Rear drum brake upgrade - Larger wheel cylinders?

Yes I have tons of updates and need to set aside time to get it all put down here.

Teaser:
On the spare axle assembly I’m prepping for install (meaning it isn’t on the truck, no miles driven) I have test fitted 1” wheel cylinders that will bolt in. I have also tested 1” as well as 1 1/8” cylinders that are a tiny bit wider and need to have a small portion of the brake shoe horn (for lack of a better term) cut off, simple procedure. I also have 3 different brake shoes and two different drums to play with regarding compound and bite. I dunno if I will actually test various combos and comprehensively report out, because hopefully the combo I choose to put on the truck at the start will be wonderful and I won’t have a need to change and experiment to get different results.

but I can concretely say that the concept of “you can’t upgrade the rear drum brakes” especially given a lot more truck weight, tire size, etc is thoroughly debunked.

I’m sure this upgrade is not for everyone. And I have no idea what will happen if you did this with a trd Offroad electronic master or a stock trd sport master. I have tundra master and dual diaphragm booster, larger caliper pistons and performance rotors in the front from 5th gen 4runner, a lot of weight in the back and 35” tires that are heavy and seem to get a lot of traction. I know I’ll benefit from more rear brake power. Just. Not sure if it will take 1 or 1 1/8 cylinders and which compound pads to achieve better braking without always locking and engaging the ABS.

Lots more to come. Just need time to sort out the pictures and come up with some verbiage describing them and the process I went through to arrive where I am with it.

 

@racebug68 glad to hear it! Looking for ward to it.

 

I don't think anyone has said it's not possible to install different sized pads/cylinders in the rear - what I think you are defining as an "upgrade." The questions have always been what evidence is there that these things improve braking performance? What has been "thoroughy debunked?"

Do you plan to provide such evidence? If so, how?

 

I dunno if it was in this thread, or on IMs with various people, but basically I heard there were no larger cylinder options available, and that even if I did it wouldn't help any cause it wasn't a large enough difference. The general trend was that oem shoes and drums were as good as it gets unless you go to disc. That is debunked the same as if someone said the oem taco front brakes were as good as it gets until someone put on the 4runner/tundra upgrade and showed it was better...

I am saying that if you feel your rear brakes could use a boost... and they are up to snuff with pad life, adjustment, etc... there are options available that will improve braking force in the rear.

So that is what I had referred to as debunked. But I get that you are skeptical.. which is good. And I dunno how much data I will be able to give you. I'm not gonna go wear out a set of tires and brakes measuring my stopping distances before and after and with various combos. But I will give feedback and can easily provide the theory on why.

If you don't already have a brake upgrade in the front, and if you don't have a 7000+ pound truck, then maybe you don't need a rear upgrade. I can understand that... but I'm telling you, my truck could use more rear brake performance to match the front, and I'm gonna do some upgrades, tell you about what I've learned, what has to be done, what I have to experiment with, and report back. And if I have negative results I can always go back to stock...

 

I'll take that as a "no." All I'm saying is that you're putting a lot of time and effort into this, which is great. But at the end of the day, you're going to try to convince us that all that time and effort is worth it. If you have no way of showing us why, other than "it rocks!" then we're not going to be convinced.

 

Pins on the bottom of the backing plates are wallowing out/pulling through and the backing plate is also bending. Personally I think these drums are junk and I have seen way more drum problems now since my last reply. Disks on the way.

 

I switched from akebono ceramics to wagner severe duty semi-metallics in the front. Huge upgrade in performance. I was happy with the akebonos when hot, but very unsatisfied in every other condition especially initial bite, especially when cold and/or wet. Biggest performance improvement is 100% initial bite in cold/wet conditions! Immense difference. So much better.

Only downsides are that they groan a tiny bit at parking lot speeds, more dust, and probably wear the rotors faster. I don't care at all though. 100% worth it. Pads only cost $45 too.

 

Looking forward to the results.

