Coil Springs vs. Leaf Springs

[OTEP]

I was hanging out at the New Isuzu Alterra Urban Cruiser Thread and our forumer Uncle Nick made a comment on the advantages of the Torsion Bar/Leaf Spring combo of the Alterra vs. the more common all coil set up of the competitors (Fortuner/Montero Sport).

Here is Uncle Nick's take on it:

If you were to use Google for research, you would find that the Fortuner in The Philippines, Africa and India has a poor record for flipping over and giving a very unstable ride.

The Montero is a "copy" of the Fortuner as far as specifications are concerned. Not as many accidents as the Fortuner, but then, not as many on the road (sold) either.

I could not find any complaints about the Alterra handling - moreover no "flips" at all.

This is why, in my opinion;

The Alterra, with smaller diameter wheels, has a much longer wheelbase and a wide track, and is heavier.

Common sense dictates that all other factors being equal, the centre of gravity is lower. It can be calculated, of course.

The Alterra has torsion bar front suspension. This results is almost no front end nosedive during hard turning and braking.

The Alterra has leaf springs at the rear. This means that the chassis is attached to the rear axle unit at four points.

Coil rear spring vehicles are attached at two points only at the rear.

Just follow a coil spring vehicle over a bumpy road as compared to an Isuzu. See how the coil spring units sway side to side as they go up and down! You will never drive anything other than Isuzu again!

On Google, there is a letter (from Africa) about a man driving his Fortuner on a gravel road , too fast. An Isuzu passed him and was going nice and straight at a higher speed than the Fortuner. The Fortuner flipped almost immediately after being passed by the Isuzu. The driver almost killed his mother, wife and kids.

There are other stories - all bad - some with fatalities. It is all on Google.

And to think, The Montero is almost a clone of the Fortuner.

By the way, Isuzu does not add bells and whistles to attract buyers. Their vehicle engineering is already proven as it does not need fixing. That is why they do not need to change the design, because it works as it is.

I could go on and on, really!

But here is a suggestion.

Visit a Toyota and Mitsubisi repair shop (Casa) and see that they always have vehicles to repair, somehow.

Visit an Isuzu Casa and you will find that they are doing PMS inspections, preparing new vehicles for delivery, doing body work, etc. BUT seldom, if ever, actual mechanical repair work.

I admit that I am prejudiced about the superiority of the Alterra.

However, facts are facts!

Ciao!

Uncle Nick.

Does everyone agree? Let's have a healthy discussion here instead of hijacking the Alterra thread and so other members can chime in also.

[OTEP]

I posted my opinions on the matter here (to save you guys from having to switch back and forth):

As for coils vs other forms of suspensions, I've already come from a torsion bar/leaf spring combo vehicle then moved to a torsion bar coil spring combo. Now I'm running four wheel coils on solid axles front and rear. It's a matter of preference I guess. And being aware that this class of vehicles handle differently than normal road cars is a plus also. I have yet to flip any of them despite the fact that the vehicles are being used both on and off road and in responding code 3 to emergency calls.

In addition I'd just like to mention that coil sprung rear axles are held to the vehicle by multiple points including the control arms (2 points on each side) to locate the axle fore and aft and the lateral rod to control side to side motion as the axle goes through its full stroke. The coil spring itself offers no other function than to dampen axle motion.

Even Land Rover changed to an all coil set up when it updated the Series Rovers (now knows as Defenders) and Toyota changed to a front coil set up when it updated the Land Cruiser 70 series. Nissan also makes rear leaf suspensions available on the Patrol GU only on the commercial cab models (the rest of the line up gets four coils). Even Isuzu's former flagship SUV was riding on rear coils. The Alterra is not in the same lineage of the Trooper but is an offshoot of Thailand's pick up wagon segment (pick up truck based seven seat wagons) while the Trooper was a dedicated platform which got axed when it was no longer economically viable.

About the only modern car (not truck or SUV) I know that still has a leaf spring is the Corvette and it uses a transverse leaf spring.

That's not to sa leaf springs don't have their advantages. They are simple, inexpensive, and robust. But when it comes to ride and handling, I'd still vote for coils. But that's just me. And that's why we have discussions like this.

[olidotcom]

hmm.. interesting to... but i have read that leaf springs type of suspensions are more durable?

any experts out there?

