Slash 5 Sport: BMW “R100/5” Roadster

BMW R100/5 Custom

BMW R100 “Slash 5” by Rind Performance… 

For the 1970 model year, BMW introduced their new /5 (“Slash 5”) Series in three sizes: 500cc (R50/5), 600cc (R60/5), and 750cc (R75/5). A replacement for the old /2 Series, the new bikes boasted a slew of upgrades including 12-volt electrics, 180-watt alternators, electric start, telescopic forks (versus the old Earles-type), better drum brakes, and a frame reminiscent of the legendary Norton Featherbed.

Meanwhile, the Type 247 “Airhead” flat-twin boxer engine was given a chain-driven camshaft that ran beneath the crank, aiding in oil delivery and making for less frequent rebuilds. The 750cc model could hit 60 mph in less than six seconds, pass the standing quarter-mile in about 14 seconds, and hit a top speed of ~110mph — not bad for the day.

Though the series would only remain in production until 1973, the Slash 5 has earned a cult-like following over the years, with stories of these machines reaching 500,000+ miles with only a couple of overhauls.

“Contrary to the initial worries from BMW traditionalists that the company had strayed too far from its function-over-form roots, the /5 motorcycle family has earned a sterling reputation for anvil-like reliability.” –Rider

BMW R100/5 Custom

Our friend Robin Ludwig of Rind Performance has long been a fan of the Slash 5 series, as his grandfather owned an R50/5. That Robin had the idea to convert his newer, more powerful 1980 R100 (980cc) along the lines of the iconic 1970s design — a modern tribute to his grandfather’s bike.

“I wanted to build something similar with today’s technical standards and a little bit more power.”

BMW R100/5 Custom

To that end, he outfitted the bike with a set of modern Showa upside-down forks, Öhlins rear shocks, Brembo brakes, sticky Metzeler Racetec rubber, and an overhauled 70-hp motor. If the performance upgrades pushed the bike into the 21st century, the design went in the opposite direction, turning back the clock to the 1970s with an authentic /5 tank and saddle.

“I shortened [the saddle] by about 6cm to make the look a little sportier. Not immediately visible to many, but in the end small details make the difference.”

BMW R100/5 Custom

Indeed. The result is Robin’s BMW “R100/5” — a custom roadster with modern performance, classic style, and the ability to carry a pillion passenger in relative comfort. We can’t think of a better way to honor the /5 Series of his grandfather’s era. This bike oozes class, and we’re told the bike goes as well as it shows. Well done, Robin!

BMW R100 “Slash 5”: Builder Interview

BMW R100/5 Custom

• What’s the make, model, and year of the donor bike?

It’s a BMW R100 from 1980.

BMW R100/5 Custom

• Why was this bike built?

Most of my conversions are single-seaters and are not suitable for riding two up. So I decided to build a two-seater that I can ride everyday with a passenger and maybe even on a short vacation.

BMW R100/5 Custom

• What was the design concept and what influenced the build?

Since my grandpa owned an R50/5 I was impressed with it, so I wanted to build something similar with today’s technical standards and a little bit more power.

Converting this legendary machine was a challenge, but the result is a motorcycle that impresses both on the road and in the showroom. Some people have to look twice to see that it’s not a normal /5.

BMW R100/5 Custom

I installed high-quality suspension elements from Öhlins at the rear and a modern Showa upside-down fork at the front. As a result, the handling has been improved and the motorcycle is even more stable on the road. The brakes were also upgraded, CNC Brembo GP calipers were installed, which are otherwise used on supersport motorcycles. When it comes to tires, the choice is Metzeler Racetec RR 18”.

BMW R100/5 Custom

In addition to the technical and stylistic revision, I also improved the comfort. I installed an original /5 bench seat, but shortened it by about 6cm to make the look a little sportier. Not immediately visible to many, but in the end small details make the difference. Converting my BMW R100/5 was a worthwhile investment.

BMW R100/5 Custom

• What custom work was done to the bike?
  • USD Fork
  • Öhlins Rear Shocks
  • Brembo GP CNC Brakes
  • R nineT Headlight
  • R50/5 Seat (6cm shortened)
  • R50/5 Fuel Tank
  • Metzeler Tires
  • S1000RR Brake Pump
  • Stainless Exhaust

BMW R100/5 Custom

• Does the bike have a nickname?

“R100/5.”

BMW R100/5 Custom

• Can you tell us what it’s like to ride?

Rides like a sporty R100 because the suspension and brakes are state-of-the-art. The engine is overhauled and has 70 hp, which is enough fun to cruise.

BMW R100/5 Custom

• Was there anything done during this build that you are particularly proud of?

I was impressed that small changes can make a big difference.

BMW R100/5 Custom

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6 Comments

  1. Elam Blacktree

    Very nice!

  2. Sorry but that just looks half finished.
    It seriously needs a rear mudguard and some, even basic, side panels would make a huge difference.

  3. I like it . I wish it had a back fender of sorts . But it’s a good machine.

  4. About as much good in the rain as a chocolate teapot.

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