I genuinely tried my hardest to shave down a automobile tire stem, boiled it in hot water, lubed it up and still I was not strong enough to pull it through the original hole. I suspect enlargement of the hole is necessary to use a stock automobile stem. This is what forced me to find the micro-stem. The micro-stem snapped right in without any hard work, no heat, no lube, just a gentle consistent tug of the blue string and it snapped through the stock hole. Here is my shaving efforts on the automobile tire stem. Still not good enough.