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Old 10-21-2007, 08:40 AM   #1
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Coil spring v. Leaf spring

I have been going back and forth with this for sometimes.
Coil spring (salem kroger, et al. ) or leaf spring (smb) for the front suspension.
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Old 10-21-2007, 10:14 AM   #2
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I wouldn't think coil vs. leaf would be a big factor. Would you think about coil vs. leaf if you were buying a new P/U? Why would the type of spring make a real difference? Why would it be the deciding point?

Seriously, look at cost, parts used, workmanship, ease of repairs, ability to customize features, wheels and tires, ability to talk to the engineer, access to the shop (where do you live, where is the shop), etc. to make your decision.

How will you use the van? Hardcore 4 wheeling? Occasional dirt road? Driving in snow? How much lift do you want? What 4wd features and parts will you need to do that?

If you are leaning towards hardcore 4 wheeling, maybe an SMB conversion is for you. If you want something without much lift, maybe Quadvan. Lower cost, less features - Quigley? For us, Salem_Kroger was the answer.

We went with Salem-Kroger because they would do what we wanted. No more, no less.

They also didn't weld over the crush zone on the front of the frame like some 4wd shops do. What would be the liability of defeating a safety feature like that in a major accident? Will it affect the actuaction of the airbags? Is it even legal do that modification and then claim the van meets safety standards? Not questions I wanted to deal with - ever!

Mike
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Old 10-21-2007, 10:50 AM   #3
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Coil vs. Leaf is a big deal in the offroad world. It's like starting a discussion on gas vs. diesel, there is never a clear resolution and it comes down to personal taste.

My personal favorite combination follows the Jeep Cherokee downsized, with coils in the front and leaves in the back. I feel like this provides the most flexiblity and stability.

That said, leaves provide simpler geometry and less parts, less alignment. But coils are supposed to ride better (the evolution of the Jeep Wrangler goes from all coil to all spring with the Cherokee I mentioned as sort of a weird cousin).

Still plenty of offroaders switch their coils for leaves and vice versa.

Here's an excerpt that might put it a little more clearly than I am:
Quote:
Coils vs. Leaves

Sorry, but we aren’t going to declare a winner in the world of springs because there is no clear cut advantage to either coils or leaves. Coil springs cost less to make, are lighter, have no internal friction, and take up very little space. The downside with coils is that they do not locate the axles. A three- or four-link suspension must be constructed to work with the coil springs to do the same job that leaf springs alone can do. Leaf springs, on the other hand, are completely modular (if you want to add or subtract lift or load capacity, just add more leaves), do locate the axles, and can also help to reduce sway. The best leaf packs will use multiple thin leaves to provide load control yet still move freely. Yes, leaf springs are heavy, prone to axlewrap, and can require a lot of mounting space. But keep in mind that a suspension’s characteristics have more to do with how the whole system is set up (and the spring rates that are used) than it does with whether the springs are leaves or coils. Hey, as low-tech as leaf springs may seem, they can be made to work with maybe just a weight penalty over the coil spring.
From http://www.4wheeloffroad.com/techart..._leaf_springs/

I'm sure there are many more pro, con and comparison opinions out there. If I was building an SMB suspension from scratch I'd probably start with the concept of rear leaf springs with airbag assist (for leveling/increased load) and coils up front. The rear leaves would help with sway, the coils lighten the front and leave the crush zone alone.
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Old 10-21-2007, 11:14 AM   #4
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i guess what i am trying to get at is, if all things being equal, which system, leaf spring or coil spring, is more capable, durable, easier to repair/maintain, field repairable?

i do like the stock system offered by salem kroger, et al., for like 2 to 5K less you get upgraded brakes, etc. over the stock smb 4x4 system

i do like the fact that salem kroger, et al. uses stock ford parts, and is very close to a stock front end found in other ford trucks, thus offering you more outlets for service/repairs, and replacement parts availability

with the smb, IMHO, i do believe they have a somewhat more capable system because of the leaf, i guess i am biased towards leaf,

also, with leaf, you are able to tweak it more/incrementally by adding or subtracting leaf spring, whereas with coil, you have to replace the whole coil

as for the smb 4x4 system, you get less and you pay more, you are left with the stock brakes on the ford van, which is quite deficient, the parts/build is not as common and somewhat specialized...as compared to ford parts/system
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Old 10-21-2007, 01:03 PM   #5
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Wouldn't you think that Dynatrac and OME components are at least as good as Ford's?
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Old 10-21-2007, 08:42 PM   #6
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Don't forget also that the SMB system comes with the atlas II transfer case that is quite possibly the best aftermarket transfer case available. SMB uses very high quality parts so I don't think it's fair to say that you pay more and get less. That said I do feel the the brakes are a little inadequate in my smb 4x4.
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Old 10-22-2007, 10:18 AM   #7
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I don't doubt the SMB parts are at least as good as the Ford parts, just that some dealers won't work on vans with aftermarket parts. With the Ford F350 components there is not that problem.

Sometimes it is easier to work with the coils. I can pull the coils out, change a spacer to adjust the ride height (or change the coils) and have it back on the road in an hour or two. Adding or changing a leaf always seemed to take all day.

Personal preferences can be the deciding factor when there is no clear choice.

Mike
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Old 10-22-2007, 10:30 PM   #8
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Mike, your right personal preferences are the deciding factor. my personal preference is to not have my van repaired at the dealer unless the repair is warantee work. Since there is no 4x4 available in a Ford van that is waranteed by the dealer none of us have systems that will be repaired free of charge. Since that is the case why not use the better quality parts and not need the repair in the first place?

Here are some facts about dealerships
1. 99.99 percent of all dealers pay thier technicians flat rate. That is by the job. Example is 1.5 hrs pay for a brake job wether the job takes 15 minutes or 3 hours that guy gets 1.5 hrs. This system does not create quality or honesty. Stories of dealer technicians tool boxes stuffed with new parts that were supposed to go on cars but did not are commonplace.
2. The most senior techs get the most profitable jobs.
3. Custom vehicles that are not bone stock are not profitable for flat rate line techs to repair.
4. Dealerships would like you to think that because they are the dealer that they could not possibly make any mistakes. The result is usually that when a mistake is made rather than own it they will make up some BS and charge you again to fix the problem!

Can it be hard to find competant repair for your car? You bet. I'd rather take my chances with a small local business where I can talk directly with the owner and the techs. That is also not to say that there are no good dealers, there are a few.

That is my personal preference based on being in the automotive repair business all my life.

Don't get me wrong here, I'm not saying that the SK conversion is inferior as I have never seen one. It may even ride nicer than my SMB which I think has several faults, like way to stiff and not enough up travel. This thing bottoms out in a 6 inch deep pot hole! All im saying is that dealer service was not on my list of concerns when I made my decision.
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