04-03-2018, 06:06 PM
I would guess that the polyurethane replacements will be firmer than the stock rubber mounts - The poly bar is 90 shore hardness. I haven't got an unused set of rubber mountings for comparison purposes but vulcanised rubber on car tyres is probably somewhere between 60 and 70 shore. The one (and major) bonus is that polyurethane is fuel, oil and abrasion resistant so it should last. It should perform OK because there's not really much movement on a rubber mounted engine when it has been bolted down. I do tend to leave one rear mounting loose to allow for chassis flex.