We invented the filament wound carbon rim.
Venn rims come from wind tunnels, supercomputers and articulated, multi-part tooling. Here is the work behind them, and the numbers you can check.
In the wind tunnel: smoke and laser trace the airflow over a Velocite bike
- 2015The first filament wound bicycle rims, and a Eurobike Award
- 10Awards and honours, from juries in Germany, Belgium and Taiwan
- 150JImpact pass mark for downhill rims; 100 J for road, gravel and XC. The UCI requires 40 J
- 5yearsWarranty on every Venn rim
The engineering behind Venn rims
Continuous development since 2015Continuous development since 2015: the first filament wound bicycle rims, a patented method, a laminate optimised by finite element analysis, a profile found by an algorithm, and the rims of today. Each step is dated, in its own pictures and drawings.
Strong along the fibre
A carbon rim is carbon filaments, each 5 to 7 µm across, held together in resin. Pulled along its fibres, the laminate is far stronger than pulled across them, where only the resin holds.
So a rim is only as good as where its fibres run and where they end: wherever a fibre ends, its load has to cross resin to reach the next one. Laminate design is the work of putting fibre where the load runs, and it is where Venn’s work began.
The first filament wound bicycle rims
In 2015 we showed the Venn Rev 35, the first filament wound bicycle rims. In the year they launched they won the Eurobike Award, the Taipei Cycle d&i award and the Golden Pin Design Award.
The method we patented
TW I607894, a patent we held (filed 2016, granted 2017, Victor Major inventor), set out the method in five steps: wind, cut, fold, join, mould. These are its own drawings.
The Var 507 laminate, by finite element analysis
For the Var 507 we split the rim into four parts and optimised each part’s layup in turn in finite element analysis, holding the others fixed. The model was first checked against test data. The same year, Venn filament wound rims won the Flanders Bike Valley Start-up Innovation Award.
- Symmetric where the laminate allows itSo the wheel does not twist as it deflects.
- BalancedEvery angled ply has its mirror, so the rim does not shear as it stretches.
- No thick block of one directionThose plies are spread through the stack, with angled plies between them to stop cracks.
The Var 77 profile, by algorithm
The Var 77 was the first rim profile designed by an algorithm. With National Cheng Kung University, a genetic algorithm driving a CFD solver generated 675 profiles, and the best became the mould. Its winding path was designed in software.
The winding film
Stills from the 2023 winding film.
The rims of today
Every Venn rim is made to the ETRTO standard, and every model goes through the same test programme before it is sold: impact pass marks of 100 J for road, gravel and XC and 150 J for downhill. The UCI requires 40 J.
Moulded spoke holes, no cut fibre
On the Venn 420, 520, 440, 540 and 620A TCD UL the spoke holes are moulded in, angled to the hub flange, not drilled after curing. The fibres run round each hole instead of ending at it.
Every listing’s specifications give the ERD, hole options and dimensions you need to build.
Quality you can measure
Moulded to a flawless wallA carbon rim is only as good as its wall, and only as smooth as the surface it is formed against.
Apart from the filament wound Var rims, every Venn rim made today is moulded in articulated, multi-part tooling against a contact surface finished to a high standard. The carbon is laid up accurately and preformed to net shape before it goes into the tool, so nothing about where the fibre sits is left to chance. Tooling and preforming like this are common in aerospace. In rim making they are not the norm.
Each cure runs under controlled pressure and temperature cycles. Together they compact the laminate fully and let the resin flow where it should: the wall comes out virtually free of voids and surface imperfections, with no clear coat needed to hide anything.
- ETRTOMade to the ETRTO standard.
- ImpactPass marks of 100 J for road, gravel and XC, 130 J for all-mountain and 150 J for downhill. The UCI wheel test asks 40 J.
- WeightWithin ±15 g of its listed weight on 29-inch and 700c rims.
- CheckedChecked before it ships.
Where it started
In 2015, Venn’s team made the first filament wound bicycle rims and won a Eurobike Award for them; Taiwan later granted patents for the method (TW I607894 and TW I634964, held). Winding was the state of the art of its time. What we learned there, about fibre, resin and moulds, is how we judge every rim today.
Recognition
10 awards and honours since 2010Juries in Germany, Belgium and Taiwan have recognised our work for design, innovation and manufacturing technology. The composites industry invited us to show it.
