Torsion beam rear axles explained

Discover the unique aspects of torsion beam suspension - the design fitted at the back to billions of front-wheel drive cars. Sometimes torsion beam suspension acts as simple trailing arms, but at other times it's more like semi-trailing arms!
Buy the book here - www.amazon.com/Car-Suspension-over-years-handling/dp/B09CRNQB9P (or from Amazon in your country)

[@jamsbong]

The enthusiasm level is incredible with this guy. God bless!

[@androo4519]

I've been looking for a good explanation of this for a while. This is really good because few others explain properly about the positioning of the torsion beam in relation to the axle centre, which is clearly critical. For years I would look under my family's cars (weird kid) and try to figure out how the suspension worked, but the torsion/twist beam doesn't look like it can work, although riding in the back of my parents' Peugeot 307, I realise that it only partially works. Not a pleasant experience! I hated the ride of the family Ford Cortina Mk3, but loved the Rover P6 it sadly replaced in our driveway.

[@JulianEdgar]

You’d enjoy the book!

[@pjay3028]

Another brilliant video. I'm loving this series so much, thanks.

[@pjd4268]

Agreeded. I was wondering about my honda fit with the modified twist beam. What do we call this then. 3/4 twist?

[@xg5zm]

They are really good.

[@phantom0456]

I had a general understanding of how a torsion beam rear axle worked prior to your video, but you really did a great job explaining how it works and the different variations of it that exist, your video was by far the best I found explaining this type of suspension. Many thanks!

[@deeiks12]

After seeing couple of your videos - i will order your book definitely. Fascinating information.

[@JulianEdgar]

Hope you enjoy it!

[@dominicfong6341]

Torsion beam rear axles are NOT completely dead yet because it is still found in the current model of Mazda 3 in which it had switched from independent type.

[@androo4519]

Far rom dead I would say. Lower spec Mercedes A-Class, Golfs and their SEAT/Skoda, even Audi equivalents use one, as does the Peugeot 308 and its clones, pretty much all supermini class cars like the Polo etc. And since cars like the Golf moved from multi-link independent rear ends to this two-tier system of twist beam for low-spec cars, you could say it's more common now than before. Perhaps it will die however - nice to see the new Renault 5, despite its size, having an independent rear end.

[@azur3125]

I think Toyota still uses them too. I remember I saw one in 2012 Yaris. I just noticed it after I got fascinated by this axle type after one in my Golf got broken and how easy it was to replace. At least compared to the multi-link rear axle on my wife's Audi which always has some bushing or link worn out.

[@poprawa]

On my laguna ii beam developed cracks about 2cm from weld, and it is case of car with 20 years of riding on shitty, Polish roads. Still, cheap and quick to replace and still very, extremely long life suspension part. In winter we have salty roads and it is fine to have corrosion-made holes in like 10 years :>

[@xg5zm]

It is very interesting. Thank you for these videos. These type of suspension was and still is very common on euro hatchbacks. One thing I would like to bring to this discussion is how immensely important are those two rubber bushes in the whole car handling. They are often overlooked and never replaced, when in fact they tend to wear very quickly. Lateral desplacement of the beam, even if small, have huge impact in the steering precision and feeling. If you have a car with this suspension with more than 80.000 or so, change them, you will feel the difference.

[@JulianEdgar]

Yes that is correct.

[@JamesBalazs]

For the Astra VXR/OPC they are commonly replaced with spherical bearings which add minimal NVH for a huge upgrade in rear end feel and stability. Definitely something I want to do to mine.

[@potatosfortots9909]

I always liked these rear twist beams because of the simplicity and effectivness. The other day I dropped mine out of the car in liess than 20 minutes! I also like the ease of modification. I looked at the twist beams of the sportier model of my car and simply recreated and welded on the steel bar they had for almost nothing.

