1. THE ORIGINAL CONDITION
Rocky MountainThunderbolt 50, 3299 euros, 13.35 kilos (photo above)
In our trail bike test from BIKE 10/2018 the Rocky Mountain Thunderbolt 50 won the test. With 130 millimetres of travel at the front and up to 140 millimetres at the rear, the 27.5-inch bike fits perfectly into the trail category. Although it scored the most points in the practical evaluation, the Thunderbolt only landed in the lower midfield in terms of weight. We were unable to tune anything on the rather heavy aluminium frame weighing 2888 grams without the shock. Instead, we successfully focussed on the rotating masses.
2. THE TRANSFORMATION
Budget: 576.50 euros | Weight: -737 grams
1 brake disc + screws: 234 + 252 g / 190 Euro
The brake discs from Trickstuff are among the really fine tuning parts. The weight of the Dächle Ultralite is a pleasure, but with a thickness of 2.05 millimetres they still offer enough meat for stable braking. The saving of 18 grams does not compare favourably with the 70 euros that twelve small titanium screws cost. However, the hollow-bored screws sold by Trickstuff are sure to please any tuner's heart.
2 crank: 634 g / 150 Euro
Every little helps. The Praxisworks aluminium crank lightens the weight account by around 100 grams and also looks good. To prevent chain drops, the teeth of the 32 mm chainring naturally have a thick/thin tooth profile.
3 carbon handlebars :221 g / 119 Euro
The Newman Advanced 318.20 is not only very safe, the affordable carbon handlebar saves a whole 142 grams compared to its aluminium counterpart in the standard version.
4 tyres: 707/744 g / approx. 100 Euro
The Continental tyre combination we fitted saves almost 300 grams compared to the original tyres and also beats rolling resistance. Hardly any other tyre combination for trail bikes rolls better than the Mountain King at the front with the Cross King at the rear.
5 handles: 53 g / 17.50 Euro
The ESI grips already have classic status: very good damping with little weight.
3. THAT DID THE TRICK
Driving report
With the original equipment, we attested the Thunderbolt an acceptable trail bike weight in the last test, where you don't have to make any compromises, at least downhill. Uphill, the small diameter (27.5 inches) of the wheels provided better acceleration than the solid Maxxis tyres. According to our weight test, the Rocky was able to shed a good 700 grams, almost exclusively on the rotating parts (rotating mass). Continental tyres, Trickstuff brake discs and titanium bolts save around 450 grams and make for more agility.
The low rolling resistance of the tyres also has a positive effect right from the first turn of the cranks. If you go on a long tour with the tuned Thunderbolt, you will save a lot of energy, even if the X-King rear tyre is a little more susceptible to punctures. The ESI grips save a further 47 grams and also provide first-class damping. The remaining savings come from the Newmen carbon handlebars and the Praxisworks cranks, which are less noticeable when riding.
CONCLUSION on the Rocky Mountain Thunderbolt by Ludwig Döhl, BIKE editor
Mountain bikes are becoming more and more downhill orientated. Sure, I also want to have fun downhill, but for me, mountain biking is more than just a craving for adrenalin. I always look at a bike tour as a whole. If you hate climbs or flat sections like the plague, you will sooner or later get on an e-bike anyway. I enjoy climbing mountains under my own steam and have therefore injected a few climbing genes into the Rocky. In all the test rides I've done for BIKE over the years, one thing has been confirmed time and again: Wheel weight and wheel acceleration are extremely important parameters for riding fun on undulating terrain or climbs.
That's the reason why I tuned the rotating mass in particular with lightweight tyres, brake discs and brake bolts. At 737 grams, the absolute weight saving is not huge, but the difference on the trail is clearly noticeable.
You can find this article in BIKE 10/2019. You can read the entire digital edition in the BIKE app (iTunes and Google Play) or the print edition in the DK shop reorder - while stocks last:
