Car manufacturers have put effort into making the front of their vehicles crumple - not the back. The front of a modern car is fairly 'soft' and designed to crumple so as to limit the maximum deceleration of the occupants and increase their chances of survival. For that reason even a fairly minor impact will cause some deformation of the longitudinal chassis rails - couple that with lots of expensive and delicate parts at the front (headlights, a/c condensor, radiator etc etc) and it is easy to see what a modest front end impact will cause the car to be an economic write-off.
In constrast, the rear of most vehicles is fairly stiff. Having seen many rear-ended vehicles over the years I notice that often the back end stay largely intact but you get a chassis deformation right above the back wheels (where the chassis has a 'hinge point') and sometimes a crease in the roof too. If a towbar is fitted then the energy tends to be transmitted further down the chassis and this can introduce a barely-noticable 'tweak' into the chassis. For this reason it is a good thing to have chassis alignment checked after any kind of significant rear impact - even if little obvious damage appears to have been done. The comment about the other car 'being the Volvo's crumple zone' is a good 'sound bite' but it is not true.
Whether the ridgidity of the rear of the car is a good thing or not is debatable, it is transmitting energy to the occupants rather than absorbing the energy. This could have nasty implications in the case of rearward facing 3rd-row seats. A lot depends on the exact circumstances of the accident.
|
I remember seeing something from Mercedes a few years ago when they said you needed two feet (metric version) to create a crumple zone.
The implication is that there is no rear crumple zone in many cars (not measured by Ncap so not done).
Not so bad if you are facing forwards and have the support of a seat back but would not like to be in a rear facing seat!
For those who commute by train the suburban trains built in the last 10-12 years have crumple zones at each end, the last row of seats is IN the crumple zone - I would not use them! Still better than the old slam door trains which were one enourmous crumple zone!
|
|
|
The comment about the other car'being the Volvo's crumple zone' is a good 'sound bite' but it is not true. Whether the ridgidity of the rear of the car is a good thing or not is debatable, it is transmitting energy to the occupants rather than absorbing the energy. This could have nasty implications in the case of rearward facing 3rd-row seats. A lot depends on the exact circumstances of the accident.
And on the relative weights of the cars. In each of my two examples, a smaller car ran into my back at about 20 mph - I was stationary.
I hardly felt a thing, but thought I had better get out and look. One car had a crumpled front bumper and smashed lights, the other likewise and the radiator bashed and pushed against the engine.
Annoying about the scratch on my tow ball cover though.
I don't know how strong the front "crumple zone" is supposed to be - strong enough to withstand my wife driving into the back wall of the garage anyway.
|
|
Just remember that in many of these vehicles,the rear row of seats,approved or not,are sited directly over tth fuel tank!!!
|
Just remember that in many of these vehicles,the rear row of seats,approved or not,are sited directly over tth fuel tank!!!
Big deal.
With few exceptions, so are the second row occupants.
|
|
|
|
If a towbar is fitted then the energy tends to be transmitted further down the chassis and this can introduce a barely-noticable 'tweak' into the chassis. For this reason it is a good thing to have chassis alignment checked after any kind of significant rear impact - even if little obvious damage appears to have been done.
Where would this be done, and is it likely to have been done as a standard repair?
My car was rear ended during it's previous ownership, the guy was totally honest and had bills for the work, the tow bar had new bolts which makes sense but is there a legal requirment for them to do this?
|
|
I should add the work was carried by SEAT themselves and apparently it was a very minor accident. ISTR the work came to about £1000.
|
There is no legal requirement. The repair just has to be done to the satisfaction of the customer and, of course, the vehicle has to pass the MoT. There are lots of vehicles running around with chassis tweak due to poor accident repairs.
Ideally the car should go on a jig, e.g. a Dataliner with laser measuring system. You then clip targets to various chassis alignment points, as shown on the screen (the software guides you through) and the software tells you if anything is in the wrong place. Takes about 30-40mins to set it up and obviously if anything is out of place then it will need pulling into alignment.
Usually the bodyshop manager will make a judgement from experience on whether it needs checking or not. People talk about measuring the distance between wheel centres, but to be honest that only shows gross distortion.
I must say that if your rear impact bent the bolts holding the towbar to the chassis then it must have been a fair whack
|
|
I think it's more due to the high tensile steel and sudden impacts (?)
|
|
|
|
|
