Rear A-arm

Guys i need your help regarding the Double wishbone suspension mounting in the rear. As we all know, in double wishbone the best suspension characteristics are obtained when the suspension is mounted on the lower A-arm. But, in our BAJA ATVs we are unable to do so in the rear due to the drive transmission shafts. Inspite of this many teams use the double wishbone type suspension with the suspension mounted on the upper A-arm. My query is does it really give a satisfactory result and what are it's disadvantages or advantages over lower A-arm wishbone mounting..?

It is NOT impossible to place the shocks in lower arm even though the drive shaft passing by

Hah, that last pic is our car from two years ago... that setup worked like crap but I blame the designer, lol

It adjusts toe. And depending on how you design your suspension, you can get toe change throughout suspension travel.

ahmed wrote: so why i see teams using just 2 A-arms without this link ( like this in the picture below) , how can they adjust the toe angle. you know that much space is needed in the rear to mount the half axles.

An H-arm has a bushing for its outboard point. It thus constrains two additional degrees of freedom then a pure A-arm, which has a ball joint instead.

Think about the motion an a-arm would restrict vs an H-arm and it should make sense to you. Think about how the tire can move with the different constraints.

hello guys,

I'm designing the geometry of the REAR suspension, and i can't see the difference between using a normal A-arm and an A-arm with twin outer ball joints

if somebody can help, please do. Thank you ^^

i need to know the name of this rear suspension setup to search for its advantages,disadvantages, joints, installation ...

do you know a suspension software to model this setup and simulate it , i need to check how camber,caster,toe, kingpin, ... change with wheel travel?

but this suspension mechanism is only kinematic if your chassis attachment points are perfectly parallel and your upright axis are also perfectly aligned.
Any angular error particularly with pivot joints all-round will cause the suspension to lock-up under bump/rebound travel as it is over constrained.

don't you think so ?

Some teams and some production vehicles use hard rubber or something similar for the bushing material so that there is alittle give to compensate for things not being perfect.

A setup with 2 H arms is better at reacting moments from the wheel loads and makes it easier to mount the shock to the upper link. The picture you attached with the single upper link is essentially the same anyway since the pivots are bushings, and those bushings will probably wear out quickly.

If you're looking for software to simulate a geometry you've already got drawn out, Lotus is useful. But to be honest, it's just to validate a design and show it's characteristics throughout the range of motion...you have to have the majority of the things you listed above (king pin, caster, etc changing with wheel rate) to get a good simulation output.

ahmed wrote: Does anybody know the advantages of the H-arm & single upper link suspension rather than the few number of links and the easy packaging ? I'm puzzled to use this setup or use a three link suspension like this in Polaris rzr