|The relationship between polyurethane's color and hardness|
The relationship between part colour and part characteristics is much discussed on automobile forums. In this article we have tried to address the issues that arise most frequently. We hope you will find the article useful. If we haven't answered your question, we'll be happy to respond to you in letters and comments.
Polyurethane itself is either almost colourless or has a faint pastel shade. Polyurethane is coloured by adding special pigments of various colours. Colour serves a chiefly commercial purpose for automotive parts — differentiation among manufacturers. A given manufacturer may use several colours to easily distinguish among products or batches of products made of materials with different properties.
One of the main characteristics of polyurethanes is the wide range of hardness exhibited by manufactured products. It varies from highly elastic, soft rubbers (15 points on the Shore A scale) to rigid plastics (97 on the Shore D scale). A product’s hardness can be controlled, i.e., we can design and then produce an item with the hardness level most appropriate to the product's purpose and application.
We mass-produce replacement parts with three levels of hardness. Each hardness level has its own colour and designation:
This is how we designate the three hardness levels for the material we use:
- 72 – from 67 to 75 on the Shore A scale
- 80 – from 75 to 83 on the Shore A scale
- 87 – from 83 to 91 on the Shore A scale
We use an additional two hardness levels when filling custom orders: 65 and 98.
We attempt to manufacture parts with a hardness comparable to that of the original in order to avoid changing the mechanical properties of the suspensions of the vehicles on which our parts will be installed. And since the rubber that parts contain usually has a hardness of from 65 to 75 on the Shore A scale, most of the silent blocks and bushings we produce have a hardness of 72 and are thus given our company's favourite cheerful orange colour.
Some of our bushings are available in different hardness levels. The main reason for this is that our customers have repeatedly asked us to produce a more rigid version of an item. When that happens, we begin producing two versions of the part and indicate the hardness in the description, allowing the customer to choose a product with a hardness close to that of the original (orange) or a harder version (green).
In addition to colour, such parts are also differentiated by the letters R (for a hardness of 72, orange) and G (for a hardness of 80, green) at the end of the stock number.
If you are unsure what level of hardness to choose, and especially if you have never installed polyurethane parts before, we advise beginning with the orange (softer) polyurethane. That will result in a less noticeable difference after replacing rubber parts with ones made of polyurethane, and the suspension will not seem stiffer. We are more likely to recommend choosing green-coloured bushings if you have used polyurethane previously and understand what to expect when replacing parts with more rigid versions.
In some cases, we believe only one hardness level is appropriate because of a part's design or operating conditions and load. In these cases, we warn customers who request fabrication of bushings with a non-standard hardness level (using harder or softer polyurethane) that installing such bushings on a vehicle can have an adverse effect on a suspension, and we do not mass-produce such items.
Above, we described in detail the relationship between the colour and the hardness of the parts we produce. The colour of our other products (fasteners, ice cleats, belts and other general-purpose products) serves a purely decorative purpose. Therefore, there is no specific relationship between colour and hardness, and the colour selection is much broader: orange, yellow, green, blue, brown and tan.
The colours available for every item are listed. If no colour choice is available or the item is currently unavailable in your desired colour, please leave a request and we will make it for you as soon as possible.
We have explained that the properties of our products are not affected by their colour, that colour only helps distinguish among them, and that colour may also help you identify the manufacturer. However, even though a given manufacturer usually employs a particular set of colours, please be aware that sometimes you will see products by different manufacturers that are coloured the same but differ in terms of quality, either by chance or on purpose. Beware of imitations and do not focus exclusively on product colour All of our products display a stock number and the address of our website, both on the packaging and on the surface of the parts.