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PostPosted: January 20, 2020, 9:25 pm 
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Joined: May 7, 2009, 6:24 pm
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Not really a car question, but about A arm suspension for a high performance sidecar rig. Typically, HP sidecar front suspension uses A arms, either longitudinally, or transversely (I'm interested transverse mounting here), using a 0 degree KPI and zero scrub radius with a modest caster angle (around 10 degrees). The problem is finding a wheel with a large enough offset to allow a zero scrub radius upright. The object here being that tire diameter has no bearing on scrub radius. Making tire selection and tire wear a problem. So...to my question. Would a "sporty" A arm suspension arrangement work if the axles of each wheel were not on the same line. Picture a Miata cut in half longitudinally. Keep the driver's side. Now put the right side front suspension on a line midway between the front and rear wheels. Picture a motorcycle with a sidecar (top view). Caster and camber designed in to keep roll to a minimum, and some kind of geometry so both wheels steer. The rear wheel would be carried by a traditional swing arm arrangement. Is there any way this arrangement could be made to work?


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PostPosted: January 21, 2020, 10:53 am 
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Joined: January 10, 2008, 4:47 pm
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Location: Massachusetts
In theory, you're just going to have to understand things like jacking and anti forces ( anti-dive, anti squat, anti roll ).

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PostPosted: January 21, 2020, 7:08 pm 
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I don't see the benefit of improving one wheel suspension out of three. The only suspension I'd have on a side car is trailing arm, sliding pillar, or for better handling, a tilting system with bike tires so you can lean to either side with the bike and the side car moves with the lean, shifting cg inside the turn. Having the side wheel in the middle of the wheelbase is fine but can make for an exciting ride over speed bumps.

For the wheel you could have one made to your spec if you don't mind steel. Stockton wheel comes to mind.

Steering is doable but would take a considerable amount of planning for symmetry in left and right turns.

I don't know about "sporty". Actual racing sidecars have no suspension on the side wheel from what I can tell.

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