[@edgarbeat275]

My 1977 Audi 100 C2 has a torsion axel. I embarrassingly knew little about these types of axels. Than the multi leaf torsion bars using bearings beetle. Or like a 206. The axel construction being the torsion bar. Quite amazing

[@MrSunrise-]

Julian: Re: stress on the welds - the torsion beam is loaded in torsion (hence the name), resulting in shear in the tube. From shear flow theory, the shear in the thin wall is approximately proportional to the distance of the wall from the centroid of the beam cross section. You'll notice that the beams tend to be rectangular rather than round, and the welds are at the ends of the rectangle, far from the centroid, and so are subject to much less shear than the regions near the centroid. Assuming a material thickness that is greater near the welds (a good assumption for the way these things are stamped), the welds are not only under lower stress compared to the rest of the section, the material in the vicinity of the weld is also thicker. Hence, it is unlikely for a properly designed and executed weld to fail in this application. Thanks for the details on the kinematics, I'd been wondering about this.

[@curiositykilledthecat1557]

Nice work! Now I understand it. I just purchased a 2008 Corolla for my daughter that has a torsion beam rear end. I was impressed by the profile of the beam. Obviously a lot of R&D involved. No problems getting a return on that investment with a car such as the Corolla.

[@somegi9]

ive seen a few rally guys running watts links on their fiestas to counter the lateral forces on the bushes. also helps with the stress on the arms themselves by taking up the lateral force.

[@heinzhaupthaar5590]

Afaik that's been a original design in quite a few cars. But I'm not sure except some Opel/Vauxhall models. Seems like a rather simple but worthy upgrade for sure.

[@fuccasound3897]

Good info! i have a citroen DS3 that uses this system and having been brought up on live axles and multi-link independent suspension systems, (60's sports cars and saloons) i was a bit mystified by torsion beam suspension, now i know! In some situations the DS3 behaves like it has a live rear axle, there is a long sweeping fast bend with a ridge right across its apex, the DS3 gives a most undignified lurch to one side as it is crossed! This doesn't bother me having driven live axle cars that would do the same. I liked your semi trailing link analogy, a design used on the IRS TR's and they always would squat down at the back under acceleration and cornering hard, the torsion beam gets round this very neatly!

[@compu85]

This is a great presentation. Have you read about how the beam axle in the Mk3 VW and Passat would shift in a controlled manner in cornering? VW billed this as a simple 4 wheel steering system.

[@JulianEdgar]

Yes, most rear suspension designs have 'steer' capabilities.

[@andrewlewis4253]

My 96 Passat (B4) has semi-trailing arms. I tossed the torsion beam in the scrap heap in favor of a Syncro setup. I get lots of toe-in as it compresses and it feels much better than the torsion beam. This is interesting info right here. The car rode like hell on airbags slammed down low. Now I know why, no torsion action!

[@yannicg]

Interesting that you mentioned the negative of poor lateral stiffness, because that’s exactly that I feel in my Alfa mito when doing a roundabout for example and hitting a pothole or general imperfection in the road, the entire car seems to shift a bit towards the outside when that happens. It’s also very noticeable under heavy cornering when there are imperfections in the road

[@JulianEdgar]

More likely inadequate damping. Lack of lateral stiffness in a rear torsion beam more likely to lead to rear toe (ie rear steering) changes, I think.

[@yannicg]

@@JulianEdgar oh ok

[@ronaldderooij1774]

I have a Mitsubishi Mirage and it has such a rear suspension. I am a big fan of this torsion beam suspension in front wheel drive "bread and butter" cars. I only experience the last disadvantage as "noticeable". It cannot cope with short bumps very well, especially when cornering. Given all the advantages, that is a very small price to pay.

[@noelanderson703]

I had a Citroën Light 15 back in the day and it had torsion bar suspension all round and one could adjust the tension, with Michelin tire's it stuck to the road like glue with a very smooth ride . for something designed in the mid-1930s it was remarkable.

[@asharma9345]

Excellent video Sir. Keep such videos coming.

[@JulianEdgar]

Thank you. You might want to look at some of the 200+ videos already produced.

