Why adjust torsion bars?

[mini696]

What are the advantages and disadvantages of tightening up the torsion bars?

[Dexter]

Ahhh, basicaly its the added lift you get from tightening them up as you say. You can tighten them or loosen them to give you more or less height.

[lay80n]

Ummm......to adjust the ride height of your rig.


Layto....

[macca81]

but the more lift you gain from it, the less flex you will achieve

[me3@neuralfibre.com]

but the more lift you gain from it, the less flex you will achieve

That's not true. You are adjusting ride height, not pre-load or rate. Travel id dependent on existing rate, load and bump stop positions.

Paul

[Tapage]

If you adjust our torcion bar in your IFS to gain lift .. perfect you get, but at the same time you loose down travel in your suspension ..

And it means if would never gat again the same up travel .. also it means less hability to copy the terrain .. coz can't drop more.

[Struth]

If you adjust our torcion bar in your IFS to gain lift .. perfect you get, but at the same time you loose down travel in your suspension ..

And it means if would never gat again the same up travel .. also it means less hability to copy the terrain .. coz can't drop more.

Yup, loss of downtrwvel = spinning front wheels = spinning back wheel = loss of traction.

A coupla Lockers will fix that though '

Cheers

[-Scott-]

And it means if would never gat again the same up travel .. also it means less hability to copy the terrain .. coz can't drop more.

Not necessarily. With cranked bars and trimmed droop stops I can still hit stops in either direction, so I haven't "lost" overall travel.

The loss of droop travel will affect ride quality but (given the limited travel of IFS to begin with) it doesn't significantly reduce off-road ability. The increase in clearance under the front cross-member DOES make a difference in off-road ability, which is why cranking the bars is worth doing.

So called "Heavy Duty" torsion bars are another subject - THAT will affect offroad ability. I have the original, 13 year old factory bars, and no intention to change them.

YMMV,

Scott

[Tapage]

cranket torsion bars and trim down stops of course will put you back in the down travel, but how about your bierfields .. ? can support this new angle ?

[-Scott-]

cranket torsion bars and trim down stops of course will put you back in the down travel, but how about your bierfields .. ? can support this new angle ?

Five years and going strong. Mitsubishi IFS tends to cope with this better than most others.

[chunks]

Do you have a steel bar or/and winch?

[mini696]

No winch, alloy bar. :(

[Yom]

Changing the ride height on torsion bar front ends usually creates some interesting handling results if you keep the original torsion bars... I wouldn't do it.

[chops_Drover]

By adjusting the torsion bar you can adjust your ride height. Yes it may not allow as much droop however it allows you to fit bigger tyres.
It also helps even the car back out after fitting a heavy b/bar or winch.

The standard torsion bar will be the most comfortable ride on road whether it is wound up or not.

However if there is a winch & b.bar etc fitted an aftermarket bar with a higher spring rate will be better suited and probably be more reliable (won't sag & need constant attention).

Oh and if wound up will put some serious angles on your cv's. This causing regular cv boot tearing and in some cases cv breakage &/or serious wear.

[me3@neuralfibre.com]

Std bars not always most comfortable. Ones in a mates Mitsubishi Van (4wd import) are too soft. Horrid ride as bottoms out al lthe time espite normal ride height. Kills shocks as they do much more work trying going top to bottom all the time.

He'll replace them one day.

Paul

[zagan]

but the more lift you gain from it, the less flex you will achieve

That's not true. You are adjusting ride height, not pre-load or rate. Travel id dependent on existing rate, load and bump stop positions.

Paul

Pre-load is ride height.

travel would depend on the bar's strength.

[-Scott-]

but the more lift you gain from it, the less flex you will achieve

That's not true. You are adjusting ride height, not pre-load or rate. Travel id dependent on existing rate, load and bump stop positions.

Paul

Pre-load is ride height.

No.

By "cranking the torsion bars" you're adjusting the angle of the arm at one end, which adjusts the angle of the arm at the other end. The change in the "twist" (and therefore the tension) in the bar is nothing. (The tension in the bar supports the vehicle's weight. To increase the tension requires an increase in weight. Where has that weight come from?)

Ride problems come because people adjust them too far, and lose droop travel. The wheel can't drop into holes, so the vehicle drops instead = terrible ride.

Edit:

travel would depend on the bar's strength.

Yes and no. All the torsion bar IFS vehicles I've seen have bump stops to limit up travel, and droop stops (sometimes, the shock absorber travel) to limit down travel. The bar would typically need to be very stiff before it limits ultimate travel.

