Picture is from the ad of those days.

Appeared 1990, with its characteristic mechanism around the front wheel, which is not a conventional telescopic fork, but a swinging arm like of for a rear wheel. Steering axle is build in the front wheel hub (so-called "hub steer") and the handle bars are connected through a few link joints.
Engine is the liquid cooled type of Ducati.
Its name "Tesi" is a italian word, means thesis, or proposition. It's because the BIMOTA chief designer MARCONI made its basic idea as a theme of his graduation thesis of Bologna Univ.

Picture is from the ad of those days.

It was a marvelously impressive chassis.
Test riding course was in a town, it didn't match to the radical character of that bike. But it made huge impact from the first turn of a small corner.
Front tire works so hard. It makes much thrust force.
That situation can be figured as the big slip angle of front wheel after a sudden full braking and banking with a telescopic fork bike. You can push front tire horribly.
You may say, gee, that's crazy on rental bike in town !
Sure it is.
But I didn't feel any fear.
This fat radial front tire is escaping against a too much thrust force. But there're no fear. Just a feeling like, ah, front tire is slipping now, that's all.
This kind of amazing feel is same at a upright braking too. Stopping force is conveyed horizontally from front axle towards the body. It makes no rotating force.
Situation of braking with conventional telescopic fork can be said like twist of steering head with long rod named fork, complying the principle of lever. We all bikers are familiar with this kind of "frame head twisting" feeling, maybe unconscious though.
Tesi differs. Most of the force from front wheel just conveys straight, it does not twist the body at all.
That brings a innovative result.
Which is, liberation from the nightmare of a front wheel lock up tumble.
A slip of the front tire does not make the bike tumbling down, just slips transversely. That's all.

Progresses of motorbikes raise its force limit, and that brings high speed comfort for the riders. But there are two antinomies.
One : Force limit is much higher than the range of usual situation. It's difficult to estimate for normal rider.
Two : When the tire breaks down, the speed is very high, already exceeds normal rider's ability.
When you feel "OOPS!", that's the end, maybe.
New bikes wouldn't break in good condition, ex, fine weather, plain road, etc. You can ride them very easily. But there're many elements that may make you tumble down in public road, ex, rain, gap or sand on road, etc. High speed comfort does not contribute to the safety in that kind of bad situation. High performance may not makes you safe. That's an ambivalence of technical progress of motorbike.
Tesi had a clear answer for it.
Transverse joint of front wheel makes high performance front tire familiar to a normal riders' safety.
That's the theme which Tesi showed.
Of course, hub steer is not the only answer. Lowered steering head can contribute to the familiarity for a normal rider. And the optimization of the other elements is the must (ex, good chassis, hopeful engine, good rear suspension setting to make its traction fine, etc.).

Actually, however, Tesi was not good for a public road. It had a inferior around a hub steer mechanism. It might be no problem for racer that can change parts by one race, but it would be difficult to maintain as a public road bike. Sure, that was the BIMOTA race like quality certainly.
So, is it good for racer then ? No. It's already too old. Tesi's cornering manner is based on a thrust force of chassis balance rather than traction control of engine or braking. Fast racer of these days has much higher efficiency and potential, which is optimized for much higher tire force, stronger chassis, higher sheet, etc. Combination of fat twin tube frame and upside down forks will maintain its advantage still for a while.
And we riders also have problem.
"How was Tesi ?" I've asked to a few riders who tested it at the same time. Almost of them said that it's not good. One says that front tire grip felt poor, and the other said the joint from handle bar to front wheel had too much clearance. They were right. They felt its characteristics of mechanism. Steering system does not connected directly to front wheel, so it should be controlled through the body rather than handlebar. It can make some strange feeling for riders who are familiar with conventional fork system.
Motorbike hub steering still leaves some homework for both of the makers and the riders.

It's still immature though, we have expectation yet.
As a matter of safety, it can be applied conjunction with some resent fashioned features, like ABS or air-bag. Over a optimization of gravity center or chassis alignment, it can contribute to establish the new generation motorbike.
But Japanese big makers show no movement. It's very disappointing.
HONDA has much properties through the developments of ELF racers. (Properties ? It may debt though.)


elf-5 ( from Japanese magazine "RIDERS CLUB" No. 128 1989-2 )


GTS 1000 ( Picture is from catalog of those days )

YAMAHA made its example only once. It was just a luxury cruiser, but not any more. It can't be appreciated as a meaning of the study mentioned above.
I'd like to hope more progress of hub steer system. That will make a real independence of motorcycle from its technical ancestor, bicycle.


There ware some prototypes of hub steer system.


RADD MC2, James Parker has made it, who also designed GTS1000 later.
Its base model is FZ750. It's so cool!
(from Japanese magazine "RIDERS CLUB" 1987.9 No. 111)

Tony Foale made a bit primitive example.
Project QL, uses BMW OHV flat as power source.
(RIDERS CLUB 1986.4 No. 94)


Malcolm Newll made Phaser in mid-80's.
(RIDERS CLUB 1983.3 No. 57 )

Sure, it's more than 20 years ago, those was the days...

Please let me know more recent example of hub steer bike.

Ombra.
Dec. 2005

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