This is intended to be an information thread to better everyone's understanding of performance testing on wheels... so that we won't be buying wheels just based on looks
I am by no means a wheel expert, so this will be a working document, and I will add more information as people reply to this thread.
Performance Standards/Specifications
From what I've read there are several major performance specifications for wheels from:
- SAE (Society of Automotive Engineers)
- TÜV (German regulatory agency)
- ISO (International Standards Organization)
- JWL (Japan Light Alloy Wheel Standard, VIA conducts the tests)
Are Performance Tests Mandatory?
It depends on where you live. In Japan for example, all alloy wheels for passenger cars (with 3, 5, and 7-number plates) to receive JWL/VIA approval to be legal for sale. In the U.S. however, there are only dimensional requirements per D.O.T. but no performance requirements.
What's Involved in These Tests?
I have to be honest here, so far I've only scanned through the JWL/VIA and SAE J2530. So experts please chime in
All these tests are based on the specific
load rating of the wheel. For example, a wheel rated at 690 kg will be applied a load derived from 690 kg.
A higher rated wheel will be applied a higher load during the tests, and hence more durable. But of course when the load rating is unnecessarily high, the wheel may become too heavy. Below are the key tests that are performed:
- Dynamic Cornering Fatigue Test - This is a test that simulates the forces/moments put on a wheel when the vehicle is turning a corner or going around a curve. For JWL, a bending moment (based on load rating, load radius, offset, etc.) is applied for at least 100,000 revolutions.
One interesting note here is JWL requires a higher safety factor (e.g. more load) for cast wheels (2.0) vs. forged (1.5). I guess this is why a properly designed cast wheel can be just as strong/durable as a forged wheel... but of course the cast may be heavier due to more material used.
- Dynamic Radial Fatigue Test - The main purpose of this test is to check the durability of the wheel disc. This is a test that simulates the forces that the wheel experiences with a tire mounted and carrying the weight of the vehicle, passengers and/or cargo.
Here for JWL a radial force 2.25x the load rating is applied for over 500,000 revolutions!
- Impact Test - This is a test designed to test the effect on the wheel in the event of an impact to the wheel such as hitting a pot hole or side impact into a curb. This test mainly checks for tire air retention and confirms the strength of the structure joining the rim and disc. The test basically involves the dropping of a weight at various locations on a wheel.
What Constitutes Pass or Fail?
Generally a wheel should not fail at the end of these tests, i.e. present cracks, be significantly deformed, or lose air pressure.
However, the actual passing criteria varies depending on the standard and test used. For example, JWL for trucks do not allow any deformation, while as JWL for cars only need to be able to hold air after the tests.
This is all for now. Will add more later.
Reference:
www.jwtc.jp,
www.wheelprofessor.com
