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Bakker GSX-R F1 SB Road Test

The focus of experiments in alternative chassis and front suspension design seems to have shifted from France to Holland recently, what with the new White Power 'Monofork', the Kawasaki-powered centre-hub RB-1 that's so far been undefeated in Dutch National TT F-Two events, and now the latest product from the fertile mind of world-famous chassis constructor Nico Bakker, whose small wooden shed of a factory employs but seven people yet produces more than 120 frames a year, for over 20 different types of engine. Bakker's latest creation appeared unheralded in the paddock at the Dutch GP at Assen, powered by a roadster VFR750 Honda engine, and caused tremendous interest on account of its unique front end design and chassis-less construction which appears to combine elements of both the ELF2 and ELF3/4, plus some original thought from its creator and his colleague Cees Smit, a former GP sidecar driver who assisted in the bike's design and construction.

A hint of the philosophy behind the new Bakker chassis lies in its name: the QCS, standing for "Quick Change System". "We were the first people in the world to offer a single-sided, rear swingarm to the public," says Nico. "And we've been working on such designs for the past three years. But what's the point of having a quick-change rear end, if you then waste time in the pits changing the front, because you choose to stick with conventional twin-leg telescopic forks? This is obviously crucial in endurance events, but GP bike racing is becoming more and more like F1 cars, where people start the race on soft tyres which give better grip, allowing them to lap faster, but which won't last the distance. That means they have to make pitstops to change rubber, and though bike GPs are less than half the length, I can see this coming to our sport as well. When that happens, people like us and ELF are going to have a big advantage, especially since race organisers will be less disposed to stop the race if the weather changes: they'll expect riders to come in and change tyres if it starts raining, instead of the farce we've just had here at Assen when they had to start the race three times just because people kept getting caught on the wrong rubber."

Grand Prix riders are a different breed than the hard-nosed men of the endurance scene, and I'm not sure I can see them taking lightly to a regime where once the race starts it continues to its planned conclusion come rain or shine — though come to think of it, why shouldn't they, if only the bikes were built in such a way as to facilitate tyre changes at both ends?

So was this the only reason for Bakker's QCS design, rather than an effort to probe the frontiers of alternative suspension design in search of improved chassis response?

"Changing wheels quickly was the main reason," admits Nico. "But if you make a bike like this then there are other benefits that come along, especially speed and ease of adjustment of the front end geometry and suspension settings, reduction in overall and unsprung weight, and improved behaviour under braking. Unlike some people, I don't think telescopic forks are so bad, especially the modern 'upside down' type like the White Power or Ohlins, because they've mostly cured the problems of deflection and stiction we used to experience, and they do give the rider more 'feel'. But they are difficult to get at in order to fine tune the suspension, and you do have this problem with changing the front wheel. So that's why we made the QCS."

The Bakker QCS imitates the ELF2 in having no chassis as such, only a pair of aluminium subframes carrying the wheels and suspension which are bolted to the front and rear of the V4 Honda engine, which therefore acts as a fully stressed member.

"The VFR is ideal for building a bike like this because of its 'square' shape and the fact that it's so strong — and heavy."

A single-sided rear swingarm, made from a special grade of aircraft-specification alloy specially extruded for Bakker in Holland (by Fokker??), is employed, combined with a vertically-mounted White Power unit whose system offers a rising rate. The swingarm is hollow, though Bakker has experimented with an alloy honeycomb filling to give an improved stiffness to weight ratio. On the QCS, he says the extrusion is strong enough without the added cost and complication of the honeycomb filling. At the front, two large alloy plates bolt to the engine and support an adapted McPherson strut-type suspension system combining elements of both the ELF2 and ELF3/4 designs, coupled with Bakker's own ideas. Like the ELF2, the WP suspension unit (a rear offering 4.5in of wheel travel or about the same as a conventional tele fork) is mounted directly to the 'chassis', with a strengthening strut to carry the forces to the rear swingarm pivot. But unlike the ELF, the QCS front suspension is operated by an articulated triangle off the lower, and sturdier, of three parallel drag links by means of which Bakker aims to spread the forces generated by braking and cornering throughout the chassis instead of at a single point as with other designs. Yet with the exception of the third drag link, located above the front wheel, which adds to the overall rigidity o the front end design, the rest of th< QCS is modelled on the ELF3/4, wit the front wheel rigid on a vertical strut (made from more extruded alloy), connected to the steering head by rotating the base of the upper one via an abbreviated steering column located in the upp part of the front chassis sub-sectio

With a 57in wheelbase, a 23-degree effective steering head angle (variable between 21 and 25-degrees) used at present, and a 3.7 - 3.9in trail adjustment, the QCS displays less radical geometry than other alternative motorcycles, and its weight distribution of 53/47% frontwards is par for the course nowadays, though that figure is arrived at without the yet uncompleted fairing, still to be fitted But by scaling 357lb with oil, water, alternator and starter motor, the QCS without fairing is a little over 10% lighter than other bikes fitted with the heavy VFR engine, in endurance trim, indicating one of the spinoffs of the Quick-Change design.

