LEAF SPRING TECH

[JERSEY JOE]

OK I have this 1987 J-20 project and I want to start thinking about a leaf spring swap. As we all know the stock springs make it ride like a lumber wagon. I am not looking to make it ride like my 2008 F-150 FX 4 and I don't need the ability to carry a total GVW of 8600 either. I will have a class 3 trailer hitch and I would like the flexibility of being able to tow my trailer and CJ 7 on it without the nose it the air stance. It's funny, when I load the CJ 7 on the trailer with my F-150 the truck stays nearly level and it still rides great while empty. HOW IS THAT DONE? Progressive rate springs?

My options:

1. new front and rear J-10 spec springs with extra rear leaves

2. current J-20 springs with reduced spring pack

3. something else

[Tornado230]

Joe,
Don't know what they did, but the '77 J-20 rides better than the '82 J-10.
Take a look at the springs when you get in the neighborhood.

[JERSEY JOE]

SPRINGS

ANYONE???

[DAHoyle]

Well, if your F150 handles it without the nose up in the air, chances are that the Jeep will as well. There is a lot more to towing than your leaves. How balanced is the trailer. If you don't have a lot of tongue weight, then the truck won't squat. That is the key. Get the load balanced, with about 500 lbs on the hitch, and you will never have a lot of squat in the rear end. Ideally, you want your tongue weight to be 10 to 20% of the total trailer weight, unless you are pulling a gooseneck.

Doug

[JERSEY JOE]

TRAILER LOADING

Doug I have not measured the tongue but I always had the CJ in the same place on the trailer. When I decided on the spot I drove the CJ on until the bed of the truck dropped a little bit. I have an equalizing hitch and the setup does not sway at 70 mph.

Anyone have a suggestion on springs?

[billyrb]

the best thing you can do is buy a new suspension, then use air-bags for when you tow heavier loads. This takes the added weight off the springs and puts it on the bags. That way, you have the best of both worlds: nice comfy suspension for regular duty, and bags to handle the heavy towing.

[DAHoyle]

Well, it seems that you want to have your cake and eat it too.

You need to decide what is more important to you. Towing ability, or ride quality.

There are no magic springs. If it was me, I would run a quality springpack like a Deaver, and tell them what you want.

Leaf springs react to weight, period. Put X amount of weight on the spring, and it is going to deflect Y amount. It is all based on the spring rate. Nothing surprising about that. Go with a soft spring, and it will settle more for a given load than a stiffer spring. As billyrb pointed out, the only way to get around that is with some sort of adjustable helper, such as air bags. The two choices you offer really don't mean anything, without knowing the spring rate you are going for. What's to say that a J-10 spring with extra leaves isn't as stiff or stiffer than J-20 springs. The reverse is also true. Take J-20 springs and pull a few out, and you may actually have something softer than the J-10 springs.

Guess what I'm saying is that you need to decide on a spring rate, and shoot for it. If you think you want something midway between a J-10 and J-20, then find out what their respective spring rates are, and you have your answer. I'm sure the information is out there.

Nobody will be able to give you a good idea what you want, until you offer a bit of clarification.

Doug

[JERSEY JOE]

SPRINGS

Thanks Doug and Billyrb for the reply. I guess my question then is should I just buy a new set of J-10 springs and add one extra rear leaf as well as some type of adjustable overload ( air bag ) and call it a day.

Are new J-10 springs available off the shelf or do they need to be custom made? You mentioned Deaver. Are they a spring company?

Once again thanks for the help

[red mistress]

spring company's

some of the major's:

Deaver
National Spring
Alcan

They have the technology to build "progressive" spring rates.
They have specs on your truck and U can tell them what you want.

I may go the custom spring route + air bags for when loaded.


Also - Good idea on trying the J10 springs then add a leaf if needed.

[Grantshire]

Stock springs with air bags is the way to go. I use them on my Suburban to level the load since I have everything from fourwheelers to an M715 on my trailer. Mine have a in-cab air pump and gauge so I can adjust on the fly.

[JERSEY JOE]

SPRINGS

Rich that's the way I would go with the onboard compressor. I think I saw it in your truck when we went to Charlottsville last year. It's just that the factory J-20 springs are way too stiff, and this truck will be empty 90% of the time. I guess with the J-10 springs it should ride as nice as my old 82 Cherokee Chief.

Dennis do you kow for a fact that I can buy new stock rate J-10 springs?

[red mistress]

84 J-Truck spring rates

REAR:

SWB J-10 standard 165 lbs/in HD option 4+1 265 lbs/in.
LWB J-10 standard 245 HD option 4+2 340

LWB J20 standard 340 HD option 3+2 510


From 84 Sales data book

I'm sure that any of the spring companies have this data and can build to whatever spring rate that you want. Also lift and progressive like the new trucks have.

[Ted Wendel]

It's just that the factory J-20 springs are way too stiff, and this truck will be empty 90% of the time.

Empty 90% of the time,it should be hauling the trail CJ-7 90% of the time.

[Kali]

for what its worth, some years you could get a "light duty" j-20 with 6800 GVW. thats slightly more than the j-10 (6200) and slightly less than the "regular duty" j-20 (7600?). maybe try finding a set of those springs?

[billyrb]

there are lots of folks running our springs that are very happy with them, for regular duty, off-road use and for towing. We also have customers that use our lift kits paired with air-bags for heavy towing that are also very pleased. Plus, saves about 30-50% off the cost of using Alcan's, etc.