From what I've seen over 15-20 years now, the MT SA (
solid axle) rear with ladder bars & heim joints is something like a SA trying to identify as a IRS, some of both worlds, but great at neither, like a compromise somewhere in the middle.
IRS will lean out on turns, more with greater speed. At lower speeds or on straighter roads, you'll never notice it. How much depends on speed, turn, springing used just like a car, and then some trikes with IRS use a "anti roll" bar that is like a crossways mounted torsion bar which ties the action of both rear wheels together via spring to eliminate some roll out … but they do let the manufacturer use softer springing for straight line comfort. Tight curves like Rt 33 coming into Va. from WVa. or up on the BRP, or down at that Dragon Tail place, etc, then you'll feel it and notice increased steering effort. If it's all you know, you'll not notice much difference. At least with IRS you don't get a loose rocking movement from side to side, like when Co-rider mounts up.
The MT system is a copy of what drag racers used for straight line drag racing, it's a bolt together ladder bar system, no welding of bars to axle. It works very well for racing where parts get inspected & replaced as needed. If it allows leaning, it has slack. I've never followed a MT that didn't lean out in twisties. Every heim joint has a ball with a hole through it held in a "race" that allows the ball to rotate or swivel within limits depending on size of the bolt going through it. To do so requires that it have clearance, so it has slack even new. As it wears, as miles of pounding add up, weather, dirt, grit, lack of lube, etc, it only gets looser. There are
8 in the system. A little slack in each heim is magnified by bar lengths, it adds up to a lean when all the slack is taken up by forces in turns.
Mine is a solid axle with a rigid welded swing arm, there is no leaning in relation to roadway unless I have a low tire. It goes up & down only. If it does anything else, there is a crack or break. Some say it rides harsher like that, but I've ridden both at speed on highways and twisties, and while I feel some more road feed back, I also like the secure feeling. At the swing arm pivot, it uses OEM type tapered roller bearings. The swing arm and axle move about those points as if "one".
I rode a buddy's 1800 Champion IRS with adjustable sway bar from here (
near Lexington) to Luray, Va. Went up Rt 11 & 340, was an enjoyable ride, very nice, but I smelled smoke. Looked underneath at a stop, it was just the sway bar end rubbing the tire's edge, it stopped smoking / smelling when it had clearance worn in. Minor issue, but it was then I noticed just how complex it all looked, compared to what I was used to seeing under mine …
like a Jaguar compared to a Model T. 
IRS shines on a vehicle with 4 or more points of contact with the roadway, but with 3 wheelers, you always sit on a tri pod. You are gonna feel the dips and the potholes, , and you'll hardly ever ride through a bad patch of pavement unscathed. People with IRS or SA trikes or MTs always seem to enjoy the rides we've been on, and that's the end goal.
Yeah, I write too much.
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Originally Posted by 3W-lonerider
