The Up Side
Predictable for a short-travel 27.5-inch bike—efficient without much mid-travel stroke to cause wallowing. The Thunderbolt's smaller wheels didn't stunt its climbing performance on a ledgy, technical course that seemed far better suited to 29ers.
Although the Thunderbolt's somewhat-conservative wheelbase can result in some twitchiness at high speeds, it also makes for a bike that's poppy, playful and easy to maneuver around tight turns and switchbacks.
Dollar for Dollar
At $5,400, the value is on par with what you'd expect spec-wise for a bike at this pricepoint, and the entry-level for the Thunderbolt is a very attainable $2,000.
Most bike models change so drastically in the span of four years that comparing generations that far apart is akin to pitting a penny farthing against a modern DH sled. Geometry, travel, suspension—technology moves so fast that these aspects of a bike rarely remain unchanged year-to-year, much less over multiple years.
But the Rocky Mountain Thunderbolt has stayed surprisingly true to its original intentions, and fairly close to its original geometry. The last time we saw the Thunderbolt, at the 2015 Bible in Central Oregon, it ranked as one of the favorites, with testers lauding it for pushing the boundaries of XC. Since then, Rocky Mountain has tweaked the travel and geometry, but it hasn't been radically overhauled, and unlike some bikes in the same category, it's not attempting to moonlight as a more aggressive bike. With its 67-degree headtube angle, 75-degree seat tube angle (in the neutral-geometry setting) and 463-millimeter reach (size large), it's almost conservative by today's standards.
And that's OK, testers unanimously agreed. It's playful, easy to ride and encourages you to take extra-credit lines, without being so long and slack that if you aren't on-point all the time, you're losing control.
"This is just a fun, levelheaded trail bike," said one tester.
The changes Rocky Mountain did make to the Thunderbolt are subtle, but effective. The head angle has been slackened by a not quite a degree, the seat angle steepened by about a half-degree and the reach is about a centimeter longer. It also has 130 millimeters of travel, front and rear, whereas the previous iteration had 120 millimeters (except for the BC Edition, which sported 130 millimeters of front travel; now the BC Edition has 140 front and rear). The resulting geometry doesn't feel exaggerated, and the ride quality makes for a bike that's poppy and responsive, but still manageable at slow speeds and easy to maneuver around tight turns and switchbacks.
Testers did feel that at high speeds the Thunderbolt could feel twitchy, not having the benefit of an extra-long wheelbase, and one tester noted that its four-bar suspension platform isn't as sophisticated as some of its competitors, but overall there are very few flies in the Thunderbolt's ointment.
Our short-travel loop was particularly well-suited for a 29er, with ledgy climbs and slow-speed tech descents on which the rollover qualities of a larger wheel diameter were beneficial. But the Thunderbolt's 27.5-inch wheels somehow didn't feel like a sacrifice as it powered through the rocky terrain, holding its momentum on the most energy-sapping bits. Its climbing prowess is predictable for a short-travel bike—efficient without much mid-stroke to cause wallowing. One tester noted that it performed well with the Fox Float DPS Performance shock in the open setting while climbing, but another preferred the extra firmness provided by the shock's 'pedal' mode on extended climbs. We all rode the bike in its neutral position, although Rocky's RIDE-9 allows for nine different settings, changing the leverage curve and geometry depending on how you position the flip chips. It's an added bit of versatility and fine-tuning that some riders may appreciate, and some may find overwhelming. Regardless, it's there to use if you want, or you can set it and forget if you aren't the tinkering type.
Our Carbon 70 model, which falls at the higher end of the Thunderbolt offerings—the alloy 10 starts at $2,000 and the most expensive, carbon 90, goes for $6,000—has a spec package that's on par with a bike at its price level. Standouts include the Race Face ARC 25 wheels mated to Maxxis Minion DHR 2.3-inch tires, Shimano XT two-piston brakes and the Fox Float DPS EVOL Performance Elite shock and fork.
Not only has the Thunderbolt stayed consistent with its identity over time, but it's also remained a bike that's made for everyone. Five years after its 2014 release, the Thunderbolt continues to be offered in five frame sizes from XS to XL, making it one of the few trail bikes that truly offers a fit for riders of all shapes and heights.
Q&A with Ken Perras, product manager
One of the first things we noted about this year's Thunderbolt is that its DNA hasn't radically changed from when we last saw it four years ago. What is it about this bike's design that works so well, and has allowed its identity to stay so consistent?
The idea behind the Thunderbolt has stayed the same since its inception as the Element MSL back in 2010. Our goal was to make a lightweight trail bike that could pull in riders from both the XC and "All-Mountain" (that category has shifted several times since then) crowds towards a do-it-all Trail platform. It's meant to be a quick-mannered bike that has a little bit extra capability at minimal weight increase to handle a wide variety of riding, from longer rides far from home to short outings at the local trail network. To me, the Thunderbolt is a bike that never questions what kind of ride it can perform on; it just does the job and does it well.
The Thunderbolt seems like it would be perfect for 29-inch wheels. Why has Rocky resisted re-tooling the Thunderbolt as a 29er, and any plans to change that in the future?
The funny thing is I get this comment often, and the answer always surprises: we already have this bike in the line and it's the Instinct! It features the same amount of travel as the Thunderbolt and similar spec through the range. The only difference is the wheel size. If someone is looking for a capable, do-it-all trail bike, then all they need to do is decide which wheel size they want to roll without thinking about geo or spec. Both bikes were built with the same intention in mind.
This is one of the few bikes in the test that's offered in full size range: XS to XL. How do you achieve that from a design standpoint, and what kind of additional investment is required to offer five frame sizes, in aluminum and carbon to boot?
With the 27.5 wheel size on the Thunderbolt, we realize that it's important to fit shorter riders whether they are adults or teens; we don't want to exclude these riders based on stature. As such, we do need to make much more of an investment to design and produce the extra-small front triangle in carbon and alloy. Additionally, the sales figures are typically lower for this size than the rest, so we are making a conscious commitment to having more riders fitting our bikes, even if the business end of it doesn't quite line up. From an engineering standpoint, it's typically not that much extra work to add a size. The time and cost investment really happens on the production side, from adding SKUs to assembling these bikes with size-specific components.