I use mine to “true” the tire after the tire store gets it as close as possible - run ‘em about 200 miles then pull them- they do affect acceleration and braking. Even regeared.
It works too- I left home on a trip with newish mud tires and centramatics-nearly turned around it shook so bad…. After 40 plus miles it quit shaking, by 75 the tires were smooth. Stayed that way.
A tire can wear true if forced, same as it can wear wrong.
Amazes me they aren’t “attached” to the rim but works.
I like to run one on my spare too. Can’t be too careful
I run them on the front but they would not fit over the drum brake on the rear so I put the other pair on my utility trailer. I like them! Simple and effective.