ENVE 3.4 SMART SYSTEM WHEELS

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ENVE 3.4 SMART SYSTEM WHEELS

The ENVE 3.4 SMART SYSTEM wheelset is essentially the ideal way to ride, a deeper rear wheel can give the rider more stability and response added to the increased stiffness in the front which results in better control.  This wheel design can give the rider more speed and increased responsiveness both in front and rear and is ideal for everyday use along with those special race days.  These wheels are also extremely attractive and can give your ride that sleek stealth look that is increasingly popular these days.  

When discussing the Smart ENVE System 3.4 with riders who have just pedaled them for the first time, the words frequently used to describe the experience are, “versatile, stable, smooth, snappy, solid, and fast”.

Pro Cycling called these wheels, “the best we’ve ridden”.

The new Smart ENVE System 3.4s just got better and are now available in a clincher model.  The 3.4s are specifically designed as a multi-purpose wheelset that can be used in virtually all weather conditions, terrains and disciplines. The 3.4s, being shallower, offer maximum performance characteristics for professional and novice riders alike in mountainous terrain, or when the wind conditions are too strong for the 6.7s or 8.9s. The 3.4 wheel system is capable of producing very low drag numbers similar to other company’s 50-60mm deep wheels, while creating a higher stability index given its shallower depth. The front rim is 26mm wide and 35mm deep while the rear is 24mm wide and 45mm deep. 

* Weights calculated using 20/24 hole count and DT Aerolite bladed spokes.
**ERD includes additional length for Pillar internal nipples (16mm)
Tubular recommended tire pressure: 100 - 140 psi
When using Non-Locking brake holders, DO NOT apply the brakes while simultaneously rotating the wheel backwards.  Failure to do so may result in ejection of the brake pad resulting in serious harm, accident, bodily injury or death. Note: Campy has redesigned their brake pad holder from 2010 (non-locking) to 2011 (locking). Make sure you are using the correct pad at all times.

The recipe for a fast wheel is no one single element; rather, it’s a combination of factors. When you start with in-frame development and blend proven aerodynamics, optimized stability, lightweight, stiffness and durability, the result is a revolutionary wheel design. Introducing the Smart ENVE System. 

SPEED

The Smart ENVE System optimizes the interface between the frame surfaces and the wheels, creating an integrated system. The front and rear wheels interact differently with the air and the rest of the bicycle. Rim shapes are optimized to allow airflow to stay attached at higher yaw angles, thus reducing drag and improving ride performance. 

• The front wheel is wider and shallower to improve stability and reduce drag in any wind condition.
• The rear wheel is deeper to reduce drag where stability is less affected.
• Wheels were tested on multiple frame designs in order to produce the maximum drag reduction. The result is a wheel system, which handles predictably, and displays superior drag results when installed in multiple bicycle frame designs.

STABILITY

Steering feedback in variable conditions needs to be predictable to have total handling confidence. Less predictable wheels have a non-linear steering response, resulting in erratic and unpredictable handling in unsteady conditions. The shape of the Smart ENVE System rim is optimized to ensure even and predictable airflow attachment. What the rider experiences is a balanced build up of side force as the angle of crosswind changes. This allows the rider to accurately predict the handling mannerisms of the wheel and avoid dangerous over correction cycles. 

• The focus on steering stability resulted in improved handling and confidence in varying crosswinds.
• Therefore, the wheel shape was optimized to produce a predictable and linear response.
• The target stability gradient was 1.0.

STRONG, STIFF, LIGHT – THE ENVE PROCESS

ENVE is renowned for developing the strongest, stiffest and lightest rims on the market. This durability is proven across all disciplines of the sport including being the first and only carbon wheel to podium at World Cup DH events. All ENVE products, including the Smart ENVE System, share this advanced manufacturing technology. These technologies involve: 

• Highest strength to weight ratio in the industry.
• Proprietary molded in spoke hole technology.
• Textured braking surface allowing for a more positive engagement and better braking in wet conditions.

Aerodynamic Stability

We can all remember the first time we pushed the pedals of our bike with a newly upgraded high-end wheel set.  It was a pure speed sensation in comparison to the wheel sets we had replaced.  Going from a high-end “non-aero” wheel to a high-end aero wheel is an equally thrilling experience.  The first time you ride an aero wheel in a road or TT bike is a special moment because you can’t believe how fast they feel. The performance improvement over a standard wheel is very significant.

Yet once someone has ridden a super-fast wheel set for five minutes, attention invariably turns to the stability of the bike through varying cross winds.  To date, most aero wheels are sold on the basis of their axial drag performance.

Traditionally, a deeper wheel gives lower drag through increased side force, so there is more load on the side of the wheel, which the rider needs to counteract with steering force.  At a certain wind angle the airflow will separate, and then the steering force has to be reduced making it difficult for the rider to maintain their desired line.  Often the condition becomes unstable and takes several steering inputs to get the bike back on line, which can potentially be very dangerous in a TT or triathlon.  This instability can cost valuable time when you need to come off the extensions to stabilize the bicycle.

