Lowering center of gravity without lowering ride height

So as I continue to pointlessly screw with the Jeep, I'm left wondering: what things can I easily do to lower its center of gravity without having to lower its ride height?

The suspension isn't conducive to significant lowering without giving up travel, and I do take advantage of the ground clearance at times, so I'd like to keep the ride height where it is.

As far as things I've already done to help the COG, I stripped the roof rack off it (not very much weight, but it's at the highest possible point on the Jeep) and I've been adding skid plates (adds weight down low). I've got some new motor / trans mounts on the way that'll lower the entire drivetrain a 1/2" relative to the body (mounts needed replacing anyway), which will just put the drivetrain closer to the skid plate that'll ultimately end up under them (so I don't give up any clearance in the end). The ABS doesn't work, so when I have time one of these weekends, I'm going to re-route the lines in the engine bay and delete the ABS pump (takes a few pounds off the front end, and it's mounted pretty high in the engine bay).

What other reasonable things can be done to move weight down lower on this thing? I'm not too concerned with total weight on this thing, although cutting weight is nice if it's not a big sacrifice to do so.

Drop the battery down low. Lower seat mounts. Steel wheels.

Lead TruckNutz.

I've been thinking about the battery, as that's ~45 lbs all the way at the front of the Jeep and up pretty high on the nose. Any good suggestions for where to move it to? I might be able to just move it down a bit and keep it in the same general area, as the thing isn't terribly nose-heavy anyway.

For the seats, I do plan to pull the seats out and see if there's a way to re-mount them a bit lower without giving up the power seats (which admittedly weigh a ton). Even with the driver's seat all the way down, I have to hunch a bit to fit with a helmet on (tall torso).

Are there speakers mounted in the headliner high up in the cargo area? Move them down.

Spare tire?

Sunroof? Glass is a lot heavier than sheet metal and a sunroof mechanism is really heavy.

Edit: wheel spacers to give you an effective wider track. Same effect as lowering your actual COG.

It does have a sunroof, unfortunately. I haven't looked into just how heavy it is or how much work it would be to delete it. I do pull the spare out for rallyx, etc. as it sits standing up on the side of the cargo area (up kinda high). And that's a good point about speakers. The soundbar over the back hatch with speakers in it does weigh about 10 lbs (pretty much the weight of the speakers, the piece that holds them is fiberglass and weighs almost nothing).

EDIT: As far as wheel spacers, I'm running a set of 3/4" spacers all around already. The wider track is good and it also had the benefit of fixing a scrub radius problem that developed when I added more negative camber to the front end (apparently having too little positive scrub can make the steering pretty unstable on these things). If I want to widen it more than that, I'll have to start attacking the fenders to still fit 255s under it without them hitting.

Window glass is heavy. Replace with lighter substitute material or just leave them rolled down all the time?

Where to put the battery is best answered by the guy with a Jeep to reference :) We put them under the trunk floor in some of our builds. If you're going off-road, make sure it's armored.

Wait, it's a jeep, with power seats, that you drive with a helmet on.

WTF is this vehicle and what are using it for?

What is the "before and after criteria" to determine the value of all this?

gearheadmb wrote: Wait, it's a jeep, with power seats, that you drive with a helmet on. WTF is this vehicle and what are using it for?

It's mostly a fun thing to screw around in that still serves DD duty (hence keeping the comfy seats), but I do rallycross it. It's not exactly fast around a course (and certainly not competitive running in M4), but it's not usually the slowest thing out there and it's pretty fun in the dirt (the suspension isn't very stock and it rotates pretty well when you want it to).

NOHOME wrote: What is the "before and after criteria" to determine the value of all this?

I don't particularly have criteria for what I want out of it, but it's one of those "if I can make it better, I might as well" kind of things. Especially when I'm already replacing a part and can do it a little differently to make it work better (like the lowered motor mounts, which was an extra $20 to customize the beefed up poly mounts I was already buying).

In order of impact:

1. Engine/transmission
2. Driver
3. Fuel tank (full of course)
4. Battery
5. Window glass

That's the big parts, or move dozens of little parts to have a similar effect.

The real answer is that a given part's impact upon the car's CG is related to both its weight and its distance from the existing CG. For example, while that sunroof isn't all that heavy, since it's so high up, its effect is probably on the order of the fuel tank on the above list, since the fuel tank is so low and its so high.

Go nuts. Section the body.

could you remove the seats for competition and put them back for DD use? Should not take any longer than changing wheels

mad_machine wrote: could you remove the seats for competition and put them back for DD use? Should not take any longer than changing wheels

I do usually fold the rear seats flat, as that drops their weight down a bit. The whole rear seat assembly is no more than 50 lbs though, and 70% of that is in the seat backs (which have to be un-bolted and are a little annoying to remove / reinstall, unlike the quick-release seat bottoms that come out in seconds). Plus, if I'm taking a second set of tires to rallycross to swap on arrival, I need to at least bring the rear seats, as I need the larger cargo floor they provide when folded flat.

Bolt a metric berkeleytonne of weight to the lowest point of the floor boards. Technically it'd work. Not ideal though.

NickD beat me to it.

Your best bet is to probably go with the Mazda Gram Theory and nibble little bits of weight from up top wherever you can. Look into lightweight batteries, etc.

Convertible. Every girl likes convertible jeeps.

interesting thought for you... you want it lower for race duty.. how about smaller diameter rims and tyres just for that purpose? Should lower the jeep a couple of inches and hopefully make the rubber a bit cheaper

There is a yellow (faster) one too,

The smaller tires are an interesting thought... I've been looking at taking one of my extra sets of wheels and dedicating them to rallycross with some new tires (for when there's no snow on the ground, when there is, I just run on my snows), although it seems like finding good, meaty tires that'll work well in the loose dirt and bits of mud we tend to get is going to make going shorter than the current 29" tires a bit tough.

I did start talking to a few other Jeep guys about the sunroof delete idea. That's definitely something I'm going to look into a bit deeper this spring. Replacing the glass with a solid panel and removing the track should cut about 40 lbs, as best I can determine. Maybe I'll just go with a lexan panel and keep the sunroof headliner so I can still slide the inner panel back and have something there other than metal (saves me needing to find a non-sunroof headliner in the right color as well as the different dome light setup, etc.) This would also be a good time to shave down the mounting bosses for the roof rack so that I can remove the lower mounting plates for it (which will remove another 6 - 8 lbs in addition to the ~12 lbs I got from pulling the rest of the rack).

I like that battery box in the floorpan idea... I'm definitely going to have to do some measuring for that. That'll help out the front / rear weight distribution a bit too.

Oh, and for the bolt a ton of weight to the floorpan idea, I'm already doing that bit by bit... It's called skid plates

If you are going to go to all this work, I would think that being able to gauge the success would be half the fun.

So, just for E36 M3s and giggles, why not measure the center of gravity before you start and then after you finish. It's not that hard to do.

http://www.how-to-build-hotrods.com/center-of-gravity.html

I really should see if I can borrow some scale and measure it. Based on info I've found online, the best guesstimate I have currently is that the COG should be around 28" off the ground, give or take an inch. Getting the COG down an inch or 2 shouldn't be too hard, I think (and there's the little functional tricks to help, like running with the fuel tank full, as it's down pretty low and holds 23 gallons of ballast). Going down much more than that without chopping up the body, gutting the interior or lowering the whole thing might be tough though.