How firm or hard are aftermarket suspension and chassis bushings? What is the durometer?

Aftermarket suspension and chassis bushings (and engine mount bushings) come in all kinds of firmness. The name for the hardness of rubbers, plastics, and polymers is "durometer."

To understand more about durometers and how the scales and ratings works, check out this Wikipedia link on the topic: https://en.wikipedia.org/wiki/Shore_durometer

This article is to help you understand a little more about what brands use what materials and durometers for their parts. The data here is not to be taken as gospel. The article will be edited over time because we will add to it as we grow our knowledgebase for you.

Hardrace

This brand produces replacement control arms and bushings, as well as engine mounts and other chassis bits, with a material they call "hard rubber." They are rubber similar to OE parts, advertised as being firmer than stock.

That is a relative statement since the durometers of OE bushings in various places around the car will vary. And when asked, Hardrace indicated that their bushing durometers will vary as well. Their statement to us was "Normally, no, durometers aren't published as they tend to be different from part number to part number."

If learning a specific durometer is critical for you, that homework can be done on request. But we would generally recommend taking their word that Hardrace hard rubber is a firmer option than OE, without the non-compliance that can come from polyurethane.

Prothane/Energy Suspension

Prothane and Energy Suspension maks replacement suspension, chassis, and engine bushings in polyurethane. To learn a little more about polyurethane features, read this FAQ from Prothane.com:

https://prothane.com/tech-help-faqs/

The FAQ however does not indicate the durometer used for Prothane bushings (red and black colors have the same firmness). Based on some searching around, most Prothane bushings seem to be 88A durometer, but some applications can be 95A.

More to come! Send us your questions and requests to help us expand this article.