Rear drum brake upgrade - Larger wheel cylinders?

I think it is worth noting here that anyone who says the rears work great or don't work or can or cannot be made better needs to also admit if their truck is vacuum based or electronic booster based. I believe that is a huge difference... some have a trd sport, some a trd offroad, and the reflection you have of how well your brakes work will depend highly on that factor.

 

The other reason semi's run drums is because they self energize unlike disc brakes and their holding power over greater surface area is significantly higher when locked. [air pressure drops or line is disconnected]

FWIW, while drums can be a PITA to set up properly and you might need to adjust them or free the self adjusters up if they freeze, they tend to last a heck of a long time and don't tend to have the warping and rust issues many disc rotors have, especially since they have become lighter [even though they have increased in diameter] as weight savings can be easy to gain. A pound doesn't seem like a lot at each wheel but weight, especially unsprung weight, is always highly sought after.

 

good point

 

I find it interesting that one of the biggest issues of drum brakes is heat fade due to the failure to shed excess heat and some modern disc brake systems using carbon fiber and ceramics have the exact opposite issue, they suck when cold and until heated up, provide marginal braking.

 

i have the electro boost brakes from the offroad. I don’t think they’re worth a damn. I’ve driven a sport and doesn’t feel much different in my opinion. I can stop my one ton with a trailer on it faster than my Tacoma.

 

This also makes rear drums typically work more effectively as parking brakes than rear discs.

Does that make more sense? Adding weight, especially unsprung weight, is not usually a good thing.

 

Delete the LSBPV and install a manual proportioning valve to the rear brake lines.

 

Are you thinking of a 1st gen Tacoma? I'm not aware of a load sensitive brake proportioning valve on a second gen. As far as I know, the rear brakes have no pressure reducing devices in-line. So to make rear brakes "work" better, you have to hamper/reduce pressure to the front, then push the pedal harder giving the effect of better rear brakes. Let me know if I'm off base on that theory...

 

Back in the drum brake days performance cars, police, taxi and station wagons usually had wider brake shoes than the regular sedans of the same model.
I did a little part catalog research for an application I'm familiar with both took the same wheel cylinder.

 

Interesting observation. thinking about it a little... I wonder if they did that for better braking performance, or for longer wear / replacement intervals, or for heat management. Maybe some of all? I can imagine that the larger pads would wear slower and be easier on the drums, at the same time of having more area to dissipate heat, etc. I'm not actually sure if a larger pad alone will brake any better, since without a larger wheel cylinder the force applied by the hydraulics will be the same, and as such you have more pad area but same overall force resulting in a smaller PSI of force pushing against the drum - so if the brakes stopped any better is dependent on whether the coefficient of friction times area, or the force applied, is dominant in the overall equation of stopping force.

 

I can tell you the first gen Tacoma and tundra drums had really wide shoes compared to the newer trucks. 1 Ton T100s had the largest. Doubt they’re easily adapted to the newer trucks. But there’s something to think about


But the diameter was smaller. So surface area wise they’re probably similar

 

In the old road tests of the day they always published a "brake swept area" figure, a measure of working brake surface.

I believe the wide shoe application was to improve performance in all the metrics you stated, heat management being the key.

Stopping converts motion to heat. Just to throw a number out let's say a particular stop is 10,000 btu.

If you have a wider shoe that 10k is spread over a larger area which gets less hot than a smaller shoe during the same stop. The less hot wider area also has more surface area so it can cool quicker.

Cooler during stop = less fade
Cooler quicker = better repeat stops
Cooler overall = longer shoe life

 

Thanks for the info, makes a lot of sense. A wider shoe alone without a change in cylinder size doesn't necessarily result in more brake force in those situations where heat/fade are not a concern. Functionally it will be better all around in the real world since heat is always present, and since cooler brakes are better brakes (when using normal shoes of course). I would certainly go with wider high performance shoes if I could get them and confirm fitment for the reasons you list. I may try to do some research about drum diameter and width and such with the other toyotas mentioned like the T-100. But for the purposes of a test on the side trying to get more stopping power, the larger shoe alone might or might not be able to lock up a wheel any easier (which is my current case with heavily loaded truck and larger tires, can't activate rear ABS on flat ground). I think looking into the larger cylinders is still more meat on the bone with less risk and challenges of part compatibility.

 

Racebug68, I would suggest making a day trip to one or more of your local Pick n Pull yards to crawl under some vehicles and pull some wheel cylinders and do some measuring.

I have been doing this kind of thing for 30+ years and learned a ton when I was big into baja bugs.

You may find what you are looking for on an older model SUV, minivan, wagon, van, or truck - foreign or domestic.

Once you find something that might be a suitable candidate, grab one or two for mockup purposes. Then if that looks like a good fit, you then source brand new ones for your build.

 

good advice. I'll look into it. There aren't many do it yourself type yards here. Almost all have been converted to you pick they pull, or full on inventory controlled used parts houses with everything already disassembled and "assemblies" available. For example I called and they will sell me a complete axle drum to drum for a insane price, (I was looking for an axle housing BTW) but I cannot just have brake parts or a 3rd member or an axle housing, etc.

 

Road trip!

 

I was going to say the same thing haha

 

It's amazing how many makes and models of vehicles over the years use identical parts, or interchangable parts that are upgrades to other vehicles.

I started going to local wrecking yards when I was 13 with a friends dad to pick parts. Then continued to do so when I got my license at 16. Packed a lunch, some tools and grabbed one of the wheel burrows at the yard and just wandered around pulling various parts from one car and seeing what fit on another.

 

In my younger days I termed that as recreational junkyarding.

 

Let me help you: https://www.toyota.com/tundra/ If you're carrying as much weight as you claim you need a heavier duty truck; the Tacomas are light duty vehicles and the brakes on them suck with the ABS system being near dangerous under some conditions.