 

dude, I'm not a manufacturer that is trying to build and sell something. Just trying to shed light on a topic that I found very little info about prior to starting this thread. I'm willing to do some testing, but that is for my purposes, not yours. That is a bold statement about what I'm going to try to do. Last I checked, I'm not trying to convince anyone to do anything, only trying to convince that there is benefit to be had and that it isn't hard to do, if you are in the boat of wanting more rear brake power like I am. As I said before, much of the feedback I got is that it either isn't possible to do better with drums, or that it wouldn't result in a meaningful change. Maybe it won't benefit anyone, maybe I'm the only one, I don't care, just trying to publish info and findings for the betterment of others.

Wow, haven't seen that before, I don't blame you. I haven't had those issues at all thankfully or I'd probably be in your shoes. Hopefully what I do doesn't cause those things.. yikes... There are benefits to discs no doubt. Cost, effort to install, and lack of good functioning/holding parking brake are downsides to the kits I've seen.

Yes, I discussed this somewhat earlier in the thread, semi metallic are the hardest biting compound of all of the options. And yes, the expense is more wear, noise, dust. But they do bite way better especially from cold, but also all the way to hot. All racing pads are semi-metallic until you get into the exotic racing stuff like carbon fiber rotors and such. I also made the switch in the front to semi-metallic when I did my 4runner/tundra/sequoia brake mods. All of those things are night and day difference in braking compared to what it was stock. Hoping for even a fraction of that goodness on the rear mods I'm making. Of all the tacoma rear shoes I could find info on, only the powerstop B871 are of a semi-metallic compound. Other "good" quality like OEM toyota, brembo, and beefed up are variants of ceramic. There are organic versions out there but those are just crap in comparison to OEM.

I think my initial trials will be with 1 1/8 cylinders, and either the beefed or brembo shoes, OEM drums. I think I will like it, hope so anyway. If I want to try more bite, I can put on the powerstop semi-metallic shoes and the powerstop matching coated drums. If I want less, then I can put on the 1" cylinders with either compound of shoes. At least that is my thought process, be able to adjust up or down from what I try first.

I have a feeling there are quite a few folks that are silently watching this thread. I gotta get on the write up portion of the research and the test fit results and detailed pictures and stuff. And I can't promise when I will have results to talk about,, as I said I have to put on a whole new axle housing, new bearings, and I'm custom making a disconnectable sway bar on the back that rides above the axle instead of below it like a tail hook. After all that stuff is done being customized, it will get installed with a new brake package. Just got confirmation from Deaver today, my custom springs are going to arrive on Wednesday. So yay, that 12 week wait is over. Need to send out my shocks to Accutune next and have those back before the big switch over can happen too.

 

Definitely watching here and interested in your thoughts. Don't need convincing that the stock Tacoma brakes aren't up to the task of stoping a heavy truck or a heavy trailer. I'm 9,600 lbs GCWR with the trailer.

 

I hear ya. Got to be careful on the details though. Towing a trailer is harder on a vehicle to stop, not questioning that. But a trailer only adds a few hundred pounds to the back axle right, i.e. the tongue weight? So your rear tires don't necessarily have more grip as a result of the extra weight in the trailer. I don't know the dynamics that happen when trailer weight shifts forward under braking, maybe that causes more tongue weight under braking and offsets the truck trying to shift weight forward and off the rear tires? All I'm saying is that the rear brakes can't do as much work (I don't think) on a 9600 lb truck/trailer combo as they could functionally do with the available traction if the truck itself weighed 9600. Does the trailer have brakes yet and if not can you add them? All that being said, I'd guess you are a good candidate for a brake upgrade, especially if you have done the front already. Your 3rd gen trd pro - is it a electronic booster or a vacuum booster? have you upgraded the front yet?

 

all OR and Pro are Electronic def curious to see how this plays out.

