Aprilia twins are growing up!
By TMX Archives on 16th Jul 08
A LONE V-twin voice in a crowded off-road market populated solely by traditional singles, Aprilia's RXV 4.5 450cc enduro bike has stood out like a sore thumb in the woods market since its launch more than two-years ago, and despite a genuinely successful run at the world enduro championships with enduro legend Stefan Merriman at the helm, the bike has not really taken the enduro market by storm like it has in the supermoto sector and remains more of a specialist' machine, ridden by those looking for something different rather than judging it purely on its merits as an enduro machine.
For 2008 the changes have been rung by Aprilia, however, and following developments and suggestions made by the factory race team the new version of RXV 4.5 arrives significantly different to the previous incarnations tested by T+MX News. We recently headed out into the wilds of north Wales to spend a day putting the RXV 4.5 through it's paces and discovered a machine that is significantly improved over previous years and big step closer in performance to the enduro market's big hitters, and certainly a bike which should be given a more serious consideration by off-road riders.
Almost two years ago, T+MX tested the pre-production version of the RXV 4.5 and found it to be a super-smooth ride but sadly lacking a bit of punch in the motor department. The 2008 version is a different animal altogether and a much more powerful machine all round.
Still running the same fuel-injected 77 degree liquid-cooled v-twin motor, the Aprilia engineers have clearly done some serious work internally to produce a much more free-revving and generally more powerful motor, while the big change for ‘08 has been the adoption of dual-map electronic management system which is rider operated via a switch on the ‘bars. The unit, drafted in directly from the WEC machines. allows riders to flick between a ‘full-power' setting and a ‘soft' setting for when grip is less forthcoming.
Drafted across from the WEC teams development also is addition of a traditional side-mounted Arrow silencer to the kit that comes with each machine which can be fitted instead of the unique OEM under-seat silencer to further boost power output and smoothen off the delivery.
Elsewhere on the bike new settings to the Marzocchi suspension units have been brought in, a new slimmer fuel tank has also been produced to improve ergonomics and rider movement, tied-in with a new bend of braceless handlebar, while the most significant development is the shedding of an impressive 4kg in weight so that the bike now weights in at 113kg.
With all these developments aimed at making the RXV 4.5 a more competitive, nimble and useable machine I was keen to see how they translated out on the going, and I was impressed with the leap forward made by the Italian team.
The engine is a big step-forward in terms of its overall performance and certainly puts out more ponies which is instantly noticeable and very welcome.
Previously the motor had just felt strangled in it's delivery and quickly ran out of steam when you wound it up, but the new model has much more power on tap all through the rev-range. Pick-up from the bottom-end is actually pretty sharp and sudden for an enduro machine, perhaps a little too so, but from there on out the bike builds power very smoothly and softly indeed, and when I got the thing really wound up out on forest fire-roads the top-end was massively improved over previous years. It really is a great motor for fire-roads.
The high-revving nature of the V-twin means that it is very different motor to ride than its competition, and it does indeed require a smoother input from your right wrist in order to minimise wheelspin and get the best out of the bike, but once you figure this out the bike is very rewarding. Smooth throttle action and maintaining momentum rather than lots of throttle and hard braking is the name of the game.
The soft-setting on the mapping system is certainly the way forward too on anything other than dry, fast conditions or a motocross track too as it backs off the bottom-end pick-up just a bit, allows the bike to rely more in its impressive torque, and makes for a generally smoother, easier to manage ride.
The box shifts spot-on under load, although it was bit stubborn going back down through the box if the throttle was shut, and really my only real grumble concerning the engine is the amount of run-on it still has when you shut-off the throttle. The high-revving nature of the v-twin motor means that it idles at a considerably higher rate than a single and as a result the bike does not drop its revs a quickly or as far as others making the bike always feel a little like it is pulling away from you. In the slower stuff it can be a bit of hindrance and although you do get used to it, the bike would be better off if it was cured a little.
Handling is also a big improvement on previous years with the suspension action in particular a lot more responsive and stable, the rear in particular is a lot more supple and makes for much improved traction, especially at speed. The front-end too feels considerably more planted and sure in all situations, and as result cornering is improved too, as is general confidence on the bike, but the bike does still feel slightly top heavy and not quite as nimble as its competition as a result. I would lay this solely on the very tall seat height and the high-riding rear-end.
At 5'11” i'm not exactly small, but even still the RXV 4.5 is a tall bike and I struggled to get feet on the floor. As a result the confidence is not always there, especially in situations where a steadying foot is needed and for smaller riders this could be an issue. Shave a centimetre or two off the height, the rear in particular and you would have a totally different and better handling bike I feel.
It is extremely comfortable to spend a long day in the saddle with, however, and generally I had a real blast riding the bike.
Clearly Aprilia has been working hard to develop the bike and the developments made to the 2008 RXV 4.5 have certainly made a significant improvement to the machine all round. It will not be to everyone's taste but it is definitely a bike that should be considered by enduro or hare and hounds guys, even trail-riders, and so of you will absolutely love it.
RXV 4.5 TECHNICAL SPECIFICATIONS
ENGINE
Type: Liquid-cooled 77° V-twin four-stroke. Single overhead cam with rocker operated exhaust valves, chain timing drive, four valve heads, titanium valves.
Displacement: 449cc
Bore x stroke: 76 x 49.5mm
Compression ratio: 12.5:1
Fuel system: Integrated engine management system controlling ignition and fuel injection
Throttle body: 38mm
Starter: Electric start
Gearbox: Five-speed
Clutch: Multi-plate in oil bath, cable operated
Lubrication: Dry sump with external oil tank. Separate gearbox lubrication
Primary drive: 22/ 56
Final drive: 15/ 48
CHASSIS
Frame: Steel perimeter frame with alloy vertical
members
Swingarm: Box section aluminium swingarm with cast body.
SUSPENSION
Front: 45mm USD, double adjustment.
Rear: Hydraulic monoshock with compression and rebound adjustment.
BRAKES
Front: 270mm stainless steel disc with floating caliper.
Rear: 240mm stainless steel disc with floating caliper.
WHEELS
Front: 1.60 x 21”
Rear: 2.15 x 18”
DIMENSIONS
Overall length: 2,222mm
Overall width: 800mm
Ground clearance: 396mm
Seat height: 996mm
Wheelbase: 1,495mm
Fuel capacity: 7.8 litres