Up-travel: What's the big deal?

toximus said:
One thing I've noticed is that none of the complete* kits in the industry mention up travel.

Genright Tracer: https://genright.com/products/genright-tracer-jeep-lj-coil-over-suspension-kit.html
Artec (they have many kits): https://www.artecindustries.com/TJ_SDF_1_Ton_Swap

Is this because they don't care about up travel?

*Yes, I know these aren't technically complete, even by the company's description, but they are complete enough for the topic of up travel.
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I'm not even sure they could list up-travel if they wanted to. Aren't there too many variables such as tire size, bump stop amount, highline fenders versus stock fenders, shock travel, etc.?

With all those variables, wouldn't it be impossible for them to list a specific amount of up-travel?
 
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toximus said:
One thing I've noticed is that none of the complete* kits in the industry mention up travel.

Genright Tracer: https://genright.com/products/genright-tracer-jeep-lj-coil-over-suspension-kit.html
Artec (they have many kits): https://www.artecindustries.com/TJ_SDF_1_Ton_Swap

Is this because they don't care about up travel?

*Yes, I know these aren't technically complete, even by the company's description, but they are complete enough for the topic of up travel.
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Chris said:
I'm not even sure they could list up-travel if they wanted to. Aren't there too many variables such as tire size, bump stop amount, highline fenders versus stock fenders, shock travel, etc.?

With all those variables, wouldn't it be impossible for them to list a specific amount of up-travel?
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Chris is correct, their are too many variables involved to give an exact spec like that. Besides for the average lift kit purchaser stating what the up travel is not great marketing fluff. You would use phrases like 20 percent longer shocks for increased wheel travel. Which is taking a 9 inch travel shock and going to 11 without saying how the travel is split or even if the other components allow for more travel to begin with. Once you start looking at things like up travel and travel split you are not the typical lift kit customer.
 
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Chris said:
I'm not even sure they could list up-travel if they wanted to. Aren't there too many variables such as tire size, bump stop amount, highline fenders versus stock fenders, shock travel, etc.?

With all those variables, wouldn't it be impossible for them to list a specific amount of up-travel?
Click to expand...

To make this conversation easier, let's forget about all other kits except Genright's Tracer kit. Bumpstops are to prevent interference, so I think we can easily agree that's a red herring. Fenders are one of the last things that typically are taken into account when figuring out clearance, but for the sake of argument Genright makes both, does their kit allow for a sane tire size to even hit their highline fenders? Genright also lists overall shock travel for their kit: 14". The only thing left to set in order to figure out what up travel is is lift height, let's suppose that's also a sane lift height relative to this type of kit of 4-5" (if you want more or less lift you can figure out up travel by easily adding or subtracting from the base line of lift). Since they are in fact selling this as a kit I hope they have install one or two on a Jeep. It doesn't take much to take the tires off and cycle the axle to figure out maximum up travel... something that I hope they did when they installed it.

All we need to know is what is the first point of interference that isn't tires or bumpstops when following their (included?) instructions.

Based on what I know and looking at their poorly angled pictures, this kit is at most getting 5-6" of up travel based on 35/37" (even possibly 40") tires and 4" of lift.
 
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toximus said:
..... Bumpstops are to prevent interference, so I think we can easily agree that's a red herring. ....
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But isn't that what we are looking for? If a component's description included a recommended amount of bump stop requirement or the amount of potential reduction, that would tell us a lot about what we can expect. We know larger tires, longer shocks, certain trusses, track bars, diff covers require BS extension. Body lifts and certain replacement fenders can often allow a reduction in the extension.

It's a lot to juggle. And quantifying that number can get tricky the further away from stock the build is. But at the end of the day, the upper boundary of the suspension's up travel is established by the bump stops (or whatever is acting as the bump stop). The distance of that travel is determined by the springs creating the ride height.
 
