Fitment Lab — tire stretch & fitment visualizer

Fitment Labtire stretch & fitment visualizer

Setup B · new

Mild stretch

Above the 7–8.5″ range; sidewall leans 9° at the flange.

Design rim ≈ 7.5″ · approved ≈ 7″–8.5″ (approx.)

Tire & rim

Tire size

Section width

Aspect ratio

Rim diameter

Rim width

Offset (ET)

Hub face from rim centreline; + = toward the outer face.

Flange

Bolts

PCD (cosmetic)

Appearance

Rim style

Finish

Colour

Custom

Finish

Lip

Separate lip colour / finish

The outer flange and the barrel in front of the spokes.

Lip colour

Custom

Lip finish

Tire

Sidewall lettering

Cutaway

A left · B right · same scale

3D view

Cutaway (cut through the axle)

Speedometer

True speed = indicated × D_B / D_A using modelled diameters (634.3 → 629.2 mm, −0.80 %).

Within UNECE R39 at all speeds

0 ≤ indicated − true ≤ 10 % of true + 4 km/h.

Factory speedo over-read on A

Most cars over-read a little from the factory. Leave 0 if unknown.

Indicated speed

km/h

indicated

100

true on A

100.0

true on B

99.2

Odometer

Per 1000 km actually driven on B the odometer shows 1008.1 km (+8.1 km).

Fitment change B vs A

mm from the hub face. + = moves toward the strut (inner) or the fender (outer).

B vs A	Inner · strut	Outer · fender
Rim edge ΔW/2 ± ΔET	+15.4 140.3 → 155.6	+35.4 50.3 → 85.6
Tire sidewall ΔSW/2 ± ΔET	0.0 157.5 → 157.5	+20.0 67.5 → 87.5
Tread edge ΔTW/2 ± ΔET	−12.6 139.2 → 126.6	+7.4 49.2 → 56.6

W rim width, SW section width, TW tread width to where the pattern ends (A 188.4, B 183.1 mm).

Model (advanced)

Tread width by aspect ratio

Belt/tread ≈ 0.77 × section width at 70-series, 0.85 at 45, 0.89 at 30. Off = one fixed factor for every size.

Flange outset

Flange roll-off

When the sidewall leans inward the tire peels back over the flange, freeing a little length. Off = the strict pinned-flange model.

Fitment Lab

Fitment Labtire stretch & fitment visualizer

Setup B · new

Mild stretch

Above the 7–8.5″ range; sidewall leans 9° at the flange.

Design rim ≈ 7.5″ · approved ≈ 7″–8.5″ (approx.)

Tire & rim

Tire size

Section width

Aspect ratio

Rim diameter

Rim width

Offset (ET)

Hub face from rim centreline; + = toward the outer face.

Flange

Bolts

PCD (cosmetic)

Appearance

Rim style

Finish

Colour

Custom

Finish

Lip

Separate lip colour / finish

The outer flange and the barrel in front of the spokes.

Lip colour

Custom

Lip finish

Tire

Sidewall lettering

Cutaway

A left · B right · same scale

3D view

Cutaway (cut through the axle)

Speedometer

True speed = indicated × D_B / D_A using modelled diameters (634.3 → 629.2 mm, −0.80 %).

Within UNECE R39 at all speeds

0 ≤ indicated − true ≤ 10 % of true + 4 km/h.

Factory speedo over-read on A

Most cars over-read a little from the factory. Leave 0 if unknown.

Indicated speed

km/h

indicated

100

true on A

100.0

true on B

99.2

Odometer

Per 1000 km actually driven on B the odometer shows 1008.1 km (+8.1 km).

Fitment change B vs A

mm from the hub face. + = moves toward the strut (inner) or the fender (outer).

B vs A	Inner · strut	Outer · fender
Rim edge ΔW/2 ± ΔET	+15.4 140.3 → 155.6	+35.4 50.3 → 85.6
Tire sidewall ΔSW/2 ± ΔET	0.0 157.5 → 157.5	+20.0 67.5 → 87.5
Tread edge ΔTW/2 ± ΔET	−12.6 139.2 → 126.6	+7.4 49.2 → 56.6

W rim width, SW section width, TW tread width to where the pattern ends (A 188.4, B 183.1 mm).

Model (advanced)

Tread width by aspect ratio

Belt/tread ≈ 0.77 × section width at 70-series, 0.85 at 45, 0.89 at 30. Off = one fixed factor for every size.

Flange outset

Flange roll-off

When the sidewall leans inward the tire peels back over the flange, freeing a little length. Off = the strict pinned-flange model.