# Glossary of Auto Repair, Tire and Rental Terms

> Plain definitions for the words on your estimate: alignment angles, TPMS, date codes, brake parts, battery tests, towing terms and more. Look it up fast.

Source: https://goodyearelitetireupland.com/about/resources/glossary/  
Last updated: 2026-09-17  
Business: Goodyear Elite Tire Upland, 1775 W Foothill Blvd, Upland, CA 91786, (909) 608-7699

**TL;DR:** Short definitions for nearly 100 **tire, repair and rental terms**, grouped by system. Each term links to the page that explains the **service** or **decision** in full.

This glossary defines the terms you see on estimates, inspection reports and rental paperwork at Goodyear Elite Tire Upland. Terms are grouped by system: tires, alignment, maintenance, brakes, electrical, AC, suspension, engine, special vehicles, towing and how the shop works. Each definition links to the page with the full explanation.

## Tire and wheel terms

- **Tire installation:** mounting new tires, balancing them, checking TPMS and torquing the lug nuts. See [tire installation](https://goodyearelitetireupland.com/tires/tire-installation/).
- **Mount and balance:** putting the tire on the wheel, then adding weights so it spins without shaking. See [rotation and balancing](https://goodyearelitetireupland.com/tires/tire-rotation-balancing/).
- **Road force balancing:** a balance that also presses a roller on the tire to find stiff spots that cause a vibration. See [road force balancing](https://goodyearelitetireupland.com/tires/road-force-balancing/).
- **TPMS:** the tire pressure monitoring system. It warns when air is low or a sensor fails. See [TPMS service](https://goodyearelitetireupland.com/tires/tpms-service/).
- **TPMS light:** the horseshoe-shaped dash light. It means a tire is low or a sensor is bad or not programmed. See [warning lights](https://goodyearelitetireupland.com/about/resources/warning-lights/).
- **Patch versus replace:** the decision to repair a tread puncture only when the tire is still sound. See [patch versus replace](https://goodyearelitetireupland.com/tires/patch-versus-replace/).
- **Plug:** a quick outside fill for a hole. It is not a proper inside patch. See [flat tire repair](https://goodyearelitetireupland.com/tires/flat-tire-repair/).
- **Date code:** the last four digits of the DOT code, showing the week and year the tire was made. See the [date code guide](https://goodyearelitetireupland.com/tires/tire-date-code-guide/).
- **Load index:** a number on the sidewall that shows how much weight the tire can carry. See [new tires and brands](https://goodyearelitetireupland.com/tires/new-tires-brands/).
- **Speed rating:** the letter that shows the speed the tire is built to handle. See the [tire care guide](https://goodyearelitetireupland.com/about/resources/guides/tire-care-safety/).
- **Tread depth:** how much rubber is left, measured in 32nds of an inch. See the [tire age tool](https://goodyearelitetireupland.com/about/resources/calculators/tire-age/).
- **Uneven wear:** tread wearing faster in one area, usually from alignment, pressure or worn parts. See [tire wear patterns](https://goodyearelitetireupland.com/tires/tire-wear-patterns/).
- **Inner-edge wear:** the inside shoulder wearing first. It often means the car needs an alignment. See [wheel alignment](https://goodyearelitetireupland.com/tires/wheel-alignment/).
- **Feathering:** tread ribs worn smooth on one side and sharp on the other, like a saw tooth. It often points to toe. See [tire wear patterns](https://goodyearelitetireupland.com/tires/tire-wear-patterns/).
- **Cupping:** scalloped dips around the tread, often from worn shocks plus skipped rotations. See [shocks and struts](https://goodyearelitetireupland.com/services/suspension-shocks-struts/).
- **Rotation:** moving tires to different positions so they wear evenly. See [rotation and balancing](https://goodyearelitetireupland.com/tires/tire-rotation-balancing/).
- **Torque:** how tight the lug nuts are, set to the vehicle spec with a torque tool. See [lug nuts and wheel locks](https://goodyearelitetireupland.com/tires/lug-nuts-wheel-locks/).
- **Valve stem:** the small fitting where you add air, and a common source of slow leaks. See [valve stem replacement](https://goodyearelitetireupland.com/tires/valve-stem-replacement/).
- **Nitrogen:** a dry inflation gas. You still need the correct pressure. See [nitrogen inflation](https://goodyearelitetireupland.com/tires/nitrogen-inflation/).
- **Spare tire:** a backup meant for short use only, especially compact spares. See [spare tire service](https://goodyearelitetireupland.com/tires/spare-tire-service/).
- **AWD match:** the rule that all four tires on many AWD cars should be the same size with similar tread depth. See [AWD vehicles](https://goodyearelitetireupland.com/vehicles/awd/).
- **Staggered fitment:** different tire or wheel sizes front and rear, so rotation options are limited. See [custom wheels](https://goodyearelitetireupland.com/tires/custom-wheels/).
- **Goodyear:** the tire brand this shop sells. See [new tires and brands](https://goodyearelitetireupland.com/tires/new-tires-brands/).
- **Custom wheels:** aftermarket rims that must fit the hub, clear the brakes and balance correctly. See [custom wheels](https://goodyearelitetireupland.com/tires/custom-wheels/).
- **Same-day mounting:** tires installed today when the size is in stock and a bay is open. See [same-day tire mounting](https://goodyearelitetireupland.com/tires/same-day-tire-mounting/).

