Tag Archives: Suspension

Ducati Multistrada Ride Review

To me, this is the bike that invented the segment of the market I was interested in. This was the bike that promised that one bike could comfortably travel all roads, be as sporting as you could want on public roads capable of touring, and handle the odd unpaved (dirt) road as well. Put simply, it had built a big reputation, spawned a subclass of bikes and had a lot to live up to!

Ducati Multistrada

Photo courtesy of Werner Bayer.

What surprised me the most about this bike, was that after I rode it, I believed the hype! Unfortunately, the local Ducati dealer has to have someone accompany you on the ride (in other words: they lead the way). The previous test-rides were more in the vain of: throw you the keys and point you in the direction of fun roads. This turned out to be a requirement of their insurance policy, but did rather control the test environment as a result. Despite their location, they had an admirable “test-loop” which encompassed some twisty roads, some inner-city and a brief burst of highway.

My first surprise on this bike, was how low the seat height felt. I could comfortably flat-foot both feet at stand-still. The accompanying sales-guy was adamant that the adjustable seat was in the highest position, so I do wonder if taller riders would find the position a little cramped, but at 5”10, with 33” in-seam, it seemed both comfortable, and natural.

I have mentioned on numerous occasions, that I’m not a mechanic. I am also not a bike journalist! I suspect they become quite desensitised to the constant stream of new motorcycles they get to ride. It allows them to be not so “caught up in the moment” when riding new bikes as to notice subtleties of the bikes they test. Me, I was too busy idiotically grinning as to how cool the Ducati sounded as I blatted it through the city streets. The base model I rode did not feature a quick-shifter. Much like the Aprilia this allowed a liberal dosage of blipping the throttle on down shifts to complement the wonderful noise the bike made on the overrun. The V-Twin (or L-Twin as Ducati call it) also gave a slight pulse through the frame. It was not buzzy, like the BMW, just a gentle reminder of the engine layout (in case you were deaf)

Also not featured on this particular model, was the adaptive electronic suspension. The front end felt a little soft. Again, that overly long travel was noticeable to me, but really, it gave good feedback through the bars. I guess to describe it, it just felt “a long way away”. Judging by the speeds I was doing on an unfamiliar bike, it must have been pretty good… With familiarity, it would be a real weapon and give the average sports bike rider a real hurry-up on the roads.

Next part of the test-ride involved a brief highway stint – during which I tested the cruise control and adjustable windscreen. I found the cruise control intuitive and easy to use although I’ve heard the button layout is harder to control with thick winter gloves. The screen adjustability too was easy to manipulate on the move, but I have really yet to appreciate the difference this makes on any bike. One thing I have always admired was how good the wind protection is on the VFR. None of the potential candidates for the role of “my next bike” could really compare favourably against it. Anyway, it was easy to adjust allowing for long highway trips to allow plenty of contemplation and comparison between screen heights. If I had to guess, I would suggest that the bar-width on the Multistrada was slightly narrower than on the S1000XR. It seemed to be a more competent lane-splitter and commuter bike, if such things are important to you.

Overall, this is a seriously impressive bike. It lives up to the hype surrounding it. In a game of top-trumps, it loses out to a similarly specced version of the BMW S1000XR in almost every category. But, I agree with a lot of the reviews I have seen on it – somehow it ends up being a more desirable bike than the BMW. The new styling with the colour matched beak doesn’t look as good as the older black-beaked bikes to me, but I would never argue with someone if they felt otherwise. That’s always going to be a subjective opinion. In my eyes, the new “Enduro” Multistrada, with its 19 inch front wheel and wire spokes falls into the “ruggedly handsome” territory, but somehow the styling of the normal Multistrada just left me feeling disappointed. If you disagree with me on that, then this might seriously be your dream bike. It really is as good as that!

Motorcycle Suspension Part 3 – Compression and Rebound

Previously, we looked at the role that springs play in motorcycle suspension.  Suspension is comprised of a spring and a shock absorber.   The shock absorber’s role is to limit the rate at which the spring compresses and expands.
Ideally, a motorcycle wheel should not lose traction with the road surface.  On a perfectly smooth surface, this is not hard to achieve!  For the wheel to grip properly, it must be pressed to the surface with some degree of force.  Luckily for us, the weight of the motorcycle provides us with this downward pressure.
Suppose for a moment we have a motorcycle without any form of suspension:  Not only is there a lack of springs and shock absorbers, but the tyres themselves provide no flex.   Once we are moving forward, the motorcycle has inertia in this forward direction.

Bike moving forward

When this motorcycle hits a bump, there is no way of “absorbing” the bump.  As a result, some of the horizontal forward inertia changes to vertical inertia.

