PPE Wheel Safety Standard and Design Specification

To cope with the need for safety in high-performance vehicles, normal road wheel standards such as a road wheel's safety is defined by several standards, common wheel safety standards JWL and TUV define several ways to test a road wheel to certify its safe for road use. Today's vehicle has the trend of increasing in power and weight aftermarket wheel modifications tend to be installed on high-performance vehicles or race use, common road wheel standards will not provide sufficient safety in a harsh environment for race-ready wheels. The goal of ProPioneer Engineering is not to meet the “minimum requirement” which is defined by common road wheel standards. Within mind, “There's no best, only better”, ProPioneer Engineering has gathered years of engineering design experience to developed a new standard for our wheels called “ProPioneer Wheel Specification” PWS which is a wheel safety standard above common road wheel standards in terms of strength.

 

Let us explain a bit more in common road wheel standards. Such as SAE J2530, TUV and JWL/VIA.

 

JWL/VIA – Japan Light Alloy Wheel, JWL its a requirement for Japanese requirement.

TUV – Its an organization defines wheel standard and many standards in Europe, required for Germany, Austria.

DOT – Used by the USA, no structural or strength test but only dimensional requirements.

 

These standards require a specific load rated wheel to be tested using several tests. For example, a wheel rated at 690kg will be applied a load derived from 690kg during the test. This number defines that the wheel is safe to carry such load indicated on the wheel. The definition of the VIA load rating is an arbitrary number matching the PCD pattern. Such as 690kg for 5x114.3 PCD wheels. TUV certification requires a wheel to be specified usage on a specific vehicle, therefore TUV uses the gross weight of the specific vehicle to derive a wheel's load rating.

 

In general, 3 types of tests are performed:

 

Dynamic Cornering Fatigue Test – Simulates the forces put on a wheel when a vehicle turning a corner. A derived bending load/moment is applied to the wheel center and spins for 500,000 cycles.

 

Dynamic Radial Fatigue Test – A tire is mounted and carrying the weight of the vehicle, simulates the durability of the wheel. TUV uses a safety factor of 1.5, VIA uses a factor of 1.5 for forged wheels (2.0 for cast wheels due to more defects during the casting process). 100,000 cycles will be tested.

 

Impact Test – A simulate a wheel hitting a pothole or side impact into a curb. This checks the impact strength of a wheel. A simulated weight will drop to the rim edge in 13 degrees, This test generally causing impact against cast wheels which its material itself is brittle. Forged wheels material, in general, behave ductile, and can pass the impact test with ease.

 

PWS detail comparison with road wheel standards

 

The PWS developed by ProPioneer Engineering uses a higher safety standard than common road wheel standards. By not disclosing too much mechanical and design details of our wheels, PPE has set a different safety standard to our wheels by the following specifications:

 

Dynamic Cornering and Radial Fatigue tests – The derived load using a higher safety factor for both tests. TUV and VIA use 1.5, PWS use 2.0, it's 33% higher in strength and stiffness.

Load rating – Instead of using an arbitrary number, or matching the need of a specific vehicle, we have no control of the wheel to be installed on which vehicle once it leaves the factory. PWS sets its load rating uses the recommended maximum allowable load of the tire. For example, if the wheel is rated at 690kg and fitted with a tire of maximum load index of 100 (which is 800-816kg with 2% tolerance), there is still a chance of the wheel being overloaded before the tire. It is not surprising to see a PPE designed 20-inch wheel with PCD 5x114.3 with a load rated at 800kg (816kg actual) which is a common maximum tire load of a low profile 20-inch sports tire with 100 indexes. By using this practice, the wheel will never overload before the tire.

 

Torsional load factor – This simulates the torsional load of the wheel that happens during vehicle acceleration and deceleration. This requirement doesn't exist in common road wheel safety standards and is not rare seeing some road wheels have twisted spokes during heavy braking in track days. With the trend of modern sports cars having more horsepower, braking power with aerodynamically improved down forces results in more grip (wheels suffers maximum torsional load just before it slips). PPE sets this new requirement to the PWS. Each wheel is designed to withstand a 2.5g acceleration and deceleration.

 

Manufacturing Assurance and Quality Control

All PPE forged wheels begin its life from a solid billet of 6061 aircraft grade high strength aluminum alloy. The billet is then heated to a specific forging temperature in a die, and are forged using 6,000 tonnes of pressure to form a wheel disc (in future, the spokes of a wheel). It then goes through a second stage forging called rim forging (or spun) to form the rim barrel using a high pressure 2D forging process. All the forged wheels then goes through a heat treatment process, forming a harder and higher strength material called 6061-T6.

 

Pattern making is done by precision CNC machining that close to a hundredth of a millimeter. Unlike molded or preformed wheels where accuracy and tolerance can be loose, all PPE wheels are made to custom offsets and PCD, all mounting flanges thickness has reduced to minimum, saving few hundred grams of weight just from the center. PPE ensure all the mass of the material of the wheel translates to strength and stiffness of the wheel. This way we never waste any unsprung rotating mass.

With all the combination of higher design standard, PPE wheels has a strength factor of 1.5 times then common road wheels standards with the consideration of high performance vehicle behaviors of extreme acceleration and deceleration.

 

How and why PPE wheels are lighter than other forged wheels on the market while it carries higher rated load and strength?

 

People often thinks things may go beyond physics when they don't understand. In natural, higher strength requires more material and translate to more weight/mass. ProPioneer Engineering has a unique way of mechanical design philosophy. In realistic, separating and spreading the effective stress over more material is a much more effective way of a weight reduction in engineering design. This is a well known way in engineering terms of reducing stress concentration. This is done by complex 3D modeling, hundreds of hours of fine tuning of detail dimensions with the aid of modern FEA (Finite Element Analysis) methods applies both to the front and back (behind the spokes) details of the wheel.

Any other advantage or hidden features from PPE wheels?

 

The concentricity (real roundness) of a wheel is a very important factor causing ride quality and wheel balance. While you can balance a wheel if the wheel itself is out of balance in terms of weight distribution, but you can never balance out a wheel if its hub center is not concentric with the rim barrels. All PPE wheels are heat treated and artificially aged before it is turned in precision CNC lathes together with the center hub in a single run. This process ensures all wheels have a good concentricity of rim barrels against the hub. While this is difficult to be done for multi piece wheels (2-pieces or 3 pieces) which requires assembly of rim barrels and wheel discs from individual parts. All PPE wheels are hub centric, and PPE will provide a set of matching center hub / bore adapters to customer specific vehicles.