More to the point, Nico Bakker estimates an endurance race pit stop to take on 24 litres of fuel and change both tyres should take no longer than ten seconds, once a suitable means of jacking up both ends of the bike quickly has been worked out. GP tyre stops — here we come.

In line with the aim of reducing time spent in the pits on this bike, Bakker has also fitted his own make of six-piston brake caliper to the single 12.6in diameter front disc brake, centrally located in the 17-inch wheel.

"We could have used a pair of four-piston Lockheed or Brembo calipers but that would have been a compromise in terms of weight, and positioning the second caliper would have been difficult with this front end design. So we made this six-piston caliper ourselves by casting it up from magnesium in the shop, with the result it weighs less than two four-piston ones, yet has the same pad area. More importantly, the design allows you to change the pads very quickly, within the time of a regular fuel stop in endurance racing. However, I'm aware that heat build-up has been a problem with the ELF3, which employs a similar centrally located single disc, and it may be we shall have to consider another design once we start track-testing the bike.'

Amid the current controversy about GP tyre changes and restarted races, maybe the QCS were the face of the future

I'm also talking to Lockheed about using their rim disc in an updated form, so long as we can change the pads quickly. We'll see."

Completed only the day before Assen TT Week began, the Bakker QCS will at first be run on the street by its creator, using the roadster VFR engine presently fitted. But track tests commenced in August with Boetvan Dulmen at the helm, and the aim is to have the chassis sufficiently developed to race in the Bol d'Orin September with a kitted VFR Honda engine fitted.

Nico Bakker intends to market the QCS in 1988 with both Suzuki GSX-R750 and Yamaha FZR750 engines fitted as well as the V4 Honda, and a street version is already planned which won't differ so very much from the endurance bike. Smaller-scale QCS designs are also planned for the 250 and 500cc GP classes, with RS250 and RS500 Honda versions already on the drawing board. Nico plans to wait for Yamaha's 1988 customer race bike plans to be announced before he makes any design for their engines. Maybe in spite of all the publicity generated by the various Elves and the Bimota Tesi, this is really what the cause of alternative motorcycle design has been waiting for: a small but active and respected chassis constructor with a receptive market and trustworthy track record whose faithful customers are ready to buy what he gives them. And if he decides that for all the practical, rather than theoretical reasons in the world, that the time is ripe to make and sell a chassis with something other than telescopic ':rks fitted to it, then perhaps its time has come. First in the world to sell a bike with single-sided rear suspension for the street or track; first with a six-piston brake caliper on two wheels, Nico Bakker may just also be the first in the modern era — like Tony Foale, Norman Hossack and the rest of the one-man shows — to build and sell a non-telescopic forked bike to the public in measurable quantities. Unless Honda's long-awaited ELF-derived roadster does appear after all at this October's Tokyo Show.

This is a fairly typical story of how a new F-One racing bike gets developed over the season. Glenn Williams began the year with an unusual single swing arm Nico Bakker chassis for his GSX-R jet after Assen had abandoned the single rear arm and gone back to a ranventional pivoted fork. The racetrack exposes a lot of fine margins and weaknesses that couldn't be apparent on the road and it took time for the team to pinpoint the single swingarm as the Rely culprit.

Over the winter, the team counted their pennies and decided to buy a new chassis. They went to see Nico Bakker in Holland who showed them ts new racing designs. Theirs cost a cool £5000 for the twin spar aluminium fame, the RG500MMO forks, the swinging arm plus three special QD rear wheels, the White Power stuck, the seat, tank, yokes, brakes, wgsand everything.

By the time mechanic Alistair Janczuk had installed the motor and transformed it into a racing projectile, it really did look the business, immaculately crafted and finished. In the paddock at Misano for the opening F-One round, they were getting more attention than the works bikes. The publicity angle is important and keeps the sponsors happy.

Daring to be different was one of the reasons they bought the Bakker chassis. Then there was the ease of tyre changing during a race.

Unfortunately, this year the F-One calendar has gradually lost its preponderance of road circuits (Vila Real and Imatra cancelled and Ulster abandoned) and the likelihood of changing tyres mid-race and still finishing in the points has diminished.

Most F1 races are 100 miles long. There are only two biggies — 150 miles around Misano and 226 at the Isle of Man. A quick tyre change could prove crucial during the longer races and a QD rear wheel is a neat facility to have in reserve.

At the bike's debut at Misano, Glenn finished 8th after losing 40secs in a slow fuel stop. He'd been impressed by how stable the bike felt on fast bends yet had noticed serious rear wheel hop on the brakes and through Misano's tighter, bumpier sections.

For the next round at Hungary, they lowered the gearing and Glenn found the rear wheel hop more pronounced. Why was it happening? The rear caliper is underslung and attached to the swing arm tending to compress the suspension under braking, yet the wheel was still getting light, leaving the ground, then bouncing. Less relevant though still odd was that the swing arm pivot was below the drive sprocket's centre, so with the suspension working, the chain was flapping around.

The best solution seemed to be to tune the rear spring and damping rates to overcome the worst of the hop. Nico Bakker confirmed that a harder spring would cure it though he must have known this ploy was at best a compromise. Glenn never got to race in Hungary because he was T-boned in practice and injured his shoulder.By the TT in June, they'd uprated the White Power shock and the bike was riding like a skateboard over the bumps. The spring was way too hard. By bumping up the spring they were effectively stiffening the rear arm too and every bump was being hammered into the rider's arms, legs and body. It was becoming a no win situation. Either the bike was unrideable over the bumps and on the brakes or you stiffened the suspension so much, it was fine for the bike but too hard on the rider. At the TT where Glenn finished 9th, it was so uncomfortable it was dangerous to race it so hard.

Over the phone, Nico was still recommending different spring rates plus increasing the ride height. Glenn thought the ride height was already way in excess of what it should be. "Our whole back end was very jacked up yet if you look at the works Skoal Bandit Suzuki's they're very low and sleek. They even file away the cases to stop them decking. If we raise our ride height any further the engine will be carried higher and so will the centre of gravity. It won't be able to take S-bends or chicanes without wobbling and it'll be quivering everywhere."

By this time, mechanic Alistair suspected that Nico wasn't letting on everything he knew about his own design. Practice at Assen was a disaster. Two rear discs exploded into pieces (peppering the underside of the ducktail). They'd been ordered in cast steel but had arrived in cast iron. They'd overheated, warped, then exploded. Having barely qualified, the Assen fiasco was completed by a bad tyre choice for the race. They fitted intermediates because rain looked imminent but the track stayed dry and Glenn finished a thread-bare and dejected 22nd.

They had plenty of time for a rethink. As a Kiwi, Glenn was riding under a New Zealand licence which this season meant that he couldn't race at British national meetings only at full internationals. Living in England and watching the rain come down while the F-One races were being cancelled or abandoned meant that by August he'd had but three proper outings.

Though he couldn't race, he did practice the bike in an attempt to sort its handling/wheel hop/suspension problems. The results of their testing was that they abandoned the aluminium swing arm. For some time they'd suspected that the rear of the single arm was too heavy. The hub and housing carrying the dished wheel, inbo disc and cush drive is in steel (t works Hondas use titanium). It v strong enough but it was maybe lOlbs too heavy at the back and weight was loading up the suspension. At Assen it proved slower than last year's stock-fra bike. After trying a dozen differei spring and damping rates, they refitted the box-section ali doubl arm. With the double swing arm, hop was gone and the rear disc . no longer overheating.

After Assen, Alistair set about reducing the seat height too. He revised the rear sub-frame, stealing millimetres wherever possible. All in, he found two inch. With the back end lower, they could even revise the front, extending the fork tops to accomodate new ban and provide a much happier riding position.

The steering head is adjustable and different shims give a range of 22 to 26-degrees. The main aluminium frame beams or spars a hollow but filled with a composite honeycomb. Access is excellent. They can swop their F1 motor for the full house GSX-R1100 lump in under an hour. All up weight is 335lbs ready to race.

With everything sorted and much improved, Glenn will be racing the bike with the 1100 mill (yet another motor nicknamed Tyson') at the end of season internationals at Mallory, Scarborough and Brands. You can also catch it at the final round of the F-One WC at Donington on September 27th.

Meanwhile, if you fancy a Bakker single sided, swing arm chassis for the road contact David Brown Motorcycles in Ashford (0233 27883). Conversion kits are currently available for Suzuki, Honda and Kawasaki 750/1100s and they've also got rather different frame kits for 900Rs, K100s, RG500s and Yamaha/Rotax 250s.