Whats more important - Weight Balance or Exit Angle?

[MNC]

When deciding on best placement of a rear diff (when going for a custom setup) which would you rate of highest importance?

Moving the diff back gives a better exit angle but worse ramp over angle and places more weight over the front diff (in terms of distribution).

Note when answering this question cutting the rear tub/chassis and/or relocating the engine/gearbox further back is not an option.

I'm interested to hear your thoughts...

[mudlva]

my thoughts

even weight on each axle would be better
ramp exit angles can be sort of over come by aproaching or departing on an angle to the hazard
having even weight per axle will allow you to hang a wheel to a certain amount and and with lockers clime over or past the obstacle with out loosing traction

[coxsy]

plus longer wheel base goves over ramps better and climbs better than short wb

[turoa]

Ive found having a longer wheelbase makes the most difference. Having the longwheel base makes it climb heaps better. Best recipe is low weight and long wheelbase. Even weight distribution is good, but to do that it means you have to move the motor rearwards. A couple of inches of wheelbase wont make much difference if the motor is hangin way out the front

exit angle = who cares. Not often you get caught on it

edit:coxsy bet me to it but how does a longer wheelbase equal better ramp over

[MNC]

Ive found having a longer wheelbase makes the most difference. Having the longwheel base makes it climb heaps better. Best recipe is low weight and long wheelbase. Even weight distribution is good, but to do that it means you have to move the motor rearwards. A couple of inches of wheelbase wont make much difference if the motor is hangin way out the front

exit angle = who cares. Not often you get caught on it

edit:coxsy bet me to it but how does a longer wheelbase equal better ramp over

So sounds like you would move diff back to gain wheelbase for climbing vs. concerns about even weight distribution or ramp over angle?

[MNC]

Interesting as above comments indicate wheelbase is more important (ie move diff back) - although votes are all for even weight distribution (which I would achieve by moving diff forward (or leaving in same place).

I'm a little confused...

[MNC]

plus longer wheel base goves over ramps better and climbs better than short wb

Longer wheel base = worse ramp over angle at same ride height.

You guys seam to rate climbing ability highly which is something I hadn't focused on before.

My truck is going to be pretty high (unfortunately) so maybe the longer wheel base is a good option over weight distribution...

[Fakey]

My truck is going to be pretty high (unfortunately) so maybe the longer wheel base is a good option over weight distribution...

That would be my thoughts on it if its going to be quite high

[niblik]

yup mnc.. tall and short = awful on hills etc.. tippy even..

[Sadam_Husain]

I wouldnt go getting too worried about it coz you'll be able to shift the diff back a bit but there isnt exactually a lot of room to move it back too much on a 40 series, longer is definately more stable

[rokhound]

Interesting as above comments indicate wheelbase is more important (ie move diff back) - although votes are all for even weight distribution (which I would achieve by moving diff forward (or leaving in same place).

I'm a little confused...

Me too, but then I don't think a lot of those who voted fully understand the implications of what you asked.
From the 3 options you gave, exit angle is the most important because it moves the axle back and hence lengthens the wheel base, so thats what I voted for.
Even weight distribution with a longer wheel base is the ultimate setup, but you stated that you didn't want to move weight about with in the rig. With an engine and trans mounted in the front, you are going to find it damn near impossible to gain even weight over both axles. That is why the guys who really rate this setup, build mid mount buggies

[muddy]

In a 40 - longer wheelbase makes a huge difference! When I put 60 series srings front and rear it moved the front forward 40mm and the rear back 90mm. Awesome difference on steep hills both up & down. And 60 series axles are a good thing too to widen the track...

[wopass]

if your engine sits behind your front axle then it is a mid mount

longer wheel base for climbing and decending for sure is awesum!!

longer wheel base reduces your ramp over coxy ask any LWB driver who gets bellied on stuff how that works and this vehicle will not suffer from ramp over problems so dont even worry bout it

weight balance? what for?? this is a bush truck not a fukin A1 GP car...
when your going up a steep hill nearly all the weight transfers to the rear any way even if your engine is up front, its all about the verticle plane and gravity and a bunch of numbers and calcs but the steeper you go the closer to the verticle plane you get so the smaller your total weight footprint is in a single point. gravitational centre and all that shit

exit angle, push the rear axle right to the back to make your wheel base longer and have the back edge of the tyres sticking just past the back of the chassis and tub, perfect!!! but entry angle is more beneficial aim for 100inch wheelbase with the 40 bro, mine came out at 98 and seems to work pretty good (so far?) but 100 would have been better

ohh and with what i think your gonna end up with

AWESUM!!!!

