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Frequently asked questions
Here are some frequently asked questions and their answers from BlackStone Tek / BST

1. What performance improvements are typically found when upgrading to BST Prepreg Composite Carbon Fibre (PPCFC) wheels?
2. Why is Prepreg Carbon Fibre Composite more suitable for wheel manufacture compared with traditional materials such as Aluminium or Magnesium metal alloys?
3. Are BST wheels supplied by HPS complete and ready to install?
4. How much safer are Prepreg Carbon Fibre Composite wheels than standard wheels?
5. What are the physical properties of Prepreg Carbon Fibre Composite that make it particularly suitable for wheels?
6. How much stronger are BST Prepreg Carbon Fibre Composite Wheels than conventional wheels?
7. Do BST wheels have TUV certification?
8. How much lighter are BST wheels than standard wheels?
9. What is the difference between wet lay-up and the Prepreg Composite construction, as used in BST wheels?
10. How long do Prepreg Carbon Fibre Composite wheels last?
11. How much horsepower are BST wheels rated for?
12. When they cost so much, how can you claim many HPS customers feel that pound-for-pound spent, BST wheels are the not only the best modification but also the cheapest?
13. Are their any special tyre fitting requirements?

1. What performance improvements are typically found when upgrading to BST Prepreg Composite Carbon Fibre (PPCFC) wheels?
UK sports bike magazine, SuperBike, performed an independent two-day test at Spain’s Almeria circuit using a Honda FireBlade - which already had particularly light wheels compared to earlier versions.

The bike was representative of a typical lightly modified road/street/track day sports bike by having; race exhaust, Dynojet Power Commander, double-bubble screen, steering damper, a two teeth larger rear sprocket and upgraded brake pads.

The rider, Jamie Wilkins, was already familiar with the circuit after having ridden there twice before. The first day’s testing took place with standard wheels and the only change for the second day was the substitution of BST wheels. Weather conditions were unchanged and the following was observed:

  • Acceleration was noticeably stronger with the rider reporting “it felt as though it had gained ten horsepower”
  • The bike could be braked later
  • The bike could be turned more easily
  • Top speed at the end of the main straight was increased by 5mph
  • Lap times fell by a full 3 seconds – although the rider did report “pulling the pin out” as he felt very confident on the bike during the second day

These results are consistent with performance gains normally found by virtue of the combination of reduced gyroscopic inertia, rotational inertia and unsprung weight provided by BST wheels and, even if a bike is not being used on a circuit, the same benefits of increased performance and rideability and - probably more importantly - reduced rider fatigue, also apply to road/street riding.

The above is simply one example of the numerous independent back-to-back tests of BST Prepreg Carbon Fibre wheels version metal wheels which have been performed and documented - many of which can be found here. After aggregating all of the data the typical on circuit lap time saving can be seen to be 0.8 sec/mile, which equates to something like a two second lap time reduction at a typical length flowing circuit (like, for example, Donington park), but for some riders the performance gains are more significant.

One of the most startling lap time reductions reported came at the very twisty Lincolnshire track, Cadwell Park circuit (you would expect to make better proportionate lap time savings the more twisty the circuit), where the experienced owner of a highly modified BMW S 1000 RR found that changing to BST wheels reduced his lap time by 5.91 seconds; further details here.

Another example came from an experienced track rider who notified us of his lap time improvements of 4.5 and 6.5 seconds respectively at Portimao and Spa Francorchamps - both circuits where he had ridden several times previously. Other than installing his BST Prepreg Carbon Fibre wheels, this rider had made no other changes to his CBR1000RR track bike since his previous lap times had been recorded; further details here.

2. Why is Prepreg Carbon Fibre Composite more suitable for wheel manufacture compared with traditional materials such as Aluminium or Magnesium metal alloys?
Wheels manufactured from metals are either cast, forged, machined, or manufactured as a combination of the three processes. Being relatively easy to manufacture and also relatively cheap, Aluminium alloy wheels have been around for many years and are common. Their drawback is they are not particularly light because of the density to strength ratio of Aluminium (how much strength provided per kilogram of material). To improve/reduce wheel weight it would be necessary to choose a material that is lighter - such as a Magnesium alloy, but this may be at the expense of strength for a relatively modest weight reduction.

The problems with magnesium are twofold: firstly its fatigue properties are poor and, secondly, so are its corrosion properties. Very often micro-porosity (in effect "holes" in the metal) occurs during the casting process, which has a negative impact on both fatigue life and potential corrosion degradation - meaning a cast Magnesium alloy wheel may not have a very long life expectancy.

