How Does Torsion/Twist-Beam Suspension Work? Why do Manufacturers use it?

Today we look at a type of suspension commonly used on front wheel drive cars known as twist beam or torsion beam suspension. This suspension is largely used by manufacturers as it is very cost effective, however it has a number of interesting characteristics.

This video was from a Patreon video request, if you like what I'm doing you can support me there with the link below.

[LukeTrundell]

I've been struggling to find information on YouTube about roll stiffness and torsion bar suspensions and this video has very clearly told me as much as i would like to know about the characteristics and tuning techniques applicable to rear torsion bars so for that - thankyou very much sir ^^

[NDSno]

Thank you very much. I've been searching forever for the reason of toe change in Torsion Beam but can't find any that can be used, as the explaination is very vague and sometimes doesn't even get to the point. Your explaination is simple and sufficient, focus directly on the problem.

[Devinfrbs]

Thank you! It makes sense why this suspension setup sometimes feels like the rear is upset over bumps. Keep up the good work.

[KYLEENGINEERS]

Just realised after seeing the comments that I didn't talk about the unsprung mass at all! To answer everyone's questions, yes, this sort of setup does have higher unsprung mass than IRS, and this will adversely affect the handling unless your track is dead smooth. And regarding the roll damping, it is true that the dampers at the back of the beam will provide damping in roll, however as they have to provide bump damping against the springs you can basically tune them to either damp bump or roll best, or a compromise somewhere in-between. The damping will always be wrong in a specific mode, but close enough for most purposes. This isn't just a problem for a twist beam setup, but is true for any setup with an undamped anti roll bar, as changing the bump damping changes the roll damping.

[Enakaji]

Nice video. What I've seen some manufacturers do to add more roll stability and a degree of adjustability to these kind of rear suspensions is add an adjustable torsion bar inside the twist beam so that you can adjust how rigid that twist beam is. I had one like that on my 1988 Mitsubishi Colt, though on my current 2007 Colt Mitsubishi kinda cheaped out on it and simply used a beefier twist beam and completely done away with the extra torison bar.

[mjzmjz]

You have explained the basic phenomena very simply. Thumbs up, Five Start. Keep it up !

[fourthdalisay]

Men I'm 17 years old but I really learn a lot in this vids pls keep it coming!

[animusfault]

Good stuff. A multi-link video would be great.

[samartz]

Always thought my pulsar sss had a solid axle, this cleared up many things. Many thanks!!

[CaniLupine]

I know this is three years old, but I immediately recognized the underside of the car at 5:32 as a 2012+ Mitsubishi Mirage/Space Star. I happen to own a 2014, and ran into issues with this particular torsion beam suspension. The axle stubs are welded to the assembly, so there is no alignment adjustment using shim plates. They have around -1.5* camber and about 0.3* toe in per side from the factory. Mine is lowered an inch on H&R springs, which nearly doubled the amount of toe in. Taking inspiration from another member of MirageForum.com, I had to attach a chain to the spring perches and use a turnbuckle to adjust the toe out towards zero. It actually worked surprisingly well!

[adyyzels]

Great job, ive put anti roll bar to my torsion beam before, but it makes it less predictable.. After took it out my car handles much better in corners..

[bradcomis]

This was great. I think it would be great if you did a video like this on the McStrut system that seemingly every contemporary vehicle is produced with. Why on earth is it so popular? It seems to me that it is horribly compromised in every way besides packaging. Is there really such a lack of space up front that dual A-arm suspension is impossible, or is it just a matter of saving dollars?

[RHBTurbochargers]

you simply use shims between the wheel bearing and axle to change camber and toe

and also there is a benefit where you can achieve a rear ride height drop with brake torque, keeping the car more flat under braking

[rocketsurgeon]

Alignments on this setup are done with shims behind the axle stubs.

[Fabio-sudf]

I like the new style. Keep up with the good work.

[justinford]

Love the content, thank you. I'm certain you have a surplus of requests but I would enjoy your thoughts and insight on roll cage design and other safety systems within the car (seats, HANS, fuel cells...)

[viktortulbya]

Im sorry off topic, but i have a question, sp ive heard formula 1 commentators mention red bull having some sort of "slippery" paint, do you know anything about that, and could paint type and or surfaces affect aero on a car?

[lucywucyyy]

im liking this video style btw, seems more professional, engineering explained is a step behind now

[puremadmentalmackay]

you can add some extra stiffness to resist roll by adding gusset(?) plats between the centre of the H down the inside of the trailing leg and some FWD rally cars add adjustable rods from the inside centre of the H to the inside of the trailing leg to give toe adjustment and camber adjustment is done via either washers/shims or shim plates mounted between the torsion beam leg and the tub axle

[georgec]

Your videos are very informative. Could you make a video about the long tail aerodynamic designs such as the McLaren F1 Longtail and other cars that use it? Is it good mainly for straight line speed and acceleration or can it be good for cornering as well if the wheelbase is shorter etc? I wonder why it's not used more often? Maybe it's useful for Le Mans cars and not for road cars? It would be great to have your insights about it.