Rhythmus RP 9L Hydration Pack

Rhythmus is a one-man project. That man is Tom Kvilhaug, who lives in Colorado and designs things for Cotopaxi by day, and spends the rest of his time riding bikes, skiing, and nurturing his new brand. He can’t possibly be a pro scooter rider anymore, because how could he have the time, but a quick google search turned up a signature model wheel, and while I don’t know a thing about street scootin’, it sure looks to me like he used to be bloody good!

Rhythmus is Latin for rhythm. So far, the brand has one bag (two if you include a tool pouch) and a funky take on a t-shirt/jersey hybrid. But Rhythmus and Tom landed on my radar one night as I was poking around and discovered its main product: the RP 9L hydration vest. I was in the middle of testing the last vest I wrote about, but I saw the Rhythmus and was intrigued. Tom sent one over for me to check out. Here’s how that went.

You might be able to chart someone’s level of experience or time spent mountain biking based on the amount of crap they carry with them when they ride. Only, though, if you understand there are two diametrically opposite schools of thought.

A rookie might be someone who carries nothing with them on a ride, because they know no better. They’ve never suffered a flat, don’t notice their right grip is a bit loose (you should look into that) or that their rear caliper is loose (you really should look into that). The other rookie – the one that you might describe as being afraid of their shadow – carries one of everything, and two of some other things. Fresh from the boy scout school of ‘always be prepared’, they’re laden down with 5 kilos of extra weight, but their anxiety won’t let them free of the fear of every mechanical they can imagine, and a half dozen they can’t.

Time passes, and many rides later, those two rookies may swap ends. The minimalist learns a few hard lessons, experiments with SWAT boxes, pockets, backpacks, hip packs, racks and straps. Every ride is an opportunity to use a new tool, and every day is a chance to buy a $30 lightweight tube. The anxiety-laden rookie also matures, and learns that 3 or 4 mechanical types make up the majority of the ones you can expect to suffer on an average ride AND be able to fix, given a standard self-sufficiency loadout. Do they meet in the middle? Probably, although they both also probably continue along whichever direction they’re traveling on their spectrum, ready to bounce off the walls of the other side and ricochet back the other way.

Tom designed the Rhythmus RP 9L for a different kind of rider, though. You see, Tom likes to do big, stupid rides, and he seems pretty obsessed with snacks. Big rides mean lots of snacks (and water, tools, and layers and stuff), and Tom wanted a vest that served his needs, so he got to work. What he came up with may have been designed to suit the needs of ultra distance riders, but I happen to think it’s pretty great for shorter rides, too, if you happen to carry things like a saw, first aid, snacks, a beer (maybe two), a jacket, a leash for your dog in case you see a dog he doesn’t like, or a bear, or a coyote he thinks he might like, plus treats for that dog…and so on.

The Rhythmus arrived, and I tried it on right away, and a funny thing happened. It just…settled right into place. More than that, though, it felt like it kind of enveloped my torso. The harness – much has been made of the harness – just wraps itself around you. As you can imagine, this is very reassuring. Once I put a little weight in there, that feeling perpetuated. Then I went riding, and I knew I’d found my new favourite riding pack. We’ll come back to that. First, let’s cover what all is going on with this pack.

Rhythmus RP 9L Features

• 4-Point Adjustable Harness: at both shoulders and down below, you can adjust the RP 9L until it fits just so. It’s pretty easy to come up with a solid fit that doesn’t bounce – exactly what you want out of any pack, and one thing vests excel at.
• Two Zippered Harness Pockets: Snacks, tools, or your phone stay close by. My iPhone 17 Pro in a case just barely fits in the zipper pocket on the left side (the right side zip pocket is too small for any phone but perfect for keys or other small valuables).
• Four Stretch Harness Pockets: Quick-access storage for gels, gloves, or small gear. There are two of these I prefer to use for my phone, more on that in a sec.
• Magnet Hydration Clip: Ensures your hose stays in place and is easy to grab on the go.
• Interior Hydration Sleeve: Keeps your reservoir (not included*) stable and accessible.
• Magnetic Closure Accessory Pocket: This is on the back of the pack, with internal organization for tools, keys, and valuables. Super easy to access and a unique take on separating compartments in a small bag.
• Modular Key Clip: Easily moves between pockets.
• Exterior Lash Straps: Ideal for securing bulky items like an extra layer or pads. A 9-litre pack is pretty big so it’s unlikely you’d need this for a layer, but it’s perfect for leg pads if you’re on a long ride and want to stash them, or else, I don’t know, something big and cylindrical…kindling for your fire?
• Reflective Prints: Enhance visibility for early morning or twilight rides.

