Tumbleweed Prospector Review: Wolf in Mule’s Clothing

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The second version of the expedition-ready Tumbleweed Prospector was released just a couple months ago, and is available now. We got ahold of a V2 sample frame and fork, built it up with 29+ tires, took it for a test ride on Ethiopia’s rugged dirt tracks, then brought it back to the rough and tumble singletrack trails and forest roads of Pisgah to see what else it can do. Here’s the full review…

A lot was said in our Meet the Tumbleweed Prospector article back in January of 2017, just after the bike and brand debuted. I highly recommend you digging into that if you haven’t yet. In summary, Tumbleweed started based on the desire for an expedition-ready bike that wasn’t currently available. Tinkerer, founder, and designer Daniel Molloy envisioned a symmetrical, long-ride-friendly bike that was perfectly planned to interface with the Rohloff Speedhub. It would also need to fit full-fat or plus tires, and maintain a standard mountain bike Q-factor (rider’s stance width governed by the width of the bottom bracket shell). To accomplish this, Daniel – with the help of several engineers – designed a frame around three custom, unique features that set the Tumbleweed Prospector apart:

Tumbleweed Prospector review, 29+

Cast Hollow Yoke

The Prospector features a meticulously designed custom cast, hollow, steel bottom bracket yoke that can accommodate 26 × 4.0” or 29 × 3.0” tires along with a 73mm bottom bracket shell. The Yoke also has the Tumbleweed logo embossed on the bottom, as well as the logotype on the drive-side stay.

Tumbleweed Prospector review, 29+

Phil Wood EBB

A custom 73mm version of the Phil Wood eccentric bottom bracket insert keeps the rear end of the bike locked into place, and allows for 0.5” of BB height adjustment (or Rohloff alignment) depending on the wheel/tire size being used. It’s a simple, precision-made piece without any moving parts, just a couple of beefy set screws that lock it in place from the bottom bracket shell.

Tumbleweed Prospector review, 29+

Molded Chainstays

The Prospector features molded chainstays formed to match the shape of the yoke legs for welding. This maintains the profile to maximize tire/crank arm clearance before returning to match up with the dropout hood for welding. It’s a very specific shape that required its own custom tooling to achieve. This was the final piece of the puzzle to allow the wide range of tire clearances.

Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Quick Highlights
  • Angles (LG): 69.5° HTA, 72.5° STA
  • Chainstay: 453mm (447-460mm)
  • Bottom Bracket: Phil Wood EBB
  • Rear dropout spacing: 135mm QR
  • Seatpost Diameter: 31.6mm
  • Max tire size: 27.5+ / 29+ / 26 X 4.0″

Past and Futureproof (wheel size)

Of course, all three of these things contribute to the biggest selling point behind the Prospector: the fact that it’s relatively futureproof. Almost five years ago, prior to creating the Prospector, Daniel rode a Surly Pugsley through South America on an extended dirt road tour. Sometime during the trip, Daniel developed knee problems that he attributed to the Pugs’ wide Q-factor (100mm bottom bracket shell). His love for full-fat 26 x 4” tires was a bit of a conundrum, and eventually was the driving force behind Tumbleweed Bikes. Fast forward a couple years, and after a lot of engineering behind the aforementioned yoke, and the Prospector was born—a symmetrical bike with a standard MTB Q-factor (73mm shell) that could run fat tires.

But as trends change, so do people’s preferences. No matter how committed someone might think they are to fat tires, they might want to try 29+, wide trail 2.6”, or 27.5+ tires and still have the ability to run fat tires for a winter ride or sandy beach expedition. This is where the Tumbleweed shines. Not to say that other bikes don’t have the capacity for multiple wheel/tire sizes, but the Prospector’s custom, rotating eccentric bottom bracket can be tweaked to accommodate different wheel/tire diameters. By doing so, it changes the bike’s effective chainstay length (447-460mm) and bottom bracket height and allows regular 29er tires, 27.5+, 29+, 26” fat tires, and everything in between. For example, the 736mm diameter shared by a 27.5 x 3.0” or 29 x 2.25” tire works great with the EBB’s spindle borehole in a forward/upward position (64mm BB drop), and with the larger 762-774mm diameters of 26 x 4.0” or 29 x 3.0” tires, the EBB can be in a lower rotation position (52mm drop) to maintain a similar standover and BB height. And in the future, when people are running 28.25 x 2.73” tires… well, there’s a setting that will work for those, too.

Tumbleweed Prospector review, 29+

What’s New

The second version of the Tumbleweed Prospector platform saw several evolutionary improvements based mostly on rider feedback and extensive group testing in Peru. Aside from the introduction of a Midnight Blue colorway and new logotype and headbadge, the most visible changes are in the Prospector’s fork. The three-pack cage mounts were moved to the backside of the fork blades by popular request. This allows cages and racks to be used at the same time, should that be needed; it’s also the preferred orientation of many bikepackers. It has internal dynamo wire routing now, which makes sense as most of the complete bikes Tumbleweed builds feature a dynamo hub. And there are now two axle choices. Option one keeps the original quick-release 135mm rear hub dropouts to allow a backup singlespeed rear hub to be specced as an emergency backup. The second option, what we tested, is the new 110 x 15mm thru-axle fork, which allows for easily swapping rigid and suspension forks while using the same front wheel.

