Suspension and cornering forces

[350TSS]

Thanks guys - I think I now understand

"It’s also giving the suspension more chance to move with bumps: think how the forks and steering react to a bump when leaning at 66 degrees!"
I do not think the suspension works much if at all after 45 degrees - any bump is a vertical deflection of the forks/frame because the fork sliders /rear shock would not slide

[Luddite]

Originally Posted by 350TSS

I do not think the suspension works much if at all after 45 degrees - any bump is a vertical deflection of the forks/frame because the fork sliders /rear shock would not slide

Got some more aspirins handy? Perhaps unsurprisingly this situation is also covered in Tony Foale's book.

Hitting a bump at a 45° lean angle creates two equal forces; one in line with suspension movement and the other at right angles to it. These forces will each be 71% of the vertical bump force.

I don't want to clutter up your excellent thread with esoteric calculations and diagrams, so I've sent you a PM with some more extracts that you can read at your leisure. Just don't blame me if you get a headache!

[Darkness]

Originally Posted by 350TSS

Thanks guys - I think I now understand

"It’s also giving the suspension more chance to move with bumps: think how the forks and steering react to a bump when leaning at 66 degrees!"
I do not think the suspension works much if at all after 45 degrees - any bump is a vertical deflection of the forks/frame because the fork sliders /rear shock would not slide

It is easier to visualise if you think of the vertical axis through the centre of the bike and rider staying vertical as you begin to corner, but the ground tilts beneath you. At 66 degrees of tilt you need pretty huge suspension movement for a small bump if the bike is to stay on line, but that movement reduces a lot in practise if the wheel can kick sideways a little. That’s changing the lean angle though, and there’s a risk of the tyre losing grip as you come off the bump, or as the wheel feels it, someone whips the ground out from underneath it.

Lighter wheels and tyres help massively, as does reduction in unsprung weight, then weight reduction generally.

As the rider can absorb some of the bumps by lifting off the saddle and flexing legs and arms the rider’s weight is less significant, but probably still better to lay off eating all of the pies!