How to Measure Bolt Patterns

How to Measure Wheel Back Space

The easiest way to measure backspace is to lay the wheel face down onto the ground so the backside of the wheel is facing up. Take a straight edge and lay it diagonally across the inboard flange of the wheel. Take a tape measure and measure the distance from where the straight edge contacts the inboard flange to the hub mounting pad of the wheel. This measurement is backspace. The above photo shows three wheels with 2″,3″, & 4″ backspace.

Measuring Wheel Offset

To calculate offset you’ll need the following measurements:

• Wheel backspace
• Wheel width
• Wheel Center line (outboard flange to inboard flange measurement / 2)

Subtract wheel center line from wheel backspace to get offset.

• If backspace is less than the wheel centerline the offset is negative.
• If backspace is greater than the wheel centerline the offset is positive.

Tip:

• To convert from mm to inches divide by 25.4
• To convert from inches to mm multiply by 25.4

Backspace to Offset Conversion Chart

The table below is a quick reference for finding offset, pick the rim width and follow the row over to the backspace of your wheel.

Typical Lug Nut Torque Specifications

Lug Size(Ft/Lbs Torque)

• 7/16″ (55-65)
• 1/2″ (75-85)
• 9/16″ (95-115)
• 5/8″ (135-145)
• 12mm (72-80)
• 14mm (85-95)

NOTICE: As with all types of wheels re torque lug nuts after the first 25 miles & at 100 mile intervals until lug torque is maintained. Always refer to Owner’s Manual for proper factory specifications that take precedence over the listed recommendations.

Wheel Terminology

• Bolt pattern or lug pattern or bolt circle is determined by the number of bolt holes and the bolt circle diameter.
• Hub Diameter or center bore is the hole at the center of the wheel.
• Rear spacing or back spacing is the distance from the backside of the wheel mounting pad to the outside of the rim flange.
• Offset: The distance from the centerline of the wheel to the mounting surface of the wheel.
• Negative offset: When the back of the bolt pad is closer to the inside of the wheel; when mounting surface is inboard of the rim centerline.
• Positive offset: When the back of the bolt pad is closer to the street side of the wheel; when the mounting surface is outboard of the rim centerline.
• Bead-LocA device which captures the tire bead between it’s flanges, usually secured by bolts to keep tire bead from dismounting. Usually used in dirt circle track or off road applications where low tire pressures are used and hitting ruts or other vehicles are common.

Bolt Pattern Reference

BOLT PATTERN #studs on circle	STUD HOLE SIZE	COMMON APPLICATION
5 on 4.5″	1/2″	Older Full size Ford & Chrysler Products
5 on 4.75″	7/16″	Chevy Camero & Most Older Full Size Chevrolet
5 on 5″	5/8″	Grand National & Most Older Full-Size GM Cars
5 on 5.5″	1/2″	1/2 Ton Ford Pickups, Most Jeeps, & International Scouts
6 on 5.5″	7/16″	Older Model Chevy & GM Pickups & Some Late Blazer & Datsun
8 on 6.5″	1/2″	All 8 Hole 3/4 Ton Trucks
5 on 7.75″	5/8″	Old Wide 5 Hole Volkswagen
5 on 10.25″	5/8″	Modified 37 Ford, Skeleton or Wide 5 Pattern
6 on 5″		6-Pin Sprint Car 5/8 Drive Pin
6 on 5″		6-Pin Midget 1/2″ Drive Pin
4 on 98mm		Fiat
4 on 100mm		Chevy Chevette, Plymouth K-Car, Isuzu Pup, & Renault
5 on 100mm		All GM A, J, & X Body Front Wheel Drive and some Mopar
4 on 4″		Vega & GM ‘80 & Older Skyhawk, Starfire, Astro & Sunbird
5 on 4″		Plymouth Duster, Scamp, Valiant, Dodge, & “A” Body Mopar
4 on 4.25″		Pinto, Some T-Birds, Other Ford Small Cars, & Some Porsche
4 on 110mm		Some Renault & Mazdas
4 on 4.5″		Older Mustangs & Capri 6 Cyl, Some Datsun, MG, Mazda & Toyota
4 on 120mm		Some Mazda & Honda
4 on 130mm		Volkswagen & Some Porsche
4 on 140mm		Subaru
6 on 8.75″		Military Pull Truck
6 on 7.25″		Military Pull Truck
6 on 8″		Military Pull Truck
5 on 6.5″		Land Rover