Field notes
Guides
The questions that come up on a driveway more than most: can this sidewall be patched, is a string plug a real repair, do I really need four tires on an AWD vehicle, does age matter when the tread looks fine, why is the TPMS light on after a swap, does an EV truck need LT Load Range E winters, and should a brand-new tire with a bead kink go on at all. The answers are not sales copy. They are published by tire makers, vehicle makers, and safety agencies — or labelled from measured field work.
These pages collect those statements with links. They are written so an independent operator can send a customer a URL instead of repeating the same explanation. Mobile Tire Services is a public registry of listed operators. A listing here is marked Listed. It is not a verification of insurance or identity.
Why a sidewall puncture cannot be repaired
USTMA, TIA, NHTSA, Michelin, Continental, and Goodyear limit a permanent puncture repair to the tread. Shoulder and sidewall injuries are replacement.
02Why a string plug is not a permanent repair
USTMA, TIA, NHTSA, and manufacturers treat an on-the-wheel string or rope plug as emergency-only. A permanent repair is a demount, a stem, and a patch.
03Why AWD needs four matching tires
Different diameters fight each other; the driveline absorbs it. Subaru, Audi, Honda, and Toyota publish match rules. Rotation keeps wear even.
04Why tire age still matters when the tread looks fine
Michelin and Continental treat ten years from the DOT date as a maximum, including the spare. Ford publishes six. Neither the United States nor Canada sets a legal maximum age.
05Why the TPMS light is on after a tire swap
Sensors stay with the wheel. After a seasonal swap the lamp is often a relearn or a missing sensor, not a flat. FMVSS 138 requires the warning; it does not program the new IDs.
06Why an EV truck winter tire must be LT Load Range E
Same size numbers can be a passenger tire or an LT Load Range E. EV trucks are heavier than petrol twins — check the letters, not just the size.
07Why to check a brand-new tire for a bead kink
A kinked bead may not seal. Look at the inner edge before mount — flat, dent, or crease is a warranty return, not fit-and-watch.