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stiffest springs (diesel specific, please dont move)

xtremejoe

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Just had my stock JLRUD weighed on a local CAT scale. The vehicle is completely stock and fully loaded (hard top, steel bumpers, cold weather option, tow option, leather etc.). Fuel and DEF were full.

Results:

Front Axle: 2720 lbs​
Rear Axle: 2420 lbs​
Gross Weight: 5140 lbs​
The good news is that with this weight I am 960 lbs less than the GVWR of 6100 lbls, which affords me a bit more payload than the 800 lbs I thought I was limited to.

But it seems to also indicate that the diesel weight is indeed heavier up front, in my case, 300 lbs heavier. This is counter then to the suggestions that the JLRUD weight is evenly distributed. Certainly not with my vehicle. This assumes that these scales are reliable. I'd like to repeat this at a few different CAT scale locations while the vehicle is still stock just to see if the numbers stay consistent.

CAT_020921.jpg
Did you end up doing any mods and see what your weight changes were after the fact?
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omnitonic

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Someone much smarter than me would have to do that in order to account for the extra weight.
I just want to say I really feel you on that one. I made the mistake of looking at the spring section in Machinery's Handbook one time, and you pretty much have to be a full blown mechanical engineer to even begin to understand a fraction of that stuff. Holy crap, springs are something we all take for granted, and mostly know almost nothing about.

Sorry to interrupt with a useless observation. Carry on my friend, and good luck on your quest!
 

Aonar

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Did you ever get around to doing this?
Short answer: No. Long answer: Plans, They do be a Changin'. Nixed the drawer and the platform. All I am waiting on is the winch plate then should be ready to install. I apologize in advance for the video. This old dog is trying to teach himself new tricks. It offers a visual of what I am doing and trying to do. (BTW, in the video you do not see the rear seat behind the driver. It is still there but down and covered. I only deleted the 2/3 rear passenger side. I run with the small rear seat covered and waterproofed. Did NOT spend the money on waterproof seat covers for the rear when only 1 would be used.)

Thanks for checking back. Things always seem to go slower than I would like!

 

Themistocles

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We actually tested this kit out a few different ways with some of our customers and dealers and for the best stance and ride feel this spring made the most sense. A lot of R&D goes into our spring and kit development, and we feel that we can't really take the spring rate much higher than 188 without starting to negatively impact ride quality. I'm not sure what has created this negative misconception towards adding more height to the spring in order to compensate for the increased rake the diesel motor causes, but I assure you these springs work and work well :like: We put a lot of time and effort into designing these springs for the JL and when the time came for a Diesel lift, we weren't surprised at all just how well they worked out! It's been our goal since this company started 20 years ago to not only design and release kits that we feel are on par with the factory suspension but greatly improve upon it and that very much holds true today, we would not put our name on any product we didn't completely believe in. Clayton Off Road is not a company to just release products to see how they perform out in the real world, there's a lot that goes into the design and launch of a new suspension system! We've had a lot of success with our current line of suspension systems for the JK, JL, and JT because of how much time and effort we put into making sure these lifts come out perfect, and with the release of the Diesel model, we took all of the necessary steps to ensure our kits give you the same amazing results! :)
I am in the middle of a Clayton 2.5" Overland Diesel install at the moment. Couple points.

The quality and out of the box articulation are both phenomenal. The one issue we are trying to resolve is up travel...and this gets into the downside of using longer springs...that get compressed more. Out of the box (using recommended added bump stop) the Clayton kit provides less than 3 inches of available up travel. I have asked around a bit and this seems to be roughly where other diesel lifts are as well. IMHO this is flat out not enough up travel. Up travel is important if you are doing higher speed driving on rough road/whoops. Insufficient up travel will result in frequent bottoming out which is not a great thing for control/traction/comfort/longevity etc. Stock up travel appears to be about 4.25". From my research 4 - 5 inches seems to be what is probably needed.

