Weight Distribution

[badmatt]

Well, I have been thinking about moving some weight around in my truck.

I'll be right around 2900-3000lbs final weight.

I have been thinking about mid mounting a lot of the weight such as the fuel cell, fire system bottle, battery, dry-sump tank to right behind the cab to keep as much weight centered in the vehicle.

Or am I going the wrong way with this and should I place the weight around the vehicle such as behind the rear wheels

Open for constructive criticism.

Matt

[Flash68]

I would think you'd want as much weight centered and low as possible, assuming enough weight was over the rear axle for the power level to be managed by the tires.

2900-3000 lbs with your power level is gonna be pretty sweet.

What are your plans for this truck? Road course, autox, street, drag --- a little of each?

[Sieg]

I believe I saw one of the new-gen auto-x trucks with the radiator behind the cab in a shroud ducting air from underneath with fans on the top side. Anything you can do to keep it low and centralized will benefit chassis balance/handling.

[badmatt]

Originally Posted by Flash68

I would think you'd want as much weight centered and low as possible, assuming enough weight was over the rear axle for the power level to be managed by the tires.

2900-3000 lbs with your power level is gonna be pretty sweet.

What are your plans for this truck? Road course, autox, street, drag --- a little of each?

all of the above except drag racing.

thats what I was thinking keep it all centralized.


Seig,

the rad will not be going in the bed, I already have enough tube running under the truck. and I still want to stick some things in the bed. LOL!

Matt.

[byndbad914]

IMO you want to keep the weight centered and low as others have said, but you want to bias the distribution to the rear. I am not sold on 50/50 but my C6 Grand Sport Vette handled really well. Most of the high end cars are 45/55 up to what many consider the optimal #s of 42/58 (Ferrari 458/Veyron/Gumpert). Only the "911" gets over 60% rear that I am aware of and that car is a whole 'nuther discussion in itself.

My mid engine car is frankly pretty darn fast on the track these days and I am at 43/57 weight right now like an Aventador. The bulk of the transaxle is behind the rear wheels (trans behind the diff, Corvette is trans in front of diff), and the radiator is in front of the front wheels, otherwise all other weight I did my best to place between the wheels.

Key to a bit extra rear weight is that it is easier to put wider tires back there (since they don't have to turn) for more lateral grip to carry the weight through the turns, and a road race car typically doesn't transfer weight like a drag car does (else when you hit the brakes going into a turn all hell would break loose) so having the weight statically biased there helps plant the aforementioned wider tires for traction out of the corner.

[badmatt]

OK so 22 gallon fuel cell mounted into the rear floor, like thats roughly 40lbs of fuel cell and 200lbs of fuel. mounted behind the rear axle and at the same level as the axle center line.

Does that sound like it would help do the trick? i can also stick the battery down behind the rear bedside to match.

Matt.

[Sieg]

Don't forget to factor fuel consumption....unlike coolant or battery weight.

[badmatt]

Originally Posted by Sieg

Don't forget to factor fuel consumption....unlike coolant or battery weight.

What 22 gallons isnt enough? hahah

[byndbad914]

if you can, it would be best to mount two cells right in front of the rearend to obviously leave room for the driveshaft to get through, and that would be the best placement.

that said, it is more costly and sort of a PITA, so behind would help. Just keep in mind that Porsche "911s" are tail happy (I quote that because they are 911/993/996/997/etc but all look like a "911" to the lay person) but don't necessarily spin. They will hang the rearend out and drift like crazy with the rear mounted engine v. a mid engine car. The mass moment of inertia is different (people call it polar, I say that is a misnomer, it is mass we are talking about) - all the mass at the center makes it spin like a top, all the mass at the ends makes it hard to spin, but also makes it hard to turn and essentially the car doesn't plow or oversteer, it just slides off the track. The main reason for keeping mass centered is to get the damn thing to turn

I plan to strip the 914 in my avatar and I am going to build a 66 Nova with all of the parts using the transaxle in the rear with a modified Corvette torque tube to get better weight distribution. I have a single, 17gal cell right now and I am going to seriously consider getting two smaller cells and place them in front of the rear tires, close to the torque tube, where the rear seat would be. That is the right thing to do from a track standpoint. It is an crappy thing to do from a street standpoint - a nice finished area there with a stereo speaker/subwoofer setup I can remove for the track and the17gal cell in the trunk over the transaxle would be better. Will have to pick my poison when that time comes.

Lastly, fuel is an interesting thing because it is dynamic weight - it is always changing, and in your case, significant at around 132lbs (6lbs/gal). Burn off some of that and then mentally compare that to around three or four 28lb race batteries on springs flopping around in the rear. Cell baffling helps but that fuel is moving period, so maybe on stiff springs The lower you put that, minimize slosh, so forth like two smaller cells in front of the axle would do is actually way better because as you burn fuel you get less affect on your handling. Mount a big tank and burn off fuel and it will affect the handling in a greater fashion.

[Sieg]

Originally Posted by badmatt

What 22 gallons isnt enough? hahah

Plenty for a Prius motor.