Centre hub steering: why not more popular.

[Ribenapigeon]

Aside from the cost. Why isn't center hub steering used more. After all its not a complexity issue really as its no more complex than a cars front suspension. The more I look into it the more interesting CHS looks and especially for sports bikes.

[stinkwheel]

The way I always heard it is it is more expensive to produce, has more wearable componants, a higher unsprung weight and is trickier to adjust.

It is better if done well but it is difficult to do well cheaply. Add in a degree of "We've always done it like that." and you get forks and yokes.

Most bikes still use chain drive for broadly similar reasons (ie. cost to produce and fear of change).

You could say the same for telescopic forks. Well made girder forks are superior but cheap telescopics are ok enough to make it not a worthwhile exercise.
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[MarJay]

Its complicated and heavy? And Despite telescopic forks being a bad idea from an Engineering point of view, they actually work very well and people are used to them.
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[Kickstart]

Hi

Telescopic forks have had well over half a century of development and it takes a long time to catch up with that.

There have only been a few hub centre steered production bikes (Bimota Tesi, Yamaha GTS1000, a scooter or 2, and maybe one or 2 more). Problem is cost, limited steering lock, wear, etc. With a conventional hub centre system you can widen the front swinging arm, but then you land up limiting the lean angle.

If you look at a Tesi there is a VERY large wheel bearing required, plus the steering within that. There are 6 rose joints just on the suspension and steering arm (all of which wear), plus any in the linkage from the bars to the steering arm. A requirement for a high quality shock (cheaper than forks, though) but then trying to find somewhere to hide the shock without it getting too hot. All adds up to the cost.

The system BMW are using these days is probably better for production use. But get the design of that wrong and you have a potential issue with the suspension doing odd things when you brake suddenly. The suspension (rather than steering) works similarly to that used on Vincents (with 2 suspension arms), and if you brake suddenly the arm moves the wrong way and the suspension locks solidly.

All the best

Keith
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[lihp]

[Walloper]

Coz they look Retard-gheyed.

End of Thread.
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[Ribenapigeon]

You would think that with modern design and manufacturing technology that the above problems could be reduced. Also CHS can be monoshock so that's a big saving. I think its more likely Stinkwheels right saying manufacturers and riders are resistant to change.

[Walloper]

[Kickstart]

Hi

A single shock is a saving (although a complex shock, with forks if you want you can put compression damping in one fork and separate rebound damping in the other), but the linkage for it adds to the cost. And nobody has yet come up with a way of having a nub centre steering system without going around the tyre horizontally (after all, that is where a large part of the advantage comes from), and it is there that you lose the steering lock.

Forks are cheap to machine up. A swinging arm is a bit complex to fabricate.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[lihp]

There are loads of performance advantages though, such as minimal diving on brakes, ability to change the steering rate etc, though I think most of the benefits of the system are more suited to race applications than road applications.

I don't think that CHS would offer enough benefits for road users imo.
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[Ribenapigeon]

[lihp]

[Snorty]

If it was good, they'd use it in MotoGP, no?
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[lihp]

[Ribenapigeon]

Its a good job I don't have a workshop, god knows what abominations would emerge from it.

[stinkwheel]

[Snorty]

[stinkwheel]

[MarJay]

[G]

I didn't think weight was a big issue for GP bikes, which are pretty heavy these days.
160kg for the season just gone, quite possibly because Ducati were struggling to get theirs down to that weight.
Apparently Honda spent their first test day working out where to put the extra weight on the bike - so I doubt an extra-expensive light weight frame is really worth it for them .

[orac]

[MarJay]

[Slacker24seve...]

[stinkwheel]

[G]

Also, in the case both - restricted in various ways to keep speed down and thus improve safety to various degrees.

Of course, in some cases it backfires, like the move to 800cc which I believe saw higher corner speeds, people trying to get on the (lower) power early and the like.