So from this, why is there a negative impression of longer springs compressed further. The answer is primarily based on amount of compression available before your springs are totally collapsed and become simply a solid piece of metal. By my measurement, the Clayton 2.5 diesel has about 6 inches of available compression at ride height. That means that no matter what else I do, I can not get more than 6 inches of available up travel (realistically only about 5.75). Now 6 inches of up travel in a JL is pretty darn good...but because our diesel springs are compressed more at ride height than non-diesel models, we are giving up some potential available up travel. I would think that a 3.6 or 2.0 with the Clayton kit would like see 6.5 or 7 inches of available up travel before the springs are completely collapsed.

The other negative is that the spring rate (number of pounds needed to collapse one spring one inch) is supposed to be part of an integrated, designed system...specifically integrated with shock valving. A spring designed for a 4800lbs vehicle when put on a 5300lbs vehicle will be comparatively softer and will want to dive / wallow. This impacts controllability of the vehicle. So if you use a longer spring (thus lower comparative rate) you should pair it with a shock that is valved to be stiffer in compression damping...and maybe...just maybe a bit softer in rebound damping. I am working with RadFlo currently to make sure the shocks I pair with Clayton kit do just that.

Quick example: Say the diesel is 300lbs heavier on the front springs (which CAT scale numbers seem to validate) than a 3.6. That means that each spring is carrying an extra 150lbs. If the spring rate is 188 (188lbs compresses the spring one inch) the spring will be compressed an extra .8 inches at rest. Now in the dynamic environment...Force is a function of Mass and Acceleration. As mass and/or acceleration increase so does force. When you add 150lbs / spring you are increasing the dynamic force applied to that spring and not by 150lbs...more like by 150lbs x (a formula based on) Acceleration. This is what leads to greater dive or a feeling of "wallowing" under dynamic use. Now in a vehicle that already has over 1,400 or 1,500lbs of load on each spring...does another 150 really change that much...not really...about 10% change (but this tracks with factory diesel springs being about 10% stiffer than 3.6 springs). But it is a factor.

So overall, is it a great big deal...no, I wouldn't have gone with Clayton if I thought it was, but it does require consideration.
 
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JDub11

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I think the bump recommendations are based on keeping the tires out of the fenders and not bottoming out the shocks. These will be limiting factors well before full spring compression. I also thought Clayton's springs were stiffer for the diesel.
 

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Themistocles

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I think the bump recommendations are based on keeping the tires out of the fenders and not bottoming out the shocks. These will be limiting factors well before full spring compression. I also thought Clayton's springs were stiffer for the diesel.
Yes, the 3 inches of added bump stop are to keep the tire out of the inner fender and liner. With the liner and oem inner fender installed you would rip those off well before you completely compressed. But by pulling out the fender liner and the inner fender you gain a lot of room. This should allow for an extra 2 inches...taking bump stop down to 1 inch and giving me 4.75 inches of up travel. Putting in another 1.5 inches of spacer could then get me to the range of my up travel being restricted by length of the compressed spring.

No, it is the same rate (188 i think). Their diesel 2.5 kit is just a normal rate 3.5 inches front springs with standard 2.5 rear springs.
 

Clayton Off Road

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I am in the middle of a Clayton 2.5" Overland Diesel install at the moment. Couple points.

The quality and out of the box articulation are both phenomenal. The one issue we are trying to resolve is up travel...and this gets into the downside of using longer springs...that get compressed more. Out of the box (using recommended added bump stop) the Clayton kit provides less than 3 inches of available up travel. I have asked around a bit and this seems to be roughly where other diesel lifts are as well. IMHO this is flat out not enough up travel. Up travel is important if you are doing higher speed driving on rough road/whoops. Insufficient up travel will result in frequent bottoming out which is not a great thing for control/traction/comfort/longevity etc. Stock up travel appears to be about 4.25". From my research 4 - 5 inches seems to be what is probably needed.

