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 is a new company from the original founders of Crankbrothers (Carl Winefordner, Frank Hermansen, Andrew Herrick) and freeride legend Richie Schley.

Sprindex adjustable spring rate coil


Sprindex coils are available in three stroke lengths: 55mm, 65mm and 75mm

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.




The DH 75mm stroke Sprindex coil (without adjuster) at 290 lb/in, its softest spring rate with maximum number of active coils

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 XC/Trail 55mm stroke Sprindex coil set to 460 lb/in


The enduro 65mm stroke Sprindex coil set to 340 lb/in

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.

Delrin Performance Adapters improve the fit between the Sprindex coil and your shock and allow the spring to twist during high deflection



  1. Tom on

    While this may be new to the cycling world, it is not new in motorsports. But it’s a heavy solution to a problem that may not exist. If you are taking coils out of action, you are still carrying the weight of those coils around. The spring perch is also heavier. So yes, this product addresses a “need”, though it comes with its own set of compromises, same as an air spring carries its own compromises.

    • i on

      Except the “set” of compromises of this is a trivial amount of weight compared to a light coil – something anyone who actually rides wouldn’t care about. The set of compromises of air springs is that they are unequivocally worse than coils in terms of actual performance.

      I’m sure you’ve never ridden a coil shock, so you’re able to tell yourself that air shocks are ok. 100% of people that have ridden both know that air shocks suck.

      • Tom on

        pick your poison – either the weight is or is not important. You can’t have it both ways. Coil springs do weigh more. And for the mechanically challenged like you, you can actually design the suspension kinematics around the air springs quite easily. But please, continue to beat your chest about what a stud you are.

      • JBikes on

        The only issue with air shocks is that they will always have more stiction than a coil unit and are heat affected. Outside that, they really only differ in spring type (linear vs progressive). They are more tunable, which can be beneficial and their progressive nature can be desired for some types of riding.

        People stating one is simply better than the other aren’t considering all factors, especially how their frame may have been designed and the riding they do.

  2. Jason L on

    Not everyone is worried about every gram, especially those who are looking at coil shocks. Adding a level of tuning to coil shocks that was previously only attainable by swapping springs is fantastic and has me rethinking my shock options on my next build.

  3. BW on

    Some of these comments seem personal and not really based on customer/user experience. As an avid road bike rider and a seasoned Product Design Engineer Manager dealing with hydraulic valves requiring springs of many different designs, I find the Spindex concept very useful, simple, well thought out, and reasonably priced. Whether or not it is unique to the entire world is not important, it is unique to the bicycle world. Many concepts are borrowed from other applications and reapplied. It takes time, much effort and money to actually bring any concept to market. At this point, all I have is admiration of Spindex getting product to market and being vulnerable to customer acceptance keeping all customer feedback is useful.

  4. Lars Thomsen on

    Hells yeah Schleyer! This is going to be so useful, especially as we are seeing a resurgence of the coil. I’ve never been a fan of ‘pre-loading’ a coil and I’m stoked the ability to tune a coil like this is now available. Thanks for including so many options straight out of the gate! Great review Jessie-May.


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