McHenry Forum - Crash Reconstruction & Simulation

A question on INCR brought asked about space saver aka donut tire testing.
The following reference was listed:

SAE Paper 2018-07-12
Passenger Car Handling Characteristics Associated with Space-Saver Spare Tires

• ABSTRACT
  • Space-saver spare tires have become near-standard equipment in passenger cars, replacing full-size spares. The properties of space-saver spare tires (cornering stiffness, self-aligning torque, etc.) exhibit some differences when compared to standard size tires. We examine potential handling changes when a space-saver tire is installed on the vehicle by examining steady-state behavior, initial step steering response, and vehicle understeer gradient as functions of the mounting location of the space-saver tire (front or rear axle). Results show that space-saver spare tires perform well and are quite capable in low-ay, linear handling maneuvers.

[COMMENT]

• We've had a couple cases involving these space saving spare tires over the years. And as a recall the main issue occurs if
  • they are used for long distances,
  • if they are run at speeds above 50 mph
  • if they are on the rear depending on the way a vehicle swerve
  These types of tires i recall saturate much quicker than 'normal' tires and so if used for longer trips so heated up, of run at speeds higher than 50 mph and particularly if on the rear of a vehicle they may saturate and help produce a loss of control
  • the locked end will lead!
  Since these tires saturate sooner than others they can cause the other rear tire to also saturate prematurely (trying to compensate for the needs required by a steer maneuver) and so the rear end essentially acts like a locked end.

We will look for more information on those past cases and add to this thread in the near future.