Tires and Wheels
Wheel Fitment Clearance Calculator
Compare inner and outer wheel positions between current and proposed fitments. Tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate.
Measurements used for additional outer poke
Replace defaults only after identifying where each value came from.
Where this result applies
Compare inner and outer wheel positions between current and proposed fitments — record the exact wheel, tire, pressure, load, and suspension configuration being checked.
Tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate — that condition defines when additional outer poke is comparable with another result.
Suspension travel, steering angle, tire growth, body tolerances, and alignment can reveal interference that a static dimension misses — for original offset, the page specifically expects current wheel offset.
Use the Altitude Tire Pressure Correction for the separate question of how to estimate gauge-pressure change from atmospheric pressure and temperature differences.
Preparing a comparable second case
Measure the installed component and the vehicle reference points rather than relying only on a catalog dimension — this workflow must also account for the fact that tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate.
- Record Original overall wheel width as measured total width of the current wheel — measure from the stated reference points and note whether the vehicle or component is loaded.
- Record Original offset as current wheel offset — measure from the stated reference points and note whether the vehicle or component is loaded.
- Record New overall wheel width as measured or specified total width of the new wheel — measure from the stated reference points and note whether the vehicle or component is loaded.
- Record New offset as proposed wheel offset — measure from the stated reference points and note whether the vehicle or component is loaded.
- Record Current inner clearance as measured clearance to the closest inner component — measure from the stated reference points and note whether the vehicle or component is loaded.
- Repeat the check only after accounting for this condition: tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate.
For the distinct decision to estimate odometer distance correction after changing tire diameter, preserve this answer and open the Tire-Size Odometer Error.
What to measure before calculating
Original overall wheel width is defined here as measured total width of the current wheel — keeping that definition intact requires you to measure from the stated reference points and note whether the vehicle or component is loaded.
For Original offset, use the quantity described as current wheel offset — in the vehicle record, measure from the stated reference points and note whether the vehicle or component is loaded.
New overall wheel width: Measured or specified total width of the new wheel — a compatible entry should measure from the stated reference points and note whether the vehicle or component is loaded.
The New offset entry represents proposed wheel offset — before calculating, measure from the stated reference points and note whether the vehicle or component is loaded.
Document Current inner clearance as measured clearance to the closest inner component — this means you should measure from the stated reference points and note whether the vehicle or component is loaded.
Because a different input set is required to estimate tread wear per 1,000 miles and remaining mileage at the same rate, use the Tire Tread Wear Rate for that calculation.
Calculation method
In “fitment changes compare wheel half-width and offset at inner and outer edges,” the entered measurements must use the reference points described above.
No term beyond original overall wheel width, original offset, new overall wheel width, new offset, and current inner clearance is introduced in “fitment changes compare wheel half-width and offset at inner and outer edges.”
Checking the equation with numbers
The calculator can be reproduced with Original overall wheel width = 8.5 in, Original offset = 40 mm, New overall wheel width = 9.5 in, New offset = 32 mm, and Current inner clearance = 18 mm.
With no other assumptions added, the result is Additional outer poke = 20.7 mm and Additional inner position = 4.7 mm.
The Tire Revolutions per Mile is the appropriate follow-up when the vehicle review also needs to estimate tire revolutions per mile with an entered loaded-circumference adjustment.
How to compare the answer
Additional outer poke answers “Compare inner and outer wheel positions between current and proposed fitments.” The additional display, Additional inner position, is a different view of the same entered measurements.
Measure both sides of the vehicle where tolerances differ — when that condition changes, compare separate calculator runs instead of blending the inputs.
Because tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate, a disagreement between additional outer poke and an outside reference should trigger a review of original overall wheel width and current inner clearance.
Questions raised by this vehicle measurement
What measurement source fits Original overall wheel width when it represents measured total width of the current wheel?
Because original overall wheel width represents measured total width of the current wheel, use a source tied to the exact vehicle, component, and operating period described by the other fields.
How does the warning “Tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate” affect Additional outer poke?
The condition “Tire bulge, camber, steering angle, suspension travel, and brake clearance remain separate” is not corrected automatically by the numeric inputs, so create a separate wheel fitment clearance case when it changes.
What assumption is expressed by “fitment changes compare wheel half-width and offset at inner and outer edges”?
In “fitment changes compare wheel half-width and offset at inner and outer edges,” original overall wheel width and original offset are treated as parts of one vehicle case.
How narrowly is Original offset defined by “Current wheel offset”?
The definition “Current wheel offset” excludes a similarly named rating or a measurement taken at another reference point.
Why does Wheel Fitment Clearance note that measure both sides of the vehicle where tolerances differ?
Because measure both sides of the vehicle where tolerances differ, keep that condition consistent or calculate another case rather than expecting the formula to compensate for it.
When should Current inner clearance be collected again if it represents measured clearance to the closest inner component?
Collect current inner clearance again when a changed vehicle configuration, component, load, temperature, or operating procedure affects measured clearance to the closest inner component.