## Alignment and steering terms

- **Alignment:** setting the wheel angles so the car tracks straight and the tires wear evenly. See [wheel alignment](https://goodyearelitetireupland.com/tires/wheel-alignment/).
- **Camber:** how much the top of the tire tilts in or out when viewed from the front. See the [suspension and alignment guide](https://goodyearelitetireupland.com/about/resources/guides/suspension-alignment/).
- **Caster:** the tilt of the steering pivot when viewed from the side. It affects straight-line stability. See the [suspension and alignment guide](https://goodyearelitetireupland.com/about/resources/guides/suspension-alignment/).
- **Toe:** whether the tires point in or out when viewed from above. See [wheel alignment](https://goodyearelitetireupland.com/tires/wheel-alignment/).
- **Thrust angle:** the direction the rear axle points compared with the center of the car. See the [suspension and alignment guide](https://goodyearelitetireupland.com/about/resources/guides/suspension-alignment/).
- **Printout:** the before and after alignment numbers, printed for you. See [alignment after new tires](https://goodyearelitetireupland.com/tires/alignment-after-new-tires/).
- **ADAS:** driver assistance cameras and sensors, which may need a check after alignment or ride height changes. See [hybrid and EV care](https://goodyearelitetireupland.com/services/hybrid-emerging-vehicle-care/).
- **Power steering:** the system that makes the wheel easy to turn, either hydraulic or electric. See [power steering](https://goodyearelitetireupland.com/services/power-steering/).

## Maintenance and fluid terms

- **Oil change:** new oil and filter to the spec for your engine. See [oil changes](https://goodyearelitetireupland.com/services/oil-changes/).
- **Oil spec:** the oil grade printed on the filler cap or in the owner manual. See [maintenance tips](https://goodyearelitetireupland.com/about/resources/maintenance-tips/).
- **Synthetic:** a type of engine oil. It still needs changing on a schedule. See the [oil interval estimator](https://goodyearelitetireupland.com/about/resources/calculators/oil-change-interval/).
- **Multipoint inspection:** a look over the main systems during a visit. See [preventive maintenance](https://goodyearelitetireupland.com/services/preventive-maintenance/).
- **Filters and fluids:** the oil, air, cabin, coolant, brake and steering items that keep a car healthy. See [filters and fluids](https://goodyearelitetireupland.com/services/filters-fluids/).
- **Tune-up:** the spark plug, filter and ignition work the car actually needs, not a fixed menu. See [tune-ups](https://goodyearelitetireupland.com/services/tune-ups/).
- **Transmission service:** checking the fluid first, then a drain, fill or flush only if the car calls for it. See [transmission service](https://goodyearelitetireupland.com/services/transmission-service/).
- **Wipers:** the blades that let you see in the rain, and a real safety item. See [wiper blade service](https://goodyearelitetireupland.com/services/wiper-blade-service/).

