Parabologic Leaf Spring Suspensions - are they good or bad?

[rippergeo]

Originally Posted by Steeroid

Cost: Why so? The FJ is one of the cheapest SUVs around. The Safari is about 1/2 the cost of an Endeavour and still features an excellent coil-spring setup. Why even the Tata Estate featured a coil-sprung setup that was renowed for its ride comfort - and that was quite some time ago.

Robustness: Coil springs are not exactly rocket science, and have been around long enough. As for robustness - if you see some of the stuff that the trucks I mentioned with coils can do, this question wouldnt come up. Lets just say that they take a lot more punishment by going to places where trucks with leafs wont be able to go to. If one were to go by this line of arguement, the whole of India would still be driving Ambassadors.

Load carrying: If you were carrying loads, you're not really worried about the comfort of the load so why bother putting coils in? The dead axle leaf spring is the simplest suspension the manufacturer can put in for load carrying applications - even bullock carts use them. You dont have to worry about 'tuning' your suspension settings in such a scenario.

my understanding is that leaf springs and coil springs can do the same thing. but coil springs provide better comfort.
why should a coil spring perform better off road? unless the car in question has rear independent suspension.

all things being equal, i feel a truck with leaf springs will go further and longer offroad,than the same truck with coil springs(unless you bring independent suspension into play)

there is no scope for tuning a suspension in leaf springs, other than varying the springs themselves, and possibly adding good anti roll bars, but that is because they are so basic, and that is what makes them cheap and reliable.

the more basic a car, the less things can go wrong with it. that thinking may be old fashioned, but it has been proven again and again.

of course, even a high tech system can be precision engineered and tested to the limits and made reliable, as reliable as a basic system, but deep pockets will be needed... and extensive technical know how(eg FJ cruiser)

and what about repairs and maintenance? which would cost more? leaf or coil?which would be easier to fix? improvisation/jugaad etc is easier on the leaf spring is'nt it?

the leaf spring has a lot of shortcomings, but we should appreciate what it offers.

if this debate is on 20 lakh SUVs having leaf springs at the rear(read Ford Endy), there is no justification, they should have done a basic coil spring set up atleast.

[jagan0677]

Originally Posted by Steeroid

...

Load carrying: If you were carrying loads, you're not really worried about the comfort of the load so why bother putting coils in? The dead axle leaf spring is the simplest suspension the manufacturer can put in for load carrying applications - even bullock carts use them. You dont have to worry about 'tuning' your suspension settings in such a scenario.

Originally Posted by Mpower

For the most part, yes. But many items like electronics and other fragile items are sensitive to ride quality and operator need to be cognizant about that.

@Mpower: If you were referring to commercial vehicles(say >3T payload), i doubt coil springs are any better on that front, practically.
I could be wrong here, but i guess, if that becomes a decision factor, air bellows/springs would score better over leafs/coils. And, even with leafs, if the consignment is close to the design payload of the truck, i dont see too much of a compromise in ride quality.

[Sankar]

Originally Posted by Steeroid

Cost: Why so? The FJ is one of the cheapest SUVs around. The Safari is about 1/2 the cost of an Endeavour and still features an excellent coil-spring setup. Why even the Tata Estate featured a coil-sprung setup that was renowed for its ride comfort - and that was quite some time ago.

There is no point in comparing vehicle costs and vehicle costs across various makes and coming to a conclusion that coils are no more expensive than a leaf.

If you leave the rest of the vehicle alone and bring into focus only the manufacturing cost of the suspension and the labour involved to install them a coil spring suspension will any day be more expensive than a leaf spring based one.

The reason is coil spring suspensions are more complicated in design when compared to a leaf spring. In a leaf spring suspension the only things involved are the leaf(s), the shackle, and the 8 bushes. Even in a basic 3 link coil spring suspension found in todays hatch there are more components involved. And n SUVs they have 5 link suspensions or atleast a 4 link at the minimum.

Robustness: Coil springs are not exactly rocket science, and have been around long enough. As for robustness - if you see some of the stuff that the trucks I mentioned with coils can do, this question wouldnt come up. Lets just say that they take a lot more punishment by going to places where trucks with leafs wont be able to go to. If one were to go by this line of arguement, the whole of India would still be driving Ambassadors.

Yes true. A coil spring as such don't have any reliability issues and even the links are sturdy. We have seen leafs brake and leaf centrebolts break. Thats why we see some buses and trucks 'crabbing' on the road.

Load carrying: If you were carrying loads, you're not really worried about the comfort of the load so why bother putting coils in? The dead axle leaf spring is the simplest suspension the manufacturer can put in for load carrying applications - even bullock carts use them. You dont have to worry about 'tuning' your suspension settings in such a scenario.

Yes. But to add to the point even leafs can be tuned but it won't be as good as any 4 link or 5 link at the end of the day when it comes to handling.

[Sankar]

Originally Posted by Mpower

For the most part, yes. But many items like electronics and other fragile items are sensitive to ride quality and operator need to be cognizant about that.

Most of our electronic items even highly sensitive ones reach us on leafs and some even on leafs minus the dampers

Thats why highly sensitive laboratory equipments and glassware come in foam packing and some packed in foam pebbles. Usually the manufacturer or packer will take an insurance by over engineering the packing of highly sensitive devices because such things could be mishandled by personnel at the depots.

[Steeroid]

Originally Posted by rippergeo

the more basic a car, the less things can go wrong with it. that thinking may be old fashioned, but it has been proven again and again.

I'm sorry but this discussion really isnt getting anywhere on this line of arguement. I'm logging out of this.