Forged magnesium suffers less from porosity but still may not last very long; i.e., sometimes less than a racing season. Several recent high profile failures of forged Magnesium alloy wheels have contributed to them being progressively banned from some high level racing classes - most notably the World Superbike Championship (WSBK) - where 17" Aluminium wheels are now the only permitted type.

If the very significant benefits of having lighter wheels are being sought - but without compromising lifespan and safety - the only entirely effective solution is to use Prepreg Carbon Fibre Composite which is not only both a lighter AND a stronger material, but also a fatigue free and corrosion free material meaning that as an engineering solution for safety critical components such as wheels it is vastly superior to Magnesium or Aluminium alloys (see subsequent Q&A’s for its technical properties to confirm this).

This move toward composite materials is not only relevant to motorcycle wheels but it is now also widely known that in other engineering areas where, for safety-critical reasons, having the strongest and longest lasting but still light materials is a necessity (such as in aircraft fuselages and wings, helicopter rotor blades, high performance road car and racecar chassis, as just a few examples) the reliance on light metal alloys is diminishing rapidly. Further information can be founds here from Cytec - the worldwide leader in composites and technology supply partner to not only BST, but also other notable and forward thinking companies such as Boeing, McLaren automotive and Airbus Industrie, to name but three.

3. Are BST wheels supplied by HPS complete and ready to install?
BST wheels from HPS are supplied with:

  • All internal bearings, spacers and seals pre-installed
  • External spacers, where required
  • Air/tyre valves
  • Cush drive (rear double-sided wheels)
  • Sprocket (rear double-sided wheels) where required - except certain KTM applications
  • Sprocket carrier (rear double-sided wheels) where required – additional wheels can be purchased without a sprocket carrier for race teams or track day users

BST wheels are ordinarily designed make use of your bike's original brake discs meaning that after fitting tyres and discs your wheels will go straight in. Please note that disc bolts may need to be replaced with new items as some bike makers specify that their originals are "one use only" stretch bolts. HPS can advise and quote you, if required, for replacements in Stainless Steel or Titanium.

4: How much safer are Carbon Fibre wheels than standard wheels?
A: Carbon Fibre wheels have been in existence for some considerable time and have been proven to be safe when designed and manufactured properly and, as with any wheel, used within their design parameters. One of the parameters is the maximum static weight of the motorcycle for which the wheels are designed (Black Stone Tek wheels are designed for motorcycles that weigh up to 280kg dry) and have more than adequate strength and damage tolerance for any usage within a road/street, sport or race environment. Safety is dependant on more than just strength, though, and whenever a bike becomes more easily controllable because of better dynamic characteristics, active safety is enhanced too.

5: What are the physical properties of Prepreg Carbon Fibre that make it particularly suitable for wheels?
A: Some of the properties of Carbon Fibre composites as used in BST wheels.
Material used - Carbon Fibre Prepreg in a woven and unidirectional format, embedded in a resin matrix, made from toughened epoxy.

- Max structural temperature: 120 degrees C
- Min structural temperature: -40 degrees C
- Corrosion resistance: Totally corrosion free
- Chemical resistance: Resistant to most dilutants such as acetone, benzene, thinners,
- Automotive fluid resistance: Limited resistance to brake fluids and acids
- Density: Approximately 1.7 kg/qdm (Aluminium 2.7, Titanium 4.5, Steel 7.9)
- Damage Tolerance: Similar to 2024 Aluminium
- Strength: Better than 2024 Aluminium
- Stiffness: Similar to 2024 Aluminium

Variable wall thicknesses can be created anywhere as needed in order to increase strength where required. Fibres are oriented in the direction of stress in order to increase strength.

6: How much stronger are BST Carbon Fibre Wheels than conventional wheels?
A: BST Carbon Fibre wheels are comfortably over-engineered for street/road use and have undergone an intensive programme of very stringent testing to verify their design and to confirm their strength and durability.

A designated test body in the UK performed the following tests and all tests were conducted on a single wheel. It is important to note that performing a ‘single wheel test’ is not usual when checking metal wheels, since due to metal fatigue behaviour, a single wheel could not withstand all the tests. To allow for this weakness in metal wheels, the test regulations actually specify that using one new wheel for EACH AND EVERY test is permissible during which it is destroyed, whereas in this case a single BST wheel withstood ALL tests and was still completely serviceable afterwards.