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So, it is clear that you can have too little up travel. Does it work the other way too, can you have too much up travel? As I"m mocking up my outboard its looking like I might be able to have 7" of up travel on a 12" shock, leaving 5 for down travel. For conversation's sake, let us say I notch the frame, extend the towers and upper links into the passenger compartment, swap to Coilovers to prevent spring bind, etc. and I tease out 8" of up travel. Or 9". What negative effects will this type of setup have?
 
kmas0n said:
So, it is clear that you can have too little up travel. Does it work the other way too, can you have too much up travel? As I"m mocking up my outboard its looking like I might be able to have 7" of up travel on a 12" shock, leaving 5 for down travel. For conversation's sake, let us say I notch the frame, extend the towers and upper links into the passenger compartment, swap to Coilovers to prevent spring bind, etc. and I tease out 8" of up travel. Or 9". What negative effects will this type of setup have?
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There's a point where you're not going to want to go through all that work so I'm not sure it's worth discussing. 7" of up on 12" of travel works great but it's going to be tricky on a 4" lift. I've got around 7.5" in my rear with 14" of total travel.
 
If your running fox 2.0 shocks you want to be as close to 6up/6down as possible in order to be in the sweet spot of the flutter stack. Or at least that was my understanding when I did my outboard
 
That's a good question. I can tell you that after the outboard in mine, I dropped about 200lbs from the rear. It raised up 1.5" and rode really stiff(put me at about 7 1/2" up and 4 1/2" down travel). I reworked the upper part of the shock mount to get the travel back to 50/50 and the ride returned to the softer ride that I had prior to the weight savings. How much of that is real I don't know. Just seat of the pants science on my part.
 
I can say I have never taken a shock apart, so I dont know what the internals look like, when @pcoplin did the shock tune for me he stressed to try and get it to 50/50 travel or as close as possible.
 
pagrey said:
If you don't know the answer to that how can you possiby discuss shocks at all and expect people to take you seriously. Seach for PSD or position sensitve damping. Some manufacturers refer to it as the control zone.
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I didn't realize that we're talking about bypass shocks.
 
pagrey said:
If you don't know the answer to that how can you possiby discuss shocks at all and expect people to take you seriously. Seach for PSD or position sensitve damping. Some manufacturers refer to it as the control zone.
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Damn dude, that's incredibly hostile. Toximus knows whats he's talking about. He tunes his own coil overs. It WAS a Rhetorical question, which is certainly a trigger, but everyone relax. We will all stressed right now, no reason to snap.

Fox 2.0 RR are not position sensitive. Very few shocks are
 
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strumble8 said:
That's a good question. I can tell you that after the outboard in mine, I dropped about 200lbs from the rear. It raised up 1.5" and rode really stiff(put me at about 7 1/2" up and 4 1/2" down travel). I reworked the upper part of the shock mount to get the travel back to 50/50 and the ride returned to the softer ride that I had prior to the weight savings. How much of that is real I don't know. Just seat of the pants science on my part.
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Remove a shock and release the nitrogen. Move the piston through the stroke by hand and see if it acts differently at different points. Report back if it does. My guess is that you have something else going on such as experiencing pressure ramp from trying to use IFP position to create rebound.
 
strumble8 said:
If your running fox 2.0 shocks you want to be as close to 6up/6down as possible in order to be in the sweet spot of the flutter stack. Or at least that was my understanding when I did my outboard
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There is no sweet spot for the flutter, the standard smooth body shock doesnt know where it's at, it's only the speed of the shaft. I recommend around half up half down to let the shock work. AT least half of the shock being uptravel is a better way to say it.
 
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kmas0n said:
Toximus knows whats he's talking about.
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Well, I'm a student of learning what I'm talking about. And I've learned from who a lot of people consider the best. That doesn't make me a master though. But I only try to speak what I know.
 
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kmas0n said:
So, it is clear that you can have too little up travel. Does it work the other way too, can you have too much up travel? As I"m mocking up my outboard its looking like I might be able to have 7" of up travel on a 12" shock, leaving 5 for down travel. For conversation's sake, let us say I notch the frame, extend the towers and upper links into the passenger compartment, swap to Coilovers to prevent spring bind, etc. and I tease out 8" of up travel. Or 9". What negative effects will this type of setup have?
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I probably should have been more clear. There is a point where too much up travel is bad when it messes up the amount of down travel. This is why the 50/50 bias is generally recommended.

For an extreme example, if you take a 12" shock and somehow managed 11" of up travel out of it, you'd be left with 1" of down travel. You need some down travel so the suspension can travel down from under the Jeep when coming across things like pot holes. Or else the Jeep will "fall" instead of the suspension traveling down.

More realistically, you'll find it challenge enough to make everything clear and have okay driveline angles with a 12" shock with 50/50 bias. Anything bigger and get out your sawzall.
 
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