[Ry_Tower]

The Alterra is really longer (wheelbase) naman, heavier but yung tracks I don't know since mas malapad actually fort at 1840 mm, MS at 1815mm at 1800mm lang alterra. But considering na halos pareho lang track width - with the same speed going in a corner - it's possible na its more stable vs MS and the Fort.

Going back to the topic, for me the info of nick is for safety concern na lang siguro. Kahit sino namang driver dapat bago ka mag-experiment na ihataw yung sasakyan sa corner, dapat mag-start ka muna sa low speed like 80-90km/h. Then once naririnig mo na yung tires making screeching sounds as you go faster, that is the sign na yun na yung max speed mo dapat sa corner. Bibili ka ba ng SUV so that you can go fast sa corners? Hindi di ba? Buy a sports car. Mas mapapakinabangan mo naman yung riding comfort ng coil spring sa front and rear.

1st post muna, analyze ko pa mamaya, paalis na eh. hehe

[SiRbossR]

yeah, leaf springs are more durable.

[sm2by]

yeah, leaf springs are more durable.

Are you sure? why do I keep seeing late model Isuzu Fuego Pickups and Multicabs, Hi-Landers, Elfs and Crosswinds with the Leaf springs broken off or sheered off... most of these occurences have lead to serious accidents....

[SiRbossR]

Well blame that problem to isuzu for having defective and weak material used for the leaf springs or better yet the owners of the said vehicles didn't bother to replace the leaf spring bushings which is essential for its alignment and durability. for the multicab, give it some slack, it's a small vehicle being overued and abused.

Look at trucks and other heavy duty vehicles that uses leaf springs, they're not having any major problems. The coil springs were introduced to give added luxury to the ride quality of vehicles. They're durable but not as durable.

[12vdc]

Are you sure? why do I keep seeing late model Isuzu Fuego Pickups and Multicabs, Hi-Landers, Elfs and Crosswinds with the Leaf springs broken off or sheered off... most of these occurences have lead to serious accidents....

^ Misaligned center bolt, poor maintenance and overloading often causes accidents..

To each his own, but it depends on the application..
Id choose coils for an SUV and sedans.. For AUV and pickups, coils front and leaves rear. Leaves can act as springs and stabilizers at the same time but articulation is still limited.
For heavy but budget-constrained applications, leaves should suffice.. Otherwise coils perform best, it can even surpass the load of leaves(but to a higher cost).. Lots of modern trucks/ buses are using coils/ airbags carrying heavy loads.

[12vdc]

Chrysler on coils vs leaf
[ame="http://www.youtube.com/watch?v=WoHF1VHNOjQ"]YouTube - Dodge Ram 1500 Suspension! Coil vs. Leaf[/ame]

And more prehestoric leaves in action
[ame="http://www.youtube.com/watch?v=Knt3nAnqd78"]YouTube - Ð?втомобильный видеорегиÑ?тратор - реÑ?Ñ?оры[/ame]
[ame="http://www.youtube.com/watch?v=XyGC_FUhC1s"]YouTube - Ð?нимациÑ? задней реÑ?Ñ?оры КÐ?ÐœÐ?За[/ame]

[olidotcom]

so.. as far as i can understand.. it really depends on what you're going to use the vehicle for... if its more on heavy weight loads, leaf spring is used. if you need more articulation, better ride, etc.. you need coils?

sorry slightly OT.. how about torsion bars? is it somewhat in line with leaf springs din?

[Ry_Tower]

so.. as far as i can understand.. it really depends on what you're going to use the vehicle for... if its more on heavy weight loads, leaf spring is used. if you need more articulation, better ride, etc.. you need coils? - basically that's it although leaves are also cheaper and easier to maintan kaya for heavy duty work sila.

sorry slightly OT.. how about torsion bars? is it somewhat in line with leaf springs din? - torsion bars are for those with double wishbone and no coil springs in the front. basically the coils replaced the torsion bar-type spring.

Hope it answers your query.

[OTEP]

Torsion bars are more a different form of spring wherein the torsion (twisting force) is used to dampen the suspension. Coils and leaves both work by compression.

[SiRbossR]

Chrysler on coils vs leaf
YouTube - Dodge Ram 1500 Suspension! Coil vs. Leaf

And more prehestoric leaves in action
YouTube - Ð?втомобильный видеорегиÑ?тратор - реÑ?Ñ?оры
YouTube - Ð?нимациÑ? задней реÑ?Ñ?оры КÐ?ÐœÐ?За

Great Find!

[miked]

SPRING TIME!!!

