Only replacing one tire when others are almost new

[turtlevette]

Originally Posted By: djb
If the original tires are really worn that little, don't bother with shaving.

The difference in rotation rate will be less than simple geometry suggests. Tires with tread blocks move on their belts, and thus rotate on the effective belt diameter, not on the outside diameter of the rubber blocks.

As a thought experiment, imagine what happens when the tread block is several inches high. Estimate that the tire is inflated so that the contact patch is square -- as long as the tire is wide.


That's a really good analysis. I wonder if experiments have been done to prove the need to worry about equal diameter tires.

 

[CapriRacer]

Originally Posted By: turtlevette
That's a really good analysis. I wonder if experiments have been done to prove the need to worry about equal diameter tires.


I don't think it is diameter that is of issue here.

Way back when ABS was a new thing, General Motors conducted a series of experiments where they substituted a single new tire in a set of worn tires. They concluded that vehicles tend to pivot around the odd tire.

They did some followup experiments to prove it was not just the new vs worn thing, but that it was a difference that mattered.

Many, many years later, Michelin conducted experiments to try to find the point at which tread depth no longer mattered - and they came up with 1/32nd being undetectable, and 2/32nds being detectable.

 

[mclasser]

Update: Got one tire replaced. Tech said the new tire could be left up front since the other tires are barely worn. After he reset the TPMS, I was good to go.