Rock Shox MegNeg
Words & Photos by Calum Laidlaw
Rock Shox recently released their updated suspension products for 2020 and one of the new components that caught my eye was the MegNeg air chamber. The unit creates a negative air spring with twice the volume of the factory can and also adds the ability to tune the negative spring. By tuning the negative spring, riders can alter how the shock feels under initial compression as well as mid-stroke support too. Rock Shox also claims the MegNeg will offer improved bottom out resistance with the use of less tokens.
Currently I’m running a Rock Shox Deluxe RC3 on a 2018 Vitus Escarpe 27.5. During my time riding the bike I’ve found the suspension to be very linear, so much so that it’s stuffed to the brim with volume spacers, one Gnardog and two normal tokens, equating to 4.5 tokens overall. For reference, with my riding gear I weigh 172lbs and I aim for 25% sag with 185 psi and 0 clicks of rebound. Having recently received the MegNeg I was excited to see if the claimed progression from the can would finally give me the feeling I was looking for.
The Mega Negative’s larger negative air chamber is designed to counteract the static pressure exerted from the positive air chamber. If you’ve ever inflated your shock to your normal pressure without compressing it while inflating, you’ll find that it takes a huge amount of force to break the stiction without balancing the negative side. The larger negative volume allows the chamber to exert a balancing force through a higher percentage of the shock’s stroke, which results in a lower force to begin the compression of the shock. This offers better traction at the rear wheel because the tire can track undulations in terrain much easier.
In the kit from Rock Shox are four tuning bands that reduce the negative chamber’s available volume. It’s like adding tokens to the positive spring, except here the benefit is a larger amount of mid-stroke support. It does come at the cost of a slight reduction in off the top sensitivity, but the options are there!
Fitting the MegNeg is a reasonably straight-forward process. If you’ve ever done an air can service on your shock in the past then the procedure is exactly the same, apart from now having a secondary can to slide onto the bottom. It’s similar to the older DebonAir can found on the Monarch shocks. If you’re not familiar with the process, Rock Shox has a very detailed service manual on their website that you can download which goes through every step with excellent pictures and torque specs too.
One thing I was a bit concerned about was the larger outer diameter of the can not fitting inside of my split seat tube design of the frame. For reference the MegNeg air can has an outer diameter of 57mm compared to the previous generation’s 47mm. There is also a small weight penalty of 58g between the two cans with one band installed.
There are a few recommendations from Rock Shox after installing the can. You’ll need at least 20% more pressure in the shock to obtain the same sag, one token should be removed from the main air chamber due to the can’s larger amount of progression and if you don’t know how many bands to put in the shock, its recommended to try two.
One of my main goals from the air can was to get my shock as soft as possible off the top, so I decided to go with 1 band in the negative chamber, I kept all my tokens in the shock (as I wanted all the progression possible) and I needed to increase my pressure by 35% to 250 psi to get my desired 25% sag.