Rear is torsion beam, nothing to adjust.
Front alignment, I don't think it is safe to do toe-out for street car. The front will be overly twitchy. Generally a little bit of toe-in is good for highway.

Floaty on high speed is common on the urban city car like Vios/City/Myvi/Axia, new Ativa. They all floaty at over 100km/h, they are design for city best 40-60km/h, efficient, light, easy to maneuver with tight turning radius, in traffic jam. Some 80km/h on inter satellite city is fine. Highway should be a couple of time a year, balik kampung use only.

There are very little things can be done without resort to full project car situation. Biggest problem is aerodynamic lift. Any road car has lift, spoiler merely reduce the lift, overall net force still upward (no or negative downforce), but bigger car has more weight and wider body thus less noticeable. Most effective is reducing the ride high, couple cm makes noticeable difference, so lower spring/coil-over helps (no need to be stiffer).

Other suspension mods are useless in the high speed straight line at regular highway. Unless you talking about Nurburgring, talking curb stone at 200km/h, then yes, but even that the mod is longer stroke and softer suspension setup, not firmer. Torsion beam, the beam structure itself is acting as ARB (that's why it is not an independent suspension). Adding rear ARB actually make the rear to slide at lower speed, remember feeling good (less body roll) is not equal to more grip. ARB is a tuning tool to balance front/rear grip (stiffer rear more over steer, stiffer front more understeer). Upgrade to stiffer rear need to come with stiffer front to maintain the balance.

Even if one determined to remove factory spoiler, replace it with a proper calculated wing (not ah beng ricer decoration). Let's assume 300kg of downforce, that's 4 adults weight. It is enough to change the pitch angle of the car, front nose will point 2-5 degrees up. (Remember modern car with HID/LED needs headlight adjustment also need compensate passengers load that influence to pitch angle) Then, in turn front become floaty, have to add front splitter to balance the car back. Bla bla bla... become fix A, break B, then C, a lot of effort + money, in the end overall drag increase, bad fuel economy as well.

In conclusion, my advice is always want/need a fast car, then buy a fast car. Frequent highway use at least C-segment. No budget either get used or delay gratification (live with what one have, then work harder for a couple more years). B-segment is best for city use.

Yes, thanks for topping up the details.
1) see I never list Proton hehehe
2) true also, otherwise it will hit the fender to an extreme
3) yes, soft enough not to send the car flying over the curb, but enough rebounce to maximize the tire contact

Me too, started with an 13 years old corolla from father which he bought used.
In exchange I paid for my sister college living allowance until she graduated. That's over 30% of my fresh grad gross pay.

Seriously I don't know, at least I never seen one. But I never search hard, I'm not their target customer anyways. I'm sure you know eccentric bolt can make McPherson struct a little bit of camber adjustment. Another example is Ferrari 488, the front double wishbone is not designed to be adjustable (I think), but since the pivot of arms are just bolted to the chassis, people simply add washer to change the camber.

Torsion Beam the wheel bearing is on structure itself, not sure (someone mentioned it can be bent, in other topic). But from my experience of the limited cars I own/owned, the limitation is space if we were to add structure. Also even multilink, double wishbone, not all are created equally.

1) This is Elantra Sport multilink. The non sport version has torsion beam and full size spare tires, while the Sport have space saver because the multilink taken more space.
This is typical multilink on the econobox chassis adapted to sport sedan, 4 arms (1 of them is trailing arm). Civic has same design. Again, not all multilinks are created equal, this of course has less degree of freedom vs the 5 fully adjustable links on a pure sport car

As you can see only arm 1 and arm 2 are adjustable. They both affect toe and camber. So this depends of the experiences of the tire shop to balance the 2 arms.
Arm 4 is blocked in this view, and non adjustable. But you may in theory replace it with an aftermarket adjustable rod. Same for double wishbone, the A shape arm can be replaced with 2 adjustable rod (in modern BMW, the A of lower arm has become 2 separated arms). I don't know torsion beam has the luxury, or is it even possible?


2) This is Volvo S60. It is common design for all the SPA platform, SUVs have same design.
As you can see, only arm 1 is adjustable. It is primary for toe, but inevitable it would affect camber slightly.
Arm 2 is kinda like lower arm of double wishbone, but as one giant flat structure (imagine you fill in space of a char A) for aerodynamic, and it is also the same arm air suspension sitting on for model with air suspension. You can in theory, replace this with 2 adjustable rods, with some CNC machining needed for mounting structure.
Then arm 3 is one of the support arm and also the spring itself. The called is transverse leaf composite spring, because it is single spring the across the chassis. This save a lot of space for flat wide trunk.
Arm 4 can be replaced with adjustable rod.


3) 488 Front upper arm of the double wishbone, bottom have same design. You can see the whole pivot structure is bolted, adding washer will move it away from the chassis, thus changing the camber, so it is matter number of washer at upper vs lower. Most passenger cars, the pivot points are part of the chassis, we can not do the same hack.
P/S: Borrowing this idea, how is the wheel bearing mounted on the torsion beam. Any potential to add washer? I don't know, hahaha



This post has been edited by constant_weight: Apr 21 2021, 01:07 PM

Aiya, better than just telling people "you stupid, this is impossible" right?

At least share something constructive, then you corrected some part of my comment, I also learned something along the way.

Win-win loh

Coilover or lowered spring, I think are overkilled for Janwy case.

Judging from his description, sub 100km/h at highway, I think what he felt was mostly of lateral g-force with just a tad of body roll. It is hard to imagine highway bend that would throw a passenger car at excessive body roll as such speed.

If at the large curves that exit/enter highway, those corners usually have banking that exactly compensate the body roll.

So I agree with Quazacolt, that he overthink and don't really need a mod.