i think a lot of us that have 2wd trucks and live in areas that accumulate significant amounts of snow throw weight in the bed to get better traction.

this winter i have got (4) 50 lb. sand bags in my bed, positioned over the rear axle (where everyone often recommends).

knowing something about forces and statics, i wonder if the weight would be more efficiently used if it was placed at the back against the tailgate though. here is the reason why (note this is not my truck, and i just assumed some distances for the calcs):

#1 - weight above rear axle:


by summing the moment at the front axle, the reaction at the wheels (R1) = (10' x 200 lbs.) /( 10') = 200 lbs.

#2 - weight at the rear, near tailgate:


by summing the moment at the front axle, the reaction at the wheels this time (R2) = (13' x 200 lbs.) /( 10') = 260 lbs. so by moving the weight farther back you are increasing the rear traction advantage you have. it would also take 60 lbs. off the front end though (equilibrium of forces, reaction at back + reaction at front = weight applied of 200 lbs), so you could lose a little front end traction (probably insignificant because of the weight of the engine, you have more then enough weight over the front wheels).

however if the back end does slip out, it will have more rotational momentum and speed due to the weight being all the way at the back.

 

yea my dad told me the same thing

 

You going for engineering? I'm impressed, never thought I'd see statics on Ranger-Forums! Lol

Although, the drawings weren't impressive

Moving the bags to the back does does transfer more weight from the front wheels to the back wheels, by creating an imaginary moment arm. And you were also right about rotational momentum. However, I'd get a few more sand bags anyways In my old 2wd I think I had 6 60# sand bags.

EDIT, and I'm sure Sully will be thrilled to see his truck as the "background" for these drawings haha. I own those wheels now!!!!!!!

 

This is precisely why I recommend not adding it at the very rear, also with enough weight positioned behind the rear axle you can cause a slight amount of leverage to reduce the weight on the front wheels as well. Nice work on the calculations and thought process.

EDIT - You already calculated the reduced front weight.

 

For weight in the back of my 2wd I have:

A shovel
A sleeping bag
A card board box
2 Tie downs

And it is scattered throughout the bed.


LOL But I used to put 4 80LB bags in the bed on the axle.

 

ha yea i am a structural engineer. and NOT a professional Paint artist lol :)

thieved the pic from cardomain. hope the owners okay with it, i grabbed it because its a sweet truck!

 

Yeah He'll be cool with it. I actually have those wheels and tires., which reminds me I REALLY need to post pictures!

Cool to know that you're an engineer, how old are ya?

 

I was really interested in this till I got to "by summing the moment at the front axle, the reaction at the wheels."

You totally lost me with all that math stuff.

I usally throw 3 concrete blocks in the back over the axle. They are 16" x 16" x 4" thick. I weighted them at work each one weighs different anywhere from 90 -100 pounds

I have never had problems getting traction. I recently switched my axles out and I'm waiting some snow this year to see how it works with the new axle

 

I haven't had any weight at all in the back of my truck so far. I really really need to get some in it, I'd need 4hi alot less, the rear end kicks out oh-so-easy with the torsen l/s.

 

yeah i had 4 50lb sandbags in the back of my old F-150 it had a goosey rear end in the wet... and it seemed to help a lil bit...

 

i had 10 cinderblocks in, hence HAD. i think that was part of the reason i went off the road. the back end started to sway, and all that weight helped it, and makes it harder to gain control of again. no more weight for me.

 

You are 100% correct.

May I remind you that while it adds traction while you have it, it hinders traction once you brake it in a corner and will effectively add to your *** end slinging around (laws of inertia!)

But I'm a florida boy so I dont know if the risk is worth the reward.