## Brake terms

- **Brake service:** inspecting the brakes and repairing only what they need. See [brake service](https://goodyearelitetireupland.com/services/brake-service/).
- **Pads:** the friction part that presses on the rotor and wears first. See [brake service packages](https://goodyearelitetireupland.com/specials/brake-service-packages/).
- **Rotors:** the metal discs the pads squeeze to stop the wheel. See the [brake safety guide](https://goodyearelitetireupland.com/about/resources/guides/brake-safety/).
- **Brake fluid:** the hydraulic fluid that absorbs moisture as it ages and can cause a soft pedal. See [brake fluid service](https://goodyearelitetireupland.com/services/brake-fluid-service/).
- **ABS:** the anti-lock braking system. Its light does not mean the pads are low. See [warning lights](https://goodyearelitetireupland.com/about/resources/warning-lights/).
- **Pulsation:** a shake in the pedal or wheel when braking. See the [brake safety guide](https://goodyearelitetireupland.com/about/resources/guides/brake-safety/).
- **Grinding:** a harsh noise when braking, often metal on metal. See the [brake wear tool](https://goodyearelitetireupland.com/about/resources/calculators/brake-wear/).

## Battery, electrical and diagnostic terms

- **Battery:** stores the power that starts the car. Heat shortens its life. See [battery replacement](https://goodyearelitetireupland.com/services/battery-replacement/).
- **Load test:** a test that checks whether the battery still delivers enough power under demand. See the [battery and electrical guide](https://goodyearelitetireupland.com/about/resources/guides/battery-electrical/).
- **Alternator:** charges the battery while the engine runs. See [alternator and starter testing](https://goodyearelitetireupland.com/services/alternator-starter-testing/).
- **AGM:** a sealed battery type that many newer cars, especially those with start-stop, require. See [battery replacement](https://goodyearelitetireupland.com/services/battery-replacement/).
- **Parasitic drain:** something that stays on after you park and flattens the battery overnight. See the [battery and electrical guide](https://goodyearelitetireupland.com/about/resources/guides/battery-electrical/).
- **12-volt hybrid battery:** the small battery in hybrids and EVs that can still leave the car unable to start. See [hybrid vehicles](https://goodyearelitetireupland.com/vehicles/hybrid/).
- **Check engine light:** an amber light that means the engine computer stored a fault code. See [check engine light diagnostics](https://goodyearelitetireupland.com/services/check-engine-light-diagnostics/).
- **Freeze frame:** a snapshot of what the engine was doing when a code set. See [check engine light diagnostics](https://goodyearelitetireupland.com/services/check-engine-light-diagnostics/).
- **Misfire:** a cylinder not firing correctly, felt as a stumble or shake. See [tune-ups](https://goodyearelitetireupland.com/services/tune-ups/).

