Since we last warmed up in the Nimbus, it's received some updates. Rab tells us that the amount of fill has increased, the cut has been reworked, and the liner material is Rab's new Atmos fabric. The price has also dropped from $245 to $215! Check out the latest Nimbus below in the first photo. The version we tested is shown second.
We're linking to the latest Nimbus, but for now, the review to follow only pertains to the version we tested last year.
Hands-On Review of the Nimbus
The Nimbus reminds us a lot of the Patagonia Nano Puff with its baffles and packability, except it stows away more efficiently in its oversized pocket, and it's much warmer. The Nimbus hits a sweet spot between not-warm-enough and too-heavy.
This jacket is one of the warmest in our review. It's warmer than the Xenon X, but it's also 3 ounces heavier.
The Nimbus uses a synthetic insulator called Cirrus, which has a fiber length that allows the material to re-loft better than other synthetic insulators. According to Rab, Cirrus insulation has the fill power equivalent of 600-fill power duck down and doesn't lose it's loft when it gets wet. In our experience, the Nimbus has one of the best warm-to-weight ratios of any synthetic jacket out there. We wore this jacket alongside the Rab Microlight Alpine Jacket (a down jacket) and found that is was less warm, more weather resistant, and only .8 oz heavier. Pretty good for a synthetic jacket.
The Nimbus is long in the torso so it stays comfortable underneath a harness without restricting our range of motion.
Weight & Compressability
The Nimbus tips the scale at 14.6 oz, one of the heavier entries in our review. One of the main reasons the Rab Xenon X has remained our favorite for so long is for its balance of weight, warmth, and durability, all in an 11 oz package. While the Nimbus can't compete in the ultralight race with jackets like the 8.15 oz Patagonia Micro Puff, it's much more durable. We climbed our fair share of offwidths and squeeze chimneys in the Nimbus, and it's somehow still going strong, while the Micro Puff got shredded after a few pitches. Like the Xenon, the pocket that the Nimbus stuffs into is generously sized, making it very easy to pack away.
While it has on of the larger packed sizes of the jackets we review, it has a generously sized stowaway pocket, making it quick and easy to pack away at the belay.
The Nimbus is more form-fitting than the same sized Xenon X. This makes it a more efficient insulator and a better mid layer, but the tighter fit doesn't feel as comfortable as the Xenon. We also feel that the hood is too tight to wear comfortably over a helmet. The hood does feel comfy on our heads stay in place without obstructing our vision. The Nimbus's hem is long, so it offers some extra warmth and coverage and stays nicely under the waistbelt strap on a backpack or a climbing harness. Two handwarmer pockets offer a warm respite for chilly hands, and there is a small internal chest pocket for important items.
We feel the hood is too small to comfortably fit over the helmet. Would could force it, but then the jacket would feel tight and uncomfortable in the armpits.
While we're aren't gutting these jackets and getting our eyes on the stuffing to compare the re-loft times of Polartec Alpha to Cirrus insulation, we can say that standing in the shower with a brand new Nimbus, we stayed dry. These jackets don't have a waterproof membrane and rely solely on their DWR treatment to stay dry. These treatments become less effective as the jackets get dirty. Anecdotally, one of our testers was caught in a downpour for a few minutes before getting in his tent to go to sleep. He stuffed his slightly damp Nimbus into the bottom of his sleeping bag, figuring that at least it would be warm, if not dry when he put it on in the morning. The next morning it was warm and dried out within 20 minutes while making breakfast in the sun.
This jacket doesn't breathe very well, but some days (like when this photo was taken) are so cold and windy that breathability is the last of our concerns.
The Nimbus isn't incredibly breathable. On cold and windy climbs, we don't think the lack of breathability is a problem, but steep hikes and long approaches, we had to take this jacket off because we'd overheat. For a jacket that breathes and insulates, have a look at the Patagonia Nano-Air Hoody or the durable Arcteryx Proton Hoody.
The Nimbus looks a lot like a down puffy, and many of our friends confused it for a down jacket. It has the look of a technical jacket (which it is), and in our eyes, this detracts from its style, but that's why style is only 5% of our rating system. We can tell you this: if you pull out the Nimbus on a cold and windy day belay, you'll love its warmth, and you won't care what it looks like.
Staying warm and racking up in the Nimbus.
The Nimbus is a great belay jacket and an awesome water resistant mid layer. We highly recommend it for anyone adventuring in weather where it's cold, but not cold enough to snow, and down will leave you vulnerable to the cold rain. It doesn't have to be freezing out to get hypothermia.
With many jackets in this category coming in at $300, the Nimbus is a great value. It easily competes with top offerings from Patagonia and Arc'teryx. We are impressed with its durability, something we feel is sorely lacking as jackets become lighter and lighter.
While this jacket didn't get an award, it still comes highly recommended! It's warmth-to-weight ratio, and durability make it a reliable partner, especially when the weather is looking squirrely. While it didn't perform as well as the Xenon X overall, it's an exceptional choice if a warmer option suits you.