But a stiffer bar will cause the body to lift further for any given amount of wheel lift (i.e. size of rock) - effectively, it will take more weight off the other front wheel, which (IMHO) is NOT a good thing for an IFS fourby.

[ADEM]

just for curiosity's sake, how much cranking of the torsion bar will start giving adverse effects? just wondering, because my navara D22 that i just bought has the normal front sitting lower then the rear that alot of trucks seem to have.

And obviously id love to even this out for the short term, till i can afford some actual decent suspension

[HotFourOk]

just for curiosity's sake, how much cranking of the torsion bar will start giving adverse effects? just wondering, because my navara D22 that i just bought has the normal front sitting lower then the rear that alot of trucks seem to have.

And obviously id love to even this out for the short term, till i can afford some actual decent suspension

As said, winding up your torsion bars will be not much different to your 'decent suspension'... when you fork out heaps of dollars for it.

You will see adverse effects when your suspension droop is gone.

Each car is different... but every mm you wind up is a mm you lose in wheel drop. Just find a good balance.

[HotFourOk]

Changing the ride height on torsion bar front ends usually creates some interesting handling results if you keep the original torsion bars... I wouldn't do it.

What type of 'interesting' results? Please enlighten me.

[spongerx]

Let's throw in some ball joint spacers to the discussion.

Lift, increased up travel, no loss in down travel but completely fawked suspension geometry.

I used some to level the nose down attitude of my Hilux and left the torsion bars at the stock setting. Works pretty well offroad. Rip outer CV boots a lot quicker now tho

[Yom]

Changing the ride height on torsion bar front ends usually creates some interesting handling results if you keep the original torsion bars... I wouldn't do it.

What type of 'interesting' results? Please enlighten me.

Ok I'll have a go.

When you change the height of any suspension setup you'll be changing what was considered to be the standard operating range of the suspension. Straight away you've changed the what the manufacturer probably worked out to be the best compromise between ride height, handling and in the case of 4x4's and FWD vehicles, drivetrain wear. (i won't start throwing around terms like camber, castor (including dynamic of both) roll centre, centre of gravity and how they related to dive/lift/squat, load transfer etc as its fairly complex and not of much interest to you lot as you're not driving sports cars...).

The main thing which simply changing out torsion bars won't achieve is related to your steering. And its not easy to change but basically due to the inherrant design of SLA double wishbone suspension any change in ride height will affect downtravel and/or uptravel distances along with steering angle geometry (yes on the majority of SLA double wishbones your steering alignment changes with compression/extension of the wheel. D21 owners in particular will know all about this with bump steer).

This is where the majority of the interesting handling will come from (unless you're racing, say paris dakar style, in which case you're not going to be just winding up the torsion bars anyway).

There's also the point that youll be putting loads on the standard torsion bars they werent meant to cope with but thats moot as its usually the shock absorbers which let you down before the bars (which DO wear out).

But yeh, it will vary between different types of vehicles. I've got first hand experience with the D21 setup and it is *pathetic* to say the least. Take a crap design and convert it to right hand drive and you have the D21. Don't know about the Mitsi's but I would imagine mitsubishi have an exceptionally road friendly design - at the expense of wheel travel however.

Cheers

[Hekta]

Ok I'll have a go.

So what your saying is, you need to get a wheel alignment after you wind up the torsion bars ?

[Yom]

Ok I'll have a go.

So what your saying is, you need to get a wheel alignment after you wind up the torsion bars ?

Made an edit as I wasnt happy with one or two things.

But no, a wheel alignment won't change the fact that you've changed the angle of every single suspension and steering part which (depending on how suspension was setup initially) may change the dynamic toe or camber to the point where it may affect driveability.

Another thing I didnt bring up is that depending on how the lower arms are mounted it can affect ride quality by transferring shock to the chassis rather than the shockie/torsion spring. This will relate specifically to how high you lift it.

[MightyMouse]

And just to add a little more, if you add more tension to the bars the control arm will no longer be parallel to the ground but angled downwards.

Working out the geometry, you end up with a shorter effective lever on the bar and therefore a stiffer ride. The effect is negligable when near parallel but gets progressively greater as the lower arm becomes more angled down.

And before anyone objects, do the calculations.......

[me3@neuralfibre.com]

It's also worth nothing that every suspension design on the planet is a tradeoff between all these factors. As are the different steering designs.