Specs

• Volume: 9L
• Weight: 640g
• Color: Black
• Material: Nylon, Polyester, Elastane, C0 DWR, PFAS Free
• Origin: Vietnam
• Optimized for 1.5L – 2L hydration bladders. Hydration bladder not included

The ‘reservoir not included’ thing may raise eyebrows, but there are two ways of looking at this. Many of you may already own a bladder, in which case it’s nice to not have to pay for another one. If you don’t own one, it makes the Rhythmus more expensive to buy if that’s how you plan to carrry your water. It’s been fall and winter during the test period so most of my rides are one bottle on the bike affairs (or a second bottle in the pack). In summer, I’ll definitely move a bladder into it.

Most 1.5L – 2.0L hydration bladders will work with the RP 9L pack, just make sure they’re 355mm (14”) tall or less. Rhythmus recommends the Hydrapak Velocity 1.5L and I’d be hard pressed to disagree.

The materials and workmanship are top notch. The pack feels and looks solid and very well-made. It’s not heavy, but it is clearly designed to endure many miles and years of hard use. Not surprisingly, the Rhythmus repair/warranty policy is rock solid, too:

…if you experience an issue due to a manufacturing defect, we will repair the item at no cost to you. If a marmot chews a hole in your pack because you left a salami stick in it, we will repair it for a reasonable cost.

Details out of the way, let’s cover how this pack works in use.

I already covered how comfortable it is. In contrast to the High Above vest I reviewed a few months ago, which feels a bit more svelte but doesn’t offer as much storage capacity, the Rhythmus feels like a utility vest when you pull it on. It does not, however, feel bulky or heavy; you’re just aware that the harness has a bit of substance to it (and a lot of pockets), and if you put a few things in there, it actually feels like a counterweight to the mass of the pack that rides on your back. As counterweights tend to do, this nullifies the weight out back somewhat, giving the pack a bit more of a balanced feel. It doesn’t feel ‘tight’ on me, which the High Above Supernatural does (I covered how I maxed out the shoulder straps on that pack – you can get extensions for it, but if you’re my size or bigger, you’d better try it on before buying). The Rhythmus will fit a larger range of sizes, and it’s designed to carry more stuff.

I love keeping my phone in one of the front chest pockets, preferably one of the more accessible, elasticized ones. However, on a recent ride, it actually fell out (steep terrain, but still). It would be great if, on one side, there was a small loop or other simple way to keep a phone strapped in, even better if it is optional, so you can leave your phone easy to reach on the go when you’re rolling on mellow terrain. It only fell out once, and I’ve simply learned to make sure my phone is in the zip pocket for serious riding. Either way, it’s much nicer to have your phone right there when you need it and also not in a leg pocket, no matter how well it may be designed to carry a phone.

The shoulder straps have a habit of twisting when I carry the pack or move it around, so that when I go to put it on, it often requires a bit of untangling before I shrug my way into it. Not a huge deal, however, one of the pluses of the Rhythmus is that it’s easy to put on, and instantly feels so well counter-balanced as soon as it falls into position. I suspect Tom may refine the shoulder strap a bit in future to prevent this. It’s a tiny complaint, and the tradeoff is that easy adjustability of the top part of the straps because they aren’t encumbered by a thick, padded strap that rides on your shoulder.

There’s a subtle little eyelet on one side near the top of the exterior of the pack, which you can use with a ski strap to hold a saw in place if you let it ride in one of the mesh side pockets. I use a Silky Big Boy 2000, which is 15” long, so unfortunately, that tip doesn’t work. BUT I can just barely zip that saw into the pack, which is one of my must-haves for pack use for much of the year.

The front pocket (with the zipper, two magnets and five internal elasticized compartments) is perfect for tools, just don’t forget they’re in there. That whole area is in addition to the main compartment, which has plenty of room for your bladder, a jacket, the aforementioned saw, snacks, and an extra bottle of (or a flask). Which is good because the side pockets, which are intended to carry a spare bottle or two, are not at all deep enough to do so. You can tuck other things in there, but a bottle won’t stay in, at least if you’re mountain biking.

Packs are very personal things, and the pursuit of perfection may be both noble and futile. I don’t expect or require perfection, but I know when something comes close and for me, the only changes I’d make to the Rhythmus are minor. As it is, it’s my favourite riding bag, and the closest to perfect I’ve yet to encounter. Even better that it comes from an up-and-coming indy designer with character.

Rhythmus RP 9L – 160 USD.