 

yup, I agree with you, the TRD OR and PRO are electronic ABS/masters. Only the TRD sports have a conventional master and vacuum booster. I am TRD sport, and have upgraded the master cylinder size to the tundra master with the appropriate vacuum booster from the same truck. So I have more volume of fluid coming from the master for a given distance of brake pedal movement. I also have more power assist on that volume of fluid due to the dual diaphragm booster. All of that is not possible with a Electronic booster in the OR/PRO. So I don't know how a front brake caliper upgrade, or a rear wheel cylinder upgrade would work with the OR/PRO trucks. I can only speak to the concept of improving the hydraulic leverage on the brakes when the sport master and booster are upgraded to tundra/sequoia versions.

 

An update to this thread original intent: I finally got my rear axle housing swapped to one that isn't bent in the last week, and a general whole-sale refresh of everything on the rear of the truck (springs, shocks, axle housing, bearings, shackle hanger reinforcement, and sway bar above axle, etc). And so the new rear brakes are installed. Not driven other than a test drive around the block yet, so brakes aren't bedded in and not fully bled either. Had to change rear brake soft lines to the axle as well, so there was significant fluid that came out and air went into the system, not to mention the new hard lines on the axle and new wheel cylinders in the brakes all have to be filled and purged. Probably take several bleeding cycles. Have some more work to do before taking the drums back off to check how things are looking and then going for a full blown bedding process and getting them really hot, broken in, and analyzing the performance.

What I have in place now, just as refresher:
trd sport. master and booster upgraded to tundra. 4runner front brake upgrade with larger and thicker rotors (EBC sport dimpled and slotted rotors), and larger diameter pistons in the calipers (14WA). EBC orange stuff extra duty brake pads (which are currently 80% worn, wondering whether to do rear brake testing with existing pads or put new ones in for the bedding process and brake testing). Rears I have 1-1/8" wheel cylinders installed (recall stock is 15/16"), and beefed up brakes ceramic pads installed, with brand new OEM drums. I also have brembo as well as power stop brake pads to try if I feel like I want to change anything.

Goal for me was to upgrade the rears to have them do proportionally the same amount of braking as the upgraded fronts. My front brakes were doing "all" the work, and wore through a set of pads quickly, and I could just tell the rears weren't doing as much as they should given my fully loaded expo truck and the additional weight I'm always hauling in the rear.

When I have more testing and info, and confirmed everything is working correctly, no leaks, no air bubbles, and bedded in I'll let you know.

 

Totally the electronic master is an interesting one. I believe it has similar part numbers to 4Runners which makes changes interesting too.

 

Changing the rear wheel cylinders to larger wheels cylinders will not help the rear brakes stop better at all, ut will do the opposite. The master cylinder will be moving the same amount of fluid to larger cylinders and the wheel cylinders pistons will move out less thereby rear brake performance will be decreased.

If you want to improve rear brake performance and stay with drum brakes the only way will be to increase the contact surface area of the shoes and the drums or change the friction material of the shoe.

 

uhh... ok, I guess you are welcome to your alternative opinion. I was going to explain with examples, but deleted it and am just going to leave it at that.

 

.....or go with a larger diameter drum. Because leverage is king. That said, not sure how feasible that would be.

 

A larger diameter drum is increasing the contact area of the drum/shoe which is exactly what I wrote.

 

kinda late but here is a tech tip, if replacing or removing components like wheel cyl or calipers, if you depress the brake pedal about 2 inches with a stick/broom handle wedged between pedal and seat, it will keep any fluid from draining from the system, and make it 100% easier to bleed a system that has no air in it. dont forget to disconnect battery to turn out brake lights, if repair takes along time

as for the rear wheel cyl upgrade, I had a 2002 ram diesel that rear drums were ineffective, after wheel cyl upgrade it would drag all wheels on gravel where before it would only lock fronts, difference stopping was night and day on pavement, also before upgrade a set of fronts would only last 20,000kms or 3-4 months (truck used for courior work) after upgrade front brakes lasted twice as long, basically fronts were doing all the work. it may not be comparing apples to apples, but same concept applies

best way I think to prove or disprove if cylinder upgrade is improvement or not is do controlled stops (set speed/distance) and measure heat with lazer temp gun, if it creates more heat (up to certain point) it would be working harder.
my two cents