So from this, why is there a negative impression of longer springs compressed further. The answer is primarily based on amount of compression available before your springs are totally collapsed and become simply a solid piece of metal. By my measurement, the Clayton 2.5 diesel has about 6 inches of available compression at ride height. That means that no matter what else I do, I can not get more than 6 inches of available up travel (realistically only about 5.75). Now 6 inches of up travel in a JL is pretty darn good...but because our diesel springs are compressed more at ride height than non-diesel models, we are giving up some potential available up travel. I would think that a 3.6 or 2.0 with the Clayton kit would like see 6.5 or 7 inches of available up travel before the springs are completely collapsed.

The other negative is that the spring rate (number of pounds needed to collapse one spring one inch) is supposed to be part of an integrated, designed system...specifically integrated with shock valving. A spring designed for a 4800lbs vehicle when put on a 5300lbs vehicle will be comparatively softer and will want to dive / wallow. This impacts controllability of the vehicle. So if you use a longer spring (thus lower comparative rate) you should pair it with a shock that is valved to be stiffer in compression damping...and maybe...just maybe a bit softer in rebound damping. I am working with RadFlo currently to make sure the shocks I pair with Clayton kit do just that.

Quick example: Say the diesel is 300lbs heavier on the front springs (which CAT scale numbers seem to validate) than a 3.6. That means that each spring is carrying an extra 150lbs. If the spring rate is 188 (188lbs compresses the spring one inch) the spring will be compressed an extra .8 inches at rest. Now in the dynamic environment...Force is a function of Mass and Acceleration. As mass and/or acceleration increase so does force. When you add 150lbs / spring you are increasing the dynamic force applied to that spring and not by 150lbs...more like by 150lbs x (a formula based on) Acceleration. This is what leads to greater dive or a feeling of "wallowing" under dynamic use. Now in a vehicle that already has over 1,100 or 1,200lbs of load on each spring...does another 150 really change that much...not really...about 10% change (but this tracks with factory diesel springs being about 10% stiffer than 3.6 springs). But it is a factor.

So overall, is it a great big deal...no, I wouldn't have gone with Clayton if I thought it was, but it does require consideration.
The bump stop height can always be trimmed down a little bit for additional up travel! Just flex the vehicle out and make some measurements accordingly before cutting. Give us a call if you have any questions of course :like:
 

Themistocles

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The bump stop height can always be trimmed down a little bit for additional up travel! Just flex the vehicle out and make some measurements accordingly before cutting. Give us a call if you have any questions of course :like:
Yes, that has already been done. First thing we did in fact after installing the suspension. With the 3 inch bump stops, there is about .75 inches before the tire contacts the fender liner at full compression...on a ramp. Meaning we could take out about .5 inches of bump stop. But taking out .5 inches of bump stop only gets me to about 3 inches of up travel. Which is not enough.

So fender liners are coming out and MC inner fenders and one inch increment bump stops (MC) replacing the Clayton bump stop are going in. Then will re-ramp and see where we are. If the fenders get me two inches I will be at 4.75 inches of up travel...I may add .25 or .5 spacers to get me to 5 inches of up travel. If the fenders net 3 inches (I doubt they will) then I will be at 5.75 inches of up travel...which will max out the available up travel in the springs. Which gets me back to the original question from Clayton that I was answering..."why does anyone have a negative impression of going with a lower rate but longer spring to gain height." The answer is because you lose potential up travel and you require stiffer shocks to control the dynamic load.
 

Clayton Off Road

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Yes, that has already been done. First thing we did in fact after installing the suspension. With the 3 inch bump stops, there is about .75 inches before the tire contacts the fender liner at full compression...on a ramp. Meaning we could take out about .5 inches of bump stop. But taking out .5 inches of bump stop only gets me to about 3 inches of up travel. Which is not enough.