[coxsy]

I know what i mean you clowns figure it out

[Muzza]

if your engine sits behind your front axle then it is a mid mount

longer wheel base for climbing and decending for sure is awesum!!

longer wheel base reduces your ramp over coxy ask any LWB driver who gets bellied on stuff how that works and this vehicle will not suffer from ramp over problems so dont even worry bout it

weight balance? what for?? this is a bush truck not a fukin A1 GP car...
when your going up a steep hill nearly all the weight transfers to the rear any way even if your engine is up front, its all about the verticle plane and gravity and a bunch of numbers and calcs but the steeper you go the closer to the verticle plane you get so the smaller your total weight footprint is in a single point. gravitational centre and all that shit

exit angle, push the rear axle right to the back to make your wheel base longer and have the back edge of the tyres sticking just past the back of the chassis and tub, perfect!!! but entry angle is more beneficial aim for 100inch wheelbase with the 40 bro, mine came out at 98 and seems to work pretty good (so far?) but 100 would have been better

ohh and with what i think your gonna end up with

AWESUM!!!!

Well summed up Wopass

It depends on what your truck is and what you intend using it for but 100 inches is a good lenght to aim for.
I am intending to move the axle back on my SWB GQ but wont quite get that lenght without a lot of work.
The other important thing to remember is the length and angle of your trailing arms. Short arms and/or steep angled ones tend to jack the truck up and do not work nearly as well as longer more flat positioned ones. This applies equally to front and rear.

[rokhound]

The other important thing to remember is the length and angle of your trailing arms. Short arms and/or steep angled ones tend to jack the truck up and do not work nearly as well as longer more flat positioned ones. This applies equally to front and rear.

That is an extremely simplistic statement as far as suspension geometry is concerned, but for most this correct. When you get to working out rear arms, you have way more to consider than length,
http://www.pirate4x4.com/forum/showthre ... nk+dummies.

This is a damn good place to start, and read all of it.

[Muzza]

That is an extremely simplistic statement as far as suspension geometry is concerned, but for most this correct. When you get to working out rear arms, you have way more to consider than length,

I agree Rokhound.
It is not that simple and there are lots of variables. The whole question that has been asked can not be answered by this simple statement " Whats more important - Weight Balance or Exit angle"

[MNC]

... When you get to working out rear arms, you have way more to consider than length,
http://www.pirate4x4.com/forum/showthre ... nk+dummies.

This is a damn good place to start, and read all of it.

Thanks, can you re-post that link cause above is not working.

Cheers,

[Bulletproof]

When deciding on best placement of a rear diff (when going for a custom setup) which would you rate of highest importance?

Moving the diff back gives a better exit angle but worse ramp over angle and places more weight over the front diff (in terms of distribution).

Note when answering this question cutting the rear tub/chassis and/or relocating the engine/gearbox further back is not an option.

I'm interested to hear your thoughts...

It is no use even commenting unless you state " what for "

Trialing , winch challenges , Rock crawling or ordinary 4 wheel driving because each has totally different setups.

The only common things are.

Lightness
Good clearence under diffs and gearbox
Good approach and departure angles

Cheers Richard

[J_Dub]

or just thinking back to most trips that you do and intend to keep doing.. what have you come across more so etc.

i rekon mostly climbing ability and clearances for dropping into shit and climbing out are priority, ramp over aint at the top o the list

[MNC]

It is no use even commenting unless you state " what for "

Trialing , winch challenges , Rock crawling or ordinary 4 wheel driving because each has totally different setups.

The only common things are.

Lightness
Good clearence under diffs and gearbox
Good approach and departure angles

Cheers Richard

OK, set up is for a club truck FJ40 - mainly farm tracks and peat bogs. So I guess out of the options you have listed above it would come under ordinary 4wding - although probabily in conditions similar to that encountered in which challenges.

Seams like longer wheel base (which will also improve exit angle although this does not rate highly) is the key focus when looking at rear diff placement from most of feedback received.

[Bulletproof]

I'll put my neck on the line.

A std FJ40 has 4 basic problems

No approach angle
Too short in the wheelbase
Too Heavy
Not enough ground clearance

Approach angle can be fixed with coils in the front. All trucks need at least 70 degrees or better because there are many little near vertical banks .
Departure angle is not that important as long as you have better than 45 degrees.

Too Short can be fixed by moving the Axle back and as Wopass says wieght distrubution is no problem with a cruiser.

Too Heavy can be fixed by reducing the body and any other things not needed. As well you need wide tyres to spread the wieght

Not enough clearance. You need at least 37 inch tyres because of the 9 inch diffs.