## AC, suspension and engine terms

- **AC service:** finding why the air is weak, warm or smelly, then fixing that cause. See [air conditioning service](https://goodyearelitetireupland.com/services/air-conditioning-service/).
- **Recharge versus leak:** adding refrigerant is not a fix if the system leaks. See the [AC performance guide](https://goodyearelitetireupland.com/about/resources/guides/ac-performance/).
- **Cabin filter:** filters the air coming into the car through the vents. See [cabin and engine filter service](https://goodyearelitetireupland.com/services/cabin-engine-filter-service/).
- **Suspension:** the parts that hold the body up, absorb bumps and keep alignment. See [suspension service](https://goodyearelitetireupland.com/services/suspension-shocks-struts/).
- **Shocks and struts:** the dampers that stop the car from bouncing. See [shocks and struts](https://goodyearelitetireupland.com/services/suspension-shocks-struts/).
- **Sway bar link:** a small link that often clunks over bumps when worn. See [common problems](https://goodyearelitetireupland.com/about/resources/common-problems/).
- **Wheel bearing:** lets the wheel spin; a bad one growls louder as speed rises. See [wheel bearing service](https://goodyearelitetireupland.com/services/wheel-bearing-service/).
- **CV axle:** the shaft that drives the wheel; a bad one often clicks in tight turns. See [CV axle service](https://goodyearelitetireupland.com/services/cv-axle-service/).
- **Differential:** gears that let the drive wheels turn at different speeds. See [differential and 4WD service](https://goodyearelitetireupland.com/services/differential-drivetrain-4wd/).
- **4WD and AWD:** extra driveline parts that send power to all four wheels and need their own service. See [4WD vehicles](https://goodyearelitetireupland.com/vehicles/4wd/).
- **Belts and hoses:** rubber parts that crack, swell or leak with age. See [belts and hoses](https://goodyearelitetireupland.com/services/belts-hoses-timing-belt/).
- **Timing belt:** keeps engine parts in time and must be replaced on schedule on engines that use one. See [timing belt service](https://goodyearelitetireupland.com/services/belts-hoses-timing-belt/).
- **Water pump:** moves coolant through the engine. See [cooling system and radiator](https://goodyearelitetireupland.com/services/cooling-system-radiator/).
- **Cooling system:** the radiator, pump, thermostat, hoses and coolant that keep the engine from overheating. See [cooling system service](https://goodyearelitetireupland.com/services/cooling-system-radiator/).
- **Overheat:** engine temperature too high. Pull over and park it, since driving on can cause expensive damage. See [warning lights](https://goodyearelitetireupland.com/about/resources/warning-lights/).
- **Exhaust:** the pipes and muffler that carry gases out; leaks cause noise and smell. See [exhaust service](https://goodyearelitetireupland.com/services/exhaust-service/).

## Inspection and special vehicle terms

- **Digital inspection:** photos and notes of your car's condition, sent before extra work is approved. See [digital vehicle inspections](https://goodyearelitetireupland.com/services/digital-vehicle-inspections/).
- **PPI:** a pre-purchase inspection of a used car before you buy it. See [pre-purchase inspections](https://goodyearelitetireupland.com/services/pre-purchase-inspections/).
- **PPI limit:** an inspection is not a promise the car will not break next week. See the [PPI checklist](https://goodyearelitetireupland.com/about/resources/ppi-checklist/).
- **Diesel maintenance:** oil, filter and fuel system care for diesel trucks. See [diesel maintenance](https://goodyearelitetireupland.com/services/diesel-maintenance/).
- **Hybrid and EV care:** tires, brakes, the 12-volt battery and alignment; orange high-voltage cables go to a specialist. See [hybrid and EV care](https://goodyearelitetireupland.com/services/hybrid-emerging-vehicle-care/).
- **Fleet maintenance:** scheduled service for company vehicles. See [fleet maintenance](https://goodyearelitetireupland.com/services/fleet-maintenance/).

