There are several critical measurements
to take into account when selecting a wheel or when replacing your
stock wheels with aftermarket wheels (wheels and rims being used
interchangeably in this article). Among these important
measurements are:
Wheel Diameter
This is the total wheel diameter when measured
from bead seat to bead seat. When replacing tires you of course
must know the wheel diameter, but this will be stamped on the old
tires. If you are browsing through a stack of wheels that are not
stamped an easy way to determine the diameter is to measure the
maximum diameter from rim to rim and then with a ruler measure the
distance from the rim down to the bead seat. Subtract twice the
distance which you measured down to the bead seat from the rim to
rim diameter and you will have the correct wheel diameter. Wheel
diameter is a critical consideration when changing or altering
brake components. It is also believed by many that 15" wheels have
a superior bead design and better bead retention than 16", 16.5" or
17" wheels.
Wheel Width
The wheel width or rim width is the distance
between the outside edges of the bead seat. Most popular rim width
for 4x4s would be 6", 7", 7.5", 8" and 10". Rims wider than this
are usually only used on trucks with extreme overwidth tires. The
tire manufacturer will publish guidelines for what rim width should
be used with which tire. In general 7" rims will comfortably work
with tires up to 10.5" wide, 8" wide rims work for 9.5" up to 12.5"
wide tires and 10" wide rims are used for 12.5" and wider. Many
rims will not be available in width wider than 8" and rims wider
than 10" are much more difficult to find.
Rim width relative to tread width has an effect on bead
retention when aired down and on the overall tire profile. In
general a narrower wheel (from within the manufacturers guidelines)
will result in a more rounded profile with a slightly smaller
footprint but with slightly greater protection of the wheel.
Narrower wheels also may retain the bead marginally better when
aired down than will the wider wheels. Wider wheel provide a
flatter tire profile and greater footprint. Since the rim is wider
it will not be as protected from the rocks as would a narrower
wheel with the same tire. The tire carcass will exert less pressure
on the wider width bead when aired down and a wider wheel may thus
be marginally more likely to lose a bead when pressures are low.
Wider wheels, with less sidewall bulge, may reduce the rubbing of
large tires on the springs at full turn.
Backspacing
Backspacing is the distance from the inside rim
surface to the backside of the wheel mounting surface. It
determines how far a wheel (& tire) sticks into or out of the
wheel well of the vehicle. Wheels with a lot of backspacing will
stick further in. Wheels with little back spacing will stick
further out. Sometimes when swapping in wider axles 4x4 owners will
switch to a wheel with much more backspacing to compensate. You
should note that the backspacing measurement is critical when
considering the wheels clearance of the suspension, braking and
steering components as well as the body. All of these must be
considered in both normal conditions and when at full suspension
travel or articulation.
Offset
Offset is the distance from the exact wheel
centerline to the inside wheel mounting surface. Offset and
Backspacing are related. A large amount of offset can change the
leverage and the loads on axle or wheel bearings and so if possible
you should stay (within reason) close to the stock wheel offset. In
addition to changing the load on the bearings changing the offset
significantly will change the turning radius (of the tire) and may
effect both steering response and steering stability.
Bolt Pattern
The bolt pattern has two essential parts. The
first is simple it is the number of bolts. The second is the
diameter of the "bolt circle". The bolt circle is an imaginary
circle which passes through the centerline of each of the hubs
wheel fasteners. On a wheel with 4, 6 or 8 bolt holes the
measurement is simple: Just measure from the center of one hole to
the center of the hole directly across from it. On a wheel with 5
bolt holes this is not possible. The next best thing, which will
provide a "close enough" approximation is to measure from the
center of one bolt hole to a line (or ruler) that is drawn between
the opposite edge of the two opposing bolt holes. The bolt pattern
is then indicated by the number of bolts X the bolt circle diameter
- for example a 5x5.5" bolt pattern is 5 bolt hole arranged around
a circle which is 5.5" in diameter. This may also be referred to as
5 on 5.5"
Need Gas Mileage & Power?- Free flowing performance exhaust can increase gas mileage and increase power. We can all benefit from increased mileage and increased horsepower & torque improves towing, mud-slinging and the ability to turn those larger tires you put on your truck. See what Flowtech Exhaust has for your gas or diesel truck.
Stickers, stickers, stickers!- You don't have to beg - you can get them for free! Just simply register and Off-Road.com will send you stickers from our participating companies. It's free and easy, so slap them on your ride, house or friends. Click here to register and get sticky...
Off-Road Videos - Check out over ten years of extreme 4x4 action,
product testing and the Off Road Nation at play. Baja racing to rock crawling, ATVs in the sand to motorcycles in the dirt, it?s all here. Rate them, share them and upload your own.
ATV Reviews - Honda, Suzuki, Yamaha, Polaris, Kawasaki, Can-Am. First rides to long-term tests, check out the latest in ATVs, UTVs and Side-by-Side vehicles of every make and model. Read expert opinions and follow custom project vehicles.
In the Business of Off-Road?- If you work in the off-road industry, you need Off-Road Business! Our magazine, eNewsletter, and website give you the latest industry news, new product reviews, and business tools and services you need to succeed! Check out OffRoadBusinessMag.com!
There are several critical measurements
to take into account when selecting a wheel or when replacing your
stock wheels with aftermarket wheels (wheels and rims being used
interchangeably in this article). Among these important
measurements are:
