WP suspension, Paralever, central strut, spring preload adjustable to
continuously variable levels by mean of a hydraulic handwheel, rebound
adjustable damping. 130mm wheel travel
Rear Wheel Travel
130 mm / 5.1 in
Front Brakes
2 x 320 mm discs 4-piston calipers, Brembo
Rear Brakes
Single 276 mm disc 2-piston caliper, Brembo
Wheels
Marvic,
5-spoke
Wheelbase
1453 mm / 57.2
in
Front Tyre
120/70 ZR17
Rear Tyre
160/60 ZR18
Seat Height
800 mm / 31.5 in
Dry Weight
215 kg / 459 lbs
Fuel Capacity
22 Litres / 5.8 US gal
The sound is instantly familiar, a
gentle scritch above the engine's exhaust note as the bike cranks through a
tight right-hand bend and my knee-scraper brushes the road. Nothing unusual
about that, in these days of sharp-handling bikes and fat, sticky tyres.
Except that the machine I'm riding is a BMW the first boxer that I've ever
cornered fast enough to get anything other than a centrestand, cylinder head
or the toe of a boot touching the ground.
This is no normal BMW, mind. The aggressively styled single-seater, powered
by the air-oil cooled motor from the R1100RS sports-tourer, is the work of
Dutch chassis engineer Nico Bakker, designer of many classy specials and
racebikes in a career stretching back 20 years.
Despite its typically restrained grey paint the Bomber, with its nose-down,
seat-up profile, is an unmistakably sporty motorbike. Styled by Martin
Longmore, who also shaped BMW's F650 single, it looks lean and purposeful
from its carbon-fibre front mudguard all the way to a single-seat unit made
from the same lightweight material. (This bike's fairing is fibreglass, but
future versions will use carbon here too.)
The fairing is cut
short enough to reveal the distinctive angled four-valve heads
of the high-cam R1100RS engine, whose exhaust downpipes curl
down and back towards the big round-section silencer on the left
of the bike. At the other side is the boxer lump's hefty
shaft-drive housing and single-sided Paralever swing-arm,
holding an 18-inch rear wheel which, like the 17-inch front, is
a genuine BMW item.
This bike's powerplant
is unmodified from its airbox to its rather tarnished exhaust
system. But although BMW's Telelever front suspension system is
also retained, most of the chassis is far from standard. The
rear subframe is
made of 22 mm diameter aluminium tubes, instead of the original
steel, and lifts the rear of the bike slightly while retaining
roughly the original seat-to-pegs relationship.
The alloy front frame member is also altered. In conjunction
with a slightly shorter than standard WP shock unit, plus a mod
to the ball-joint at the top of the upper shock mounting
bracket, the result is to lower the Bomber's front end relative
to the R1100RS. Steering geometry is adjustable, the rake
through three degrees and the trail using a choice of two
locating plates. The figures are sportier than the RS's
equivalents, though Bakker won't reveal exact dimensions.
The other major
chassis change is to the Telelever set-up's main horizontal arm,
which Bakker has shortened slightly and relocated to add a
little extra dive under braking and put more weight on the front
wheel. The front brake system, with its four-piston Brembo
calipers and ABS, uses original components, but Bakker says that
the suspension geometry changes make a difference to the way the
anti-lock system operates. (The rear disc is smaller, as it is
less useful on a single-seat sportster.)
The Bomber certainly felt very different to any conventional BMW
as I sat astride the rather tall seat and reached forward to
clip-ons mounted 20mm below the Bakker-made aluminium top
steering plate. The shock's remote reservoir was clamped inside
the fairing on the right, joined to the vertical damper unit
positioned in front of the big alloy fuel tank. Clocks and
switches were standard BMW, but the low screen added to the
sporty feel.Other sensations were more familiar, such as the
bike's sideways lurch from the flat-twin motor's longitudinal
crankshaft, and the clunk from the ABS system as I pulled away.
The BMW's Motronic fuel injection gave a typically crisp feel at
low revs; the five-speed gearbox was just as slow-shifting as
ever. I headed off into a typical Dutch downpour glad that the
fairing, although insubstantial by BMW standards, provided a
reasonable amount of protection from the elements.
That was equally true later, after the rain had stopped and the
roads had dried out, when the Bakker bike was comfortable
cruising along open Dutch main roads at an effortless 100 to
110mph. At that speed the screen kept the wind off my chest,
there was very little vibration through the solidly mounted
handlebars (1100RS bars are rubber-mounted), and a twist of
throttle sent the Bomber surging obediently if rather gently
towards an indicated 130mph.
Acceleration at lower speeds was hardly dramatic by super-sports
standards, though with a peak output of 90bhp pushing a bike
that weighs 215kg dry (20kg less than the standard R1100RS), the
Bomber was pretty lively. Midrange response was strong, and in
the lower gears the motor pulled hard to the redline at 7300rpm,
though the vibration that increased noticeably above seven grand
discouraged such thrashing.
