Garage Files – Swapping Air for Coil Shocks
When it comes to rear suspension, you really only have two choices in springs, that is, unless you’re riding a modified catapult (SoftRide) or a stack-of-rubber-bumpers (ProFlex elastomer) system from the ’90s. Any real suspension design today uses either an air- or coil-sprung shock to keep the rear wheel in check. There are advantages and disadvantages to each. Traditionally, riders looking for weight savings and simplicity gravitate toward air, and riders looking for a plush and consistent feel on the roughest terrain would gravitate towards coils. Today, though, air shocks are getting more resilient and coil shocks are getting lighter. As a result, we’re seeing riders looking to experiment with both to find the best overall ride for their terrain and style. For this “Garage Files,” we took a Pivot Mach 6 and went through step by step how to properly swap the shock from an air to a coil. To find out if this was an upgrade, we’ll have to hit the trails and do some serious testing. If you’re looking to swap shocks, this is the right way to do it.
1-Our Mach 6 came equipped with a Fox Float X shock. We’re going to swap it over to a coil. It’s important to note that the Mach 6 would not work well with most coil shocks. In fact, the Push ElevenSix we’re about to install has been custom-tuned for this bike and is the only coil shock that’s approved by Pivot for the Mach 6 at this point.
2-Our Push ElevenSix shock will add a marginal amount of weight to the bike. The advantage of going to a coil in this case would be most helpful for an aggressive rider who loves long descents. Coils are typically better with small bump compliance, have a naturally linear spring curve, and dissipate heat better for consistency on long and rough descents. Air shocks tend to be lighter and are much easier to adjust. They also have a natural progressive spring curve that resists bottoming on big hits.
3-We’re going to remove the Float X for this experiment, but we’re not calling this a straight “upgrade.” The lightweight Fox shock has some serious performance that we’d highly recommend for most any rider. The Float X features an EVOL air sleeve that’s designed to mimic the feel of a coil shock and simplified versions of everything the ElevenSix offers. However, there are very aggressive riders out there who can simply benefit from using the real thing. The ElevenSix shock has a tremendous adjustment range and has been hand-tuned by the suspension wizards for the specific test rider.
4-Start by removing the shock mounting bolts. Be sure to support the shock when doing this to prevent the shock from falling and leaving a big paint chip in your downtube.
5-Many designs will require the shock body to be rotated to allow clearance to remove. Don’t worry, whether it’s a coil or an air shock, the body and shaft can be easily rotated by hand without damage.
6-Our Mach 6 uses this custom piece of hardware for the shock mount. Whatever mounting hardware your shock uses, if you’re changing shocks, you’ll need to be sure you have the right size. Shock hardware is most typically measured at the width and the inside diameter. For example, the most common size is a 22-millimeter width reducer with an 8-millimeter bolt (inside diameter).
7-Any time you’re working on suspension, it’s best to take the extra step and clean everything. Whether it’s hardware, seals or anything else, spend some time thoroughly cleaning things before reinstalling.
8-For shock hardware like this, it’s okay to use nearly any bike- specific grease. If you’re working on internal suspension parts, be sure to use the appropriate grease that won’t eat through the vital parts. For mounting hardware, as long as it’s not boat trailer grease, you should be fine.
9-Reinstall the shock hardware.
10-Now, begin to install the new shock on the bike. You may need to use the same gentle twist technique to allow the shock reservoir to clear the downtube. Remember, whether it’s a coil or air shock, the body will always twist relative to the shaft without any risk of damage.
11-Once centered over the bolt hole, begin to hand-thread in the shock mounting hardware. This is better than using a wrench, as it can prevent cross-threading.
12-Align the second shock mount with the frame.
13-It will be necessary to support the rear wheel to allow the shock to align. If you’re having trouble with this step, you can remove the rear wheel to remove weight. We were able to simply support the wheel with one hand to get the job done.
14-Torque is critical when it comes to suspension. Many bikes have the torque values etched right on the bolts to make it easy.
15-We set our Syntace torque wrench to 13 newton meters and put in the appropriate bits. Every bike’s torque setting is different. Check online if the bolts are not etched.
16-Don’t forget to torque all the bolts you hand-tightened to prevent cross-threading.
17-See those numbers? They mean something. This is a 450-pound spring, which means it takes 450 pounds of force to compress the spring 1 inch. Springs usually come in 50-pound increments and are used to adjust sag, the same way air pressure is used with air- sprung shocks.
18-Measure sag the same way with coil shocks you would with air shocks. The shock should use up about 20–35 percent of the travel, while on the bike, balanced in the riding position. You may need a friend to help you take this measurement. This Pivot’s shock has 57 millimeters of stroke*, so at sag, the shock should compress roughly 11–20 millimeters.
*Shock stroke measures how much the shock can compress before bottoming out. It’s different than rear-wheel travel. When measuring this, you’re only measuring the amount the shock compresses and not how much the wheel has moved through its travel. This 6-inch-travel bike only has a 2.5-inch stroke shock.
19-If your setup doesn’t work with your current spring, it’s time to swap for a different one. We’ll demonstrate with this Fox DHX 5.0 that’s been “pushed” for the step-by-step.
20-With the shock off the bike, unthread the preload collar to give the spring a little freedom to move.
21-Then, move the spring out of the way and gently push up on the bottom-out bumper. This will free the spring retention collar.
22-The slotted spring retention collar can now easily be removed.
23-With most shocks, the spring will now slide easily over the mounting hardware for an easy replacement with the correct one.
24-Install the new spring and replace the spring retention collar. The slot of the collar should be anywhere except lined up with the tip of the spring coil when doing this.
25-Re-thread the preload collar so that it begins to preload the spring. Every shock should have a little preload on it. However, if you have to run more than two turns’ worth of preload, it’s time to go up to the next spring weight.
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