Putting The “Sport” In Sportster: Thunderbike’s Custom SPS 4

The Harley-Davidson Sportster S is perhaps one of the more confusing motorcycles out there. Don’t get me wrong, many people probably love this machine to bits, however, I’m not a big fan of HD’s modern sporty cruiser. 

Don’t get me wrong, it’s a fast bike, and with the Harley-Davidson 1250 Revolution-Max engine, it’s got some real sporting chops to it in some capacity, however, the confusion starts with the choice of footpegs, the choice of front tire, and the overall ergonomic package that suggests that this is more of a cruiser than a bike with “sport” in the name. 

Thunderbike recognized the sporting potential in this bike, noting its engine as being “extremely agile. Paired with a modern chassis. The wide rev range brought on by variable valve timing is also rather fit for purpose, and those 122 horses are a big help as well. It’s a “perfect basis” for Thunderbike, who wanted to build another supersport custom project. 

Now, the changes didn’t actually revolve around the Revolution-Max engine, but rather, everything else around it. While the Sportster S’ chassis can handle the rigors of riding, if you want to bank it in and lean on the tires, the stock setup puts you in a rather unideal position to really turn, at least in comparison with sportbikes and sport nakeds. 

The 160-width front tire had to go, but in its place, the Thunderbike team opted for a 21-inch front with a 3.5-millimeter rim, which happens to fit a 120-width tire, the standard on most sportbikes and sport nakeds in the market today. The result is better handling, but there is more to that than just new rubber. The new wheel also allowed Thunderbike to fit two 340-millimeter brake discs on the front wheel which is a set of Thunderbike GT Wheels that come in at six by 18 inches in the rear, and 3.5 by 21 inches in the front as previously mentioned. The two calipers are also radially mounted and the upside-down fork was also modified to accommodate the extra caliper. 

Next up was fixing that seating position. The difference looks night and day here, as the Sportster S’ forward-set pegs have been set aside in favor of rear sets, which is a Thunderbike kit and it basically transforms how the bike rides. From low-slung and in the bike to dynamic and on top of it. The pegs are also complemented by the reshaped seat that was also touched by Thunderbike to allow for more support for the rider. Furthermore, a flat bar was fitted to match everything up. 

Finally, other parts from the Thunderbike SPS series of parts were fitted which include radiator cowling, engine cover, pulley cover, shock absorber cover, headlight cowling, grips, indicators, and more.