[@MePeterNicholls]

Fascinating 👍🏼 thanks for doing this. I’ve got a 2004 mini and a 2020 focus 2.0 diesel both with independent rears* , and my focus mk1 had independent rears too. So I always wondered what torsion beam was like *multi link

[@dipling.pitzler7650]

another disadvantage is reduced ground clearance specially when used in FWD Vans like Renault Traffic , these often have to drive around on muddy or sandy building sites with an already compressed suspension due to heavy cargo.

[@djquick]

Wow! Just came across this channel. How have I not seen it sooner! Subbed!

[@JulianEdgar]

Don't forget to check my 300+ previous videos.

[@djquick]

@@JulianEdgar watched many today. Really like this content!

[@paradeinberlin]

This is an exceptional video, thank you!

[@JulianEdgar]

The book’s even better!

[@ibakedit5850]

Thanks for the video. Do high spring and damping equate to less compliance/ride comfort?

[@JulianEdgar]

Yes.

[@dimdimis2936]

Great video! I have a question Mr. Julian. Two same cars (Golfs), one with torsion beam on the rear axle and the second one with a multi-link, should have the same behaviour, in terms of comfort, when BOTH wheels hit a transverse bump/pothole, assuming that the shocks are same? Thanks in advance.

[@JulianEdgar]

Not easy to answer eg depends in part on the unsprung weight of the two different suspension designs.

[@luvr381]

Now I need to see if you have a video about why Macpherson strut suspension is so ubiquitous.

[@JulianEdgar]

Yes, covered in my book.

[@dinostalieris3998]

Perfect analysis, thank you! Just a question: if you add a spring spacer at the springs of a torsion beam (in order to raise the ride height at the back), do you affect the spring preload?

[@JulianEdgar]

Depends how long the dampers are, but yes normally that would be the case.

[@dinostalieris3998]

Thanks for your reply! This applies also when the damper and the spring work separately? I mean when it's not a coilover.

[@dinostalieris3998]

I mean a design Similar to the design your are describing at 6.06 of your video

[@JulianEdgar]

The length of the dampers dictates the preload (if any) on the spring. Fitting spacers to the springs would normally change the preload, because the dampers don't get any longer.

[@motorlogic-luisnunes4123]

Hi, from a performance point of view, I never really understood why anti roll bars are installed in conjunction with the stock torsion rear beam instead of bracing the existing setup for more rigidity, is there a benefit to it or just marketing?

[@JulianEdgar]

Allows easy manufacturer adjustment for different models. Just change the bar, not the whole torsion beam axle.

[@khalidacosta7133]

Just to note - the Peugeot 306 / 206 etc did not have a torsion beam... it had a fully independent torsion bar setup. Quite a smart system really which was very low maintenance!

[@rimmersbryggeri]

That was the answer to my question since I just bought a 206 and wondered why the trailing arms are on individual bearings if they are supposed to be rigid. My thought was something like what you stated but was not sure.

[@DevinderAthwal306]

The 306 also had a passive rear wheel steering mechanism as part of the bushing arrangement.

[@larsjrgensen5975]

I do not agree 100% about the low maintenance, the family 106 needed a replacement of the entire system because it rusted together, leaving the car with no suspension at all. The replacement version had multiple lubrication spots to fill op the torsion beam system with grease, to prevent the system from rusting into a solid piece again. The same system generally works well on a lot of trailers though, so designing it correctly is key.

[@khalidacosta7133]

@@larsjrgensen5975 Just because YOUR suspension system wasn't reliable, doesn't mean ALL of them were unreliable. Most cars I've seen with 200k with no work needed to be done on the suspension. That does take a lot of doing!

[@larsjrgensen5975]

@@khalidacosta7133 Just because YOUR suspension system was reliable, doesn't mean ALL of them were reliable. I wrote that it works very well on trailers, but it is not a 100% perfect system. If they spend time and money on developing a way to renovate the system on a peugeot, there must be a market and need for it. The 106 had around 160.000km on it, when it locked up and became very dangerous to drive. A friend of mine had a Renault 19 with the same design, one side broke at 190.000km. A 306 in the family locked up like the 106, but i do not know about the km, so it does not count. We have a bad climate here, with a fair bit of road salt, that could maybe explain some of the higher failure rates.

