Roehr wanted his superbike to be 100-percent American made so what other options would he really have for the engine other than the H-D V-Rod? Well, nothing really as the well of American-made motorcycles is pretty dry these days.
One man, a shed and a dream. This sums up the Roehr 1250SC pretty well. But where most would think this implies shoddy engineering and seat-of-the-pants design, take a quick look at the quality and fit and finish of the American-made V-Twin Superbike and one can’t help but be impressed. It really is quite staggering. Keeping this in mind as you ride the supercharged Harley-Davidson
V-Rod-powered sportbike and the level of performance is just plain awesome. But the key is to do exactly that and not try and compare it to the million-dollar-plus engineered Japanese or Italian sportbikes, because, well, that’s just not fair to the one man, his shed or his dream.
The Roehr is kind of like a supped-up Mustang or Ford GT. It’s 100-percent American made and beating at the heart of the beast is a liquid-cooled, big-bore V-Rod engine with a supercharger on it, much like those fast-Fords. Why a V-Rod you might ask? Well, despite the fact it’s made for a cruiser and quite heavy, according to Roehr it’s engineered to be durable and for the most part it’s about the only decent American-made engine capable of making the kind of power they wanted for this bike.
“It’s basically the VR1000 Superbike engine of old but reengineered for the cruiser,” explains company founder Walter Roehr. “The engine is great and well-made, and can handle loads of horsepower being pumped through it. The only downfall is the weight. The engine itself weights almost 100 pounds and in a 400-pound bike that’s a lot. This is why having it make good, useable power was a key. As well as trying to make the rest as light as possible.”
167.5 hp and 99.5 lbs-ft of torque at the rear wheel! That's impressive by any standards.
In fact, the V-Rod engine was actually developed in conjunction with Porsche AG originally. Bet you didn’t know that, did ya? The result was an 1130cc (now available in 1250cc) liquid cooled, DOHC, eight-valve, 60-degree V-Twin engine, named the "Revolution" by H-D, with performance characteristics only a large-bore short-stroke architecture can provide. But Roehr needed even more for his motorcycle so he fitted a supercharger to his beast, but we will go into that in a minute. The internal configuration of the Roehr superbike engine has a relatively stock 1250cc V-Rod engine with a 105mm x 72mm bore and stroke, 11.3:1 compression ratio and 5-speed transmission. Handling the exhaust duties are a set of custom-fitted R1-spec Akrapovic carbon mufflers mated to hand-fabricated headers.
As revolutionary as the V-Rod engine is, it’s still a cruiser engine so the power is nowhere near what Mr. Roehr needed for his big-buck modern sportbike. And while it is possible to make the engine quite fast in naturally-aspirated from, the more logical and cost-effective way to reach this goal was to think outside the box. Forced-induction was the logical choice for this application so the RSS (Roehr Supercharger System) was born.
The Roehr-designed Bi-Metal frame features both Chrome-Moly and T6 Aluminum in the same unit.
Inside the RSS sits a Rotrex C 15-60 centrifugal unit that weights only 6.4-lb and is no bigger in size than a typical small car alternator. Inside is a patented roller-drive mechanism that provides an “extremely high step-up ratio.” The ratio is 12.7:1, which means maximum air from the slimmest possible size. Other tidbits inside include a special bypass valve that is designed to re-circulate unneeded air back into the compressor during certain operation, such as idle, cruise and deceleration, which effectively unloads the unit and reduces drag on the engine. This basically then negates the supercharger and lets the engine function as if it were stock in those less-demanding situations.
The bypass valve shuts under acceleration and allows the compressed air to pressurize the intake system. The Rotrex is also designed to deliver air in proportion to the motorcycle’s driven speed, by virtue of a system that increases the speed of the SC-unit to match the bike’s engine speed. The idea is that as a result power delivery will be as smooth as possible and it seems to eliminate that aggressive “hit” usually associated with forced-induction. This works from just above idle all the way to the rev-limiter. The small size and relatively low boost of the system also eliminates the intercooler typically needed with a supercharger, which aids in keeping weight down. And as for actual engine cooling, that comes in the form of twin side-mounted radiators, intended to keep the bike as slim as possible.
Housing this very untraditional engine is an equally unique frame. Featuring a Bi-Metal beam design, the unit is constructed as a blend of 4130 Chrome-Moly steel and T6 Aluminum. By blending the two his aim was to tune the proper flex characteristics into the bike, as a motorcycle frame needs to be much more than strong and stiff – it needs designed-in flexibility, mostly laterally, to allow it to function properly at both low and high speeds as well as while it’s leaned over. This is known as controlled-flex and is what provides the rider feedback and offers some level of dampening when the bike is carving through a turn.
Top-shelf components such as Ohlins suspension and Brembo brakes grace the Roehr 1250SC.
The chassis as a whole is designed with computer-assisted finite element analysis and the main beams are produced using large-section, thin-walled 4130 steel. This is bonded and bolted to “extremely strong, stiff, yet lightweight” billet aluminum swingarm pivot plates. This combination is where the ‘Bi-Metal’ name comes from. Mated to this is a single-sided swingarm to round out the basic chassis.
As for the suspension, they spared no expense and went straight for the top – Ohlins. Up front are the Swedish suspension expert’s Road & Track fork and out back their fully-adjustable (compression, rebound, spring preload and ride-height) rear shock. Equally as top-spec are the Brembo brakes: Monobloc 4-piston calipers gripping a pair of 320mm rotors up front and a 2-piston lightweight caliper gripping a single 245mm rotor on the back. Mated to those are big-buck Marchesini wheels shod with Pirelli Diablo Corsa 3
rubber (120/70-17 front and 190/55-17 rear).
