Ride Quality 
Whether ripping through windy, flowy singletrack or descending a rock garden the Rocky Mountain Thunderbolt 770 MSL is smooth as silk and very well balanced – especially when the geometry is dialed for that specific terrain. The 130mm of front travel combined with a slack head tube angle is well suited even for highly technical terrain, and the FOX fork is plush and smooth in the big hits, with solid small bump performance as well. And the rear shock is equally smooth over the rough and very stable with precious little bob while climbing.  

Stiffness-to-Weight/Power Transfer
As one of the lightest bikes in the category, the Rocky Mountain Thunderbolt 770 MSL has a distinct advantage in stiffness-to-weight, and the frame’s rigidity doesn’t disappoint either. While it’s not a pure racer, lock this bike out and she explodes over power climbs and when sprinting through the flats. The slacker front end gave some minor flex through the head tube and fork, but it’s negligible unless you’re an aggressive racer—and most of this can be eliminated by putting the bike in its lowest and most forward position.  

Climbing/Efficiency
Again, while it’s not a pure XC racing bike, the Rocky Mountain Thunderbolt 770 MSL climbs almost as well, and more comfortably thanks to the more relaxed geometry. Even without locking the shock, there’s very little pedal bob unless really hammering. But locked out it’s a joy on the climbs with its relatively light weight and stiff bottom bracket area. And if your ride is all about getting to the top as fast as possible, just dial the geometry forward and enjoy even more power. The only downside is standup climbing – the slack front end (when not set all the way forward) is a bit too high, and there’s a small amount of flex.  

Descending/Handling
The Rocky Mountain Thunderbolt 770 MSL is, in general, a very solid descender for what the brand says is an XC bike – our testing shows it descends much more in the Trail category, especially when the geometry is on the slackest setting. That adjustability can be a blessing and a curse however, since when it’s set for one extreme, it diminishes performance on the other. If going down is your forte, or you’re just riding particularly technical descents that day, set it to full slack. That combined with the 130mm of front travel allows this bike to feel highly confident and not at all tippy over fairly rugged terrain. However if the trail is more flowy, set it forward and the bike rails corners with more stability and a straighter track. Bottom line, we love having the option.

Components: Drivetrain, Shifting and Brakes
There are very few folks out there who will ever need more than a Shimano XT 1×11 drivetrain, and the Rocky Mountain Thunderbolt 770 MSL is able to keep the cost down by employing this excellent and reliable drivetrain. We especially appreciate the XT shifter’s ability to shift multiple rings with one push, and even use the trigger finger to shift with a pull (along with the traditional thumb push). Why won’t SRAM do this!? Plus the RaceFace Turbine cranks are certainly a bonus here, as they’re some of the lightest and stiffest out there. XT brakes are also some of our favorites, with testers reporting they often prefer them over XTR for modulation – the only downside here is the lack of Ice-Tech rotors and pads, especially for serious Trail-style riding.  

Wheelset
The wheelset on the Rocky Mountain Thunderbolt 770 is a combination of Shimano’s XT hubs and Stan’s ZTR Crest rims. Stan’s rims are always respectably light, and the slightly wider profile of the rims gives a solid platform for wider Trail-oriented tires, but will also work fine with semi-slicks on race day. However for more gnarly descending a wider rim would be appreciated. The XT hubs are always a safe bet, if not the lightest and stiffest out there – and we’d always like to see straight pull spokes, at least in front, instead of the J-pulls on both wheels here. 

Value
Considering the versatility the adjustable geometry gives the Rocky Mountain Thunderbolt 770, and its relatively inexpensive price of $5300, it’s arguably the best value in this group. For the money you get a bike that can easily switch between an XC racer and a full-blown trail bike, with high-end (and high value) components and an excellent carbon frame.