I was recently asked by a rider ‘what type of feeling and or setup constitutes a perfectly balanced bike?’ This got me thinking….
Bare with me please. Think of riding a motorcycle like sitting astride a log suspended by springs with a wheel at each end. The harder you accelerate and brake the faster you go and the more weight is transferred back and forward.
The harder you pull the front brake to stop the more support you need from the front springs (not to mention low speed compression damping and oil level/air gap) to prevent the transfer of too much weight to the front and ultimately the front tyre. If the front suspension dives fast and deep and/or is running at the bottom of the stroke for too much of the lap, you won’t stop as well as you could, you won’t have enough support to push against while braking, you may feel like you are going to fall over the front of the bike and the rear will lift off the ground.
Our job as a rider is to increase speed but at a certain point this excessive weight transfer will make the tyres loose grip, when with less weight transfer they would cope with that same lap time without a problem, lap after lap.
Similarly , the harder you accelerate from a corner at half-lean the more weight will transfer to the rear, the more the rear suspension stroke will be used and the lower the rear suspension will sit. Too much transfer to the rear can cause the bike to squat, run wide, then ground clearance, grip and wheelies can become a problem.
I believe we need a little weight to transfer rearward automatically as soon as we come off the brakes. No transfer to the rear and you run the risk that as soon as you crack the throttle (initial throttle) the rear tyre will spin up and let go instantly, before the weight has had a chance to transfer there. It can very quickly let go beyond the point of no return. It’s well over a decade since my last one, but the memory is lasting, including the sounds (a little free rev of the engine, followed by huge forces and silence. Then a nasty reminder how hard Asphalt feels). A little greedy with the initial crack of the throttle before the weight transfers rear is enough to do it. The risk of this is accentuated when running an extra hard rear tyre and/or a high rear preload and/or a high rear ride height settings.
These days traction control does a great job of preventing many trackday riders from having this horrible experience but I believe it also masks setup problems much like anti wheelie does on exit. For example, if a rider is lazy and lets them self sit up and slide rearward during corner exit, and/or their bike is badly setup for corner exit, anti wheelie and traction control will make their job easier, but they will never exit as fast as they would if they fixed the underlying problems.
I focus on getting my bike to stop well and be stable under very heavy braking and turn in. Then after the initial crack the throttle at full lean I want the bike to turn well enough for me to turn and aim in the right direction in the shortest possible time, enabling me to get up off the edge of the rear tyre so I can add more throttle, and as I feel the rear tyre pushing into the road and deforming (creating a bigger contact patch) I feel more secure and can add more throttle (hopefully 100%).
Basically, everything about bike setup is a compromise. Too much of anything causes a problem. Not enough of those very same things causes another problem. Making this all the more difficult is the fact that as a riders speed increases so does the level of support they need from their suspension. A bike that is close to perfect becomes too soft when the lap times drop by a few seconds. I noticed a pattern unfolded at each WSBK championship race I competed. I told my mechanics that my bike was very good so please keep it the same for the next race. They did. During the first session at the next circuit I complained it was so bloody hard it didn’t soak up anything, and it doesn’t turn! They softened up the suspension (a couple of clicks off damping and turns of preload and/or fitted a lower spring rate in one fork). Then they added one mm of rear ride height (at the shock) to steepen up the geometry to get the bike to turn. It’s was great! As I got confident with the new circuit and my lap times came down I found the front suspension was on the bottom and I was pushing the front tyre… so the team hardened it back up to support the extra load I was now putting on it. Finally, to get the last second during qualifying I’d have to lower the rear ride height back down one millimetre to allow me to pull on the front brake a little more and force the bike into and around the turn a little harder without pushing the front tyre, and it still turned OK because the extra load I put on the front made the front run lower in the stroke, putting the geometry and weight balance back into the ballpark where it worked best / I liked it, and the initial crack of the throttle through to early acceleration could be done quicker (without hesitation). Eventually we got used to this routine and understood what was happening, but at first the mechanics are rolling their eyes and I don’t blame them.
My belief is that the ‘balance of the bike’ is what a rider should focus on. The damping only needs to be in the ballpark to get you 90% of the way there. I get my suspension from Ohlins with springs fitted that they recommend for my particular bike, rider weight and speed. The damping settings that they supply have been developed by more than one high level racer on the same model motorcycle that I am using, during the race season prior, at many circuits. I don’t need better. I bolt the shock and forks into my bike, double check that the damping and preload settings are where the Ohlins guys recommend I use them, and I ride it. From there I play with small adjustments to the balance of the bike (ride heights front and rear and spring preload front and rear). Sometimes I find I need a spring change to get the preload settings back in the ballpark if they have crept too high or too low indicating the spring is to soft or too hard.
Mucking about with the clickers in my opinion is for the final adjustments, otherwise you are just masking another problem.
I am not a rider who likes working on my bike more than riding it, but I do believe it’s important to try things. I recommend trying small suspension setting changes even if you are happy with the bike. How do you know that the bike can’t be better unless you try? The key to success in this area is the following:
– Don’t start testing changes before you know where you are going (know the circuit) and are relatively up to speed (doing constant lap times).
-Write down all your bikes settings before you change anything so you can put it back if you get lost or want to test the new setup you have found against the old setup at a later date. Back to back is always a good final test.
– Only make one change at a time so you can understand exactly what that change did.
-write each change down, test it well and put it back if it’s not better (less chance of getting lost).
The great thing about testing setting changes is, you will start to understand the feelings that each change makes and eventually be able to make an educated guess what your bike needs when you are not happy it. It’s good to start with bigger adjustments in the beginning (2-4mm or clicks for example). Then, as you get closer, half the size of the steps (1-2 mm or clicks for example).
The balance I’m looking for;
Enough support from the front forks and low enough in the rear to be able to brake late and turn in hard at half lean…… but not so much front support (high front and low rear) that the bike will not turn well during entry, mid turn, and also causing the front to lose contact with the ground excessively under acceleration leading to instability during change of direction.
I want the bike high enough in the rear and low enough in the front to turn well in the mid turn so I can get the bike aimed in the right direction in the shortest possible time and up off the edge of the rear tyre in preparation to open the throttle. But I also need enough weight on the rear that when I let go the front brake and crack the throttle open some weight has already transferred to the rear tyre gaining some grip so I can start to accelerate without delay.
Please don’t forget that tyres play a huge part in this puzzle. A good tyre that delivers a higher level of grip or absorb bumps better (because of its higher profile or different construction for example) can make a problem that was really bothering a rider simply go away. I remember asking my crew Brent Stephens (now a long time Rossi mechanic) and Mike Webb (MotoGP race director) to make the rear shock harder in my factory motorcycle whenever they fit the new Dunlop Qualifying Tyre. “Really?” They asked. I remember replying “that rear tyre is so good, you guys could fit a piece of wood in there (for a shock) and it would still work great!“.
Good luck on your never ending Holy Grail chase, the perfect bike setup. Once you have found it please enjoy the moment because once another rider goes faster than you can how can your setup be perfect? LOL. Let’s face it, it’s only perfect as long as you can go faster than everyone else.
Simon Crafar trained and worked as an official Ohlins technician for Grand Prix.
(Photo credit: www. trackriders.eu)