And while some of the components are sourced out, the design of the bodywork and its composite construction are done by Mr. Roehr himself – although they do take some direct design cues from Ducati’s of yesteryear up front and Yamaha
’s of recent-year out back. But a lot of this is a matter of form following function, you see, as the chassis has a very Ducati
-like layout to fit the large V-Twin engine and the tail section uses R1
-sourced exhaust, thus these design elements are more than pure copies. As a result, I must say, I do like how it looks.
Feeling the Power
Power from the supercharged V-Twin is extremely useable.
We were able to sample the machine both on the track briefly and more extensively on the roads. And first things first, this is a machine designed for the street. So, to be fair this is where we based most of our evaluation. Good thing, too, because in the world of B-roads and canyon passes the Roehr is right at home. It works reasonably well at the track but without a doubt, the power and the unorthodox way in which it’s produced, is more suited for street riding. Very few production motorcycles utilize forced-induction so this wasn’t something I was used to. In fact, it was the first sportbike of this kind I’ve ever
Thankfully, it’s well engineered and the ‘scary hit of power’ commonly associated with other forced-induction-powered bikes just doesn’t exist on the Roehr. But, that’s not to say it isn’t fast. In fact, it’s quite the contrary. Power comes on from low rpm smoothly and gets the American-made 1250 moving with some serious steam. As one can see from the dyno chart it makes 167.5-hp at the rear wheel, which is nothing to scoff at on any level.
This type of power delivery is exactly what is needed to make it a fun and entertaining sportbike on the street. And while Walter himself can tell me how great that engine is and the potential it has until he’s blue in the face, it’s hard to get your head around it until you actually ride the thing. And after riding it on the roads, there’s no question the supercharged V-Twin philosophy works very well.
Hey, is this thing legal for the Daytona Sportbike class?
On the track, not everything is quite as glowing though. It certainly feels like a racebike but it is on the heavy side to be considered a pure track weapon and since we were riding it at the same time as our open-class bikes at Infineon Raceway during our 2009 Superbike Smackdown we were able to feel how it stacked up against the 1198 and the latest from the Big Four. Starting with the positives it certainly hustles around the track good enough that I wouldn’t hesitate to use it at a track day. Although it needs some higher-spec tires if you plan to push it hard. The Brembo brakes are very good and the suspension components have the potential to handle anything the average Joe can throw at it. We found it was a little soft for our preference but we didn’t get much opportunity to make adjustments since we were at a Pacific track Time track day.
Seating position and ergonomics feel very much like a Tamburini-era Ducati. The reach to the bars is a bit stretched out, the tank is long and skinny, the riding position is aggressive and the cockpit itself is reminiscent of the Italian Twins. It’s no surprise that the bike behaves in a similar manner as well. Both geometry and layout are similar since there are not too many ways of fitting the long motor into such a compact frame. As a result steering is a bit heavy initially, but once set in the corner and on its side is very stable and solid, offering ample feel to the rider through the bars.
Considering sitting between those Roehr-engineered frame spars is a massive V-twin engine from a cruiser, the performance is pretty amazing.
The Roehr superbike
bike feels good once we get it up to speed on the track. It handles very similar to the 1198 though it simply doesn’t have the gearing to keep pace with its Italian counterpart. Initial power is on par but it runs-out quickly as we were often hitting the rev-limiter while finding that happy medium between getting a good drive and battling to keep traction from the stock Diablo Corsa tires. The trick is to run it a gear higher than you think and carry a bit more speed in order to keep the engine in the meat of the power. The linear power delivery comes on down low and in the middle of the rev range but don’t let it dip below 4000 rpm because there isn’t much usable power available down low when you’re trying to go fast around a race track. It has a lot of torque, 99.5 lb-ft to be exact, which is awesome on the street or the track. The torque curve reveals a linear spread across the range, similar to the horsepower curve which climbs smoothly from 4000 rpm on up to the 9250 rpm peak. The problem is that the engine hits redline before ten-grand so there’s not much margin for error when connecting corners on the track because it builds quickly. But, like we said earlier, this motorcycle was not intended to be a race bike. It’s a hand-crafted American-made superbike for people who are tired of following the crowd. It’s unique and it’s pretty fast, plus it gets around the track fine if you aren’t hoping to qualify for an AMA National.
The single-sided swingarm is very Ducati-looking. In other words, it looks good...
Much of the reason the Roehr can hold its own on the track is due to its well-engineered frame, swingarm and the top-level suspension components. Sure, it’s on the heavy side, tipping the scales at 490-lbs full of all fluids, but it carries the weight pretty well. This may sound high at first, but it actually is only 14-lbs heavier than the 476-lb wet weight of our 2009 Yamaha R1
, and I would venture to guess the H-D engine weights double that of the light inline-four in the Yamaha.
So everything sounds amazing, right? For the most part, keeping everything in context, the Roehr is an amazing machine. But that context involves riding it mostly on the roads. The track isn’t where it’s designed to be and while it can hold its own, it’s definitely not where it’s most at home. It would be okay for the occasionally track day to mix in with the weekly canyon runs, though it’s not going to be the basis for a race bike. So, where does it belong in the grand scheme of things? It is the culmination of one man’s vision, his dream of making a motorcycle from scratch that incorporates his design and his goals. It may not be the bike to lure Gixxer punks away from Suzuki
but it will appeal to a more affluent club. The rider who wants to be different, who wants to stand out from the crowd and be able to boast of a supercharged V-Twin and a list of top-shelf components that will keep any bench racer happy for quite some time. The only real hurdles for Roehr are going to be price and timing. The demand for a $42,500 sportbike can’t be huge right now, but we will be pulling for the official launch of the Roehr 1250SC Superbike to be a successful one.