Excessive Ramp angle is not that important if you have diff locks

Cheers Richard

[MNC]

OK - so these are my current solutions to thise listed problems:

I'll put my neck on the line.

A std FJ40 has 4 basic problems

No approach angle
Too short in the wheelbase
Too Heavy
Not enough ground clearance

Approach angle can be fixed with coils in the front. All trucks need at least 70 degrees or better because there are many little near vertical banks .

Have coiled front - Approach angle will be greater than 90 degrees.

Departure angle is not that important as long as you have better than 45 degrees.

Too Short can be fixed by moving the Axle back and as Wopass says wieght distrubution is no problem with a cruiser.

OK, this really is the answer to my question.

When the rear end goes in I'll push it further back to gain wheelbase rather than worring about even weight distribution.

Too Heavy can be fixed by reducing the body and any other things not needed.

My truck is slowly getting lighter all the time - rust is the main cause of this

As well you need wide tyres to spread the wieght

Not enough clearance. You need at least 37 inch tyres because of the 9 inch diffs.

This will not be an issue with the rubber I am running.

Excessive Ramp angle is not that important if you have diff locks

Cheers Richard

Will be running front and rear difflocks. I suspect that ramp over angle will not be an issue for this truck any way - if anything it is too high.


Thanks for all your comments guys, makes the decision making process of this build that much easier.

Cheers

[rokhound]

Richard has hit it on the head. As you sound like you will be going with linked suspension the other major ground clearance issue that all std leaf sprung cruisers have won't be affecting you, and that is the spring under diff. My old 60 series was an absolute pig with these often holding up progress even on 36" swampers (and trust me, 9 years ago these were not a common sized tyre ).
I also agree with who ever it was who stated that around the 100" wheel base is a good place to start.

Now with all this information and a build that has made Nibz look like lightning, get into it

[MNC]

...Now with all this information and a build that has made Nibz look like lightning, get into it

Patience my brother, patience

I do appreciate all the comments and advice. Its better to go into these mods informed about impacts and understanding what it is you are trying to achieve.

At the end of the day I'm just trying to build a fun club truck but I seam to enjoy the build almost as much as the driving (odd I know but I have always been this way).

[Heath]

I seam to enjoy the build almost as much as the driving (odd I know but I have always been this way).

I can relate to that.

[darinz]

Richard said it pretty well.

But if you are doing this then I'd slow down and do a lot more research before comitting to a plan.
I'll say exit angle is irrelevant. Build the wb you want then cut what you don't need off!
Weight distrubution is really important but equally so is weight transfer, anti squat and wheel base.

I guess it depends how much you are cutting things up but I'd start with as high an approach angle as possible. Engine as far back as practical and a wheel base of at least 100" but more like 106 to 112 depending on other factors.
If the truck is tall then I'd go for high antisquat as that will help reduce weight transfer and keep the front wheels on the ground. And also improve high climb ability.
For a tall truck I'd also go with a long truck for the reason Ben talked about above.
Weight is easy, less is more simple.
50-50 weight is idea but don't fall into the trap of putting weight over the back of the rear axle to counteract the motor at the front. (been there done that and created a dog!) It doesn't work in a 4x4. It may do on road etc but not when you have big suspension travel.

If you custom building links and spring mounts etc then I'd make sure you got the truck as low as you posibly can. Axle basically touch the chassis at full compression should be the goal. Basically any way you look at it the lower the COG the better the performance. Sure it effects things like approach, ramp and departure angles but there are other ways of dealing with them. Well maybe not ramp but then everything is a compromise!

[Bulletproof]

What I said on here applies to a Landcruiser and not a hilux.

So I will put my head on the block again.

Hiluxs are completely useless for 4 wheel driving without major mods but when done will out perform most.

Why dont hiluxs perform.

1 Weight distribution is completely wrong for 4 wheeling because they are designed to carry a tonne weight.

2 No articulation because of overload springs.

3 No departure angle because of over hang.

4 Early ones have no power to pull the skin off a rice pudding.

How to fix.

1 Move the front axle forward and add weight behind rear axle.

2 Remove overload springs or fit coils .

3 Raise the level of the tray to 1100 to give a 45 degree departure angle. Also stops floatation in deep water.

4 Fit a turbo or supercharger.

What not to do if you dont want to stuff them.

1 Cut off behind rear axle

2 fit a V8

Cheers Richard

[chevrolux]

Sh!t. Better pull the chevy out then

[rokhound]

Yeah me two. I didn't realise that fitting a v8 would totally stuff my rig, but then again I don't think richards would have a shit show in hell of driving where mine has gone.
I guess it must be a different strokes (or stroking) thing
Hmmmmmm ..........................