 

That was pretty good, reminded me of the CE classes I just finished, but I agree with you. Do you have a lsd or are you running an open diff (like me)? The funny part is, I have 280 lbs all the way back (4 70 lb sand bags) and sometimes I still can't get out of my driveway

 

i am 28. graduated from Purdue in 2004. yea post pics of your truck! looks awesome too from your avatar :)

heres my truck:


wheels are getting painted black this spring (already did the centercaps)

i was going to get a 4x4, but my parents had this truck (a 2wd) as a 3rd vehicle that didnt get driven often, and were looking to get rid of it. i knew they took care of it, plus they let me buy it from them interest free :)

next fall i am going to get a decent set of A/T tires, think that will help a good bit.

 

Here are the pics I posted the other day....






You should definitely paint the wheels black, and buy some 31x10.5x15 BFG A/T's! That's what I've got on my 98 2wd:

I think it looks good..

I think you should paint those wheels black, and get the 31x10.5x15 BFG A/t's, they'lll fit. Plus, they're AWESOME tires, in snow, rain, etc. Go white letter out too. They'd look awesome on your truck, I totally promise, esp with the black wheels!

 

great trucks!

those tires would be pretty mean :) dont want to worry about the speedo being off a lot though.

 

You don't have to worry about it being off much, I think mine was MAYBE off 2-3 at 60, checked that with my GPS.

 

I have always put the weight on the back. I ain't a math guy. :)) I have never run into a dangerous light front end from it (shocks do some countering to this). The one thing your calculations don't take into account is when she breaks loose. The extra weight is at the outside of the arch. When your rear end breaks loose you will understand what I am talking about. My fix for this is practice in an empty snowy parking lot and training myself to use my brakes, throttle and steering to counter the effect. There have been several times over the years when I used my brakes to pull the front end away from the guardrail and then used gas and steering to bring the rear end over then I just kept going down the road.

Nice job on your calcs. :)

 

When I used to put weight in the back, I would put it against the front wall behind the cab. This gave me the weight without adding too much to the spinning momentum.

 

^^^ thats a good point i had my 4wd truck fully loaded with firewood saturday when we got 8 inches of show and it helped me get around better with 4wd. but it also was alot harder to stop and turn and all that

 

Wow, and to think I'd NEVER see any of that again!!! LOL

Now those are the type of problems we should of had in school, but noooooooooooo, we had to worry about cantalever, rotational, and friction forces on plain objects. LOL

I'm a Civil Engineer, graduated in 03. One thing I gotta hand to the Mech guys is all that math you gotta do. I couldn't stand all those math courses.

Pretty surprised you even thought of this though........but as stated before, the more weight behind the rear axle, the less weight being applied on the front wheels, where you want weight so you can steer. As much as it may sound good on paper, weight should be placed directly over the rear axles (because that's mainly where we need it, to keep that *** end plated for traction.)

 

Civil engineering eh? Didn't you have plenty of statics courses to take? I LOVE statics, everything about geometry, etc. I thought Civil was geared more towards that?(Bridges, etc.) I personally love the mechanical side of it all though.

 

I don't put any weight in my truck. I slip and slide around a little bit, but I'm always able to get where I need to go. The roads around here are kept plowed and salted most times. You just gotta know how to drive in snowy weather.

 

I usually just let whatever snow falls in the bed ,stay in the bed, that's more than enough weight for me.

 

Whatever you place in the bed for traction, please make sure that it is not prone to load shift - that can be extremely dangerous - nothing like a couple of hundred pounds of stuff slamming around in your bed under acceleration, braking or turning, or just bouncing around.

Can't argue with the logic or numbers in your calculations; further back, the weight may well give you better traction, but will have a greater effect on handling, as you noted - practice driving in an empty snow covered parking lot if that's how you want to place the extra weight.

Weight over the axles gives the extra traction with the weight directly over the contact points with the road (the tires), and probably offers less disruptive changes in handling characteristics, though, now that I think about it, close to the centre of the vehicle may be more "neutral" in a handling sense; and, now that I think about it, "directly over the axle" may also be a legacy of how/where we place/balance loads on single axle trailers; and, with a nod to traditionalists: "That's the way it's always been done - or so my pappy tells me!"