Brianj5600
TJ Expert
Maybe - but it certainly doesn’t work that way the first time.
(And on this forum - I certainly would not tell anyone the length of those arms….)
Or your shock split.
Maybe - but it certainly doesn’t work that way the first time.
(And on this forum - I certainly would not tell anyone the length of those arms….)
It really kinda does. The rig is going to tell you what you can and can't do. If the calculator tells you to hang the end of the rear arm down 6" below the frame, you know that's stupid so you are going to go back and make changes to the numbers to get something not so stupid. You know that putting the arms right in front of the axle tube fucks with where the uppers need to go, so you drop them so to make it better and get your uptravel civilized so you don't shove the uppers through the tub floor. You know if you tighten up the vertical separation at the frame too much, the geometry is going to suffer so you do a body lift and move them up some without going through the floor. The blueprint and the constraints of the platform are right in front of you, they tell you most of what you can and can't do.
I want an arm length that stays out of trouble and is long enough to do the job. The longer a link is for a lower, the stronger it has to be. I don't want to deal with that.
I love everything about this statement. It took me a long time to understand what you have explained very concisely and succinctly here and it has been very valuable. It really does apply in every single place where we modify the vehicle - another nice example is seeing where the rear drive shaft on the Rubicon models starts binding and how that limits what can be done in terms of setting up useful rear travel in a typical lifted setup. Likewise for belly skid setup with 241/auto. The list goes on, but the message is very clear.
I love everything about this statement. It took me a long time to understand what you have explained very concisely and succinctly here and it has been very valuable. It really does apply in every single place where we modify the vehicle - another nice example is seeing where the rear drive shaft on the Rubicon models starts binding and how that limits what can be done in terms of setting up useful rear travel in a typical lifted setup. Likewise for belly skid setup with 241/auto. The list goes on, but the message is very clear.
I used a calculator when I build my current suspension (triangulated four link, 3 link front) and took this exact approach. At the time I did not know much about suspension geometry - I still know only enough to be dangerous - but the calculator did help me locate and position my links. Since I basically built my setup from scratch, I would have had no clue otherwise. I do understand the impact of an estimated CG, but the calculator helped me with a great starting point.
For me, the real benefit of the calculator was that it helped me understand how making changes to link locations and arm lengths impacted anti-squat, roll center, etc. It was also a great mechanism for me to get feedback on link locations as I was designing the suspension from those on the forums who know better than I.
In the end, I’m happy with how it works - and for me it works pretty well. I don’t think that would be the case if I had not used the calculator.
I strongly suspect that if you were to build another one for a buddy, you'd walk over, grab a handful of arm lengths off of your rig, set his axles in place at ride height and grow some tabs and mounts to the ends of the arms. And, you'd never give a second thought to what the calculator says it is supposed to do.
(And on this forum - I certainly would not tell anyone the length of those arms….)
Or your shock split.
This is what probably gets lost in these discussions more times than we can count.The caveat needs to be that we are building recreational rigs that do recreational things by folks who enjoy recreating with our rigs offroad. We aren't racing, we aren't hill climbing, we aren't rock bouncing, and we aren't building purpose built narrow function vehicles. We want all around rigs that are very good at most things.
Talking about shock split does not have to become pretentious. Like I mentioned earlier in this thread there is no reason to not discuss why something may or may not work from a different platform to a TJ. Do I think the comical 20up 80down splits some buggies run would be good for a TJ the answer is no. I think that if you want a well balanced rig that can drive to the trail, run all day and drive home you need to have a bit more balance. Does that mean that if your current spring/shock setup gives you a 40/60 split that it is the end of the world absolutely not it is still all about acceptable ranges.
Talking about shock split does not have to become pretentious. Like I mentioned earlier in this thread there is no reason to not discuss why something may or may not work from a different platform to a TJ. Do I think the comical 20up 80down splits some buggies run would be good for a TJ the answer is no. I think that if you want a well balanced rig that can drive to the trail, run all day and drive home you need to have a bit more balance. Does that mean that if your current spring/shock setup gives you a 40/60 split that it is the end of the world absolutely not it is still all about acceptable ranges.
Talking about shock split does not have to become pretentious. Like I mentioned earlier in this thread there is no reason to not discuss why something may or may not work from a different platform to a TJ. Do I think the comical 20up 80down splits some buggies run would be good for a TJ the answer is no. I think that if you want a well balanced rig that can drive to the trail, run all day and drive home you need to have a bit more balance. Does that mean that if your current spring/shock setup gives you a 40/60 split that it is the end of the world absolutely not it is still all about acceptable ranges.
In case anyone is wondering after Brian's comment - I'm at 6 up / 8 down. What's that, 43/57?
42.8, at least get that part right.
