Some images of 1996 LS400 front bumper, without cover taken in pick n pull yard.

Seeking input on ways to improve how bumper is fastened to the chassis.

12mm hex (non washer head) with 8mm (?) thread is inadequate..


Dissimilar metal corrosion at base of fastener has corroded through bumper.
Positioning stud sans nut? Fasteners used to affix our front bumpers.
Would respond well to an upgrade....
No clamping at front....through-hole only..
The rear flat aluminum back plate cannot possibly cope with torsional force...

Anyone;

Tapping chassis threads to M10 threads a possibility?? (Captive nut, threaded insert or tapped chassis? )

Inserting a fitted solid (Aluminum) spacer in the gap with longer bolt (shoulder bolt) so clamping can occur at forward and rear verticals of bumper profile?

Possibility for affordably increasing torsional rigidity at furthest point forward and rearward bumper?

 

These are meant to sheer in impacts, i wouldn't affix them any more solidly than they were from factory.

 

The structure would require fortification before any modifications are effective

I have seen several bumpers where the steel fasteners have weakened the Aluminum bumper through electrolysis and broken through....if you expand the image you can see that is the case here too...

Anyone know if the chassis side tapped threads are a sliding/positioning square nut, captive insert, or tapped into chassis?

Tapped thread size would have to be capable of larger bolt diameter to accomplish anything.

Sorry Toyota but do not like this design...

Have never seen such puny bolts clamping a bumper on an automobile of this size and stature.....

 

....in several scenarios I have looked at, there is nothing left to shear from because the bolt underside/clamping side has eaten through the Aluminum bumper...and is not holding anything.

So if increased shear force represents any shear force at all then isn't that safer than none??

Suggested repair other than simply replacing bumper??

 

A sample size of "several" isn't really comforting here.

If you want to start running some empirical tests to determine the shear properties of the factory setup (something Toyota did) before you change something simply because it "seems" more sturdy or "better" then go ahead. Otherwise, I would leave it alone.

 

No testing by me...I'll leave that to Toyota.

Perhaps they will peruse the posting...

Several posts about fasteners used on LS400

Some are adequate while others need help..such as transmission crossmember or gas/ brake pedal bushings ..negative grounding fasteners, etc.

Perhaps you can agree YODAONE postings present engineered solutions and improvements to real problems.

Here, I am interested in increasing structural /torsional rigidity... improvements to front and rear bumpers....

Structural.foam has been acquired and will be employed .

So am not dissuaded, but am seeking creative input.

Thanks.

 

The most i would recommend is maybe changing to stainless bolts to prevent the corrosion. But even that changes the material properties considerably.


Out of curiosity, are you a mechanical engineer by trade? If not I wouldn't be one to try to "improve" crash protection areas...

 

Toyota engineers have demonstrated that increasing torsional rigidity through reinforcement and bracing of the front bumper provides significant compliance with Federal front bumper safety and crash worthiness standards.

...have a look:

 

Since you were taking photos of the LS in a salvage yard, and the bumper cover was already removed, how can you be sure, with 100% certainty, that someone else hadn't removed the bumper previously, such as a body shop or DIYer and affixed it improperly with this hardware? What if it had been involved in a light impact fender bender and this crash structure had been deemed reuseable by whoever worked on it before?

Unless you remove your own bumper and confirm this, I'm not taking any of this into consideration as valid truth since there are a number of ways that this vehicle you're looking at could have ended up in the salvage yard.

 

Look, this project is not for everyone.

My bumper looks the same. Have seen a 1998 with front and rear cover off.

This may surprise some, but one of the things I enjoy most about posting on this site is the negative reaction towards improvement .... because when that comes around and someone attempts to criticize modifications, which they are unfamiliar, as sound, I simply direct the respondent to Toyota, who has adopting the idea in newer models...and even then Toyota's evolutionary example meets resistance.

Feel free anyone to contribute to the project.

Thanks.

 

I don't understand why you keep picking apart this car for all your perceived imperfections when most of the things you "analyze" are perfectly fine as they were designed by the Toyota engineers.

Unless you plan on using your LS400 in a demolition derby, the bumper how it was designed is perfectly fine in coping with the stresses of an accident.

It seems like you've chosen the wrong platform to fault. Why not begin with a German car from the early 90s? BMW? Mercedes? those would keep you busy finding actual faults in the design where things weren't engineered to be reliable. Japanese engineers, especially with this flagship platform for Toyota in the late 80s-90s were some of the best in the world and with you picking it apart like they didn't take any consideration into safety, design and functionality is very disrespectful.

 

First, I don't understand why you don't understand...
Second, a car is an inanimate object so being disrespectful requires a sentient being on the receiving end.
The unfortunate reality with this automobile design, as well as countless others is that fasteners were an afterthought...
While this vehicle was not prone to rust as others in its class, certain body fasteners used was specified to facilitate volume production.

The transmission crossmember fasteners are a case in point.

The front and rear bumpers, in my opinion, are another.

The fact that Toyota elect to fortify current models to improve torsional rigidity, thereby comfort and handling, is enough.

Meanwhile, feel.free towards contributing to the project