How to check which bolt pattern you have on your trailer.
Identifying Bolt Circle Patterns
The bolt circle diameter is sometimes referred to as P C D(Pitch Circle Diameter). It is usually measured in mm but most people use the normal inches standard measurement, i.e. 4 3/4 or 4.75 inches converts to 120.65mm. In day to day reference, you would say that, "My rim has a 5 X 4 3/4 wheel pattern." Meaning that the rim has five bolts or studs and an imaginary circle of 4.75 inches is formed by the lug pattern.
How To Measure Wheel Patterns
In our case, we will be talking mostly about the 4 1/2 Ford and the 4 3/4 inch Chevy bolt circle patterns. The accompanying pictures will illustrate how we measure these bolt circles.
As you observed in the picture the bolt circle is projected through the centerline of the holes or studs. On the FIVE bolt circle, the spacing is measured from the centerline of the top bolt to the base of the arc of the bolt circle at the bottom. Another way to estimate that distance is by taking the distance between the centerline of a bolt hole across to the back side of the hole.
Just for reference, we included the way the bolt circle distances are calculated for other bolt patterns.
Ford Pattern
5 on 4-1/2 5 x 114.3mm
AMC Gremlin, Hornet, Pacer, Javelin, Matator, AMX
AMC - most models (exc. Jeep) '40-'89
Chrysler/DeSoto - all full size RWD cars (exc. Imperial) '37-'89
Dodge van (to 1985)
Dodge 1/2 ton PU (2WD to 1985)
Dodge - all full size cars & P.U.'s '37-'89
- Dart, Demon, Swinger '73-'80
Ford 1/2 ton van (1960s-era Econoline and 1968-74 E100s)
Ford Granada, Monarch
Ford - All full size cars '49-'72; '79-'85
- Fairlane '62-'79
- T-Bird '55-'71; '77-'79
- Mustang (5-bolt) '65-'73
- Maverick 5-bolt all
- Mustang SVO '85-'86
- Ranchero '68-'84
- Aerostar, Probe, Bronco II/Ranger to '89
Honda Accord FWD (mid-90s - present)
Lexus RWD
Lincoln - all '70-'72; '80-'89
Mercury - all full size cars '52-'54; '61-'72; '79-'85
- Cougar '67-'79
Mopar '73-up "A" body
Plymouth - all full size cars '37-'89
- Barracuda '70-'74
- Duster, Valiant, Volare '73-'80
Toyota 2WD pickup truck (Hilux, Tacoma)
Toyota Camry 92-present
Ford Truck Pattern
5 on 5-1/2 5 x 139.5mm
Ford F100/F150 late 1940s-1996; some F100s c. early 1980s have the 5 x 4.5 bolt pattern
Dodge Ram 2WD pickup/van 150/1500 1986 - present
Jeep CJ to 1986 (includes J-series 1/2 pickups to 1973)
International Harvester 1/2 ton pickups incl. Scout SUV to 1980
pre-1960s era Mopars
Lincoln RWD to 1960
Toyota Landcruiser early 2000s
Chevy Pattern
5 on 4-3/4 5 x 120.65mm
Buick - Regal, Century, Special (most mid-size) '64-'80's
Chevrolet - all (exc as noted elsewhere) '49-'89
Corvette all
Corvair '65-'69 5-bolt
GM compact and midsize
Oldsmobile - 442, Cutlass, F-85, Toronado
(most mid-size) '60's-'80's
Pontiac - GTO, LeMans, Firebird, Grand Prix
(mid size) '64-'80'sChevy also uses 5 on 5