[@robingray1302]

An excellent explanation indeed !!!

[@JulianEdgar]

Glad you liked it. You might want to also check out some of my 200+ other videos.

[@VishnuRajam4x4]

Superb video!

[@MrTheAndu]

What do you think about Opel Astra J rear torsion beam axle coupled with a Watts link? Was the Watts link placed there to limit the amount of toe out on the outside wheel? If so, as you say, couldn't this be mitigated by a better bush design?

[@JulianEdgar]

I have no technical information on the Opel Astra J.

[@KingOath]

My Toyota Avensis with torsion beam rear end has what looks to be a significant amount of negative camber and toe-in included in the design. Why is this necessary? At first I thought it was broken but it’s meant to be that way. I can’t see the need for negative camber on the rear of a front wheel drive car?

[@JulianEdgar]

Because all cars need front and rear grip, irrespective of their driveline configurations.

[@PyleHD]

Hi Edgar, loving you series. How would this torsion beam compare with torsion bar which had independent wheel suspension, like peugeot 306 as someone mentioned before. I suppose having independent suspension must be much better than having this beam setup. Thanks

[@JulianEdgar]

It depends how the independent suspension is arranged - torsion bar springing can be used with a whole variety of suspension systems. (I don't know the Pug system in any detail.)

[@zonoscopePictures]

@@JulianEdgar I was going to ask about the difference between Torsion Beam and Torsion Bar. I *assume* they are different?

[@JulianEdgar]

@@zonoscopePictures 'Torsion beam' refers to a type of suspension system, as covered in this video. 'Torsion bar' refers to a type of *spring* - a bar that is twisted. So anti-roll bars (sway bars) are torsion bars, and torsion bars can be used as the main springs in all sorts of suspension systems eg double wishbones, semi-trailing arms, etc.

[@celeron55]

My Fiat Scudo van has a torsion beam rear axle, but it has a panhard rod to take lateral forces. So lateral forces can be quite simply solved just like that.

[@JulianEdgar]

Yes and no: there will still be a relatively flexible trailing arm component unless the torsion beam is acting only as a dead axle.

[@nukedathlonman]

It's a simple design....Not overly sporting, but just pure simplicity. Now it isn't attributed it to bad welds or excessive forces, but broken torsion axles on the Ford Windstar is all too common. It was attributed it to salt exposure... It was so common enough Ford issued a recall. I tend to attribute it to many factors of all the cycles they see, with the road salt/brine accelerating the process. But if you haven't seen a broken torsion axle - there are lot's of pictures all over the net of Windstars with broken torsion axles. Is it a common problem altogether, no... But given all the attention is generated - it likely soured companies from the design.

[@rupakkhadka9507]

Anybody know why my Fiat punto grande active 1.2 petrol tear down nearly middle of Torsion beam ?

[@jonienglish3231]

Julian any Video of DOUBLE BALL JOINT SUSPENSION GEOMETRY and BENEFITS ???

[@JulianEdgar]

What is double balljoint suspension? Double wishbones?

[@jonienglish3231]

@@JulianEdgar I seen some Audi have 2 upper ball joints

[@jonienglish3231]

@@JulianEdgar en.m.wikipedia.org/wiki/Multi-link_suspension

[@JulianEdgar]

OK, multi-link suspension. Pretty common these days, especially on the back on RWD cars. Yes, they have benefits in holding toe angles and giving defined camber curves - but I often think the benefits are a bit overstated. Multi-link suspension is covered in my book.

[@michaelstanbrough6115]

Your videos are lways interesting. Where is the roll centre located at static heigh and where does it move to in bump, both two wheel bump and one wheel bump, and roll.