  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+

The cable routing has been tweaked by a few millimeters here and there, too. The chainstays are shorter by 5mm, and the bottom bracket has been raised by 5mm since the majority of Tumbleweed’s customers have built their bikes with 27.5+ wheels instead of 29+ wheels, as Daniel originally anticipated. The smaller wheel size works fine with the original Prospector since the eccentric bottom bracket allows for height adjustment, but raising the BB gives a little more pedal clearance for those rocky, technical trail rides.

Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+

Prospector vs Surly ECR (or Krampus)

When thinking about the most relevant bike to compare with the Tumbleweed Prospector, it seemed fitting to look at the Surly ECR. After all, both are built for big tires and dirt touring, both are loaded with mounts, and each has the proper provisions for a Rohloff drivetrain. However, as it turns out, the Prospector is geometrically closer to the first generation Krampus. And, as mentioned, it kind of shares some roots with the Pugsley. So, for the sake of geometry and utility, let’s stick with the ECR and current iteration of the Krampus.

First, the Prospector is a bit longer than the current ECR. It has a longer wheelbase (1152 vs 1111mm), 9mm longer reach (429mm), although it has about the same chainstays (453 vs 451mm). The BB drop on T’weed is lower (64mm at lowest EBB point vs 80mm). And the Prospector has a 0.5° slacker HTA (69.5°), which is nestled just in between the ECR and the Krampus (69°). See more numbers comparing the ECR, Krampus (KR), and Prospector (TW) below:

Geometry Data
TW
ECR
KR

Stack Height (mm)
636
633
612

Reach (mm)
429
420.5
448

Headtube Angle
69.5°
70°
69°

Seat Tube Angle
72.5°
72.5°
73°

BB Drop (mm)
52-64
80
65

Chainstay Length (mm)
453
451
435

When thinking about these numbers, it’s pretty clear that the Prospector is geometrically sandwiched between the two. However, in my opinion, it handles much more like the Krampus than the ECR—two bikes which I’ve put more miles on than almost any other—or at least the first generation Krampus.

Tubeset

While trail riding on the Prospector, I immediately noticed the frame’s unique feel. It has the stiffest rear end I’ve ridden to date. And, as it turns out, when Tumbleweed had the frame’s stays tested for Gates Carbon Drive compatibility, it exceeded the stiffness requirements several times over. But, at the same time, the tubing has an undeniable dampening quality that seems to soak up trail chatter and bumps extremely well. The combination of these two qualities led me to believe that the Tumbleweed’s tubeset was something quite special.

  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+

When I asked Daniel about it, here’s what he had to say: “For frame tubing, we went with the very best available from the big tubing [company] in Taiwan that supplies most of the other high end steel bike brands. Most of the other brands create their own tubing brand or label for their bikes, but I didn’t really see the need to do that. The tubing varies depending on size of frame, but the front triangle is triple and quad butted oversized tubing, with extra reinforcements at the head tube so that there is no need for an external gusset. The chain stays are custom formed to match the yoke and dropouts, and are not butted, and the seat stays are a standard straight gauge tube.” Adding to that, the small and medium frames have a slightly smaller diameter top tube to make them a bit lighter and proportional for their intended rider size.

Tumbleweed Prospector review, 29+

While I am generally impressed with the tubeset, I go back and forth on Tumbleweed’s decision to use a 31.6mm seat tube. While this might be nice for dropper posts and general stiffness, I wished at first that it fit a 27.2mm seatpost (without shims) so I could use my beloved Cane Creek eeSilk seatpost.

The Build

Being a fan of 29+ for big dirt tours, and having recently been smitten with the lighter and more nimble 29 x 2.6” standard, I thought I’d build this bike around 29 x 2.8” tires.

  • Fork 110 BOOST
  • Rims I9 Hub; WTB KOM Tough TCS i35
  • Front Hub I9
  • Rear Hub Rohloff SPeedhub
  • Tires Terrene McFly
  • Handlebar Salsa Salt Flat
  • Brakes TRP Spyke Mechanicals
  • Crankset Shimano SLX
  • Saddle Selle Anatomica H2
  • Seatpost Thomson Elite 31.6
  • Frame Pack Porcelain Rocket 52hz (Tumbleweed specific)
  • Front Bag BXB Goldback
  • Rear Bag Revelate Terrapin
  • Accessory Bags Rockgeist HoneyBox
Tumbleweed Prospector review, 29+

Although this build is somewhat on the heavy side (32.6 pounds / 14.8kg)—without pedals, but including the 52hz framebag—it only felt heavy when hoisting the bike. Surprisingly, once pedaling it, the Prospector feels relatively spritely when accelerating, and once it’s moving it barrels over everything and maintains inertia more than any other bike I’ve ridden. I would attribute both of these qualities to the responsive and stiff rear end. And in contrast to its weight, it also feels rather nimble on the trail.

