Why do struts have to be replaced in pairs?

Dear Car Talk

Dear Car Talk | Nov 01, 1998

Dear Tom and Ray:

I've got a simple question. Why do struts have to be replaced in pairs? I have a
'93 Cavalier that had new struts put on a year ago after getting hit while
parked. The same thing happened this year, and the left front strut was bent. My
mechanic said he could only replace the struts in pairs, even though the right
one wasn't damaged. I'm looking for an answer before I present the bill to the
person who hit me, in case he questions it. -- Denise

RAY: Well, Denise, there's no technical reason why you have to replace them two
at a time. The problem is, the mechanic may only be able to buy them two at a

TOM: I don't know about all companies, but Monroe, for instance, sells most of
its struts and shocks in pairs only now. So your mechanic may just be passing
along this inconvenience to you.

RAY: In most cases, people are replacing struts because they're worn out, not
because of an accident. And since they tend to be installed in pairs, they
usually wear out about the same time. That's why they're usually replaced in

TOM: But I wouldn't worry about explaining that to the guy who hit you. I think
he's more likely to question the new upholstery, the four new alloy wheels, and
the new Bose sound system.

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