Weird Automotive Terms Explained: Rag Joint

You know what’s fun about cars? I mean, there’s lots of fun things about cars, that’s why we’re here. But specifically, at this moment, I’m thinking about how cars are full of a vast array of wondrous and strange parts, and all those parts have names, and sometimes those names themselves are strange. So it might be fun to look into the entomology of these names, see what the insects’ opinions are, then dig into the etymology of the names, and find out why things are called what they’re called! Today I want to talk about a strange one: the rag joint.

That’s an evocative name, right? Rag joint. It sounds like a dive bar that caters to the textile industry, or something like that. It’s not that, though, it’s a bit less exciting. Or maybe more, depending on your own personal prejudices?

The rag joint tends to be used most often in steering columns, though they have shown up in drive shaft and other shaftly applications as well. Here’s a pretty typical habitat for a rag joint as seen in some Ford products:

See that bit highlighted in blue? Here’s an actual one:

photo: Borgeson

As you can see, a rag joint is a sort of shaft coupler, where we have two separate metal bits on either end that couple to the shafts, and in between is a disc or multiple discs of a flexible material, originally leather but more commonly rubber, usually reinforced rubber, much like the rubber material tires are made of. In fact, rag joints often use recycled tires for that middle bit.

A rag joint isn’t something that would replace a U-joint or a CV joint; it’s not about changing direction, it’s more about being forgiving. What I mean is that a rag joint’s flexible middle section absorbs vibrations and compensates for when things aren’t perfectly aligned. It’s a device made to soften the impact of slop in a system, like the system that makes up your car’s steering.

The rag joint absorbs and damps vibrations from the road to keep them from abusing your poor hands as they grip the wheel. Here’s a little video explaining them :

Now, why are they called rag joints? Well, for this odd term, I think it’s sort of obvious: the middle rubber bits are sort of like rags. I’ve heard explanations that say the ragged ends of the reinforcing cords inside the rubber contribute to the name, but I tend to think it’s more about the overall look and feel of the thing: it feels like a sloppy thing, and the middle does have a stack-of-rags like quality about it, doesn’t it?

I like rag joints because they acknowledge the imperfection of the world, and don’t just sit around complaining, they actually do something about it. It’s also a bit amazing that something as crucial as a steering shaft coupler relies on a disc of old tire rubber! But they’re tougher than you think! Cars – especially American ones – used them into the 1990s, and if your steering feels loose or wonky, it’s not a bad part to check out and replace.

Car Terms I Learned From Song Lyrics: Charabanc