Leaf Spring vs Linked Coil Spring Rear Suspension

I notice that the 4th gen has a linked coil spring rear suspension option and this brings up a question that I have never heard a good answer to.

What are the pros and cons of the two types of suspension?

I've heard countless answers to this question that leave me unsatisfied. I'm looking for an answer that would satisfy an arm chair mechanical engineer; not the answers that fill up a google search on the topic.

Related to that question, I've long wondered if leaf springs do not follow Hooke's law. Does the force required to displace the spring increase relative to spring displacement? If so, that could an advantage for a truck that is intended to carry widely varying payloads.

If the answer to my second questions is yes, does this mean that the 4th gen linked coil spring equipped trucks are worse at being work trucks?

 

payload on new tacoma is way more than old one with Leafs. coils ride better . less to no axle wrap compared to weak little stock leaf springs on current gen. changing coil springs is generally easier than changing coils.
leaf springs are cheaper and easer to make and install. thats why older vehicles had leaf springs before coils. bolt leafs to frame bolt axle to leaf done.

 

Like the much maligned on this forum Ridgeline ?

 

Leaf springs are probably the cheapest/crudest way to suspend the rear end and keep it aligned front to back and laterally. With coils you need additional suspension components (links) to keep the axle from moving because the coils don't have any fore/aft or side/side rigidity. For the additional cost of a coil spring suspension you get a better ride and potentially better handling if its designed properly. And since the springs (either coils or leafs) are semi-unsprung weight, lighter is better. I'm pretty sure a coil suspension weighs less than leafs.

 

But the stock springs are bad and need immediate upgrade. What color are they?
Kidding. This is interesting.

 

Solid axle, leaf spring located rear drive arrangements fall in the "Hotchkiss drive" classification.
The best "engineering" aspect of this arrangement is the defined roll center and the ease of changing out the spring packs to match needs.

The down side of the solid axle design is that when one wheel hits a bump, it upsets the grip of the other wheel.

Multi- bar located solid axles can put the roll center just about anywhere, but once the vehicle is designed, that's it. And it may NOT be the best for different objectives. Solid axles still upset the off wheel traction. Alternate Coil springs that suit the different perches and mounts may be costly or difficult to source (supply and demand issues) .

 

From what I understand, it will be difficult to make a coil spring suspension that is as progressive as a leaf pack. This matters, for instance, for a heavy overlander trying to climb a steep hill at an angle: as most of the vehicle weight shifts to one rear corner, the vehicle has a much higher risk of rolling over. Installing a stiff enough coil to counter that characteristic greatly compromises ride quality. (See the Tipover Challenge on the Hell's Revenge Trail in Moab – a "challenge" that has never been much of a challenge for 2d and 3rd gen Tacomas.)

This problem on the 2024 Tacomas is possibly compounded by the fact that the leaf-sprung trim levels of the new chassis have switched back to a compression shackle, away from the tension shackle and shackle hanger that the Tacoma utilized from 2005-2023. It seems to be the opinion of many on this forum that tension shackles and hangers are better for heavier payload and overall stability in turns.

 

There are progressive rate coils but most put in air bags to compensate if they will haul heavier loads.

 

At least for the the 2nd and 3rd generation Tacomas, there are no off-the-shelf airbag systems that don't limit suspension travel. Yes, you can install Daystar cradles to allow maximum droop, but the air bag assemblies still limit uptravel – I had them on my truck and did the measurements.

Your point stands that there will undoubtedly exist a solution at some point. My point is simply that there is an inherent weakness in coilover suspension that will require adding extra parts to our trucks to remedy.

 

No I meant there are airbags to supplement the coil springs if need be. Also I think it's an option on some trim lines on the 4G Tacoma.

 

I see you drive a LC. Do you have experience with air bags and coils? On coil spring applications, do they limit droop or stuff? I didn't find applications from manufacturers such as Firestone, etc., to be satisfactory for my leaf sprung truck, unless I was willing to do some serious custom fabrication work for the airbag mounts. Even then, there were still issues with periodic failures from leaking.

 

I have heavy rate springs so I don't need air bags but some of the guys in LC's I rock crawl with and have lighter duty springs do have air bags if they tow or just haul stuff in the cargo area. Those that have them love them.

 

Very interesting - thanks for the insight

 

https://youtu.be/FtAP774EaIA This about as good as it gets for a discussion on pros/cons. Its over an hour long, buckle in.