Filament wound carbon rims
For winding continuous fibre around the rim profile instead of laying up cut sheets by hand. A first for bicycle rims.
Venn Rev 35
The same rims won at Asia’s largest bicycle show, the year they launched.
Venn Rev 35
Taiwan’s leading design award, for the rim that started the filament winding era.
Start-up Innovation Award
The first award of its kind, presented at Velofollies in Kortrijk, for Venn filament wound rims.
Velocite Helios Aero
The aero frame that won the combined iF Design and Taipei Cycle d&i award in the bicycle category.
National Entrepreneurship Award
One of ten, chosen from 80 applicants, followed by the Taiwan Excellent Enterprise Quality Award in 2011.
Invited by the composites industry
At JEC Asia 2019 the JEC Group highlighted Velocite for its pioneering work in composite processing. Victor Major spoke on the advance of thermoplastic composites and the questions the industry has to answer: scaling production volume and making structures recyclable.
Research that ends up in the rim
Every Venn rim starts as an engineering question, not a styling exercise. We work with universities, research centres and material makers, and the results go straight into the laminate.
Fibre chosen for its job
- Toray T1100Ultra-high-strength fibre, now in our newest rim laminates
- Toray T800The main structure: high strength and stiffness
- Toray T700SWhere toughness and impact resistance count
- High modulusStiffness where it is needed, without the weight
Aerodynamics, computed and then measured
We design our own profiles with computational fluid dynamics, then prove them in the wind tunnel. Bicycle brands large and small, and OEM rim factories, have used the same work for their own products.
- Designed for the riderHandling in a crosswind matters as much as drag in a straight line.
- Profiles for each disciplineRoad, gravel and mountain rims each get a shape that suits the tyre and the speed.
- Checked in the wind tunnelSimulation first, then measurement on real wheels.
Effectively zero lift, in every condition
The Var 507 was never about the lowest drag figure in one wind tunnel setting. Its profile puts the aerodynamic centre just behind the axle, so gusts and passing traffic send effectively no feedback to the handlebars.
The first rim profile designed by an algorithm
With National Cheng Kung University, a genetic algorithm driving a CFD solver generated 675 profiles. We fixed only the tyre (25 mm), the depth (77 mm) and the widest point (30 mm; without that limit the optimum was 42 mm wide). The shape itself was left free. Concave and bulbous candidates stayed in the search untouched, and had one of them been fastest, we would have made it. The leading candidates were then built in 3D and simulated as whole wheels, and the best became the mould. No bicycle rim had been designed that way before.
Quality control, with the numbers
Every Venn rim model goes through the same test programme before it is sold. The only thing that changes is how hard we hit it.
The rest of the programme, with results
From the Venn 520 TCD UL wheelset test pack, as an example:
| Test | Result |
|---|---|
| Fatigue | 596 km on the rig, about 1,000,000 cycles: no cracks, bulges or spoke detachment |
| Riding run-out | 4 hours and 130 km of continuous running: rear wheel run-out within 0.1 mm |
| Spoke hole strength | Every hole above the 300 kgf pass level |
| Lateral rigidity | 133 kgf/mm (0.40 mm under 53.2 kgf) |
| Tyre retention | 120 psi held for 8 hours, flatness and deformation within limits |
| Heat | 110 psi at 80 °C: rim width changed by 0.05 mm |
| Build | Flatness 0.15 to 0.18 mm, roundness 0.20 to 0.22 mm, before and after tubeless inflation to 120 psi |
- Gravel tooA Venn 440 TCD UL measured 0.18 mm flatness and 0.19 mm roundness, and deflected under 4 mm at 5 kg lateral load against a 5 mm limit.
- Backed by a 5-year rim warrantyAnd 2 years on complete wheels.
Rim brake rims that take the heat
Our rim brake models use a custom high glass transition (Tg) resin. It keeps its stiffness well beyond what hard braking on a long descent normally produces, with good pads and well-adjusted brakes.
- about 216 °CStorage modulus onset: where stiffness starts to fall
- about 236 °CLoss modulus peak
- about 240 °CTan delta peak, the figure usually quoted as Tg
Rims engineered from first principles.
Choose your rim, or talk to us about wheels and OEM projects. Complete Venn wheelsets are at vennwheels.com.