Indeed there is. Here is what you need...
1) A 2 Kg weight exactly (as close as you can get) (e.g. a piece of block iron or lead)
2) A short piece of copper tube or the barrel of a disposable pen
2) A nail (not spiral) that is about 25 mm (about 1") longer than the tube.
3) a thin file to notch the nail in 1 or 2 mm" intervals.
Make a depth gauge:
- File the business end of your nail so that you have a square 1 mm x 1mm at the tip
- Place the tube on a hard surface and drop the nail into the tube. At least 1/2" of the nail head must stick out the top of the the tube. The length of the tube is not important as long as it can hold the nail properly (anywhere 2" to 4 " if adequate)
- Mark the nail at the rim where it sticks out with any sort of marking. Then with the file/saw, cut notches 1mm or 2mm apart at the mark and higher along the nail. If you put 10 cuts 2mm apart that will obviously cover 20 mm or about 3/4" of the nail. You now have a depth gauge.
Record a baseline:
- Place your depth gauge on the tire (uninflated is best) and gently place your 2 kg weight on the nail. The nail will sink into the tyre. How far it sinks is unimportant per se. If you record the depth, you will have a basis for comparison with other tyres.
- Do the same for a tyre you believe is harder
- Do the same for a tyre you believe is softer
Compare measures
2 Kg per square mm is the force that you are applying. The depth the gauge sinks x force is a good measure of work needed to compress the rubber and hence is a good mesaure of "softness" i.e. 2Kg/mm sq per mm is the "softness", if the gauge sinks 1 mm.
