BJ74 TD Build Thread - Stoffregen Motorsports
- Thread starter Stoffregen Motorsports
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Stoffregen Motorsports
Explorer
Thank you guys. It's turning out nicely. Very subtle, yet extremely capable.
Stoffregen Motorsports
Explorer
That's a good question. Back when everyone was doing two shackles per leaf spring on the rear suspension, I was not sold. I figured it was pointless for the reason you mentioned. But, I have come to see it as a good problem to have. If the travel is limited, the un-sprung weight of an axle hanging in the air can try to pull that corner back down, possibly affecting your stability while completely crossed up. If that tire is planted on terra firma, there's not going to be that added weight working against you. Also, if you have a locker in that axle, the weight of the axle and wheel/tire combo can add just enough traction to help get you over that obstacle.
It's a no lose situation. Nothing bad can come from it, and possibly something good.
Stoffregen Motorsports
Explorer
I agree.
thethePete
Explorer
^ Also, I don't personally care to use shocks as limit straps...
Truck looks top notch as always. Fantastic work!
Truck looks top notch as always. Fantastic work!
Metcalf
Expedition Leader
Interesting. I don't know if I agree, but I think you articulate (ha) your position well.
I could expand if your curious, but I don't want to muddle up such a nice fab thread.
Stoffregen Motorsports
Explorer
I always love a good debate, so feel free to expand on your point of view.
The beauty of building custom rigs from the ground up is that I get to try out new things and test theories. Theories are great, but untested, they amount to squat. There is another aspect of building; that of splitting hairs. It is possible that one way of doing things is better than another, but where the rubber hits the road (pun), either way will work out just fine. Finally, the last aspect of what we are all doing in modifying our rigs, nothing is permanent. If we try something, and we are dissatisfied with the results...cut it off and do it over.
I may sound a bit defensive, but I assure you, I am not. The only way to make these projects turn out in as short a time frame as possible (this one has been here almost a year now) is to make decisions and get them done.
Stoffregen Motorsports
Explorer
And any and all input is valuable, so thank you for your insights.
Metcalf
Expedition Leader
Cool. I thought I would ask first.
The main issue I see with captured coils, and/or zero preload, is the lack of 'control' in the suspension of that last few inches of extension. I think are few different things that stack together, which makes identifying the root cause a little challenging. I always tend to notice that the tire isn't really doing it 'job' on a suspension with captured coils ( or coils free to drop out ). It seems to me like the tire has been disconnected from having much positive effect on the chassis. We know that it has less weight on for sure (unsprung weight transition, and actually worse than a drop out style coil). We know the suspension may be close to the limits of extension travel ( ie bad geometry ). The shock also seems to lose control over that corner, which is perhaps something to do with the zero or even negative spring rate.
I see captured, or drop out, coil systems as a patch over a proper coil design for the sprung weight of the vehicle and the shock length required. There are limits that you have to work inside, I do realize that. Coil free length vs rate vs block height vs diameter ( for coil stability against bowing ) is usually what we have to work within.
There is a plus and minus to a lot of this as you mentioned. I try and look at what a lot of other disciplines in this sport are doing. It seems one of the biggest things to come out of the KOH type racing is suspension tech with high un-sprung weight, and especially with a beam/solid axle. One of the major trends in that seems to be that many cars are running the lightest spring rate that will hold up the car along with a decent amount of preload. It is fairly rare that you see anyone running a tender coil these days. You still see the odd one, but they seem to have gone away. I think tender coils are akin to zero rate drop out coil suspensions in a lot of ways.
Just a few thoughts.
Stoffregen Motorsports
Explorer
So you're suggesting that because the suspension is unloaded that there might be wheel hop? The triangulation of the control arms (both vertically and horizontally) was designed to control the axle through it's cycle of travel so there shouldn't be anything weird going on when the tire is dropped out.
Also, the shock is pressurized so up until the point of full extension, there is some pressure applied to the ground.
Also, the shock is pressurized so up until the point of full extension, there is some pressure applied to the ground.
marshal
Burrito Enthusiast
i would like comment on this: if you haven't tried to compress a fox or king shock loaded with 200PSI of nitrogen by hand, then you really cannot fathom how much pressure these shocks create. if anything, these race quality shocks are worthy of contributing to spring rates.