Durometer guide for cast polyurethane
What durometer means for cast polyurethane parts, with everyday comparisons for bushings, bump stops, pads, spacers, and wear parts. Titan Works casts any durometer up to a hardness of 95.
Request a quoteDurometer is the hardness of an elastomer, measured by pressing a calibrated indenter into the surface per ASTM D2240. Titan Works casts any durometer up to a hardness of 95. Higher numbers are harder.
Durometer in everyday terms
| Durometer | Feels like | Typical cast urethane use |
|---|---|---|
| 40 | Pencil eraser | Soft isolation pads, gaskets |
| 60 | Tire tread | Vibration mounts, soft bump stops |
| 70 | Shoe sole | Spring inserts, isolators |
| 80 | Leather belt | Bushings, bump stops, pads |
| 90 | Skateboard wheel | Firm bushings, spacers, wear strips |
| 95 | Hard hat liner | Load-bearing spacers, rollers, metal replacement parts |
What hardness changes
Load capacity rises with hardness. A harder part carries more before it deflects a given amount.
Deflection and feel fall with hardness. A softer bushing rides quieter and absorbs more; a harder one gives sharper response.
Rebound varies with formulation more than hardness, but harder parts generally return energy faster.
Abrasion resistance is highest in the middle of the range, roughly 80 to 95, which is why wear parts cluster there.
Tear strength generally rises with hardness.
Choosing a hardness
Start from the part you are replacing. If it was rubber and worked but wore out, match or go slightly harder in urethane, since urethane carries more load at a given hardness. If it was rubber and rode harsh, go softer. If it was aluminum or plastic, start at the top of the range, around 95.
If you are designing new, tell us the load, the deflection you want at that load, and the temperature range. We will suggest a starting point, and for anything ride-related we recommend pouring samples in two or three hardnesses and testing on the vehicle.
Dual durometer
Some parts benefit from two hardnesses in one piece: a soft face for initial contact and a hard core for load. Cast urethane can do this in a two-shot pour. Progressive bump stops sometimes use it.
How we control it
Hardness in cast urethane comes from the formulation and from getting the ratio and cure right. Our dispensing machine controls the ratio. Cure schedules are documented per part. We check each lot with calibrated durometer gauges and record the result. A spec of plus or minus 5 points is typical and comfortable.
Questions about a specific part? Send it over.
