A groove around the outer edge of a wheel rim to provide a lock for the tire bead.
Jacketed Gasket
A gasket having metal grommets around bolt and water holes.
Jacking
Modifying the suspension to raise or lower one corner of an oval-track race car in order to provide better handling characteristics.
Jackrabbit Start
The sudden acceleration from a standing start.
Jackshaft
A shaft found in most overhead cam engines that is used to drive the distributor, fuel pump, and oil pump.
Jacob's Ladder
A triangular control linkage to center the rear axle assembly found on some rear-wheel-drive race cars.
Jacobs Brake
A device more commonly known as Jake brake.
Jake Brake
A hydraulically operated compression braking system used to slow the truck by alternating the engine's exhaust valve opening time; named for its inventor, Jacobs.
Jalopy
A low-budget, dirt-track racing car rebuilt from an older vehicle.
An old automobile.
Jam Nut
A second nut tightened against a primary nut to prevent it from working loose; used on inner and outer tie-rod adjustment nuts and on many pinion-bearing adjustment nuts.
Japan Automobile Manufacturers Association (JAMA)
An international trade association of Japanese car, truck, motorcycle, and bus manufacturers.
Japanese Industrial Standard (JIS)
Japan's equivalent of the DIN in Germany or the SAE in the United States.
Jeep Trail
A road or trail suitable only for a 4WD vehicle.
Jeeping
Driving a 4WD vehicle, generally off the road.
Jet
A calibrated passage in the carburetor used to meter fuel flow.
Jet Car
A race car powered by a jet aircraft engine for open course competition.
Jet Valve
An intake valve, located in a pre-combustion chamber, that admits a highly concentrated air/fuel mixture into a stratified charge engine.
Jig
A fixture for holding work.
A device used as an aid to straighten the frame of a vehicle.
Joint
A junction of members that are to be joined or have been joined.
Joint Penetration
The depth a filler metal extends from its face into a joint, exclusive of weld reinforcement.
Jounce
The inward reaction of the springand shock absorber when a wheel hits an obstruction.
Journal
That part of a rotating shaft that turns in a bearing.
Journal Size
The finished diameter of a crankshaft journal.
Judder
A low-frequency vibration of the clutch or brakes.
Jug
A carburetor.
Juice
The current in an electrical system.
A special racing-fuel formula.
Any fluid, such as brake fluid.
Jump
To begin early rapid acceleration in a rolling-start race before the green flag.
To make an early, sudden start off the line in drag racing before the green light.
To bypass the ignition switch to start a vehicle.
To jump start a vehicle.
An obstacle that causes an off-road vehicle to become airborne.
Jump Out
A condition when a fully engaged gear and sliding clutch are forced out of engagement.
Jump Start
Using battery jumper cables to connect an able battery to a disabled battery to start the vehicle.
Jumper Cable
Two heavy-duty cables used to connect two batteries, as for starting a vehicle.
Jumper Wire
A wire used to bypass electrical circuits or components for testing purposes.
Jumpers
A term used for jumper cable or jumper wire.
Junction Block
A device on which two or more junctions may be found.
Junior Fueler
An old drag-racing term for a lower-class fuel dragster.
Junior Stocker
An old drag-racing term for a lower-class fuel stocker.
Junk
Anything that is so badly worn or deteriorated that it is of no further use.
Junk Box
A vehicle that has been rebuilt from well-worn parts.
A vehicle that is ready to be scrapped.
Junker
A vehicle that is ready for the junk box.
Junkyard
A vehicle salvage business that sells used parts.
Joint Tenancy
Ownership that is shared by two or more persons.
Please note that the definitions included in this Auto Glossary reflect the manner in which these terms are used on the Duipee.com website, which in some instances may differ from their meaning in other contexts.