We'd like to announce a new partnership with ELKA suspension. We've worked very closely with them to custom-valve, and custom tune the rear suspension to the linear chassis of the VF2. The results of pairing the linear active 4-bar with the linear coil shock, with the right amount of compression dampening and rebound have been stunning.
For those of you that haven't heard of ELKA, they are a leading suspension manufacturer for ATVs and other sports equipment. They produce all of their products in-house and offer high-quality CNC machined parts for their products and technical custom prowess to all of their products and customers. The results on the CHUMBA VF2 prove that this will be a well-suited partnership.
We begin testing with sponsored Yamaha ATV rider Dustin Nelson who has done extensive consulting work for Yamaha's R&D division. He's proved instrumental in maximizing suspension performance for our bicycles as well.
We are providing a very limited run of ELKA Stage 5 shocks with the VF2, so if you are interested, give us a call (888-997-2666) or e-mail (info@chumbaracing.com) to discuss these exciting new developments!
Elka Suspension’s approach to the mountain bike market isthe same that made it successful in other markets such as ATV, Side-by-SideVehicles and Motorcycles: we analyze the vehicle’s geometry (bike) and adapt ourproduct to get the most out of it. Our customers thus benefit from the sameadvantages they would get from a personalized suspension tuning (i.e. Push)straight form the factory, without any additional charges. Below is asimplified explanation of the process our R&D staff will go through inorder to develop a custom-tuned valving for any bike design, using the newChumba VF2 and EVO G2 model as an example.
1. During initial product development, our engineers have donedata acquisition on many bikes with various suspension designs. This helpedthem understand what is happening at the wheels on any kind of terrain,independently from the bike design. The data logged was the bike’s speed andthe position, velocity and acceleration of the wheel. This allows them to calculatethe forces at the wheel that needs to be absorbed for all kinds of impacts.
2. The designer / engineer / product manager of the bikemanufacturer provides us the following information:
a. Bikemodel name and year(s)
b. Wheeltravel
c. Leverageratio curve (graph showing the variation of the ratio throughout the wheeltravel)
d. Mountinghardware dimensions
e. Additionalinformation input about the intended use, suspension feeling goals, performancegoals, etc.
3. When that information is not available (or not enough), we getthe actual bike in our R&D labs and measure it to get the data we need. Wealso further use the bike for testing with our development racers and riders.
4. Our engineers will process that data using a special software(Bike Checker’s Linkage) to analyse the geometry, determine how the shock needsto work to optimize certain ride characteristics based on the leverage ratioand linkage design. Using the data logged on the trail combined withdynamometer testing, our engineers are able to replicate wheel movement on thedyno at the shock level and therefore create a dynamic calculation chart togenerate data for shock tuning, independently from the bike’s geometry andsuspension design.
5. For example, Chumba's VF2 uses a relatively linear leverage rate curve from beginning to end; being slightly regressive during the beginning towards the latter half of its stroke, with a slight amount of progressiveness towards the end of the stroke for increased bottom-out resistance. This gives a deep, supple feel during the beginning and middle of it's travel providing a bottomless feel, but also a slight ramp-up towards the end to preventing bottoming out when the maximum amount of travel is used. Given this information, we've been able to dial in the appropriate amount of compression and rebound to compliment this feel.
On the other hand, Chumba’s new EVO G2 model uses a similar shocksize/stroke as the previous generation but has a slightly higher leverage ratiowith a slightly more progressive curve from fully extended until the lastquarter of the wheel travel where it becomes digressive. That means the bikewill feel smoother initially, then will feel gradually stiffer and use lesstravel on mid-sized bumps to finally tend to be easier to bottom-out. It alsohas a mild anti-squat effect built-in to improve pedaling eficieny. To get themost out of this design, our shock needs to have less low-speed compressiondamping than the previous generation in order to keep and smooth initialfeeling with just enough pedaling “platform”. The shock also needs to have astrong damping and high threshold point for the high-speed compression circuitto prevent harsh bottoming-out. This is how we can tune the shock to achievethe best ride possible from a suspension design.
6. The engineers will produce some prototypes that arecustom-valved and will test them on the dynamometer to generate data that willhelp validate if the valving provides what the bike needs at the wheel. Oncethese results are good, they will send the prototypes to the manufacturer fortesting and approval.
7. Once the manufacturer has approved our tuning, it is thenoffered to the general public in the aftermarket and sometimes as stock on thebike (OEM) or as an upgrade by the manufacturers.
8. That’s what involved for each you see on our huge applicationlist !
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