The spare goes on unbalanced
Most pickups and farm trucks carry a full-size spare, often slung under the bed. It may have been there for years. It was probably never balanced, and if it was, the weights may have been knocked off by everything the truck has driven over since.
When a tire fails out on a ranch road or on the highway, that spare goes on and the truck carries on. On a rear axle at low speed, the vibration may barely register. On a front wheel at highway speed it usually does, and many drivers just put up with it until the flat is repaired.
The trouble is that the repaired tire often never goes back on. The spare stays in service as a regular tire, unbalanced, sometimes old and dried out, and the shake becomes part of how the truck drives.
What to do about it
After using the spare, bring both tires in. Have the original repaired or replaced and balanced, and decide whether the spare goes back under the bed or into service. If it stays on, balance it.
Check the spare's age. A tire that has spent years under a truck may have plenty of tread and still be old. Look for cracking in the sidewall and the tread grooves.
Check its pressure, occasionally, while it is still the spare. A spare that is flat when you need it is not much of a spare.
Other occasions worth a balance
New tires, a vibration at speed, and any time a tire has been dismounted for a repair. A vibration that survives a balance may be the wheel, and wheel refurbishing is at this store. A tire damaged on the road can be dealt with through roadside assistance on commercial units. Alignment is not offered here; Tucson aligns cars, light trucks and heavy units. The national tire and wheel balancing page covers more.
Other stores nearby
Tucson and Casa Grande also balance tires and wheels.
About this store
The Willcox store carries all nine Purcell tire categories and is managed by Mark Laster.
See the national tire and wheel balancing page for all 51 locations.