Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 01 Mar 2007

The Impact of Plus-Sized Wheel/Tire Fitment on Vehicle Stability4

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Page Range: 23 – 40
DOI: 10.2346/1.2698541
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Abstract

Plus-sizing in the tire industry is the growing practice of replacing a vehicle’s original equipment wheel size with a larger diameter wheel and replacing the tire with a lower-aspect-ratio tire of the same diameter. This practice is normally associated with aftermarket sales, and there is a growing trend for vehicle dealerships to fit these larger wheels/tires to new cars. This paper discusses the general practice and its effect on some of the performance characteristics of vehicles. A vehicle taken from the NHTSA New Car Assessment Program’s rollover “Star” rating program is used to illustrate the impact of plus sizing on static stability. Some of the dynamic tire effects that could influence vehicle stability are discussed, and preliminary testing data on the dynamic impact of plus sizing are presented.

Keywords: plus-size tire fitment; vehicle stability; fishhook test; NHTSA Star rating
Copyright: The Tire Society
FIG. 1.
FIG. 1.

Effect of plus-size fitment on static stability factor.

FIG. 2.
FIG. 2.

Test vehicle with NHTSA-style outriggers and wheel lift sensors. The steering controller and tire video equipment are specific to this test center.

FIG. 3.
FIG. 3.

Comparison of steering wheel angles during testing for tire-size comparison.

FIG. 4.
FIG. 4.

Linear velocity of vehicle center of gravity at minimum tip-up speed for wheels at near-zero offset. Note that the vehicle tip-up occurred at about 1.25 sec for all tire configurations.

FIG. 5.
FIG. 5.

Vehicle side-slip angles for wheels at near-zero offset. Note that the side-slip angle decreases with tire size.

FIG. 6.
FIG. 6.

Comparison of front tire deformation of P225/75R15 (left) and 31×10.50R15LT (right) at maximum tip-up. Wheels are zero offset in both cases.

FIG. 7.
FIG. 7.

Comparison of front tire deformation of P225/75R15 (left) and 285/50R20 (right) at maximum tip-up. Wheels are zero offset on left and −2 mm offset on right.

FIG. 8.
FIG. 8.

Yaw rates for each of the three tire/wheel combinations having near-zero wheel offset.

FIG. 9.
FIG. 9.

Front-wheel slip angles for the near-zero wheel offset tests.

FIG. 10.
FIG. 10.

Rear-wheel slip angles for the near-zero wheel offset tests.

FIG. 11.
FIG. 11.

Steering wheel angles for 285/50R20 comparison on different wheel offsets.

FIG. 12.
FIG. 12.

Vehicle center-of-gravity linear velocity at tip-up for 285/50R20 tires on different wheel offsets.

FIG. 13.
FIG. 13.

Vehicle yaw rates for 285/50R20 tires on different wheel offsets.

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