If a chassis is twisted, can it be repaired?

[Matra et Alpine]

1mm is a lot in tolerance term though, in imperial unit that's like 40 thousands of an inch, when in making most parts tolerances are calculated in +/- 5 thou or less....Its unlikely that you will get a 40 thou shift in chassis structure in a "minor" collision like a regular fender-bender and such. I'd imagine if it gets shifted by 1mm, the accident will require extensive service anyway.

RM we're talking monocoque road vehicles here.
1mm of chassis is nothing.
20mph knocks on suspension can easily pull the front chassis location out by 1/4"

[rev440]

Yeah you can do it. Ive seen people I know do it many times heck ive done it on a quad and Ive seen people do it on cars shouldbt be hard If you lived by me Id do it for you.

[PerfAdv]

Not related to Civic, but maybe a portent of things to come

Reportedly, if the aluminium-intense front structure on BMW 5 & 6 series is bent more than 1mm out of shape it cannot be repaired* and has to be cut out and replaced. This skyrockets the cost of repairs so even lightly damaged examples are being declared a total loss

* because then declared no longer insurable, also voids conditional factory warranty

I've read the subsequent discussion.... I think this little bit of technical leakage about repair/replace parameters might mislead some into thinking this is a BMW issue, when it's really an aluminum issue. Any car made of aluminum would require the same type of repairs.

Aluminum unlike steel is not malleable and the substructure in front of the passenger-cell must be mostly extruded aluminum in the M5/6. So once bent it can't be bent/beaten/pulled back, as this will weaken it considerably.

What surprises me is that 1mm is so small but 1mm measured exactly where? For example if the engine support beam is bent 1mm at 5-10mm from where they're attached, that's huge. Whereas, 1 mm bend at the bumper attachment side is minuscule.

So it goes back to the issue of structural strength being compromised once the super rigid Al is bent, otherwise 1mm can be compensated easily with an alignment adjustment.

[RacingManiac]

RM we're talking monocoque road vehicles here.
1mm of chassis is nothing.
20mph knocks on suspension can easily pull the front chassis location out by 1/4"

20mph collision is definitely no fender bender though........hitting something at 20 mph is enough to rip the front bumper off and totaled the rad....and to expect cheap repair cost for that kind of damage is already expecting too much....

The article made it sound like the chassis can be out simply by blowing on the car or a shopping cart hitting it(exaggerated). Modern car is fragile but not THAT fragile....especially with the bumper these day designed to be undamaged from a 5mph collision and pretty much self destruct from that point on and the high impact foam underneath it does most of the work. Of course repairing the BMW's bumper aren't cheap....

[Matra et Alpine]

20mph collision is definitely no fender bender though........hitting something at 20 mph is enough to rip the front bumper off and totaled the rad....and to expect cheap repair cost for that kind of damage is already expecting too much....

? Saabs could survive 20mph with only minor dfoermation of their bumpers
I've repaired many cars after 20-30 mph bumps and it's not that expensive.
Mind you I've seen some at 5mph that were right offs
There isn't a cast rule about it.

The article made it sound like the chassis can be out simply by blowing on the car or a shopping cart hitting it(exaggerated). Modern car is fragile but not THAT fragile....especially with the bumper these day designed to be undamaged from a 5mph collision and pretty much self destruct from that point on and the high impact foam underneath it does most of the work. Of course repairing the BMW's bumper aren't cheap....

The article is no doubt exagerating and highlighting those cars that DID suffer but won't have identified how many other crashes there were with no damage. When Minis were VERY common it was equally common to find front tie-rod mounts pulled out of place. And as has been already said, aluminium operates in a doffernt way to steel, the author is likely forgetting to consider that too. It's a choice. You want a light weight car then you pay a penalty.

[6speed]

How much do you think I could make from selling it for parts? I imagine about 3-4000, right?

[johnnynumfiv]

How much do you think I could make from selling it for parts? I imagine about 3-4000, right?

I duno about that high, but what ever it is, it'll be profit.

[RacingManiac]

I do wonder how the new Jags will do though, seeing how they are literally using the skin as stressed parts as well....

[nota]

I've read the subsequent discussion.... I think this little bit of technical leakage about repair/replace parameters might mislead some into thinking this is a BMW issue, when it's really an aluminum issue. Any car made of aluminum would require the same type of repairs.

Aluminum unlike steel is not malleable and the substructure in front of the passenger-cell must be mostly extruded aluminum in the M5/6. So once bent it can't be bent/beaten/pulled back, as this will weaken it considerably.

What surprises me is that 1mm is so small but 1mm measured exactly where? For example if the engine support beam is bent 1mm at 5-10mm from where they're attached, that's huge. Whereas, 1 mm bend at the bumper attachment side is minuscule.

So it goes back to the issue of structural strength being compromised once the super rigid Al is bent, otherwise 1mm can be compensated easily with an alignment adjustment.

Well put & I agree. And I guess this issue (ultimately) encompasses the contractual & legal onus on insurers and repairers to repair client vehicles - including their structural integrity - back to certifiable manufacturer-standard

At this new level of design sophistication, gone are the days of the cheap fix from your 'wreck-o-mended' smash repairer. Mending cars is becoming an increasingly complex and challenging business and manufacturers like BMW feel obliged to bring structural repairs in-house, to protect their customers' interests as well as their own

However the onset of unrepairable, throwaway cars is getting ever closer. And you can bet that BMW 5/6 insurance premiums are on the rise

Where exactly on the subframe is the 1mm distortion measured from? I dunno but from my interpretation it seems anywhere. Despite aluminium's undoubted strength, in the real world a crash impact can come from any direction, including diagonally. Previously, chassis rails could be pulled back into alignment with a car-o-liner but not any more

Speaking of alignment, many cars with Macpherson struts don't even have provision for camber adjustment. Does BMW 5/6 use struts? If so, are they adjustable?

[nota]

Saabs could survive 20mph with only minor dfoermation of their bumpers

Sorry but I don't believe that

[Matra et Alpine]

Sorry but I don't believe that

It was a Sabb 99 Turbo.
HUGE rubber bumpers with deformable foam behind and shock-absorbing rubbers to the chassis legs.
The Mini ended up lookin glie a Riley Elf as it pushed the back in at bumper height.

[nota]

My mistake, I took your claim literally. Because yeah I know those deformable bumpers, they protrude about 6" max from the bonnet line, don't they? So obviously in 6" there is no way they can fully absorb a 20mph-0mph decelleration

The new Saab 99 bumpers are the first in the entire automobile industry that have been certified as capable of withstanding 5 mph front and 2-1/2 mph rear end impacts in an SAE barrier without sustaining any damage whatsoever, the 1972 thus exceeds the Federal bumper regulations for 1973 model automobiles.

Although several auto makers have introduced new bumpers for 1972 only Saab has yet been certified through independent laboratory tests as being able to withstand the SE barrier impacts without damage. Tests of the Saab bumpers have been conducted at an independent automotive safety laboratory in this country.

[Cyco]

A friend had a Saab C900 and had a person crash into him as he was waiting at a T intersection (he was trying to turn righ onto the main road) and the Saab suffered only a cracked headlight and discoulored bumper.

The Corolla that crashed into him (tried to turn left going far to fast) was towed away with the radiator pushed back to the engine....