Sprindex is a new spring system for coil mountain bike shocks that, for the first time, will allow the rider to adjust and fine tune the spring rate of their coil shock, without changing the coil. What is the spring rate, you ask? Spring rate is the amount of weight required to compress a spring 1 inch. Rider weight, riding style and terrain are all factors that might make one want to adjust the spring rate of their suspension. Coil shocks are widely regarded as superior to air shocks for rear wheel suspension but their practical usability has suffered greatly from a lack of adjustability, until now.
Sprindex adjustable spring rate coil
In order to change the spring rate on a coil shock you have to swap out the coil for an entirely new one. It costs a lot of money of course and coils only tend to be available in 50 lb/in increments, though some are available in 25 lb/in increments. What are the chances of either the 400 lb/in or 450 lb/in coil having the perfect spring rate for you as an individual? Pretty slim is my guess, especially considering that a 10 lb/in difference is all that is required to see a noticeable difference in behaviour. That’s before you even start to consider terrain factors. A casual pedal around the trail centre is likely to have a different optimal spring rate to a day of dedicated descending at the Atherton Bike Park, for example.
The lack of adjustability leads to riders generally opting for coils which are a little on the stiff side, as it is preferable to riding one that is too soft and might therefore bottom out too easily. Thus, sadly, many riders are out shredding on suboptimal spring rate coil shocks, and not making use of the full stroke length.
To adjust the Sprindex coil spring rate, hold the coil with one hand and twist the dial with your other hand, or vice versa. The spring rate value is identified by the printed number on the coil displayed through the dial opening. The Sprindex coil isn’t directional so you can fit it in any direction in order to optimize accessibility for adjustment.
Spring rate is determined by 4 factors: wire diameter, coil diameter, coil material, and the number of active coils. The Sprindex coil spring rate is adjustable through altering the number of active coils in the spring, and it can be done on the trail by hand without any tools. Fewer active coils makes for a stiffer spring, while more active coils make for a softer spring.
The Sprindex springs are allegedly lighter and more durable than ordinary steel springs as they’re made with the highest tensile steel available, with each coil designed for the stress of the highest possible adjusted spring rate.
Pricing & Availability
To ensure there is a Sprindex coil for as many coil shocks that are on the market as possible, three different coil lengths are available; a 55mm stroke XC/Trail coil, a 65mm stroke enduro coil, and a 75mm stroke DH coil. All are available at local dealers and direct from Sprindex for $140 a pop. Sprindex provide a rather extensive chart on their website specifying which Sprindex fits specific coil shocks, including Marzocchi, Fox, MRP, DVO, X-Fusion, Cane Creek, Ohlins, Rockshox and Push.