Piston Slap: Bouncing Back or Sprung Out?

John writes:

You recommended to one writer that he consider replacing the springs on his car (as well as all other wear items in the suspension). Other then the obvious broken spring or the car sitting of the spring stops, when and how do you evaluate the need for springs? Do you recommend stock setting or performance springs for replacement?

Thanks, John (Jag, Kia, Miata, Chev)

Sajeev answers:

The most obvious sign of a worn out coil spring is a super plush ride combined with a saggy ride height at any corner. Funny tire wear or an impossible to find groan could also be a sign of bad coil springs. If you drive on suspension punishing roads (Boston-like urban, or unpaved rural) and drive a vehicle that’s 5+ years old with 100,000-ish miles, odds are a saggy coil has sprung its last proper rebound.

This isn’t obvious like a leaky air suspension bladder puking out pressurized air, but metal fatigue is for real. Even when not felt: springs, much like headlight bulbs, go bad very slowly.

While shocks/dampers affect ride, they can’t do a darn thing if the springs collapse to the point of no return. A proper ride height check is good, or just measuring right height from left to right with a few fingers. If one side has less space between your fingers, you just diagnosed the problem. (speaking from personal experience)

Fortunately there are quick fixes for many cars: something like Monroe’s Quick Strut saves you money (labor hours) or time (in your garage) as you replace both the shock and strut in one shot, cheaper than changing the strut itself. Nice.

Last question: stick with stock or go performance aftermarket? That’s a personal preference for which you gave me zero personal insight. I normally default to retaining the stock spring, as it has the correct rate to ensure a fine ride/handling balance and won’t bottom out when loaded with passengers/cargo. It’s always the safe bet. But…

Bonus! A Piston Slap Nugget of Wisdom:

When it comes to shocks/struts/dampers or whatever you like to call them, that’s a different story. Some of my favorite performing vehicles use stock springs with aftermarket shocks of the premium performance variety: Koni or Bilstein for starters. Most drivers need a stock spring (even if they don’t want to admit it) but they certainly want superior control over the spring’s up/down motion. Aside from well sorted out performance cars, you’d be shocked at just how much better an OEM spring and performance damper work together to bring a big-ass smile to your face when hugging a corner or two. And that’s even more reason to stick with stock springs.

[Image: Shutterstock user VikiVector]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.