Bike moving over bump

Once the bump “ends”, the ground “falls away”.  The motorcycle being subject to gravity loses its vertical inertia and returns to the ground.  The vertical velocity is not overcome instantaneously. Rather, it is subject to the laws of gravity.  Depending on the speed of the motorcycle and the size of the bump, the wheel(s) will remain in the air for some period of time.
With the benefit of suspension, not all of the motorcycle needs to be subjected to the vertical inertia caused by the bump.  If the bump is small, the springs may absorb the bump.  As we saw previously, the spring will “want” to return to its state of rest.  The spring will expand in whatever direction cannot suppress the force that the compressed spring now has.  If the bump has ended, the spring will likely expand downward, otherwise the spring will expand upward.  The spring extending upwards is effectively transferring the vertical inertia to the rest of the motorcycle.
As noted previously, the spring continues to oscillate shorter and longer of its “at-rest” state, until all its kinetic energy is expended.  The suspension unit helps regulate the extending and compressing of the spring, by forcing oil to pass from one area of the suspension unit to another.  The oil can only pass through small valve holes.  Because a liquid cannot be compressed, the oil passes through the valves at a set rate.
Adjustable suspension allows the size of these holes to be altered, allowing a faster or slower rate of oil transfer.  Different systems handle the transference of oil in different directions.  That is, when the shock absorber is being compressed, oil is transferred by one set of valving, and when the suspension expands (or rebounds) a different set of valving operates.  The first set of adjustable valving gives you the “compression” setting, and the return valves gives you the “rebound” setting.
In recent years, suspension has been further refined by having two lots of compression valves.  These are known as “high speed” and “low speed” compression valves.  This “speed” refers to the speed that the suspension compresses.  Fast compression is needed to handle surface irregularities (i.e. bumps) whereas “handling issues” arise from slow compression motion.  Unfortunately, I have not had the chance to study suspension with this feature, so how the shock absorption works and which valving is used is as much a mystery to me as the next person.  (Unless they happen to work for Ohlins).
As you may well be aware, oil viscosity affects its flow rates.  A more viscous oil will therefore be slower to transfer through the valves than a “light” oil.  Oil has a tendency to become less viscous as it heats up.  Forcing oil through small valves tends to lead to the oil heating up.  (The kinetic energy of the oil movement is exchanged as heat, due to the friction caused by the fact that the oil cannot move freely.   This of course affects the compression and rebound rates of the suspension.  The bumpier the surface, the more this becomes an issue.  This is an unavoidable fact, but that does not make it desirable!

To combat this, suspension units have been designed to carry as much oil as possible.  More oil, means more oil to heat, meaning more energy required to do so.  A bigger oil reservoir also means a larger surface area in contact with the oil, drawing excess heat out of the oil.

That is about it for how the parts of suspension fit together.  How to make the most of the suspension you have, is a story for another day.

Photo attribution:

http://www.flickr.com/photos/nathanwells/1084352488/in/set-72157601369471448/ courtesy of Nathan Wells.

Motorcycle Suspension (Part 1)

Motorcycle suspension has a variety of roles to play.  While rider comfort is one of the roles, the most important role is actually keeping the tyres in contact with the ground surface.  As the ground surface is rarely perfectly smooth, this means wheels need to travel “up and down” relative to the rest of the motorcycle to stay in contact with the surface.  This comes back to the laws of inertia.  The bike with its mass and velocity will not “track” to the bumps and so the suspension alters the distance between the road and the bike’s sprung mass.

After my own spectacularly underwhelming career as a motorcycle racer, my interest in motor-sport (and in particular motorcycle road-racing) has remained.  Club level racing is a great way of witnessing the enormous difference in talent from the A-graders down to the “also rans”.    I have attended club-days as a spectator and they provide an insight that watching top-level competition does not provide. 

One such revelation was the difference between suspension that has been set up well, and suspension that has not.  The event that stands out in my mind was at Victoria’s Broadford circuit.  At the end of the front straight was a particularly bumpy entry into turn one.  The riders would be braking heavily for Turn one, across a series of “ripples” that had formed in the track.  Watching the bikes at either end of the field (i.e. the fastest riders and the slowest riders) revealed vastly different “behaviour” from the bikes:  The fastest bikes were smooth and composed across the bumps.  The slowest, jumped and skipped across the bumps.  If you watched the two and were asked which ones looked faster, you would have probably guessed the wrong way around.  Put simply, the slowest riders were trying far harder to control their bikes, whilst the fastest riders didn’t look to be expending hardly any effort at all! 

There is obviously more to being good at motorcycle racing than having decent suspension, but the difference was striking.  Bad suspension fails to keep in contact with the road surface.  A wheel in the air, has no grip.   Good suspension also relays the “feel” of the road surface through to the rider.  The feedback given allows a rider the ability to judge the grip levels available.

Motorcycle suspension has an extra limitation applied to it, that cars do not have:  Motorcycles lean.  If you hit a 25mm high bump (approximately one inch) when travelling in a straight line, the suspension needs to compress 25mm to avoid the bump being transferred through to the rest of the motorcycle.  Once the motorcycle leans over, compressing the suspension changes both the vertical distance between bike and ground, as well as the horizontal distance. 

Amy O'Mara from 2008 ASC Round at Qld Raceway

By recalling year nine trigonometry, we see that if you hit a 25mm bump at a 45 degree lean angle, the suspension now has to travel 29.4 mm.  Increase the lean angle to 50 degrees (from vertical), and the distance the suspension needs to travel increases to 33.6 mm.  (And you used to complain that you’d never use the stuff you learnt in maths in real life!)

On a lot of roads, the notion of a bump only being 25mm high is laughable.  In the real world, motorcycle suspension does not prevent some of the bump being transferred to the rest of the motorcycle.   Some transference is necessary or else the rider cannot feel what the bike is doing.  Bump (or “shock”) absorption occurs not only through the motorcycle suspension, but through the flexing of the tyres and indeed the motorcycle chassis.  If I recall correctly, in the early 90s, a lot of race bike manufacturers would make their frames with as little “flex” as possible in an attempt to improve the handling of their machines.  They reasoned that such an approach worked for car racing.  However, they found that some chassis flex (in certain directions) actually improved the handling of their bikes. 

In terms of components used for motorcycle suspension there are some fairly common approaches and a few that are less common.  Most modern sports-bikes consist of two front telescopic forks with internal springs controlling the front wheel and a single rear shock absorber with an external spring, controlling the rear wheel.  This is a fairly-standard evolutionary design, but by no means the only one.  Like most aspects of motorcycle design, this system is a compromise and alternative systems offer alternative advantages and disadvantages.  But that is a story for another time.