Rear drum brake upgrade - Larger wheel cylinders?

Not interested in a different platform for more reasons than I care to go into, mentioned that in original post think. This thread is about upgrading rear brakes for loads that aren't 'normally' seen with daily drivers - not recommendations of a different truck (which I would also exceed the factory GVWR on btw), you aren't considering the various factors that go into a GVWR or GAWR from the factory and why they are that way for the masses (which are long since replaced in my application), your abs must suck a lot more than my 2005 trd sport, perhaps you could benefit from a brake upgrade too... thanks though

 

keep the truck and put in an upgraded axle with disc brakes. Very simple and easier than fiddling with technology from the early 1900s

 

One challenge with that is the cost of a good axle assembly, strong but also narrow enough. Tundra for example is too wide. And I already have 4.56 gearing and ARB air locker. Seems way easier to order some 1” cylinders, testfit, and then experiment with different pads and drums for more bite. 13% boost by the cylinder alone, and presumably a few percent with pads that are known to be more aggressive than the stock ceramic, if I can get 20% on paper I think I would be able to feel it in the real world, and I think that would be good enough, run it and not much different than a standard brake job. Have you priced a bolt in Dana 60 from ECGS? With a locker and discs in the right width, using the correct speed sensors and brake cables, and you need a different driveshaft too. $$$$$

 

Looks like the only option that fits all of your criteria is to swap in a Cummins with Jake brake! Rear 'brakes' upgraded there you go!

 

LOL, this sentiment of a complete change of something major sure keeps coming up,,, I guess I have ostrich syndrome and my head is buried in the sand, perhaps I need to admit that I’m way outside of the intended use of a Tacoma.

maybe if I don’t see or hear it than it won’t be true?

 

it is big money but you gotta pay to play. The other benefit of a larger axle with disc brakes is strength increase and longer life of components. Overkill is underrated. Again you have to remember these axles in the 2nd gen are the same size as the ones from 1983 which weighed half what these do. You can get a junkyard Dana 60 or sterling 10.5 and get the C&C version, the WMS is less than the pickup versions. If you think the brakes don’t work well then you must not have tried the parking brake yet, they don’t work worth a damn either. So no need to worry about hooking them up.

 

@racebug68 I detailed my drum rebuild from last summer over here: https://www.tacomaworld.com/threads...performance-pads.523829/page-52#post-26413771

 

Sorry, I just don't subscribe to what you are saying, both in the need for a different axle assembly or with what you are saying with discs. So far I don't have any issue with bearings, diff, gears or any of the wear components. Maybe if I had dual transfer case setup, real slow speed torque multiplied thing with 37's... I would run into breaking gearsets or axles or whatever, but I don't. Also, truck has 170k and to my knowledge (I've owned since 95k) it still has the original rear shoes and drums. And for the record, my ebrake works extremely well, have tested, and it will lockup both rears EASILY at speed, and holds VERY firm stopped. I remember spooling my winchline, was difficult to get a setting on the ebrake that I could run the winch under tension without locking and dragging the rear wheels. That is just all to say that I don't feel I 'need' to pay big to play here... just want a boost in rear brake performance.

Thanks, I will take a look at it. Much appreciated!

 

Still sort of shocked that nobody in all of Tacomaworld has come forward with their experience or thoughts on upgrading the wheel cylinder size. This is commonly done in the OEM/factory for the same basic braking system to make it work for a different vehicle with different weight bias, towing capability, front brakes, tire size, etc. For a Dana60 you can go to a chart and find wheel cylinder sizes in 1/32" increments.

I did find some evidence of the 4Runner folks (3rd gen) doing rear wheel cylinder upgrades to compliment a front brake upgrade (TBU = Tundra Brake Upgrade) I will be pushing forward, ordered a 1" bore rear wheel cylinder, I hope that it isn't a dead end when it gets here with different threads or mounting bolt spacing, overall width, etc. From pictures and specs that I could find it looks to be very similar, will compare and document when the order gets here.

 

Please do update us on the wheel cylinder size effects! I think most people are either too scared to mess with drum brakes, they can be a major PIA without the right tools. Or, they just upgrade to disks.

But there are those of us like myself that have upgraded the front to a BBK, and unable to upgrade the master cylinder due to having the electronic one. And therefore skipping the rear disk conversion.

 

I suppose I'd like to hear more first hand reports with folks that have put various rear disk upgrades on the back, retaining the parking brake. Looks like there is a super fancy stop-tech rear brake kit that is mega money, and also the changeover conversion parts for the FJ or 4 runner or something. Maybe there are more kits out there that I don't even know about.

I don't buy the idea that just because it is a disk it is better than drums in every way. I'd like to hear what master cylinder/vacuum booster, what size caliper pistons, brake pad brand/compound, and the owners impressions of the kit, for brake power, performance, heat, and parking brake. The rear drums are very proven, hence the reason why so few have upgraded I think.

 

Well I have nothing to add on increasing the drums performance, but I am definitely going to watch this thread.

I think the only way a rear disc upgrade is going to compete is if you swap booster and or master cylinder as well, and for me personally the parking brake still needs to be operational. As much as I dislike working on drums it’s probably easier to keep them on the truck.

