DT Swiss OPM O.D.L. 120 29″ Fork

Fork Geometry

The OPM in the 120mm, 29” version features a 45mm offset, which is decidedly at the low end for forks in this category. (We discussed this in our recent review of the Rockshox Reba, which also has relatively little offset.)

Offset is how far forward the fork’s axle sits from the center of the steerer tube. This is also referred to as the amount of “rake” a fork has. As detailed in the image below, trail is the distance between the headtube angle, projected to the ground, and the center of the contact patch of the tire (which is directly below the fork’s axle). More rake = longer offset = shorter trail, which gives a bike a bit more perky and responsive handling.

Marshal Olson reviews the Rock Shox Reba RL 29'er fork for Blister Gear Review
Rake Vs. Trail

Many 29” forks are trending toward larger offset, with 51mm offset arguably being the “new normal.” Compared to forks with that geometry, the OPM feels a bit less stable. I don’t want to overstate this point—I’ve been happily riding 29” forks with 45-46mm offsets for years—but I think this is one of the areas on the OPM where there’s room for improvement.

Air Spring

The OPM uses a traditional air spring in the left leg of the fork, and uses a steel negative spring in the right leg to help keep the ride supple. The upside is that this is quite simple, and there’s not a whole lot to go wrong with it. The downside is that the negative spring, and the suppleness in the beginning of the fork’s stroke, aren’t really tunable.

I found that the OPM’s air spring felt pretty good through the first 2/3 of its travel. It was supple at the beginning of its stroke, and handled mid-sized hits fairly well.

I did, however, find it to be a bit too progressive. In the bottom 1/3 of its stroke, the spring ramps up very quickly. I generally run a shorter-travel fork like this with around 15% sag, which on this fork worked out to about 60psi.

Noah Bodman reviews the DT Swiss OPM O.D.L. 120 for Blister Gear Review
Noah Bodman on the DT Swiss OPM O.D.L. 120, Whitefish, MT.

Even with the fork set up with that amount of sag, I wouldn’t use the bottom 1/3 of the travel on most rides. It was only if I started jumping off of pretty tall things that I managed to bottom out the fork.

That balance of progressiveness is always tricky on trail-oriented forks such as this. I think the OPM is a bit too progressive for a relatively short-travel, trail-oriented fork, but there are also plenty of other comparable forks that are too linear (such as the Reba).

The downside here is that, while a linear fork can be made a bit more progressive, it’s difficult to impossible to make the OPM more linear. I could, of course, lower the air pressure to use more of the fork’s travel, but then it was too soft for the first 2/3 of the stroke.

Damping

The OPM uses a closed damper system where the oil is separated from any air in the fork by a floating piston. While this sort of system potentially adds a bit more friction and complexity due to having some additional seals, it prevents issues with aeration of the oil by keeping it separate.

This arguably has some benefits over an open bath system where the oil is free to mix with the air. The OPM’s closed system also potentially keeps the oil fresh a little bit longer, potentially prolonging intervals between service.

For external adjustments, the OPM has a rebound adjustment on the bottom of the right leg, a 3 position Open / Drive / Lock lever at the top of the right leg, and a low speed compression adjustment on top of the ODL lever.

While the rebound knob certainly had a noticeable effect, I found the increments between clicks a bit too large. I’m a bit picky about my rebound settings, and I had a lot of trouble getting the rebound speed dialed to my liking; I’d say the changes for each click on the OPM’s rebound knob are the equivalent of 2 clicks on a Rockshox or Fox fork.

The three position ODL knob was easy to use, but I left it in “open” for nearly the entire test. Personally, I’ve never been a huge fan of lockouts on forks; I don’t do enough out-of-the-saddle sprinting for them to be all that useful. That said, if you like a firm lockout, the OPM will take care of you. While there is a blow-off in the lock position, the lockout is very firm and it took a decent sized hit to get the fork to budge.

The middle “Drive” mode was a bit disappointing. RockShox and Fox both employ a roughly similar 3 position setting, and I often use this middle setting on pumpy, flowy trails where a bit more support out of the front end is welcome.

Ideally, in this middle setting, the fork retains most of its small bump sensitivity, but dramatically increases the mid- and end-stroke support. Admittedly, this is a tricky balance to hit, and certainly not one that Rockshox and Fox hit perfectly, either.

The Drive mode on the OPM is clearly designed with the intention of providing support, but I felt like its execution fell a bit short. The OPM’s great small bump sensitivity all but disappeared in Drive mode, and the fork felt too stiff. It felt more like a poorly executed lockout than a supportive setting designed for flowy trails.

Noah Bodman reviews the DT Swiss OPM O.D.L. 120 for Blister Gear Review
Noah Bodman on the DT Swiss OPM O.D.L. 120, Whitefish, MT.

On the flip side, those who complain that the RockShox and Fox 3 position adjustments don’t offer a sufficiently large change from the “Open” setting certainly won’t have any such gripes with the OPM: the difference between “Open” and “Drive” is very apparent.

The external compression adjustment knob only really seemed to make a noticeable difference in “Open” mode, but in that setting, it worked well. I could essentially use that knob as a substitute for the Drive mode—adding a few clicks would keep the fork a bit more supported in corners and when pumping through rollers.

Bottom Line

The DT Swiss OPM seems a bit confused. On one hand, it’s the lightest fork in our test, and has a super solid lockout. Based on that, I’m somewhat inclined to recommend this to someone who might have an XC race background, but wants a more trail-oriented fork.

But on the other hand, it has a very progressive air spring, which means that it’s great for bigger guys or those who are inclined to jump off of large things, despite the fact that they’re on a relatively short travel bike. The issue there is that this is a pretty light fork, and while it’s not what I’d call a noodle, it’s probably not burly or stiff enough for those sort of riders.

Added into the mix is the fact that this is the most expensive fork of the bunch. That’s somewhat to be expected since it’s quite light and has a relatively sophisticated damper, but it also reinforces the conclusion that this probably isn’t a fork that’s the best choice for a broad segment of the market. Also, given its high price, I’m a bit disappointed that the damper adjustments aren’t a little more refined.

Ultimately, the OPM treads a pretty uncommon line between two opposite ends of the spectrum: it has internals that favor a large, aggressive rider, but it’s strapped to a chassis that’s probably better suited for the XC crowd.

That unique blend makes it a tough fork to pin down, and while it’s not without its faults, it’s also a legitimately good fork. For those looking to keep things light, but also looking for a fork that can withstand hard hits without getting crushed, the OPM is an excellent choice.

1 comment on “DT Swiss OPM O.D.L. 120 29″ Fork”

  1. Excellent, detailed review. Exactly what the gear junkie in me was seeking. Looks like I’ll hang-on to my Dual Air, 120mm SID XX G2 a bit longer!

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