I am curious where the 20/80 split trend came from. Is it that they cannot fit more up because they are trying to stay low? Is it because that is their desired ratio? I’ve heard some mention that uptravel is not important for rock crawling specifically, but I have had many instances where I am balanced on a few boulders and the tires are stuffed way up in the wheel well. Without that uptravel, the body would undoubtedly have leaned over more. The 50/50 split is undoubtedly better for a well balanced multi task rig because it also unlocks go fast ability. But I would argue that I use uptravel a lot even while slow crawling.
When I recently started learning about geometry I read the college boy paper and the Gods of Suspension thread, some other online articles about 4-link and 3-link suspension designs, and finally the Dave Kishpaugh GC thread. One of the things the college boy paper stated was that the platform was being built around the suspension rather than the suspension around the platform. <snip>
<snip> Of course, in the practical real world performance of a TJ I don't have the resources to do testing, so I came to accept that I have to trust those who have. That is probably where a lot of us are. The main thing is understanding that you can work out all the numbers, but it is basically meaningless apart from an academic exercise. What works on the trail is what counts and when you're talking about TJ's/LJ's you are looking at that platform, so bringing buggies in doesn't help the conversation go anywhere.
In case anyone is wondering after Brian's comment - I'm at 6 up / 8 down. What's that, 43/57?
I thought it was like 5/9.
You can't translate something that you can build around a suspension design to something you have to design suspension around and that is where everyone loses it.
Post 219 and I have not read any of those resources you referenced. I just know how it works.One of the things the college boy paper stated was that the platform was being built around the suspension rather than the suspension around the platform. That statement means a lot because the platform has limitations.
When I recently started learning about geometry I read the college boy paper and the Gods of Suspension thread, some other online articles about 4-link and 3-link suspension designs, and finally the Dave Kishpaugh GC thread. One of the things the college boy paper stated was that the platform was being built around the suspension rather than the suspension around the platform. That statement means a lot because the platform has limitations. However, I was still under the impression from other articles on crawlpedia and elsewhere that I needed to plug numbers in a 4-link calculator. I asked about the best one and got mostly shunned. Ok, well, you don't know what you don't know. I felt it was pretty hard to get anywhere. I did get a calculator and played with numbers for a couple of hours on a computer that wasn't mine (which slowed me down). I did find it helpful to at least see what manipulating the numbers did to AS and IC, but, of course, it doesn't tell me what the rig will do on the trail (and articles out there such as Crawlpedia state that 140%+ AS is good for rock crawling, which is discrepant information). I haven't punched any numbers in the calculator since that day. I eventually did realize that most of this was looking at it statically, which renders the numbers irrelevant for offroad performance. As I read more here I finally started to understand that it was really about experimenting with various length arms (which changes the arc travel radius of the axle) and mounting locations (changing the IC and centering the axle when triangulated properly). Of course, in the practical real world performance of a TJ I don't have the resources to do testing, so I came to accept that I have to trust those who have. That is probably where a lot of us are. The main thing is understanding that you can work out all the numbers, but it is basically meaningless apart from an academic exercise. What works on the trail is what counts and when you're talking about TJ's/LJ's you are looking at that platform, so bringing buggies in doesn't help the conversation go anywhere. I'm sure I screwed up something in this post, so I am ready to receive my lashing. Thanks to those who have given out eggs to help me get a little ways down the road to understanding.
When I recently started learning about geometry I read the college boy paper and the Gods of Suspension thread, some other online articles about 4-link and 3-link suspension designs, and finally the Dave Kishpaugh GC thread. One of the things the college boy paper stated was that the platform was being built around the suspension rather than the suspension around the platform. That statement means a lot because the platform has limitations. However, I was still under the impression from other articles on crawlpedia and elsewhere that I needed to plug numbers in a 4-link calculator. I asked about the best one and got mostly shunned. Ok, well, you don't know what you don't know. I felt it was pretty hard to get anywhere. I did get a calculator and played with numbers for a couple of hours on a computer that wasn't mine (which slowed me down). I did find it helpful to at least see what manipulating the numbers did to AS and IC, but, of course, it doesn't tell me what the rig will do on the trail (and articles out there such as Crawlpedia state that 140%+ AS is good for rock crawling, which is discrepant information). I haven't punched any numbers in the calculator since that day. I eventually did realize that most of this was looking at it statically, which renders the numbers irrelevant for offroad performance. As I read more here I finally started to understand that it was really about experimenting with various length arms (which changes the arc travel radius of the axle) and mounting locations (changing the IC and centering the axle when triangulated properly). Of course, in the practical real world performance of a TJ I don't have the resources to do testing, so I came to accept that I have to trust those who have. That is probably where a lot of us are. The main thing is understanding that you can work out all the numbers, but it is basically meaningless apart from an academic exercise. What works on the trail is what counts and when you're talking about TJ's/LJ's you are looking at that platform, so bringing buggies in doesn't help the conversation go anywhere. I'm sure I screwed up something in this post, so I am ready to receive my lashing. Thanks to those who have given out eggs to help me get a little ways down the road to understanding.