[@JulianEdgar]

Not a depth I am going into here. I can recommend several textbooks and papers if you're interested.

[@michaelstanbrough6115]

@@JulianEdgar if you have them. That would be great.

[@JulianEdgar]

@Michael Stanbrough The references I used when writing the section on torsion beam suspension were: Held, V. & Hiemenz, R., Designing Twist Beam Axles in Encyclopedia of Automotive Engineering, John Wiley and Sons, 2014, and Heibing, B. & Ersoy, M., Chassis handbook : fundamentals, driving dynamics, components, mechatronics, perspectives, Vieweg + Teubner, 2011. However, I am not sure they will fully answer your questions.

[@dubsydubs5234]

The VW GTI did have a anti roll bar it was built into the V section of the beam.

[@JulianEdgar]

Yes, many cars with torsion beam rear suspension have an anti-roll bar within the beam.

[@dubsydubs5234]

@@JulianEdgar You said there wasn't one on the VW beam and you are correct for all but the GTI models. I did see you mention other vehicles. I just felt like commenting as I was a VW mechanic for 35+ years. 👍

[@Oockeshoek]

I've got a Twingo 2 (same as Clio 2 but newer), also has this design. It's lowered, it handles great but indeed ride comfort is crap

[@tommyb6611]

Hi, My car has thos type of rear axle and I am curious How can I upgrade this into an electric drive format. Keeping the combustion engine in the front, powering the front wheels and somehow upgrading this type of rear with an electric motor.

[@JulianEdgar]

Anything is possible but it would be a major engineering exercise.

[@tommyb6611]

@@JulianEdgar If it piqued your interest and lets say intellectual curiosity, as someone that knows a lot on car suspension, i could suggest tackling this idea, thinking a "what if, how i would do such a change". Not needing a large EV motor (like lets say a tesla or any other powerful beasts) but one that could serve every day driving in a phev, like a 9 inch electric motor or an 8 inch one, with some 20-30 odd kW output...or maybe smaller hub motor setup in each rear wheel, which might not involve any suspension change

[@JulianEdgar]

To be honest I think the days of doing home-brew electric conversions is gone. Depending on where you live, it would likely cost a lot more than buying a secondhand electric car. And as for a hybrid, you could never match a Prius in outcome - and they're now very cheap indeed.

[@tommyb6611]

@@JulianEdgar yeah, factory electric cars are not too appealing, they have devolved in terms of quality plus they use everything integrated, only touch screen, minimal buttons and very expensive to repair. In fact the EV conversion will just start to bloom, because plenty of owners of older cars would want to continue to use them and enjoy upgraded performance of the EV tech as opposed to the new low cost EVs at stupid overpriced price tags. A conversion is 10k-15k using tesla batteries (so expensive) Ah, there are shops that charge for a EV conversion 3 times that from the snobs that don't care, that is a different story, but with 10k an EV conversion is a realistic price. What used EV do you find with such a low price? Nissan leaf is junk, was a failed engineering from the start, Now, then you get to keep your beloved current vehicle that has much higher comfort than the sparse plastic cans of the first gen EVs and also the benefit of electric drive.

[@daos3300]

bush design for roll understeer - what does this entail, just the level of hardness, or something else?

[@JulianEdgar]

It can involve differing bush hardness in different planes and the bush orientation - but also inclination of the trailing arms to horizontal, use of additional toe control links, etc.

[@helixworld]

Is it possible to get a rear wheel alignment with this suspension?

[@JulianEdgar]

It depends on the car and how much effort you want to go to, but usually, yes.

[@compu85]

Yes, you can shim the hubs where they bolt to the axle.

[@GustavoDVillarreal]

Is this book coming out in digital form?

[@JulianEdgar]

No. Digital books immediately get pirated.

[@GustavoDVillarreal]

@@JulianEdgar I only buy digital books now (Kindle or Apple Books; easier to highlight, reference, read anywhere), but I had to make an exception for your book Optimizing Car Performance, and now I know there is no point in waiting for a digital version of this. Thank you!

