Coil Springs vs. Leaf Springs

**OTEP** · March 13th, 2011 03:04 PM

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:

Originally Posted by Uncle Nick

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** · March 13th, 2011 03:18 PM

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

Originally Posted by OTEP

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** · March 13th, 2011 03:21 PM

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

any experts out there?

**Ry_Tower** · March 13th, 2011 03:59 PM

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** · March 13th, 2011 04:43 PM

yeah, leaf springs are more durable.

**sm2by** · March 13th, 2011 10:50 PM

Originally Posted by SiRbossR

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** · March 13th, 2011 11:56 PM

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** · March 14th, 2011 12:09 AM

Originally Posted by sm2by

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** · March 14th, 2011 12:18 AM

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?Ð²Ñ‚Ð¾Ð¼Ð¾Ð±Ð¸Ð»ÑŒÐ½Ñ‹Ð¹ Ð²Ð¸Ð´ÐµÐ¾Ñ€ÐµÐ³Ð¸Ñ?Ñ‚Ñ€Ð°Ñ‚Ð¾Ñ€ - Ñ€ÐµÑ?Ñ?Ð¾Ñ€Ñ‹[/ame]
[ame="http://www.youtube.com/watch?v=XyGC_FUhC1s"]YouTube - Ð?Ð½Ð¸Ð¼Ð°Ñ†Ð¸Ñ? Ð·Ð°Ð´Ð½ÐµÐ¹ Ñ€ÐµÑ?Ñ?Ð¾Ñ€Ñ‹ ÐšÐ?ÐœÐ?Ð—Ð°[/ame]

**olidotcom** · March 14th, 2011 04:52 AM

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?