In our minds, this was going to be a lot more exciting. Our plan to test a Ford Mustang GT with a space-saver spare in place of the full-size rubber at one corner seemed not just imprudent but also stood in direct violation of the advice of the owner?s manual and our attorneys. Mom also weighed in against it. The manual was most explicit: ? . . . do not exceed 50 mph? it warned, with another warning on the diminutive donut. But we defied all that because we wanted to see how much emergency performance you can expect when your car is wearing a spare.

Some suppliers are known to use the same compound on their mini spares that they use on superbike tires. And our spare did indeed have soft ­rubber. Pre-test, we measured 4/32 inch of tread depth on our space saver. Post-test, though the wear wasn?t consistent, tread depth was reduced to roughly 2/32 inch. The OE fitment Pirelli P Zero Nero All Season tires offer 10/32 inch of tread depth when new. Surely there would be fire?actual flames!?from the mini spare as we relentlessly circled the skidpad, reducing the donut to smoldering rubber in only two laps. If we weren?t handy with the extinguisher, the conflagration might just consume the entire Mustang in a matter of seconds. There would be explosions, air tankers, and rescue choppers. Monkeys and zombies would sprint to escape the inferno. Perhaps not, but you get the point. It was sure to make the typical cars-and-coffee Mustang debacle look like mere curb rash.

Results...