Sprindex Introduces Adjustable Spring-Rate Coils

As coil-sprung shocks gain popularity among the trail-riding crowd, there's increasing demand for the conveniences offered by air-sprung shocks. MRP recently introduced progressive coil springs to the market, offering a taste of the late-stroke support that's both natural and now adjustable on air shocks. And nearly all high-end coil shocks include a climbing switch.

But adjusting your coil shock to suit your weight or your riding style has remained rather imperfect. You have two methods available to you when dialing in your coil shock to fit your body. There's preload, which on a coil shock is done by tightening the nut that the coil rests against on the shock body. And there's spring rate, which you choose when buying your spring. But neither is perfect. Excessive preload will sacrifice your shock's small-bump sensitivity, which sort of goes against the very reason for running a coil shock in the first place. And when you choose your spring rate, you're stuck with it until you can get back to your garage and switch it out.

For a primer on spring rate, it's usually the first of the two numbers that are printed on your coil. A 400 x 2.8 spring will take 400 pounds of direct force to compress it one inch. Spring rate changes based on the thickness and diameter and material of the coil. But also by the overall length of the coil or, to put it another way, by the number of active coils. Most brands offer spring rates in 50-pound increments. But depending on your bike, a body-weight difference of 5 pounds might require a 25-pound shift in spring rate. That means many riders will end up between ideal spring rates. Plus, what if on Wednesday you're going for a packless lunch loop, and on Sunday, you're going for a fully-loaded epic? Or what if both of those days featured a jump-filled flow trail and a rock-covered minefield? Your only choice would be to crank your preload or swap your spring to match and, again, neither solution is ideal. Enter the Sprindex.

Normally, a new product doesn't require three paragraphs to describe the problem it's meant to solve. But Sprindex is not a normal product. The brand-new brand was formed by three founding members of Crankbrothers, Carl Winefordner, Frank Hermansen (whose first names combine to make the titular "Crank") and Andrew Herrick. They also received input from living legend, Richie Schley. They embarked on the seemingly simple mission of making the coil shock more adjustable and, in turn, helping bring that nice, buttery-smooth coil-shock performance to those who opt for air springs out of convenience. And of course Sprindex wants to give existing coil users more to love. Here's how it works:

Basically, the concept limits a shock's number of active coils. If you imagine a coil unrolled into a long piece of wire, the shorter that wire, the harder it would be to bend. Made of a "glass-reinforced polymer," the Sprindex device essentially locks out a portion of those active coils, shortening the wire and making it harder to bend or, in this case, to compress.

The device sits at either end of the coil and extends with a satisfying "click" in 5-pound increments. Sprindex springs are sold in 50-pound increments, so you'd by a '400-450' or a '450-500' spring. Sitting against the Sprindex device is a low-friction Delrin adaptor. It's meant to make sure the device is fitted to the various shapes of the various shock brands it's compatible with, as well as provide a no-stick surface for the coil to twist on as it compresses. The compatibility chart is too long to post here, but rest assured, one of the three lengths offered by Sprindex will probably fit your shock.

Sprindex designed its concept around its own coil, which is of the new, fancy, light-weight variety. On that note, it's got the fancy price of $140, but that's not far off from what Fox sells its light-weight SLS springs for. We haven't gotten enough time on one yet to let you know if it's worth it, but if Sprindex has found a way to make the coil shock more accessible and more usable to more riders, it probably will be. Stay tuned.