High-rev performance could fairly easily be uprated with some
mild engine work. Bakker is hoping to put together a tuning
package, in conjunction with his German distributor, that would
include fuel-injection, exhaust and possibly internal engine
changes. There's also scope to uprate handling performance by
swapping the standard wheels and front brake calipers for
lighter racing parts.
That would further add to the agility of a bike which, although
sporty by BMW standards, retained many of the donor R1100RS
model's handling characteristics including the need for a fair
amount of handlebar pressure to get it to change direction in a
hurry. Anyone who's ridden a standard RS could imagine how
Bakker's bike felt: basically like a firmer, slightly
quicker-steering version of the original Telelever model.
Despite the extra brake dive that Bakker has engineered in, the
bike‚s nose still dipped only very slightly when the anchors
were used hard. Partly for that reason, the Bomber needed rather
more effort than I'd expected to tip it into a bend. Once
cranked over the bike tracked very accurately, though it had a
slight tendency to stand up under braking. BMW's Paralever
system did its normal good job of reducing the drive shaft's
effect on handling, though the big twin still felt much more
like a Guzzi Daytona than a Ducati 916.
Suspension at both ends was slightly firmer than standard RS,
and the front shock's travel, at 90mm, was 25 per cent down on
the original. Most of the time that felt just about right,
giving the bike taut feel at both ends. If anything the front
was a fraction firm, working best with the compression damping
wound right back. Bakker is planning to revalve the shock
slightly, so that this bike's minimum setting will become the
midway mark on production versions. That didn't stop the front
end tracking smoothly in corners, even when conventional forks
might have used most of their travel dealing with braking and
bumps. Despite its wheelbase being 20 mm shorter than the
R1100RS's (at 1453mm) the Bomber still felt quite long and tall
for a sports bike, and I took a bit of time to get used to
throwing it into tight bends with the necessary confidence. But
the harder I pushed it, the better the Bakker machine felt.
Steepening the steering geometry from this bike's midpoint
settings could have quickened up the steering, though Bakker
admitted that there would be a trade-off in stability,
particularly under braking. This bike's tyres both had rather
worn-flat profiles, which didn't help. As it was, a big handful
of front brake was enough to get the Bomber's rear wheel
waggling in the air as the bike stopped very hard indeed.
Modifying the front suspension arm had certainly made a
difference to the way BMW's anti-lock system worked. The ABS was
now much less inclined to cut in, which allowed seriously hard
use of the front Brembos in conjunction with the generous grip
of the ubiquitous Michelin Hi-Sport radial front tyre. The rear
Hi-Sport, a 160/60-section 18-incher, looked skinny by current
supersport standards but gripped well on the road. No solid bits
dragged, despite some pretty hard cornering, although how the
boxer's sticking-out pots would fare given slick tyres and a
racetrack remains to be seen.
Some of the bikes Bakker plans to build will probably find their
way into twins racing, but most will no doubt be sold for road
use to BMW fans eager for the sporty boxer the factory has never
made. There may be some direct involvement from Munich, too. BMW
has asked Bakker to visit and demonstrate the bike, confirming
that the Dutchman, who has worked on development projects for
the factory in recent years, is held in high regard there.One of
those projects was the racebike that Bakker developed in 1991
and 92, and which was ridden to several top-six places in German
BoT races by Herbert Enzinger. That bike also featured
Telelever-style front suspension, although its two-valve engine
required a much more substantial frame than the Bomber's. At the
time there were rumours that the factory was planning to build a
roadgoing version, but that never happened.
Bakker says he hopes BMW will like the Bomber enough to want to
put something very similar into production, although the German
firm's long-standing wariness about getting involved in the
super-sport sector of the market makes that a long shot. Much
likelier is that Bakker will be allowed to buy engines and the
other parts he needs to build bikes himself, as Bimota is doing
for its soon-to-be-released F650-engined BB1.
That would remove Bakker's current need to acquire a donor bike,
as he did for this first machine, and would make producing the
Bomber simpler and cheaper. Current price for a complete bike
like this one is f40,000 (about £15,000), or f26,000 (£9500) if
you supply an R1100RS with the necessary parts. A frame kit
costs ff16,000 (£6000), including all suspension and bodywork,
but excluding engine, electrics, wheels and brakes.
Bakker's
hand-built bikes have never been cheap, but that price is not excessive for
a stylish, well-made and rapid sportster that handles better than any BMW
I've ridden before. Never mind the usual set of panniers for this boxer. The
only accessory a Bakker Bomber pilot needs is a fresh pair of knee-scrapers.
Any corrections or more information on these motorcycles will be kindly appreciated.