- Cornering fatigue: 100,000 cycles at 530Nm
- Radial fatigue: 500,000 cycles at 5200Nm
- Torsional fatigue: 100,000 cycles at 400Nm
- Impact test: 337.5kg from 150mm (JWL)

The front wheel was designed for a 135kg static load and the rear wheel for a 145kg static load (this translates into a bike with a total dry weight of 280kg). Modern sports bikes normally weigh between 160-220kg and race bikes rarely exceed 170kg, so these static load design parameters comfortably exceed normal conditions.

The Eurotype Test Centre has tested the rear wheels where both conventional and offset versions have been subjected to cornering fatigue testing in excess of 1,000,000 (one million) cycles at 590Nm.

The graph below shows a range of tensile strength figures to indicate the spread of properties associated with different alloys. More information can be found on the Net Composites web site. (an
independent research firm).

7: Do BST wheels have TUV certification?

A: Yes, BST have TUV certification for both their ISO 9001:2000standard manufacturing processes and facility and for the wheels.
TUV requires testing on a wheel type per-model basis, so to verify strength and compliance of the predominant wheel designs, the Suzuki GSX-R1000 and Ducati 748/916/998 series were chosen for certification.

8: How much lighter are BST wheels than standard wheels?
A: Standard wheels are have become lighter in recent years anyway as bike manufacturers fight for magazine headlines and performance gains. However, it is still possible to make very significant weight savings. GSX-R1000 wheels have been used here as a typical example of a modern sports bike as it has wheels that are among the lightest. On older bikes, the weight savings with BST can even greater.

Weight Examples quoted here include bearings, spacers, seals, sprocket, cush drive, valves, but exclude. discs & tyres

Standard GSX-R1000 wheel weights
Front 4.360Kg
Rear 7.529Kg

BST with Aluminium Alloy hubs wheel weights
Front 2.380Kg – weight saving 1.980Kg / 45% lighter than standard)
Rear 4.638Kg – weight saving 2.891Kg / 38% lighter than standard)

Total weight saving 4.871Kg

9: How long have BST wheels been in development?
A: One of BlackStone Tek’s aeronautically qualified design engineers, Chris Adrian, started developing Carbon Fibre wheels in the early 1990s, some of which have been used on GP bikes since then. This current BlackStone Tek range of wheels has been on sale for around 12 years and, during that time (due to the continuous improvements being made to the prepreg carbon fibre materials provided by BST's supplier - British company ACG/Umeco) the already immensely strong wheels have become 30% tougher.

10: What is the difference between wet lay-up and the Prepreg construction, as used in BST wheels?
A: In a wet lay-up manufacturing process, the fibres are positioned in the mould dry and the resin is applied with a brush. The resin is mixed by hand and inconsistencies can be found after mixing. This is a relatively inexpensive process, but the resulting part is normally heavier and the Fibres can distort during the lamination process meaning the process is less controlled. This method does not lend itself to the Autoclave process which cures the part under controlled heat and pressure.

In the Prepreg process used to manufacture BST wheels, the resin is applied by machine onto the Fibres in a thin film. Therefore, the resin is very even and controlled. The layers are laminated by hand but can be positioned much more accurately. The parts are then cured under a high pressure and temperature environment (Autoclaved). This results in a well-compacted laminate with better properties than with wet lay-up. Laminate properties in Prepreg Carbon Fibre can be 10%- 20% better than wet lay-up at a lower weight (because less resin is used to do the same job). This Prepreg and Autoclave process is perhaps more commonly known as the process used to manufacture the exceeding strong, but light, chassis centres (often known as ‘tubs’) for Formula 1 race cars.

11: How long do Carbon Fibre wheels last
As Prepreg Composite Carbon Fibre is a fatigue-free material, their lifespan will always exceed that for wheels manufactured from alternative materials and wheels originally made decades years ago by BlackStone Tek’s design engineer, using earlier and less sophisticated technology, are still running today with any defects.

12: How much horsepower are BST rims rated for?
A: BST wheels are safe up to 1900Nm torque. BlackStone Tek uses the torque measurement rather than horsepower, as it is torque that is driving the wheel. If your bike generates more than 1900Nm of torque we would like to see it, as a standard 2002 GSX-R1000 normally tests at around 99Nm…

13: Are their any special tyre fitting requirements?
A: As Carbon Fibre wheels are much stronger and more durable than metal wheels, there are no special requirements when fitting tyres, and the correct standard tyre fitting procedures should simply be followed as with any motorcycle wheel, see video below...


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