Changing the ride height is in no way more wrong than installing spring spacers in a car, it's an acknowledgement of a particular deficiency (clearance) and a tradeoff gaining that clearance with other factors.

In my surf, the tradeoff was well worth it for the driving I did. In a mates D21 Navara, the wound up front end tore itself to pieces regularly. He was still happy with the tradeoff, but ended up selling the vehicle as the capabilites vs overhead became excessive.

Get off the case. Live axle gives more travel than IFS, but IFS is better on road. Airbags vs Coils. Rack n pinion vs rod steering. Jeep rod steering (Toe variability) vs Toyota (bump steer bu consistent toe). Ackerman angles. Ani Dive, Anti Squat. Roll Centres, panhard rods, watts linksand whatever you call that thing Disco's run. CV angles. Uni Joints vs Double Cardans and angular velocity compensation. Rotational harmonic frequencies. Solid vs 2 part Flywheels. Chassis harmonic dampers on patrols. Suspension harmonic dampers on Discos. Every singel one of these is an aknowledgemnt of limitations and choices.

Crank it a bit, keep it reasonable. The manufacturers make the choice for the masses, you don't have to agree with their choice.

PS. Lube the threads first so you can turn it back if you want, and jack the car, then crank it takes the load off the thread. Threads tend to be rusty and strip.

Paul

[-Scott-]

And just to add a little more, if you add more tension to the bars the control arm will no longer be parallel to the ground but angled downwards.

Working out the geometry, you end up with a shorter effective lever on the bar and therefore a stiffer ride. The effect is negligable when near parallel but gets progressively greater as the lower arm becomes more angled down.

And before anyone objects, do the calculations.......

I'm not going to argue about the reduced effective lever, but I want to know how you're adding more tension to the bars? Adjust the angle of the short lever at the chassis end, and the long lever at the control arm end changes angle too. To increase tension in the bar, there needs to be a change in angle of one wrt the other.

By your theory of reduced effective lever length, if the wheel carries the same proportion of vehicle weight, with a reduced lever length, there's LESS torque being applied to the torsion bar (same force, smaller radius.) That doesn't sound right to me, but I can't spot the flaw.

Give me some more time...

[chikoroll_]

just for curiosity's sake, how much cranking of the torsion bar will start giving adverse effects? just wondering, because my navara D22 that i just bought has the normal front sitting lower then the rear that alot of trucks seem to have.

And obviously id love to even this out for the short term, till i can afford some actual decent suspension

jackaroos have are strictly 2" lift limited (unless you go for the diff drop)
it's not a biggy considering that tritons can get more lift... but the reason the tritons can get more lift is cuz they are stock standard 4" lower than the jackaroo's
(2003 triton, 170mm clearance)
(1998 Jackaroo, 270mm clearance)

compared against my cousins triton 2 weeks ago


the reason your navara is angled, is cuz it's a ute.... it's designed to carry a load... when it has a load the back will droop

[Yom]

And just to add a little more, if you add more tension to the bars the control arm will no longer be parallel to the ground but angled downwards.

Working out the geometry, you end up with a shorter effective lever on the bar and therefore a stiffer ride. The effect is negligable when near parallel but gets progressively greater as the lower arm becomes more angled down.

And before anyone objects, do the calculations.......

I'm not going to argue about the reduced effective lever, but I want to know how you're adding more tension to the bars? Adjust the angle of the short lever at the chassis end, and the long lever at the control arm end changes angle too. To increase tension in the bar, there needs to be a change in angle of one wrt the other.

By your theory of reduced effective lever length, if the wheel carries the same proportion of vehicle weight, with a reduced lever length, there's LESS torque being applied to the torsion bar (same force, smaller radius.) That doesn't sound right to me, but I can't spot the flaw.

Give me some more time...

Most torsion bar IFS i've ever come across have only had adjustment at the chassis end. In otherwords, more suspension height = more strain on torsion bar. And thats not much as its just tojos and dattos! :p

Never ever laid eyes on the undersides of a Mitsi. I wouldn't be suprised if the mitsi front end is far more complex and better designed than the cheap utility front ends I've come across.

Cheers.

edit: I'm confused. apparently th d21 does have a-arm adjustment but ive never seen it. And it definately does not put any extra strain on the bars themselves if you adjust the chassis and a-arm sides the same amount.

[MightyMouse]

Your reading a bit too much into "add more tension", I was simply ( well perhaps not.. ) meaning wind them up.

Some times the words don't always come out right.....