Four-Tire Wear Comparator
Compare tread readings at all four wheels. Find the average, largest gap and uneven wear patterns that may indicate alignment issues.
Compare tread readings across wheel positions.
Four-Tire Wear Comparator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Four-Tire Wear Comparator Works?
The Four-Tire Wear Comparator works by collecting a tread reading for each wheel position, computing the average and flagging positions far from the average. The tool uses 4 steps.
Measure each tire
Measure the inner, center and outer grooves of all 4 tires.
Enter readings by position
Type the readings for left front, right front, left rear and right rear.
Compute the spread
The comparator returns the average, the largest gap and each tire's deviation from the average.
Read pattern flags
The comparator flags inner-to-outer gaps over 2/32 in (1.6 mm) as edge wear.
Four-Tire Wear Comparator Formula
The Four-Tire Wear Comparator formula is Deviation_i = TD_i − mean(TD), and the spread is max(TD) − min(TD).
TD_avg = (TD_LF + TD_RF + TD_LR + TD_RR) ÷ 4d_i = TD_i − TD_avgS = max(TD) − min(TD)E_i = |TD_inner − TD_outer|- TD_i
- Tread at position i
- S
- Spread across the set
- E_i
- Inner-to-outer gap on one tire
Worked example
Readings of 6, 7, 8 and 5/32 in give an average of 6.5/32 in (5.2 mm) and a spread of 3/32 in (2.4 mm). The right rear tire sits 1.5/32 in below average with inner edge wear, a sign of toe or camber error.
Four-Tire Wear Comparator Conversion Table
The Four-Tire Wear Comparator conversion table shows a sample check of 4 wheel positions with average, deviation and wear pattern.
| Position | Reading | Deviation from average | Pattern |
|---|---|---|---|
| Left front | 6/32 in (4.8 mm) | −0.5/32 in | Shoulder wear on outer edge |
| Right front | 7/32 in (5.6 mm) | +0.5/32 in | Even |
| Left rear | 8/32 in (6.4 mm) | +1.5/32 in | Even |
| Right rear | 5/32 in (4.0 mm) | −1.5/32 in | Inner edge wear |
| Average | 6.5/32 in (5.2 mm) | — | Max gap 3/32 in (2.4 mm) |
What is Four-Tire Wear Comparator?
A Four-Tire Wear Comparator is a tool that compares tread readings across all 4 wheel positions to show uneven wear. Uneven wear across a set points to alignment, pressure or rotation problems.
Front tires on front-wheel-drive cars wear 1.5 to 2 times faster than rear tires. Regular rotation every 5,000 to 7,500 mi (8,000 to 12,000 km) evens out the set.
Edge wear on one tire points to that corner's alignment. Center wear points to overinflation. Both-edge wear points to underinflation.
What are the uses of Four-Tire Wear Comparator?
There are 4 main uses of the Four-Tire Wear Comparator, including alignment checks and rotation planning.
Alignment checks
Spot a corner with edge wear.
Rotation planning
Move the deepest tires to the fastest-wearing axle.
AWD compliance
Keep the set spread inside the AWD limit.
Service records
Log 4-position readings at each oil change.
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