[@Random-nf7qb]

How about a comparison between old double wishbone designs, modern macpherson and modern double wishbone? Many old cheaper cars had double wiahbones at the front(fiat 124, lada 2101 and others), I wonder how it compares to more modern macpherson strut designs.

[@JulianEdgar]

In short, double wishbones as a suspension system are superior to MacPherson struts, irrespective of age.

[@Random-nf7qb]

@@JulianEdgar but those old cars have heavy arms and probably not that good geometry. I am not an expert, those are just my thoughts :). Thanks for the reply btw.

[@JulianEdgar]

@@Random-nf7qb My reply stands: double wishbones are intrinsically a better suspension system than MacPherson struts. Plenty of old double wishbone systems were light and had excellent geometry. You'd enjoy the book, I am sure.

[@Random-nf7qb]

@@JulianEdgar Ok, thanks!

[@helixworld]

I wonder if you cover the Holden HQ in your book. It has interesting double wishbone front-end geometry. I think there are some issues with 4-link live axle rear suspension, such as a high roll centre, some roll-steer effects etc. Not the best for stability. The Holden VB with Macpherson struts is likely to be an upgrade.

[@williambelford9661]

Isn't the torsion beam suspension just a variation of the torsion bar suspension patented in 1923?

[@JulianEdgar]

No, quite different. Torsion bars provide the springing medium; in a torsion beam system the springing medium is completely separate. Perhaps you'd enjoy the book?

[@williambelford9661]

@@JulianEdgar so what exactly does the torsion in "torsion beam" refer to? Doesn't torsion, by definition, refer to a twisting action which is what differentiates a torsion beam axle from a beam axle?

[@JulianEdgar]

Torsion bars provide the vertical movement's suspension springing. A torsion beam axle does not use its axle in torsion to provide vertical springing; it uses its torsion to provide roll resistance. A torsion beam suspension is nothing like suspension using torsion bar springing - torsion is used in completely different ways in the two systems. Therefore torsion beam suspension is not just a variation of the torsion bar suspension.

[@williambelford9661]

@@JulianEdgar so a torsion beam is a glorified anti-roll bar.

[@JulianEdgar]

Yes, that is a better way of putting it than suggesting it is just a variation of torsion bar suspension. However, unlike an anti-roll bar, the torsion beam is solely responsible for the wheel location as well. Have you actually watched the video?

[@juliussmith4001]

Thank you,

[@JulianEdgar]

You are welcome!

[@TC-V8]

Gives anti lift under braking but my Citroën AX GT comically jacked up the rear suspension when using the handbrake on a hill.

[@JulianEdgar]

Yes, cars with anti-lift rear suspension will rise when the handbrake is applied and the car attempts to roll backwards.

[@khalidacosta7133]

Pretty sure the Citroen AX used torsion bar setup which was independent. Very different to a torsion BEAM suspension.

[@bikeaddictbp]

@@khalidacosta7133 The forces involved in anti-lift - which lead to lift when the car tries to roll backwards - are exactly the same, though. Now, with Citroen being Citroen, it's likely that the spring rates were quite soft, which amplifies the amount of this motion.

[@Mladjasmilic]

It also makes plenty of room for placing spare wheel.

[@JulianEdgar]

Yes, good packaging.

[@TC-V8]

I often hear torsion beam suspension has better tyre wear - would you agree?

[@JulianEdgar]

Better than what?

[@janeblogs324]

Less?

[@rtz549]

GM Bolt uses this beam.

[@janeblogs324]

These videos would be much better if you didn't record them in the dunny There's so much echoing bass in the voice audio

[@torisaurio]

another con is that you can't adjust any geometry

[@JulianEdgar]

On many cars with torsion beam rear suspension you can adjust the alignment eg by shims behind the stub axle mounting plate.

[@2-old-Forthischet]

...but the engine is sitting the wrong way!

[@mytype4271]

clarkson was wrong