26: Wheel Cylinder

TD told me he was replacing a wheel cylinder. Being married to a car guy, I know he's done this before on other vehicles but to be perfectly honest, it never peaked my interest.

(He loves it when I bother him when he's under the truck)

Today (thanks again to Wikipedia) I educated myself on what the whole deal is with wheel cylinders:

A wheel cylinder is a component in a drum brake system. It is located in each wheel and is usually at the top, above the shoes. ("Shoes" ...I started paying attention) Its responsibility is to exert force onto the shoes so they can contact the drum and stop the vehicle with friction. What connects these wheel cylinders to the shoes are usually small rods shaped like a birds beak. The wheel cylinder consists of a cylinder that has two pistons, one on each side. Each piston has a rubber seal and a shaft that connects the piston with a brake shoe. When brake pressure is applied, the pistons are forced out pushing the shoes into contact with the drum. Wheel cylinders must be rebuilt or replaced if they show signs of leaking.

Can't say it's fascinating information, but it is very educational.

In Abbey's case just one rear cylinder leaked. Every time the brakes were applied, a little bit of fluid came out. (Like a leaky bean bag chair that squirts white Styrofoam balls when someone sits on it).

Not fixing this issue would mean that eventually you could hit the brakes and have nothing happen. I can't think of  single scenario where that is a good thing.

On older vintage vehicles you watch for drips under the car and the way the brake feels when you mash the pedal.

So TD dutifully changed out the old for the new.



For the wheel cylinder challenged, it is the funky little thing that looks like
a large bedazzled and filthy D-sized battery at the top of the big brown round thing.





This is a new one. They are rather pricey,
..and not really all that interesting except for that bird beak description from Wikipedia 



It pushes on the half-circles (shoes) to help stop the truck.
You need them.

Every time we get a new part for the truck I say it's too bad the shiny new whatever-it-is can't be seen once you get everything back on. In this case, suffice to say I guess it's good just knowing it is there and works. That, and the fact that it makes TD happy.

I never really understood or cared about how brakes work, and now that I see it from a mechanical standpoint up close and personal I have to say...I'm sorry I know. This is equated to the "no one wants to know how the sausage is made" scenario.

I find it very disconcerting seeing springs and half circles, and D-Battery-shaped pieces, and what Wikipedia above calls "bird's beak" points, that all come together and work in unison in some mechanical wonderland to stop a vehicle that zips down the road at a whopping 35 m.p.h. I don't know what I expected to see in terms of truck brakes, but something more robust would be preferred.

Ignorance is bliss.