As a result, before development began, the Smart ENVE team established an overall objective of developing wheels that optimized aerodynamics and stability.  The team established a process to put a metric to the level of stability of the bike in a crosswind.  Thus, the ENVE Stability Index (ESI) was born.

ENVE Stability Index (ESI)

This is by far the most important variable, and it has taken extensive research to define a wheel shape that is both fast and stable. All three wheel systems have a very similar level of stability, and are optimized for speed and ride-ability.

Traditionally, wheel testing in the wind tunnel is done in steady state; where the wheel is held for a period of time at a constant angle.  In the real world wind gusts, gaps in the hedgerows and buildings will cause instantaneous changes in wind angle.  The science of wheel stability has led us to look at transient aerodynamics or unsteady aerodynamics.

In fact, it’s only in recent years that Formula One has started to look at transient aerodynamics.  Smart’s experience in F1 aerodynamics actually started when he was a trackside engineer and the racecar did not produce the down force that it did in the wind tunnel.  This led to an extensive correlation study to understand the differences between steady state wind tunnel data and transient real world aerodynamics.
 
The team’s research in the wind tunnel showed that the wheels with poor stability had a non-linear steering torque response curve.  So when the wind angle fluctuates by more than a few degrees at a given yaw angle, the variation in steering torque can be quite high.  In certain cases its necessary to reduce the steering force (away from the wind) and this tends to make the rider feel unbalanced and often oscillate and lose the desired path of travel.?

The team’s key conclusions were:

• Within reason riders could handle a build-up in side force on the wheels by shifting their weight around slightly on the seat and turning the wheel into the wind so that it felt stable.
• Having some steering force build up was preferable to a totally neutral steering force in a crosswind.  However, this needs to be limited so that the difference in steering torque is not too high in very gusty situation where the wind angle changes.
• The biggest problem for all the testers was steering stability and the unpredictability that most of the test wheels demonstrated.  To have total confidence, the wheel needed to be very predictable so that required changes in steering input were minimal.

From this, the team set out to establish the following performance metrics and objectives:

All wheels should ideally have a linear response to steering input vs. steering angle.  In the real world this is very difficult to achieve so the metric was defined which related to the linearity of the curve.  The Conventional wheel has an index of 0.27; ENVE/Smart aimed to get our products as close to 1 as possible.

ENVE Benchmark Test at 50 KPH

Steering Torque in Nm at  50kph vs. Yaw Angle (degrees) Apparatus drag removed, data normalised to 50 kph. Front hubs only.

ENVE Steering Torque Gradient (ESG)

To explain the concept of steering input it is necessary to understand that a gradient of zero would represent a wheel with no force change.  However, we found that riders wanted some steering force so that they could turn into the wind and “balance” rather than have a wheel that tended to wander. 

Most riders liked the feeling of increased steering torque with wind angle.  But if the gradient was too high, then when the wind switched from 15 degrees to 0 there was a large difference in steering torque. 

Some of the difficult to handle wheels had gradients of 0.15 NM per degree.  The team decided to limit the ENVE steering gradient (ESG) on the wheels as follows, so that the stability performance in gusty conditions for each application was met.

Graph 1 (Steering Torque (Nm) vs. Yaw Angle (deg.))

The Conventional wheel exhibits a very non-linear steering torque vs. yaw angle response. This is a wheel that we field-tested and all riders reported stability problems. A perfect stability gradient is 1.0. 

Wheel Type	ENVE Steering Gradient	ENVE Stability Index
Popular Road Wheel	-0.027	0.602
Popular Aero Wheel	0.022	0.060
Smart ENVE System 3.4	0.067	0.988
Smart ENVE System 6.7	0.089	0.981
Smart Enve System 8.9	0.108	0.977

The Smart ENVE Systems

Rather than selling a huge range of depths and leaving the consumer to decide which wheel was appropriate for the application and conditions, the team wanted to minimize the wheel choice and make it as simple as possible for the consumer.  The wheel range consists of: 

Smart ENVE System 3.4 – Multi Purpose Wheel System (now shipping)

• Light and stiff as any climbing rim.
• Shallow steering gradient and excellent stability so can be ridden in any wind conditions.
• Main category of use: Sportive, Novice multipurpose wheel for road, tri and TT, Professional /Amateur racer in hilly terrain, and for use in extreme weather conditions.

Smart ENVE System 6.7 – Road Racing/Multi-Purpose TT/Triathlon Wheel System (now shipping)

• Fastest wheel set when installed on a bike in the mid depth category.
• Stability Index suitable for amateur and pro riders in all wind conditions, and novice on calmer days.  Sufficiently stable to be used all day long in TT/Triathlon endurance rides.
• Best weight and stiffness in class.

Smart ENVE System 8.9 – TT/Triathlon Wheel System (available in 2012)

• Fastest wheel set when installed in a TT frame.
• Higher steering gradient for TT and triathlon. Usable by TT and experienced triathletes in all but the windiest conditions.
• Class leading weight and stiffness.