Just to add up to the discussions above.

A spring by definition is any type of material, when distorted, returns to its original shape. They are usually used in conjunction with shocks/dampers which control the suspension movement.

Functions of a spring
1. Support vehicle weight
2. maintain ride height
3. Keep the tires in positive contact with the road surface.

Basic Types of Spring
1. Leaf Spring
2. Coil Spring
3. Torsion Bars
4. Coilover (modified set-up)

Spring rate is the amount of force that is required to move a spring and measured in lb-in.
Load rate is the amount of weight the spring is designed to carry at ride height.

Now with regards to the pros and cons of those springs.

LEAF SPRINGS
Rugged, simple and oldest form of spring technology. A standard of auto suspension for decades but the role is slowly being reduced even in applications where it has been the stalwart (pickups).
These uses a series of steel plates of varying length (tapered) and thickness bound together to form a pack. Some uses monoleaf and multileaf. Number and thickness of leaves dictate spring rate and load capacity. Length effects ride quality and width handles stability.
Leaf springs are progressive-rate springs. They grow stiffer the more they are compressed which makes them superior for heavy loading.
They are also modular just like our LEGO toys. You can change ride height or capability by adding or removing leaves. Higher quality packs will use multiple, thinner leaves to reduce fiction and this makes them more durable . If one leaf snaps, other leaves will carry the load home.
There are also two stage spring packs. In addition to the progressive-pack, an overload leaf (horizontal) leaf is added to gain maximum load rating while retaining good ride characteristics when unladen.
Most importantly, leaf springs control and locate the axle without the use of control arms. But if the centerbolt breaks, the vehicle will dog-track. Imagine running the vehicle a little bit sideways.
Leaf springs are also more stable when loaded
In short, the pros are: they locate and control the axle, superior stability when loaded, simple and easier to lift.
Yet, the cons are: they are harder to tune for ride, heavy weight, take up a lot of space, susceptible to noise and prone to axlewrap (the leaf tends to make an "S" shape) especially on high loads under high torque and sudden acceleration.

[miked]

COIL SPRINGS
A coil spring is a steel metal wire that has been wound into the shape of a helix to resist compression. Excellent ride characteristics and low noise. Compression coil springs are the most common type of auto springs.
Spring rate is determined by the thickness of wire and pitch of the winding. Basically we have two types, the linear-rate and variable-rate. For the linear spring, the pitch or distance between winding is the same and you would experience the same vertical travel rate as you go over bumps while the variable-rate somewhat acts like a progressive leaf spring. The pitch is different. The upper portion have wider spacing between the windings while it is closer at the bottom (wound up with with varying pitch) and acts like this: soft on the first then harder later.
Benefits of coils include compact size, ability to precisely tune the suspension and wheel travel. They do not also involve internal friction and weigh much less than leaf springs.
Yet, coil springs do not locate the axle and therefore require links to work. Those links add up to the cost and complexity of design but it is the main reason why coil-sprung suspensions are good at resisting axlewrap unlike in leaf springs.
The taller the coil, the more they are prone to deflection (bowing) which can diminish their effectiveness over time and causes interference to suspension neighbors. Additionally, they can weaken and sag over time and not as durable as leaf springs in heavy duty applications.

In short (again), the pros are: quiet, better ride, easier to tune, lighter weight, eliminate axlewrap, capable of big articulation BUT need links, can sag over time of if overloaded, more suscetipble to sway, expensive to retrofit, limited lift heights and not as robust as leaf springs.


TORSION BAR
Perhaps the least common of the springs but are still used (in my case, just like Isuzu Pickups/Fuegos) where the IFS uses torsion bars.
Torsion bar/spring is a long metal bar that is attached to a fixed mount on the chassis on one end and attached to a moving part of the suspension and is mounted perpendicular to the direction the torsion bar is mounted (ex. lower control arms).
As vehicle moves up and down, torsion bar twist on its axis, resisting the suspension movement and returning it to center. Thickness and length of the bar determines it strength, spring rate and load capacity.
They are known for their durability and ease of replacement and maintenance.
Changes in ride height are achieved through "twisting" or "cranking" of the bars by adjusting preload through the adjuster nut connected to the chassis. But this will limit downtravel diminishing ride quality. Other negative effects will come out if it goes beyond the generally accepted "safe" range of 1.5-2 inches (depends on the vehicle)
Drawbacks are a lack of progressive or variable rate option (less flexibility when loaded especially going over harsh terrain along with limited wheel travel.
Pros: durable, simple, easy to make minor adjustments in ride height
Cons: Spring rate not progressive, limited wheel travel, few aftermarket options.