  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+

Case for the Rohloff

Although the Tumbleweed Prospector is equally suited for a 1x drivetrain, it was conceived around the Rohloff Speedhub internally geared hub. While some people dislike the Rohloff for its notable weight imbalance, others love it. And there’s no denying that its excellent gear range and maintenance-free design make it almost perfect for long-term bike travel. However, it’s not always easy to mount, tune, and remove/replace. The Surly ECR, Troll, and Ogre all have specially designed dropouts and tugnut inserts that allow easy tuning to compensate for chain stretch, but the horizontal dropout is challenging at times, depending on where the chain falls in length. It can slip and misalign when not tightened properly. And the Pugsley is a completely different animal. It’s hard to line up, requires that you loosen the brake caliper to get the wheel in and out, and you have to build an offset wheel, which compromises the strength of the wheel itself.

Tumbleweed Prospector review, 29+

The aim of the Tumbleweed was to perfect the Rohloff interface using a vertical dropout that has no risk of slippage and makes it easy to remove and reinstall the wheel. To adjust the chain tension, you simply loosen the worm screws on the bottom bracket shells and rotate the eccentric BB. It’s a pretty simple and elegant solution, although I found that it takes a little elbow grease, and you’ll need to carry a full 4mm hex wrench to reach the rotation bolt in the EBB. That said, the Prospector’s EBB changes the position of the cranks in relation to the saddle, which might bother some people, as it changes the rider’s body position and likely changes the saddle height. A slider keeps the saddle height and crank position fixed, but effects the wheelbase, which can be good or bad.

Also, to best accomplish Rohloff optimization on the frame, the Prospector has 135mm dropouts. This is slightly limiting if you’re looking to use a wheelset on two or more bikes, or if you’re interested in a stiffer BOOST (or Super BOOST) rear wheel.

And while the interface is really well done, I had one issue with it. The Prospector uses the Rohloff’s shifting mechanism with the cables pointed down so they route on the chainstay. This is the most popular way of routing the two shifter cables for a Rohloff, it seems, but I had grown accustomed to having them point up, form a gentle loop, and then route along the top tube. Reason being, I found the stack of cables at the chainstay to be a little messy. It took a lot of zip ties to get them to stack in a triangular pattern (two Rohloff shifter cables and brake cable) and not risk rubbing the tire. Then again, once it was done, it was a non-issue.

Pros

  • Insanely capable and versatile
  • Surprisingly nimble and quick
  • Elegant attention to finishing details
  • Tubing choices and frame design are great for far-flung trips as well as local trail rides
  • Standard MTB Q-factor even when used with 4” tires
  • Loads of mud clearance (especially in 27.5+ and 29+)
  • Brick red 52hz frame bag is awesome

Cons

  • Heavy (especially with a Rohloff)
  • Lack of more efficient routing for stack of cables at the chainstay (when Rohloff is mounted)
  • Dropouts are limited to 135mm
  • Expensive compared to some other steel framesets (although it comes with Phil Wood EBB)
  • Limited to 4″ tires on 65mm rims
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Tumbleweed Prospector review, 29+
  • Frame (as tested) Large Prospector (110 Fork)
  • Weight (w/o pedals) 32.6 pounds (14.8kg)
  • Place of manufacture Taiwan
  • Price (frame/fork) $1,450
  • Price (frameset + Speedhub) $2,700
  • Price (52hz Framebag) $220
  • Manufacturer’s Details Tumbleweed.cc

Wrap Up

As larger bike manufacturers dabble in off-road adventure cycling, and many skirt around it in favor of the popular gravel category, it’s prime time for small and nimble bike companies to perfect genre-specific products within the bikepacking and off-road touring niche. The Tumbleweed Bicycle Company is an excellent example of such an institution. Daniel and his team of engineers, testers, dirt bags, and bike nerds have worked carefully through a thought out series of prototypes to perfect the Prospector for backcountry bike travel. And the result supersedes that intention. Albeit a little heavy compared to a lot of carbon, titanium, and maybe even some steel bikes, the Prospector has a buttoned up geometry that has proven capable on singletrack, gravel, and just about anything in between. And despite its weight, it maintains a surprisingly nimble feel on the trail.

The Tumbleweed Prospector isn’t cheap, but if you’re looking for a future-proof, apocalypse-proof bike that purposefully blends standards, looks really sharp, and redefines what a backcountry-touring bike is—on its own terms—I think it’s well worth the investment.

Tumbleweed Prospector review, 29+

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