The most obvious answer would be “when they are broke.”
All springs have a finite life, that is, one day they will
break. But also due to use, wear, age, and other factors, springs lose their ability
to hold weight. Though they aren’t broke, they are weak and should be replaced.
Close Up Inspection
OK, so you crawled under your vehicle and given the springs
a good visual inspection and you have not spotted any broken leaves or coils.
Even though you do not see anything broke, how do the
springs look? Can you see daylight through any of the leaves? Are any leaves
missing? Are the leaves fanned out like a deck of cards?
Are the U-bolts in one piece and straight up and down?
Take a good look at the spring eyes. How do the bushings
look? Egg shaped? Dry rotted?
Are any of the coils bent or distorted?
Now get back out and stand at her side.
Make sure she is sitting on level ground and the tires are
at the correct air pressure.
Stand off to one side and take a good overall look at her.
How does the front sit as compared to the back? And how does the back look as
compared to the front? Is the whole vehicle too low? Just one end? Is it too
Now go stand at the rear. How does she sit side to side?
This is fun, so go do the same thing standing at the front.
Incremental Loading Inspection
Now repeat the standing visual inspection but with someone
about your size sitting in the driver’s seat. After going around the car again,
throw someone in the passenger seat and repeat.
Don’t stop now, you’re on a roll. Add some luggage or at
least the stuff you take to cruise night or the car show.
Does adding more weight change the stance to a point to
where she just looks butt ugly?
Let’s now check out how she rides and handles. Take a drive
on smooth roads. Then find some not-so-smooth roads. Hit some bumps. Go through
a few good dips.
Any bottoming out? Funny clunking?
Now the handling. Does she dog track? Pulls? Wanders? Change
lanes when going over bumps? How about any new shimmies at speed?
Right after the road test is a great time to check the
shocks. Feel them. Friction is created as a shock works up and down, and we all
know that friction creates heat. So, if the shocks are warm or even a bit hot
when you wrap your hand around them, they are fine.
If you see, feel or think there is a problem with any of the
above tests, then chances are the springs should be replaced.
If it is time for new springs, now would be the time to
think about how you would like her to sit and ride. New springs can get you