COILOVERS
A spice girls moment when 2 become 1. Coil-over-shock absorbers set-up. Even more compact than coil sprngs, this includes a shock absorber and coil spring in one unit. Coil spring is mounted to the shock and not the car.
Greater heights are achieved without considerable coil deflection. Plus they are mounted in bearing preventing bind under articulation.
Changing spring rates is as easy as pulling the unit and swapping to a different coil. Threaded bodies allow preload and ride height to be easily changed while coilover is mounted on vehicle.
Biggest drawback is the expense as well as fabrication may be required to fit on a vehicle.

Take your pick. But just keep this in mind: "All springs are application-specific. There is no such thing like the universal spring." Parang t-shirt kumbaga na one size fits all.

[Fotonista]

Question po (Sana di OT)...

Are all leaf-spring matagtag? The ride is a bit uncomfy for the rear passengers. Bago lang kasi yung sasakyan, I'm thinking if further usage of the vehicle will soften the ride or talagang ganun sya? If ever, what are the ways to make the ride a bit comfortable? (bawas leaf, palit shocks, etc).

Thanks.

[Ry_Tower]

Question po (Sana di OT)...

Are all leaf-spring matagtag? The ride is a bit uncomfy for the rear passengers. Bago lang kasi yung sasakyan, I'm thinking if further usage of the vehicle will soften the ride or talagang ganun sya? If ever, what are the ways to make the ride a bit comfortable? (bawas leaf, palit shocks, etc).

Thanks.

No. Somehow Isuzu and the leaf spring of the CRDi Strada seems to be better than previous leaf springs that they have. Puwede bawas ng leaf spring or to retain the height pa din, I reco that you use shorter and cut leaf spring as spacers to replace a full leaf at each side for more comfy ride. Dagdag sa FC kasi yung 2 bags of sand trick and not advisable if ot a pick-up.

But don't do anything without knowing the results and taking into consideration how you use your ride.

[Wh1stl3r]

Pansin ko din sa torsion bars you need to crank them periodically pag nagiging matagtag na yung ride. They become harsher with more kms of usage so you need to keep adjusting them every so often.

Re: suv/pickup rear suspensions I think what makes the Fort and other top heavy suvs roll more than the Alterra is the higher center of gravity vs the track and not necessarily the suspension. The reason they don't change anything in the design is probably because they can't justify the cost of changing the suspension vs the benefit of projected sales from those changes.

Having a longer wheelbase and wider track is better but saying a vehicle being heavier is an advantage is silly.

*Ry
Yung Dmax matagtag pa rin, malayo dun sa ibang Isuzu hehe. Thick leaf pack + light rear end = horse-like ride when unladen. Sana bawasan nila yung leaf pack, most owners never really get to use the full payload capacity.

[niky]

Yeah. Instability in handling is due more to the height and suspension tuning of the Fort and the Everest than due to what suspension they're using. The Alterra's low ride height, I feel, is more of a factor than anything else in the equation.

Leaf springs don't have to be stiff... but that's how they tune Isuzus. Makes for better load-carrying capacity, I guess.

[Ry_Tower]

Pansin ko din sa torsion bars you need to crank them periodically pag nagiging matagtag na yung ride. They become harsher with more kms of usage so you need to keep adjusting them every so often.

Re: suv/pickup rear suspensions I think what makes the Fort and other top heavy suvs roll more than the Alterra is the higher center of gravity vs the track and not necessarily the suspension. The reason they don't change anything in the design is probably because they can't justify the cost of changing the suspension vs the benefit of projected sales from those changes.

Having a longer wheelbase and wider track is better but saying a vehicle being heavier is an advantage is silly.

*Ry
Yung Dmax matagtag pa rin, malayo dun sa ibang Isuzu hehe. Thick leaf pack + light rear end = horse-like ride when unladen. Sana bawasan nila yung leaf pack, most owners never really get to use the full payload capacity.

Agree with you bro, bawasan or ireverse yung isang maiksi would do although i would reco na palitan ng medyo mas maikling molye (acting like a spacer) na leaf spring para mataas pa din tindig but softer na ride. works wonder talaga lalo na if hindi nga heavy duty hauling yung pick-up.