S.O.A. flex, what gives! - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
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post #1 of (permalink) Old 09-12-2000, 01:49 AM Thread Starter
 
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S.O.A. flex, what gives!

What is the deal with spring over Jeeps flexing so well [img]/wwwthreads_images/icons/mad.gif[/img]? Seems like a stock CJ7 will ramp 700 then someone puts the leaves on top of the axle and the darn thing ramps over a thousand. I've got a fairly flexy Toyota truck and on a good day I'll flex 800 if I'm lucky, what gives!? I'm tired of you short wheel-base guys flexing through the trail when my longer (which should mean flexier) truck almost rolls over?

Can someone explain the reasoning behind the increased flex that occurs after a spring over is done?



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post #2 of (permalink) Old 09-12-2000, 06:34 AM
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Re: S.O.A. flex, what gives!

I honestly think it's a weight distribution thing.My dads yoder is within an inch wheelbase of my scrambler and he ends up on his side all the time.That 4 banger and empty bed just dont have enough leverage.I would like to know how some of those toy's flex like they do so we could do it to his.

post #3 of (permalink) Old 09-12-2000, 06:38 AM
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Re: S.O.A. flex, what gives!

There really is not that much flex... it is more a matter of track width and wheelbase.

The shorter and wider a vehicle is, the higher it's ramp score but the less the axles actually articulate relative to one another to reach 1000 (or any other given ramp score)...

If you shortened your sheelbase down to 95" or less your 800 ramp score would be over 1000 too [img]/wwwthreads_images/icons/wink.gif[/img]

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post #4 of (permalink) Old 09-12-2000, 08:57 AM
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Re: S.O.A. flex, what gives!

it seems like to me that a set of stock wrangler springs would flex great on a toyota. they are designed for lighter wieght vehicles (yj's had no v8) so i think they would work on toyotas too. drm is the man to talk too on this though. from what i've read he has built quite a few toy susp. i am kinda interested too.

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post #5 of (permalink) Old 09-12-2000, 09:06 AM
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Re: S.O.A. flex, what gives!

Many people have gone to stock YJ springs under the front of their Toyota's - the spring dimentions match up pretty well and give some good flex. About the only problem with them is they really do not offer much lift for a Toyota - only about 1.5" to 2" of spring lift. I have also installed 2.5" lift YJ springs under the front of a Toyota and they offer closer to 4" or 5" of suspension lift, good flex, and a great ride (Especially with RS9000's).

I considered this on my Toyota, but went with longer Toyota rear springs up front and dropped spring hangers instead [img]/wwwthreads_images/icons/smile.gif[/img]

I think the flex I get is pretty good, but having a 105" wheelbase means I can flex more than a shorterwheelbase vehicle like a Jeep but they will "score" higher on RTI. YJ's tend to do really well since they are wider than CJ's and Toy's even in stock form....

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post #6 of (permalink) Old 09-12-2000, 12:52 PM
 
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Re: S.O.A. flex, what gives!

Actually DRM I dont think you are giving the flexability enough credit. The best RTI I could get on a 22 degree ramp with a Pro comp 4" lift was 800. Then when I really started seriousely building my suspension. I lengthened my wheel base from 92" to 97" performed all my modifications and the last time I got on a ramp at the Summit Racing Truck fest West I ramped a 1343 on 25 degree ramp. I had nearly 5 more inches of WB which is completely contrary to the shorter the better RTI theory. Most of the extra flex with all things considered equal, comes from the fact that you have to use less arch to get your lift and thus have more flex and the fact that the springs we are using are not designed for SOA and thus flex more by not suspended by the their design set up. This is also why spring wrap becomes a problem.
Without a doubt SOA is one of the best set ups available for a CJ or YJ, and the myths about them leaning to much on side hills is a bunch of BS. My current configuration out flexes and out performs the Warn XCL system and all other commers I have played with on the trail.

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post #7 of (permalink) Old 09-12-2000, 01:34 PM
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Ramp score mythology

Don't get me wrong, there are many ways to make a CJ/YJ flex VERY well as you seem to have found out... but it is a matter of simple math to see how the wider the track width and the shorter the wheelbase, the less flex a vehicle has for a given ramp score.

Using your example - you scored an 800 on a 22 degree ramp with a 92" wheelbase. That means you traveled 73.6" up the ramp. With your new 97" wheelbase, you would have to travel 77.6" up the 22 degree ramp to get the same score of an 800. BUT, assuming no other changes besides wheelbase, and the same track width, a score of 800 with a 97" wheelbase vs. a score of 800 with a 92" wheelbase vehicle means that the 97" wheelbase vehicle has more flex (it traveled further up the ramp, so the axles are at more extreme angles in ralation to one another).

To put this into "so silly it is obvious" terms, imagine a vehicle say a 40" wheelbase that has a track width (sidewall to sidewall for example) of 100". a vehicle like that could quite possibly score a 10,000 on a 30 degree ramp... Even at a 1000 on a 30 degree ramp, that vehicle would hardly be flexing the suspension at all [img]/wwwthreads_images/icons/smile.gif[/img]
As you can see, the shorter the wheelbase and the wider the track width, the better the ramp score - but not necessarily meaning better flex.... That make sense?

As to your Jeep's example of such a great increase in ramp score, you obviously made other changes to get that much of an increase. But to further prove my point, imagine your same suspension setup that scored a 1343 on a 25 degree ramp if you shortened the wheelbase back to 92". Your RTI would jump up to a new score of 1410 [img]/wwwthreads_images/icons/wink.gif[/img]

On a related note, RTI just cannot account for the width factor and give a relevant number for comparison between a variety of vehicles. RTI should either be changed to account for width, or a new way of measuring articulation should be used: such as angle finders on each axle measuring the degree of the articulation of each axle, then finding the difference in the angles and calling that your "score". This would eliminate all of the "cheating" methods commonly used in RTI testing, and tell you who REALLY has more flex [img]/wwwthreads_images/icons/smile.gif[/img]

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