Rocky Mountain Thunderbolt 770 MSL2015 Red-1-7

A few years ago when 29ers where still as widely misunderstood as fat bikes, there was a trend of building up mini DH bikes out of four inch travel slopestyle bikes. Those bikes were (and are) about the most the fun you could have on a trail, but they were terrible for racking up miles.

Of course, this is the year 2015. My next door neighbor drives an electric car, mountain bikes cost more than your average bathroom remodel, and manufacturers are finally making little bikes that rip both uphill and down.

With a 120mm of travel front and rear, and 27.5″ wheels, the Rocky Mountain Thunderbolt is marketed as an “XC Trail” bike. A mountain biker’s mountain bike, if you will. Our test bike, the 770 MSL, retails for an MSRP of $5,499, which places it squarely between the Carhartt and Gucci camps.

Rocky Mountain Thunderbolt 770 MSL2015 Red-1-5

Up front is a matched RaceFace Turbine cockpit. Bars are of the 740mm aluminum variety across all the sizes, but stem length varies between 60-80m….And yes, that is a lot of cables.

The various levers control the front and rear shifters, dropper post, and shock. Considering all that, everything is actually very neatly routed.

Rocky Mountain Thunderbolt 770 MSL2015 Red-1-4

That said, things do feel a little crowded. For example, in the stock configuration, the lockout lever blocks the shifter paddle. It’s a minor inconvenience and one that can be remedied by shuffling the controls.

Rocky Mountain Thunderbolt 770 MSL2015 Red-1

At the center of the Thunderbolt is the Ride 9 system. This set of dual counter rotating chips allows you to adjust the suspension to work better for lighter or heavier riders (linear or more progressive), and adjust the geometry to be slacker or more upright (aggressive versus efficient).

It’s a system Rocky uses on several different models and we’ve always found it be simple to use and creak free.

Rocky Mountain Thunderbolt 770 MSL2015 Red-1-3

A few years ago, the company switched from bearings to bushings on most of their full suspension models, to help reduce weight and improve stiffness. We had a Altitude 790 MSL for long term review and didn’t experience any reliability issues, although we did have to regularly disassemble and clean the pivots to squelch the occasional creak. To remedy that issue, and simplify mechanics lives, the Thunderbolt now features grease ports. High Five!

Rocky Mountain Thunderbolt 770 MSL2015 Red-1-9

The water bottle contingent will be pleased to see proper mounts on the inside (and underside) of the front triangle.

Rocky Mountain Thunderbolt 770 MSL2015 Red-1-2

All complete versions of the Thunderbolt (both the carbon and aluminum models) are currently spec’d with two or three by drive trains. The only exception is the BC edition, which retails for $6,399, and has a 1x drivetrain, a 130mm fork, and wider bars.

2015 Rocky Mountain Thunderbolt 770 MSL Geometry

All versions of the bike are available in five different sizes -XS-XL, and share an extremely low standover height, and compact chain stays.

On The Trail:
Rocky Mountain Thunderbolt 770 MSL2015 Red-1-6

The marketing kit sets the bar very high for the little Rocky. What we know so far is that it’s light and playful. In the stock setting, the geometry is middle of the road for a 120mm travel trail bike, but hopefully the adjustability will deliver a ride that suits the needs of a variety of test riders. My personal preference is for a slacker more progressive ride, so I’ll be experimenting with that end of the spectrum, before handing the Thunderbolt to our token Strava Assasin.

The bounty of cockpit controls is still overwhelming, but as I’ve become accustomed to the remote shock lever, it’s something I wish more bikes came with. The Rocky’s suspension is efficient when climbing and offers excellent traction, but it’s active during out of the saddle exertions. The three position (climb, trail, descent) lever does an excellent job of quelling pedal feedback and each mode has a distinct character – climb mode is sports car stiff, while descent mode is Cadillac plush.

After the first few rides, the only thing I can complain about is chain slap, which is a simple fix. Once we have the opportunity to get this bike dirty and play with more settings, we’ll report back with long term impressions.

Rocky Mountain



  1. This is a fun ride, but I would advise anyone getting a Thunderbolt MSL (or probably any bike for that matter) to be sure to completely disassemble and reassemble the bike to make sure everything is as it should be – out of the box, mine had the chain installed improperly (routed wrong around the pulleys), brake pads installed backwards, brakes that needed to be bled, a bunk rear shock, and some odd choices for spec’ed component sizes that I had to remedy out of pocket after purchase (surprise – Rocky now specs its Small frames with 175mm cranks – wtf.). Also, the rubber washers/dust seals on the bushings fall off really easy, so ask your shop/dealer for extras.

  2. There was a time when I wanted lock-outs and adjustability. Now? Make a bike that works well for its intended purpose and has minimal adjustments, namely for rider weight. I will get on that and ride it with a smile on my face.

    I will say I do like Canyon’s Strive concept. Just would like it as a XC–>Trail instead of Trail–>Agg AM.

  3. This bike rides amazing. I generally try to stay way from Horst Link’d suspension bikes, but this little wonder is far more pedal-efficient than any of its four bar relatives. It just shreds up and down the hills.
    Ride 9 is brilliant and allows you the set the bike to behave anyway you want, and the super short chainstays combined with the long(ish) top tube makes this thing playful like no other.
    Rocky Mntn has a winner here.

  4. On the other hand, I do hate the colors and graphics for 2015 Thunderbolts, all but the BC Edition. I just hope they make the color scheme on this year’s BC Edt available as frame only for 2016.

  5. Love this bike. In the realm of fantasy purchases I would get the BC edition, admittedly mostly based on the killer paint job. The others being so ugly and all. And then go against the grain and turn it into a super-light XC bike with a 120 mm RS-1 or DT Swiss Race fork and XX1 drivetrain.

  6. @Heffe, you need to test a DT Swiss ODL fork if you haven’t, that things is amazing. The damping curve is phenomenal and it probably has the stiffest 32 chassis out there.
    As a matter of fact I am waiting for the new carbon version of the ODL to come out to build my next XC Trail bike around it, hopefully using a ’16 Thunderbolt frame if the guys from Rocky come out with less eye-soreing colors and graphics. That right there is my dream machine for the endurance races I plan to do next year, and for XC Trail ridding in general.

  7. I second that BLUE >even Yeti’s ASR CARBON ENDURO build has Fox Factory Float CTD front and rear at $4,199! GREAT bike i have built one up for a customer

  8. How did anyone think that 29ers were fat bikes before fat bikes were at thing? That doesn’t make any sense. People did think that 29ers were for dirt sidewalks … correlation/causation.

  9. AFS- in this case you’re not wrong, as Rocky uses a pretty active variant of FSR, but to say that is a basic characteristic of horst link is just wrong. Move the pivots around a centimeter or two in the right direction and you’d have a metric f-ton of anti-squat.
    The shock’s compression tune and available lockout is why this bike pedals OK, nothing to do with the linkage.

  10. I just got the Thunderbolt 750 MSL, swapped the wheels for better and lighter ones (notubes arch ex and crest with DT 240s hubs, sapin xray spokes), and this bike is a rocket, did not know until now a bike could be that much fun !

  11. This bike isn’t a horst link bike, the rear pivots are on the seat stays, not the chainstays. I service plenty of ABC pivots, not AFS and I’m quite impressed this year with the ease of service. As previously mentioned, don’t lose those o rings from the pivots, dirt can contaminate the bushings easily without them.

  12. I wonder if the tester/author had/has a good itch going on right now. The pics were taken while surrounded by poison oak. I’ve had so many battles with the vile weed that its the first thing I look for when near green.

    Love the bike. RM makes sweet bikes.

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