Manitou Mara Pro Shock

[Aside on Negative Springs: If a refresher on what a negative spring is and how it works would be helpful, I’ll do a quick rundown here. In an air-sprung fork or shock (for brevity, I’m just going to say “shock” in the rest of this section, but it applies to both), the main air chamber is referred to as the positive spring. It serves the same function as the coil spring in a shock that uses one — it’s the spring that supports the weight of the rider and the bike, and provides the force to rebound the shock from its compressed state. Air shocks, however, add a second spring to the picture — the negative spring. The negative spring is more commonly a second air spring; i.e., another chamber of compressed air, though sometimes a coil spring is used. The negative spring’s function is to oppose the main / positive spring, mostly at the top of the stroke, predominantly in the name of improving small-bump compliance.

The negative spring works exactly opposite to the positive spring: as the shock is compressed, the negative spring extends, and vice versa. In the case of an air negative spring, this means that its volume is lowest (and therefore, its pressure is highest) when the shock is topped out / fully extended, and its volume increases (dropping the negative spring pressure) as the shock is compressed. The effect of the negative spring is therefore highest at topout, and mitigates as the shock compresses.

The need for a negative spring in an air shock comes down to the fundamentally different behavior of an air spring vs. a coil spring.

A coil spring has a fixed length in its “relaxed” (i.e. unloaded / unweighted) state, and at that length, it exerts no force to extend itself. If you remove the spring from a coil shock, it doesn’t try to extend longer until it runs into the opposite walls of your garage. That’s what the compressed air in an air spring wants to do, though, so it is exerting force to extend the shock, even at the fully extended position. A negative spring that counteracts this force early in the travel, to better emulate the behavior of a coil spring, greatly improves the performance of an air shock.

Unlike most modern shocks, the Mara Pro’s negative spring doesn’t self-adjust to match the changing air pressure in the positive spring, so the degree to which it balances the forces at topout is mitigated substantially — especially at higher positive-spring pressures. Below I’ll go more into how this plays out when you’re actually riding the Mara Pro.]

Ok, back to the Mara Pro. Its damper is a mono-tube design, like the majority of mountain-bike rear shocks, but has a few tricks up its sleeve as well. Perhaps most interesting is the design of the Mara Pro’s internal floating piston (IFP) that’s used to compensate for the displacement of oil through the shock as it cycles. While the layout of the IFP in the Mara Pro’s reservoir is conventional, the piston itself is a bit different than most. The center of the Mara Pro’s IFP is made of a stretchy rubber, with the idea being that the shock can start moving (and thereby displace oil through the damper) without the IFP itself starting to move.

The goal here is to reduce breakaway friction — if the shock can start moving without needing to overcome the static friction in the IFP (because the IFP can stretch, rather than slide, to accommodate the first bit of motion), the amount of force needed to get the shock to start moving is reduced. It’s a clever idea, and the Mara Pro is impressive in how low-friction it feels, especially for an air shock.

The Mara Pro’s climb switch (the two positions of which are, amusingly, labeled “Work” and “Party”) is large and easy to actuate, and sits on the side of the shock body for easier access. The switch routes oil flow through a dedicated circuit, instead of adding preload to the standard compression valving, which is an increasingly common design that’s shared with the EXT Storia Lok V3 and 2021 Fox Float X2 and DHX2, among others. The advantage of such a design is that it allows the climb switch valving to be configured independently from that of the shock in open mode, and therefore creates more tuning possibilities for configuring the shock.

Starting with the Mara Pro’s compression adjusters in the middle of their ranges, the air can set to the mid-volume setting (o-ring installed, no additional volume spacers), and the recommended 125 psi, the Mara Pro’s small-bump compliance was reasonable, if not outstanding, and I was able to use full travel reliably without bottoming harshly. But the midstroke support was lacking. Pumping the bike through compressions in the trail was met with a distinct lack of pop back out, and the rear end of the bike was settling too deep in the travel through sections of rough chop — sensations that were especially apparent when paired with the exceptionally supportive Manitou Mezzer Pro fork up front.

So, I then removed the Mara Pro’s air can o-ring to open up the can to maximum volume, and then ran higher air pressure. Doing this helped somewhat with midstroke support, but came at the expense of a great deal of small-bump compliance. Cranking up the low-speed compression had a similar effect. Despite experimenting with a huge range of settings, I struggled to find a combination that both offered the midstroke support I was looking for, while also maintaining decent small-bump sensitivity and / or avoiding excessive ramp-up deeper in the travel.

As I alluded to before, I think this is mostly down to the air spring. The tuning decisions that are in conflict with each other are as follows: running middle-of-the-road settings yields somewhat soft midstroke support. Increasing air pressure and increasing the air-can volume to still use full travel at the higher pressure does improve midstroke support, but comes more severely at the cost of small-bump compliance than with most air shocks, because increasing the positive air pressure doesn’t proportionately increase the negative pressure, and leads to the shock feeling quite stiff early in the stroke. Lowering the pressure to improve small-bump sensitivity directly reduces midstroke support (and requires lowering the air-can volume to regain bottom-out resistance, but that’s not a problem in and of itself).

To be fair, as I’ve mentioned a whole lot here on Blister, midstroke support is something I personally care about a lot about in my suspension (more so in forks than shocks, but in both to a large extent) and there are absolutely riders out there who won’t be bothered by the Mara Pro’s limitation. In particular, riders who need to run relatively low air pressure in their shocks (due to whatever combination of rider weight, bike leverage curve, and personal preference) will suffer fewer drawbacks in this regard — remember, the negative-spring pressure is effectively the same for everybody, irrespective of positive-spring pressure. Especially if you fall into that camp and don’t tend to find yourself looking for a very supportive suspension setup, you might not have any complaints. But heavier, more aggressive riders looking for a lot of support out of their suspension should be more wary.