Many of our customers have relayed to us stories about how they were told that they needed to replace their vehicle’s shocks/struts because they had X miles on them. The shops often show a shock absorber replacement interval poster to evidence their claim. Is there something more to this?
Here is an article from a place that sells shocks and struts, so they have a lot of reason to push shock sales; but they confirm the same things we at CarScope have always felt and observed about shocks and struts.
This article was originally posted on ShockWarehouse.com on this page. The article’s original intent was to dispel various shock/strut “myths,” so in addition to getting their valuable testimony against mileage-based shock absorber replacement intervals, you’ll get some other valuable information as well.
Q. The tire store in town says I have to change my shocks / struts every 30,000 miles [CarScope note: or 50,000, 75,000, or whatever mileage-based recommendation they give] …
A. The shocks and struts we carry in most cases are considered an upgrade by the U.S Government, over the stock, O.E. suspension units. They can be changed at anytime, even right after you purchase a new vehicle. If the vehicle you drive is not up to your expectations, or un-controllable, you may want to consider better parts for your suspension to improve it’s handling and safety. Also, you may have special needs for your vehicle that may not have been incorporated into it’s design, such as some off-road driving, or towing.
Also, despite what some people say, there is no time limit, by years or miles, on when you have to change a unit. Though we do recommend, as part of normal maintenance, to routinely give your suspension a visual inspection to make sure it is in good, safe, working order.
Q. Changing the shocks / struts on my vehicle will make it ride “better” or “softer”…..
A. How a vehicle “rides”, or “feels by the seat of your pants”, depends on many different things.
1. Tire pressure: (make sure yours is set at what your owners manual says, NOT what the tires says).
2. Wheelbase: (short wheelbase vehicles tend to be more rough).
3. Tire & Rim Size: (Shorter or less forgiving side walls (low profile tires) tend to be more rough).
4. Road Conditions: (Rough roads are rough roads, some roads are worse than others).
5. Suspension type: (Torsion bars and leaf springs can be less forgiving than coil springs).
6. Using performance or lowering springs: (Typically these would be stiffer and have a different rate).
7. Lifting a vehicle: (With stiffer springs and tighter suspension parts).
Shocks are only ONE part of a suspension. What you “feel” is a combination of the list above, and other things, including all the other suspension parts, from swaybars, springs, frame-type, etc. Shocks (or Struts) are only ONE part of the total suspension.
Remember: a shock or strut’s PRIMARY function is to hold the tire in contact with the road. Just changing the shocks / struts is not likely going to change what the vehicle manufacturer built into a vehicle’s characteristics. Car companies spend MILLIONS of dollars to make a vehicle feel a certain way when driving. Spending a few dollars on shocks is not likely to alter what they have done.
How a vehicle rides is something that cannot be “plotted or graphed” scientifically, it is a matter of opinion. There is no ‘measurement’ or ‘scale’ for ‘ride’. 10 people can drive a vehicle, 5 will says it’s a Lincoln ride, the other 5 will say it’s a dump truck. It’s up to the individual.
We do not recommend buying shocks or struts specifically for trying to change the “ride” of a vehicle, that is not what shocks or struts do. The products we carry typically are designed to give a vehicle better handling, control, and safety. Will they maybe change the “ride”, what you feel in some way? Probably. Can that be predicted ahead of time? No.
We know it’s a tough decision sometimes to choose the right shock. But we want you to purchase a product for the right reasons, and get something that’s right for you and your driving.
Q. Shocks and struts have a strap on the them to help with installation….
A. The straps serve only one purpose, and that is to fit the unit in the box. All the manufacturers use certain size boxes. If the boxes they use are, say, 20 inches long, and a strut or shock is 29 inches long, that unit will get a strap to compress it to fit in the box. And if the shock is shorter than 20 inches, then a strap is not needed, since it fits in the box with room to spare.
Sure, sometimes they can help with an installation, but that was not the intended use of the strap.
Q. Heavy Duty Shocks always say Heavy Duty on them…
A. The term “Heavy Duty” is a generic one. It is our opinion that a shock that has more dampening power and durability over an OE or low pressure design unit, is for heavy-duty use. To us, that means any shock that is a monotube design. CLICK HERE to find out why monotube shocks have better dampening, run cooler, and last longer, that’s a matter of science. Any company can slap the word ‘heavy-duty’ on their packaging, but that term does not give you any facts.
Note that not every vehicle needs a ‘heavy-duty’ shock either. There is nothing wrong with using a low pressure gas unit if light-duty use is all you need.
Q. Heavy Duty shocks have a thicker body diameter than a light duty shock……
A. Some shocks represented as a ‘heavy duty’ shock will be a twin-tube low pressure design. Those kinds of shocks get a lot of cavitation and heat, so shock manufacturers give them a large body resevoir to hold extra oil, to try and keep them cooler (such as a Monroe Magnum).Monotube shocks are a more modern design, and do not generate as much heat and aeration, so those kinds of shocks do not need the extra oil, and are slimmer in size / diameter.
Q. Shocks / Struts will hold up my vehicle or change it’s height….
A. Shocks (or Struts) do not really hold up a vehicle. For example, if you ever took shocks off your pickup-truck or RWD car before, you know when you set it down off the jack, it sits pretty much the same as it did before you took the shock off. What “holds” the vehicle up is the coil springs, leaf springs, or in some cases, a torsion bar.
There are shocks which can help, or add additional support, such as Monroe Load-levelers orMonroe Air-shocks. But no shock (outside of some kind of racing unit) is really designed to support a 3000-5000 lb. vehicle. There is a limit to how much a shock can help (for instance, just changing shocks on a half-ton pickup truck will not automatically make it a one-ton model.)
The primary uses of these type products is to keep the rear of the vehicle level with the front, so you have a more balanced suspension while driving or towing.
(On strut installations, it is important you get the springs seated correctly, or that can effect installation, and may effect height. Follow your repair manual’s instructions carefully, every vehicle is different).
Q. The more gas pressure inside a shock / strut, the stiffer the valving or ride will be…
A. That’s not really the way it works. The Nitrogen gas only prevents aeration (foaming bubbles) inside the unit. How soft or stiff a shock / strut is, that is determined by valving.
Aeration inside a shock or strut ‘kills’ the dampening ability of the unit, so the higher the pressure (for instance, Bilsteins have 360 psi ), the less chance you will get any aeration and heat, and less chance the units dampening ability will fade.
Valving in a shock or strut is calculated using “Rebound” and “Compression” figures. While shock manufactuers rarely publish these figures, their engineers work hard to come up with the best valving for maximum control and performance.
Phew! As you can see, there are a lot of details that go into suspension service. If you notice any symptoms that might indicate suspension problems, feel free to contact us about making an appointment.
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That’s it for now! See you next time.