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I'm interested in what's been done with the front suspension. It actually has Triumph 2" drop spindles. Sort of the best of all worlds. It looks like they have a spacer that is much longer then normal welded to the bottom of the upright to replace the trunion. I had something like that in the drawings for my car, but it doesn't work with the Miata front spindle because the boss is at a large angle. If you add a spacer it really changes the KPI and maybe would foul with the brake disk. It might be a good idea for Pinto/Mustang II spindles though. You can get them dropped, but the stock ones are cheaper and also come in a 7 degree KPI version.

Also it looks like there are adjustment holes for the front and back of the upper wishbone and either the holes are at different heights or it's actually set up for pro-dive? It's hard to tell. It would be interesting to ask the driver what he thinks about driving the car using the different adjustments he has available. It's one thing to hear someone likes how they setup their car and another thing to hear it from someone that can actually change how they set up their car...

The oval track places sell these in 1" increments in steel and aluminum and also a couple of diameters up to around 36" long. I think I have also seen them in titanium, but those catalogs are not for riffraff.

If you can get them long enough I would beef up the vertical near the dash.

From the Vsuspension thread which I didn't want to pollute further ...

Discussing SkinnG's understeer/no turn in dramas - although I tend to believe it's a rear roll center too low issue, there is another possibility and that's a problem with short links causing roll steer, relevant to this thread.

The possibility is that in chassis roll the outside link's chord lengths are shortened causing the rear axle to steer inwards creating understeer - although the fitment of an anti roll bar will help (because the car doesn't roll so the links don't shorten pulling the axle forward as much), this is another problem that can be eliminated with longer links.

When driving the car this is an easy one to pick up on, turn in real hard intentionally kicking the rear out, rear starts to move out but almost immediately returns to understeer.

And since I practice what I preach, here's my 29.5" (actually 750mm because I work in mm's!) - sorry about my stupid phone that hates night time ...

I firmly believe in longer arms.

I am not very keen on arms outside the chassis on a street car - I fear they might be a pinch point for myself or passengers.

At rest, the trailing arms (while parallel) are angling upwards towards the front of the car (a result of raising the rear to try and counter poor turn-in and understeer). In roll, the outside trailing arms would push the axle back, whilst the inside trailing arms would pull the axle forward. This should tend toward roll oversteer. Cool, eh?

As an aside, on the street, you can seriously feel the chassis torquing with throttle. If that's the right term. Chassis movement is very related to throttle movement. Acceleration makes you want to steer right to keep it straight, and deceleration makes you want to steer left to keep it straight. (or vice-versa, I forget). Longer arms would reduce this effect.

It's always cool to read someone making a change and clearly understanding why they are making that change

Cheapracer PM sent. If you are like me you hardly ever notice the message counter.

This would reduce understeer in steady state cornering. The picture for turn in is more complicated. I consider turn in to be the transition before you get to an even pitch and steady state cornering. So before the car has rolled which would be the beginning of the transition it would have no effect. You would likely be braking so the car may be pitched forward while your starting to roll and then this will fight you a bit. On the plus it will help you get power down by making the car looser as it pitches back under acceleration.

When you lay with the roll center height that changes your geometric anti-roll and that effect is instantaneous with lateral acceleration. So it occurs before the car rolls and would be more significant during the transition.

I agree with you that it seems the normal arms are too short. Bump steer in the rear while in a straight line is disconcerting. When the links are not parallel this also introduces anti-squat and anti-dive forces...

Presuming you mean "not parallel" from side to side of car, it also induces pro-roll as the outside goes to pro-squat and the inside anti-squat in roll.

This is also why too much anti squat is not good especially with short links and why I figure there's at least one advantage to leading links over trailing - Marcos cars have a reasonable good handling reputation.

Must try it one day.

No, I meant in the longitudinal direction. I didn't try to figure out how much it would be. If the trailing arms are closer together at the front then the rear, in the height of their mounting points, that would cause anti/dive and anti/squat. Since moving the axle up and down will cause it to rotate a bit. So brake torque and engine torque would work for or against that.

If you look at the left ( port ) side of the car, the axle will try to rotate counter clockwise as it rises. This is the same direction as the brake torque which means there will be a force to raise the axle under braking. That's anti-lift, which will help keep the chassis more level in braking. If you apply engine torqe the axle will try to rotate counter clockwise, that will resist rising and that will be anti-squat.

You've described that the trailing links should have a converging angle to prevent bind in roll, so that means the above change as the car rolls maybe? I guess at some point it may not have these anti effects when rolled, but I don't have this four link stuff figured out yet...

I assume that your tubes are 25 mm tubes? What thickness?

And what is your SWAG (silly wild-donkey'd guess) as to the minimum needed between the back plate of the brakes (the "inside edge) and the side of the car frame to pull off this configuration?

I still think I could pull this off but only if I bend those trailing arms a bit...