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Thursday, November 6, 2008

A Little Fact on Car Torsion Beam Suspension

1. Recently I have posted a crash that involves Toyota Vios and the palma tree where the car become bananized after hitting the tree. You can find the post from HERE.

2. I would like to thank Aminashaari for providing feedback and info as follows:

Actually it's the not the break system that's the issue. The problem lies in the inherent characteristics of torsion beam suspension system that loads up the front end of the car during hard braking. Torsion beam suspension (featured in most entry level cars to save cost and space - including the Toyota Vios) provides a simple, laterally strong solution to rear suspension systems of budget and compact cars.

The downside is that this simple suspension configuration tends to exaggerate load transfer to the front end during hard braking making the rear end very light and prone to loosing traction. In the hands of a novice driver, this can be dangerous. Though I haven't seen the CCTV footage, from your description (pivoting under braking), sounds like a textbook case of brake induced oversteer.

Short wheelbase hatchbacks are more prone to this than booted sedans with similar setup. It is safe to conclude that the car entered the corner at high speed and understeered due to the wet conditions. Typical to normal drivers, he would lift off from the throttle, jammed on the brakes and at the same time over corrected the steering to compensate for the understeer.

Current models with similar suspension setup (that I know of):

Proton Savvy
Perodua MyVi
Honda Jazz
Honda City
Toyota Yaris
Nissan Latio

3. In short, whatever car you have, please be more careful, especially during wet and raining time. But to think that in this case only car to be blamed is unfair coz the road design and road furniture also have big weight on this problem too. Lots to be done, and lots to be addressed on the road safety issues. Slowly but surely. Lets hope for a better future.

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3 comments:

Anonymous said...

Perhaps before coming to conclusion, you should watch this:
http://www.youtube.com/watch?v=ZSqGPyWroes

You can also watch on further advanced safety features such as ESP/VSA/VSC.

If the car that crashed was a Civic with the acclaimed double-wishbone suspension (let's say without ABS); I wonder what will the write up be.

Personally, I've driven multilink suspension car but without ABS before and experience wheel lockup. It doesn't matter what's the rear setup, if it locks up, you need to let off and control.
I've also experience ABS function on a car with ABS when the wheels lockup occur and you can feel how you still can maneuver and correct your steering.

Lastly, those advanced safety feature, such as ESP which consist of several features like CDC, etc. I've also felt it function during emergency situations of during hard cornering and suddenly oncoming car appears; On a normal car without ESP, there most likely be a risk, but if without ABS too, it'll be worst situation.

Chad said...

Very interesting reading, probably doesn't apply to all makes and models though.
I have a torsion beam rear in my track car and all day long I'm going from 120MPh down to 30MPH in less than 120Feet, never once experienced the back end coming round under braking, wet or dry.
If the bum's coming out it's under power :)

Drop Suspension said...

A novice driver doesn't know the risks involved. Poor loss.