So fender liners are coming out and MC inner fenders and one inch increment bump stops (MC) replacing the Clayton bump stop are going in. Then will re-ramp and see where we are. If the fenders get me two inches I will be at 4.75 inches of up travel...I may add .25 or .5 spacers to get me to 5 inches of up travel. If the fenders net 3 inches (I doubt they will) then I will be at 5.75 inches of up travel...which will max out the available up travel in the springs. Which gets me back to the original question from Clayton that I was answering..."why does anyone have a negative impression of going with a lower rate but longer spring to gain height." The answer is because you lose potential up travel and you require stiffer shocks to control the dynamic load.
It actually does not sound like you lost any up travel, even on a regular gas model JL you get the same 2.75" of space between the bump stop and bump stop extension, which is almost an inch taller than factory, and when fully flexed out will equal about 4" total of shock travel when the bump stop is squished and is enough to completely fill the wheel well with a 37" tire! Of course, if you're looking to remove the inner liner and get a little more flex you could definitely get a smaller bump stop extension in there to allow for some more travel, the kit is just designed to work perfectly with a stock setup. We actually tested and had some customers test out higher spring rate coils for the diesel instead of the added height and it did not provide the same ride quality and feel we look for in our kits. Hopefully you're able to get the build exactly where you want it, always happy to help out however we can of course!
 

Themistocles

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It actually does not sound like you lost any up travel, even on a regular gas model JL you get the same 2.75" of space between the bump stop and bump stop extension, which is almost an inch taller than factory, and when fully flexed out will equal about 4" total of shock travel when the bump stop is squished and is enough to completely fill the wheel well with a 37" tire! Of course, if you're looking to remove the inner liner and get a little more flex you could definitely get a smaller bump stop extension in there to allow for some more travel, the kit is just designed to work perfectly with a stock setup. We actually tested and had some customers test out higher spring rate coils for the diesel instead of the added height and it did not provide the same ride quality and feel we look for in our kits. Hopefully you're able to get the build exactly where you want it, always happy to help out however we can of course!
Thanks...yeah, I agree. In the nearly year of research I did before I decided to go with Clayton, what I came to was that a rate higher than about 190 or 195 was likely going to be uncomfortable in the Jeep. If I remember right yours is 188. If my math is right you would need a rate of about 205 to get compression the same as a non-diesel model. But I just don't see 205 being a viable rate. Also the added compression gives me a little added droop before the spring unseats. So agree, I think your approach with taller springs with about the highest comfortable rate is right, which along with you all being open about your spring rates and your high build quality was why I ended up with Clayton. But the key here is that a softer comparative rate (rate : vehicle weight) does have an impact...and that impact needs to be taken into account when building the vehicle. It is not good or bad...it just is.

However you raise a really important point, that is very helpful. How much compression are you expecting in your bump stops under dynamic load...so not an a ramp, but under a good sized hit/shock on the trail? If I have a 3 inch bump stop, how much is it going to compress when I slam the front end into it on a whoop I hit too hard or drop my tire off a ledge? In other words what is the minimum height I should plan for from that bump stop?
 
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JDub11

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Someone with more experience can correct me if things have changed, but when I was involved with race cars spring tolerances were + - 10 percent. That means a 188 spring could be 206 or 170.
 

Themistocles

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Someone with more experience can correct me if things have changed, but when I was involved with race cars spring tolerances were + - 10 percent. That means a 188 spring could be 206 or 170.
I am totally self-taught on this, so could be wrong. But that variation would be about 1.6 inch difference in ride height 170 - 206 for a Jeep. It would also mean potential for substantial imbalance in height between sides or front to back....unless all springs were tested and matched prior to shipping...and if testing springs, why would you allow the big discrepancies to get through and be shipped. This level of discrepancy would mean a 2.5 lift would really be somewhere between 1.75 and 3.25....i dont see a variation in ride hieght that significant going unnoticed or undiscussed. Especially if my right side was 1.75 and my left 3.25. IRL my rear 2.5 inch springs gave me exactly 2.5 on both sides. The likelihood of that occuring if the range really is +/- 10% is vanishingly small. Such discrepancies would also be pretty easy to catch in the qc process.
 

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Did you end up doing any mods and see what your weight changes were after the fact?
no mods at the time of this weight but I have since had the MetalCloak 2.5" GC lift added along with new bumper and winch. Will re weigh and see what it looks like now.
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