Fender Design - Wheel Arch Challenge

• What’s the purpose of a fender?

Fender is a vehicle part that frames a wheel well. It prevents sand, mud, rocks, liquids, and other road spray from being thrown into the air, other vehicles, or pedestrians by the rotating tire.

• What is wheel arch?

The wheel arch is a profile of the fender, which encloses a tire. This profile is larger than the diameter of the tire, because the fender doesn’t move with the tire suspension. Therefore, the wheel arch should provide enough room to allow the full range of tire motion on the suspension without touching the interior of the wheel well.

It also plays a major role to prevent sand or debris from hitting the pedestrians or other vehicles.

• What kinds of wheel arch regulations exist?

The regulation for wheel arch depends on the region. Here are 3 different regulations as examples.

1. Japanese Regulation

• Measure clearance L of tire, hub, cap to fender in three different positions, A (Central vertical axis), B (30° forward), C (50° rearward), and produce clearance check chart to validate.
• Clearance must be greater than 5 mm in all the three positions.
• Wheel guard requirements: The clearance should be more than 5 mm at a line 30° forward and 50° rearward from the central vertical axis of wheel.

2. European Regulation

• Measure clearance L at five sections SA-SA, SB-SB, SC-SC, SD-SD, SE-SE, and produce clearance check chart to validate
• At all five sections the clearance L should be greater than 10 mm.
• Wheel guard requirements: The clearance should be more than 10 mm at all five sections. Where the five sections are as followings, SA (central vertical axis) SB (30° forward), SC (50° rearward), SE (the section passes the point, which is on the wheel arch projection line and 150 mm away from central horizontal axis), SD (the section passes the mid-point of curve CE).

3. US regulation

• Measure clearance L at every 10° gap section from -20° to 180° and make the clearance check table
• All values should be greater than 5 mm.

• Calculate Wheel Arch Gap - European Standard

In European standard, the clearance between tire and fender should be greater than 10 mm. However, this surface data doesn't meet the regulation because its clearance at every given point is not greater than 10 mm. To fix this problem, you can request a styling team to open wheel arch area more for wheel.

	SA	SB	SC	SD	SE
Gap (mm)	9.9489	10.0000	0.1137	2.9024	5.9755
Pass (> 10 mm)	Fail	Fail	Fail	Fail	Fail