[paragon]

If Gen-Right can make one for the TJ that fits in the rear frame rails and has some serious protection and carries 31 gallons of fuel why can't we have one for the JK? I've asked Gen-Right and they said they have been asked by DC to not build a tank for that location. However if we all send an email asking for a larger capacity heavily protected fuel tank to fit in the traditional TJ location maybe, just maybe they will build us some. I'd gladly loose that little trunk area for 10 or more gallons of fuel set in the middle of my JK and with some serious protection.

It's a safety issue. If you get rear-ended hard enough by some idjet, the fuel cell will compact and likely cause a fire in an otherwise survivable crash.

Placement of the fuel cells in vehicles have become a bigger issue due to a few lawsuits where someone sued due to a fire resultant from a crash. Notably GM trucks where their saddle-bag tanks were on the outside of the framerails and the multi-billion Dollar Chevy Malibu lawsuit where the fuel cells were deemed to be too close to the rear of the vehicle.

 

[paragon]

I think plastic can still be "welded", but I don't think I'd want to risk on the gas tank.

I've seen those plastic "welders" and have considered buying one. Especially as bad as I am about chopping stuff up. But my artistic skills are really too lacking to make use of one.

 

[paragon]

Agree,...when I wheeled at Rausch, the thing that stopped me the most was being high centered on the Gas Tank Skid, so I would anticipate a hit on the tank & use a dab more skinny pedal to go up & over. If that tank was 2" farther up in, that would solve a lot of our problems, and an aftermarket Skid wouldn't even be an issue. At this point I was using the Skid as a Slider all day long. An aftermarket Skid of that size would weigh a ton, because I know my "Skidrow" Engine Skid is pretty heavy at that size, we all would need Hemi's installed.. I would take the reduction in capacity(thinner Tank) for the tank to be recessed 2".

I'll preface to say that I don't have my JK just yet and certainly haven't wheeled it. But, honestly, regardless of what you do, you are going to use something as a slider. You are going to belly up on stuff no matter what, because you will be trying different obstacles due to the different abilities offered. So if you were to change it up, you would likely just be doing something you couldn't do before.

What appears to me to be most advantageous is a tank that is shorter in the front and taller at the rear and slightly longer. It is now high in the rear anyway, but if the bottom front of the tank was tucked up further and the tank itself was a little longer, it might accept the same amount of fuel but have a higher clearance that at the most critical point.

The rear part of the tank hanging low is not as critical as the forward portion since it's getting closer to the rear tires and you have the Dshaft dropping anyway.

 

[paragon]

I built a custom tank for my Isuzu. It held over 40 gallons of gasoline. It was mounted in the back and between the frame rails. I never had an issue with this arrangement. Couple this with a solid steel bumper, an excessive skid plate for the already 1/4" thick gas tank, I don't think any vehicle on the road today could puncture my gas tank, unless they were traveling at missile velocity or were significantly larger than me such as a 25 ton semi. Then at that point I think survivability would be a non issue as the difference between being compacted into a 2'x3' square verses being compacted into a 2'x3' square then catching on fire is mute point.

I say let everyone else crumple.

Besides, I'd much rather have the weight of the gasoline centered over the middle of the vehicle than only on one side such as is the case now with the factory tank.

Plus added weight just behind the rear axle will add down force on the rear axle and provide more traction on the rear tires.

And yes, excessive weight the further away from the rear tires could make it easier to flip over backwards, unless you provided some sort of rear stinger to stop you from flipping so easily.

I'm going to be building my rear tank as a custom project. I'll be able to hold more gas than all of you and go on longer desert excursions without the need to have more gas cans.

So in other words, you haven't convinced me this is a bad idea yet.

Well, personally, I'm not here to convince you it's a bad idea. But I think it is a bad idea.

A fuel tank is not going to tuck nicely behind a fabbed rear bumper and the dynamics of a crash are not simply about linear bumper to bumper impacts. A fuel cell hanging low in a potential impact area has been shown to be a bad idea, through lawsuits.

You will be driving a lifted vehicle. IF you try to build a cage to protect the cell from a crash, you are then impacting the departure angle. If you simply utilize a typical bumper, a car is likely to make underneath the bumper.

But on to the point PhilD brought up, which is what I would also consider. It's not as much about flipping over backwards. It's about maintaining a F/R weight balance for stability, traction, etc. But, the CoG will be changing dramatically which will throw the suspension dynamics off which will likely mean making adjustments to the suspension to accomodate the change (if you want to maintain the the suspension dynamics). A question would be how big of a change to the suspension would have to be made to make the Jeep still work.

I don't know... if it was a trail-only rig, it might be different. But just a little food for thought.

 

[paragon]

I agree with your logic, but again this doesn't convince me but actually reinforces (in my mind) the justification for having it in back.

The 2 heaviest pieces underneath the JK is the engine and a full gas tank. The engine is right above the front wheels. Placing the tank in the old muffler spot will have the tank just behind the rear wheels. Plus it will be centered over the left and right side of the vehicle as opposed to one side that makes the left and right characteristics different from left to right. It is easier to roll on a side hill if the down side is the passenger side vs the opposite.

Having the tank in the back opens up a more likely chance of it being hit in an accident where you are rear ended. However my tank has a significant frame mounted skid plate plus the tank it self has a gap between the plate and tank and the tank is 1/4" thick. I have dropped off of 4' ledges onto my gas tank and have only managed to merely mar the skid plate and in one occasion put a crease into the skid plate. However nothing yet has penetrated through to the gas tank. So this isn't the average joe factory skid plate that yes if my tank was a factory flimsy pie tin and plastic tank I would have damaged the tank.

Now using the same situation, so now with a low hanging side mounted factory gas tank you are just as vulnerable from a broadside impact such as those that take place at intersections.

I'll take my heavily reinforced rear mounted and protected tank with a skid plate/super slider any day over the way the factory tank is currently mounted.

Just my 2 bits. Again I'll let everyone else crumple.

We'll disagree on the "safety" stuff as there's too many variables to keep in play.

But, my point on location is that your suspension setup will have to change. When setting up a suspension the CoG is calculated so that the instant center, anti-squat and all the other junk can be dialed in. You are significantly changing that by moving all of that weight, therefore you will need to re-tune your suspension to accomodate the change.

And I really think I am simplifying it quite a bit through my ignorance.

 

[paragon]

Good discussion...
Not to butt in... but how is the COG changed all that much by shifting weight? By the fuel consumption the COG changes as the weight of the gas is lessened, coupled with the fact that you maybe carrying tons of gear and spare part in the back behind the seat (my spare **** and tools = 30lbs). Take along some camping equipment... This wouldn't require suspension mods.
My JK squats a little to the side when I fill up already.
More info please...?
I have been on the trail with several loaded JK's and they only squat a little.
Wouldn't the Airlift 1000 air springs remidy this squating problem?

Maybe someone with better articulation and better understanding of suspension dynamics could better explain it.

But here is a link to an article that was written by the guy that owned Nth Degree, Jim Frens, and it might articulate the effects of some of what you are saying.

http://www.jkwheeling.com/viewtopic.php?f=6&t=38