 

Right??!! I agree with you and more. I have the booster/master upgrade, which I love btw, since my truck is a trd sport. But still very hesitant on doing a disc conversion for many reasons. First and foremost, disc isn't better all the time everytime, it will depend on the piston size, and ratio to the master size as well as the brake boost efficiency - as well as the situation you want to improve the brakes, i.e. improve fade, or improve cold performance, etc. Discs are better at handling heat, but for me at least, I haven't gotten into the situation that my rear brakes are fading, smelling hot, etc. I want them to work really well, right from cold all the time. Second, the parking brake function is impossible to argue that disc is better - drums win hands down. Third, cost is a thing, and the disc kits are not cheap... at all. Fourth is that if you think doing a rear drum brake job is hard - then don't do a disc conversion... If I'm not mistaken, don't you have to take off the drum backing plate? I haven't had it all apart myself, but I think that doesn't just come off easily, it involves removing the axle and actually pressing the bearing housing off the axle? According to SOS website (where I don't have access to instructions) it is 8 hour job for a qualified brake technician with all the right tools and smarts and NO HICCUPS along the way.

Drums have less rotating weight, but more pad surface area, and larger average diameter. But also less thermal mass for heat absorption, and also have a less linear brake force as the shoes move outward and begin to bind with the drum and rotate slightly, so slightly less modulation. Also the springs and adjusters are another point of failure, if the adjuster binds up then you dramatically loose brake capability as the shoe wears. But they work great cold, have awesome parking brake function, and are cheap...

Mainly ease and cost are the benefits to just make the existing rears work better than they did. It is beyond me how anyone can say it is not worth it, but I cannot prove it yet. If you have larger tires than stock, then you can benefit from more brake force, especially if you carry more weight, or tow a trailer, etc. Maybe if you lived in Ouray, or somewhere deep in the high mountains, with LONG LONG downhills then heat and fade could become an issue when towing or something, just riding brakes for miles... But I've been on many long downhills at speed, never felt like brake overheating was a thing for me personally. Before the master/booster and 4runner front upgrade, I can report that my truck was downright scary to stop at any temperature, glad I got rid of that setup, and I think the upgraded rears will also be a welcome addition, even when we admit that the rears do less of the braking when the weight transfers forward. What many don't take into account though, is that in many applications like mine, there is still substantially more weight and tire contact pressure to pavement than stock, even when the weight is transferred forward during braking...

Anyways I will do a comparison of the new wheel cylinders when they arrive. Maybe they will be fundamentally different and this whole discussion will be a waste. Maybe that is why nobody else has tried it

 

Re your hydraulics; going to a bigger cylinder will require a larger volume of pressure. I haven’t done the math, I’ll leave that up to you. But, expect your current master cylinder to not feel same.
Force=AxP.
V=AxL.
V= area squared x length.
Therefore, to get higher force applied, larger cylinder, OR, smaller master cylinder piston.
With smaller cylinder piston , fluid displaced is smaller, and may not provide the pressure wanted without increasing stroke. We’re talking minuscule here, but….

edit: a=r squared, not a square

 

Agreed. Have a tundra master cylinder already, which is bigger bore... as well as the dual diaphragm vacuum booster which applies more pressure. That alone will make the rear brakes work better than they did originally, but still looking to improve the rear like the fronts were when I changed the calipers for larger pistons, larger diameter and wider rotors, etc...

Thanks for the facts, appreciate the details and reasoning with data, good stuff.

 

OP, once you have this implemented, it will be really interesting to hear your experience over the course of a few months’ use. The fact that the rear brakes on the Tacoma last freaking forever is to me indicative of brakes that don’t get actuated very much. I think once you have the truck all buttoned up with the new wheel cylinders and you’ve adjusted the shoes to your liking, you are going to notice a difference. However, I’m willing to bet that you will find that any improvement declines over time as the shoes wear from additional use.

In my younger days, I owned a ‘68 Plymouth satellite which had drums all around. My local parts store had higher-end shoes with a better temperature coefficient in the linings, and these had much better fade characteristics. When I first installed them and got the brakes adjusted up perfectly, that thing stopped so much better than it ever had before. But within a few weeks, the performance felt degraded, which was really just the position of the pedal where they started to engage. I could adjust them up (and often did) but it wouldn’t last. There is a thread here on TW recently where the author said much the same thing about his experience trying to make the rears perform better.

One other thought I had about the wheel cylinder upgrade is that you will need a higher volume of fluid to push the pistons the same distance as with the originals. So unless the master cylinder is changed to one that can do so, I don’t know that the relative balance in the braking from front to back can be improved just by swapping the wheel cylinders.

 

I'd second guess that lasting forever bit. Mine were making noise around 85k miles. And when I took them apart they had significant wear, and even chips out of the pad.

 

You have to look at them from the side to know how much pad material is left haha

The one in the background looks really good

 

Not a lot. OEM pads on bottom. I installed the top left pads from TRQ

 

sub'd.

OP keep us updated. I'm heavy as well and tow a trailer. Looking to do the T4R front disc upgrade soonish. Would love to improve the rear drums without breaking the bank!