Heeltoe Explains

A note about squeaky shocks

I get asked from time to time about squeaky shocks so I thought I’d make a post about it.

Why do shocks squeak? Well, there are a number of reasons. And trust me when I say it is really not a brand-specific issue. I spend a lot of time on Acurazine where people tend to complain about Tein dampers squeaking. Well, they don’t really buy anything else there with any great volume so of course, more people have noises with Tein! In reality, any shock can develop a squeak and I will give a few reasons why!

I will preface the following by mentioning the “science of a squeak.” Squeaks are caused when there is a moderate pressure-force over a small cross-section. Usually, the ideal squeak would involve a rigid item that encounters some flat surface with minimal abrasiveness (in other words, more smooth surfaces provide higher friction). Like nails on a chalkboard, right? Or rubbing your finger on a dry slip-n-slide. You need some pressure and some friction to make a squeak.

Worn shaft seals or shock shafts.

As the seals wear they can become firm and loose lubrication. As shafts wear they can heat and become harder than normal. The seal provides the pressure, and the movement of the shaft against the seal provides the friction. Hence you can get a squeak. This noise can be remedied by applying some light liquid silicone spray lube to the shaft. Try to not use anything with petroleum in it as it can break down the seal further and/or attract dirt causing a leak!

Bubbles in shock fluid.

More prevalent with street-use twin-tube dampers where there is high-pressure nitrogen gas in direct contact with shock oil. Vibration and heat can cause the gas to emulsify into the oil. When you get bubbles in the fluid and it passes through the small orifices in the shock piston you can get a noise. The pressure is caused when the oil forces the bubbles through the piston. The friction is provided by the variance in coefficient of friction of material going through the piston (oil, then air, then oil, then air as bubbles pass through). The system can be designed to minimize sounds from one material, but not both. This situation is a lot less prevalent in mono-tube shocks as the oil and nitrogen are divorced. 

It’s a performance shock. Compromise is built in.

To a certain degree, you need to expect that if there were no compromise in noise or ride the automotive engineers would have put a superior handling system in the car from the get-go! Therefore you might expect that part of the reason you are getting squeaky shocks is that they work better in other ways than non-squeaky shocks.

One instance is that the viscosity of the fluid in performance dampers may be thicker than stock and the piston orifices many times are smaller, or adjustable in size. Thicker fluid through a tighter hole: Pressure = hydraulic pressure of the oil forcing through the holes. Friction = higher viscosity fluid inherently “sticks” to the surfaces it contacts better and has a greater resistance to flow…stick, resistance….FRICTION caused by the fluid itself!

Temperature Change.

To add to this point, many people notice more squeaking as temperature drops and with some ability to warm up it goes away. Lower temps increase viscosity which only enhances this effect of fluid friction causing the noise. Temperature change can also cause seals to swell or contract, or change in suppleness.

In closing…

There are a number of other reasons why a suspension system might make a sound. Loose fasteners, worn bushings, etc. Shocks themselves can make noises like squeaks in varying conditions which don’t necessarily indicate a failure. Assuming all else is normal the noises you are hearing from the shocks may not really much to be alarmed about.