## Towing and U-Haul rental terms

- **Hitch inspection:** a check of the hitch, ball, pin and lights before you tow. See the [towing inspection](https://goodyearelitetireupland.com/u-haul/towing-inspection/).
- **Tongue weight:** how hard the trailer tongue pushes down on the hitch ball. See [hitch and tow package](https://goodyearelitetireupland.com/u-haul/hitch-tow-package/).
- **U-Haul:** the trucks, vans, trailers and dollies rented on this lot. Call (909) 608-7699 to reserve. See [U-Haul rentals](https://goodyearelitetireupland.com/u-haul/).
- **In-town rental:** pick up and return the equipment at this location. See [in-town rentals](https://goodyearelitetireupland.com/u-haul/in-town/).
- **One-way rental:** drop the equipment off at a location in another city. See [one-way rentals](https://goodyearelitetireupland.com/u-haul/one-way/).
- **Tow dolly:** a two-wheel trailer that lifts a car's front wheels. It does not suit every car. See [tow dolly](https://goodyearelitetireupland.com/u-haul/tow-dolly/).
- **Auto transport:** a trailer that carries the whole car with all four wheels off the road. See [auto transport](https://goodyearelitetireupland.com/u-haul/auto-transport/).
- **Cargo van:** a smaller enclosed rental for small moves and deliveries. See [cargo van](https://goodyearelitetireupland.com/u-haul/cargo-van/).

## Terms about how the shop works

- **Need versus want:** what must be fixed now for safety versus what can wait. See [need versus want](https://goodyearelitetireupland.com/why-choose-us/need-versus-want/).
- **Written estimate:** the number on paper before any work starts. See [transparent pricing](https://goodyearelitetireupland.com/why-choose-us/transparent-pricing/).
- **Invoice match:** the final bill matches the estimate you approved. See [transparent pricing](https://goodyearelitetireupland.com/why-choose-us/transparent-pricing/).
- **Diagnostic fee:** a charge for finding the cause of a problem. We tell you first if one applies. See the [cost and pricing guide](https://goodyearelitetireupland.com/about/resources/guides/cost-pricing/).
- **Road test:** a drive after brake, alignment or vibration work to confirm the fix. See [our process](https://goodyearelitetireupland.com/about/our-process/).
- **Wait versus drop-off:** whether you stay while we work or leave the car. See [what to expect](https://goodyearelitetireupland.com/why-choose-us/what-to-expect/).
- **Key drop:** leaving your keys after hours. Call to confirm before using it. See [key drop](https://goodyearelitetireupland.com/contact/key-drop/).
- **Comeback:** the same problem returns after a repair. We look first and do not argue. See [service guarantees](https://goodyearelitetireupland.com/about/service-guarantees/).
- **Former name:** this lot ran under a different business name before it became Goodyear Elite Tire Upland. See [the name change](https://goodyearelitetireupland.com/about/formerly-route-66-auto-repair/).
- **Goodyear Elite Tire Upland:** the tire and auto repair shop and U-Haul dealer at 1775 W Foothill Blvd, Upland, CA 91786. See [about us](https://goodyearelitetireupland.com/about/).
- **Call:** the fastest way to reach the desk is (909) 608-7699. See [phone and email](https://goodyearelitetireupland.com/contact/phone-email/).

## Frequently asked questions

### Why does my estimate use words I do not know?

Repair parts and tests have specific names, and estimates need to be precise. If a word is not on this page, ask the service advisor. We would rather explain a term twice than have you approve something you do not understand.

### What is the difference between rotation and balancing?

Rotation moves tires to different positions so they wear evenly. Balancing adds small weights so each tire and wheel spins smoothly without a vibration. They are often done at the same visit but solve different problems.

### Is a plug the same as a patch?

No. A plug fills the hole from the outside. A proper repair seals the inside of the tire with a patch and fills the puncture path, and only when the damage is in the repairable part of the tread.

### Can I suggest a term to add?

Yes. Email hello@goodyearelitetireupland.com with the word and where you saw it. If it shows up on our estimates or rental paperwork, we add a plain definition here.

## Related pages

- https://goodyearelitetireupland.com/about/resources/
- https://goodyearelitetireupland.com/tires/wheel-alignment/
- https://goodyearelitetireupland.com/services/digital-vehicle-inspections/
- https://goodyearelitetireupland.com/contact/request-a-quote/

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Call (909) 608-7699 or book at https://goodyearelitetireupland.com/contact/book-appointment/