choice you go with will work just fine. I have never used a stand alone proportioning valve with a combo valve, but it sounds kind of funky. I can't say if you will have problems or not, but to be on the safe side, I wouldn't, but if you do decide to go that way, post back with your results.

[Chatt69chgr]

Thanks Is-it-Ever-Done for the reply with answers to my questions.  I really do appreciate the time you have devoted to me on this.  You made a good point about the proportioning valve.  Looks like the best thing to do is just use the exisiting distribution block which has the brake warning light switch in it and plumb in the adjustable proportioning valve in the line to the rear.  I would add that I am not a "numbers" type either.  Just mentioned that bit about where the lines exit as there is a lot of controversy about this.  What makes sense is to run the lines out on the fender side to keep them away from the hot exhaust manifold.  Another good thing about using my existing disribution block is that I can order a new set of brake lines for the car as it now sits and know that they will be correct and will fit.

I edited my previous post per your request.  I also sent you an e-mail with my contact info but am not sure if it went thru.  Will resend it after I post this reply.