11" Rear drum swap and brake upgrades in general - nerding out

[MomoJeep]

Background
So I've decided to swap my 10" rear drums for 11". I have a hardtop and a backseat and like to be able to carry people and gear on expeditions, plus large tires, and sometimes I tow a boat right at the #2000 max towing capacity... therefore need brake upgrade(s). I plan to go in steps and do the experiment of noticing the effectiveness of different upgrades, as noted below. I know most people probably would just go rear disc. But I like that this swap doesn't require a MC swap, and some other things, including that many say the disc conversion parking brakes usually aren't very good. I was messaging with Moses Ludel back when he used to offer Q&A advice on his website, and he was very much a proponent of the effectiveness of drums (while still noting the drawbacks). He also mentioned that Prop Valve's have another function most don't realize; it engages the rear brakes just before the front kick in, to increase stability when braking.

Brake upgrades and effectiveness
(1) Dual diaphragm MC - I honestly did not notice a significant difference over my stock single-diaphragm (Or maybe my expectations were too high)
(2) Braided SS brake hoses - the idea is that the rubber hoses can swell a little under pressure. Also hard to notice the difference, but gives me peace of mind.
(3) 11" Rear Drums - in progress
(4) Aftermarket grooved front discs and hi-performance pads from EBC performance brakes. They say 20% stopping power. We shall see..
(5) Put surge brakes on the boat trailer so I don't have to do bigger conversions on the Jeep for towing purposes!

I will do (3) before I do (4) to notice the difference of just the 11" brakes. I'll do the experiment for you, so you don't have to ;-)

For the 11" swap
- Luckily the 11" parking brake cables (different mount style) are the same length, but otherwise swap right in. They are for a CJ7, but were never made specifically for a CJ8.
- Welded new "shoe pads" on the backing plates and grinded flat back to original height. There were deep grooves from 40+ years of use.
- Taking backing plates in for blasting and powder coating (today). Apparently powder coat is resistant to brake fluid (paint is not). Possible exception is that "Eastwood" makes an epoxy paint specifically designed to resist brake fluid. I considered a DIY job, but opted for power coat.

Pics to come...

 

[MomoJeep]

Update: The 11" conversion went well. The only hitches were:

- that the "flattened" or rectangular spring that keep the strut bar from rattling between the shoes was not included in the brake hardware kit. And the parts stores did not have any information on it. I wasn't sure where I was going to find one and how I would know if it was the right one for the 11" brakes. Luckily I was able to track it down and source it online.

- One of the backing plates was damaged from a spun bearing, and I didn't notice it until after getting it powder coated. Before pressing on the bearing we measured it, and material was missing about 0.030" deep. This is right where it pressed on the bearing stick-out to get pre-load on the 1-pc kits. I had .050" of stick-out, minus the .030" groove, equals 0.020", which is the minimum stick-out needed. So I rolled with it. Also the groove was not uniform depth. In other place it was almost non-existent. The machine shop guys, as well as the tech at Moser, said not to worry. It doesn't have to be flat. That bearing is going to alight itself anyway under the weight of the vehicle, and being pushed in by the backplate anywhere along the outer race, even if this pre-load pressure is unevenly distributed on the race. I hope they're right!

Other than that, I was a little disappointed that I did not feel a noticeable difference in the braking. However, I'm still very glad I did the conversion, here's why:

Going from 10" to 11" is about a 10% increase in Diameter. (also 1/4" wider shoes, but I'll ignore that for now). So if you assume 10% increase in Diameter translates to 10% more braking power, and then multiply that by 0.2 (rear = 20% of braking), we get 2%. I would not expected to actually feel a 2% difference.

But I'm glad I did it because:

(1) My rear 1-pc axle kit outer seals started leaking, and the retainer plate was warped. I did not know how or why that happened. But now I think I know why. The biggest limitation of drum brakes is that they can't dissipate heat very well. With 32" tires, they are already pushing their limits. Then add towing a 2000lb boat and gear. I have experienced significant brake fade with this setup. Which is due to overheating the brakes. I think that heat is what probably caused the seal/RTV to leak and possible also the retainer plate to warp. Hopefully the 11" will be more appropriately matched to the tire size and loads.

(2) Brake fade. When towing my boat I'd experience pretty serious fade when trying to stop quickly at highway speed. That's also due to overheating. Hopefully that won't be a problem anymore.

(3) Backing up, down steep hills and even on boat ramps... You've probably all experienced this. The rear brakes are weak and the front brakes lock up and drag. I *DID* already notice better braking performance while doing the adjusting procedure, backing down hills and hitting the brakes. It feels good to have better stopping power and control of the front wheels when backing down steep hills.

(4) And I'll admit, I just think it's cooler this way.

 

[MomoJeep]

Has anyone else done this conversion and noticed (or not noticed) a difference in braking force? Vs. other benefits..?

 

[barrys]

2000 pound boat trailer probably does not have brakes. If not, adding them should solve your brake issues when towing. Swap the whole axle for one with brakes.

 

[John N]

Has anyone else done this conversion and noticed (or not noticed) a difference in braking force? Vs. other benefits..?

I’ve done your 1, 2 and 3. Mine stops pretty well. My duel diaphragm setup is the Navaho from OffAgain. I don’t know who made my braided stainless steel lines. My rear drums are stock on the Scout II rear 44, they’re 11” x 2.25 or 2.50” (don’t remember exactly). My front 44 has Wagoneer disks, which are larger, too. My Scrambler weighs in around 4200 lbs.

 

[MomoJeep]

Question: going from 10" to 11", are the Wheel Cylinder Links going to be the same? the "links" are the little metal dowel pins on each side of the cylinder that push on the Brake Shoes. The internet seems to only sell them from 1978 on up. My 11" Drums are from 1977...

These seem to be for 10", but what about 11"?
https://www.quadratec.com/products/16751_02.htm

 

[MomoJeep]

CONCLUSION... OK, after a few thousand miles I can now say I'm GLAD I did this conversion! I think the new pads/drums needed time to bed each other. But now the brakes respond better and don't fade on long stops pulling the boat. And best of all, I'm pretty convinced the reason my real axle seal failed was too much heat from overheated 10" drums while pulling my 2000# boat!