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Front Suspension Cycling Results


Brianj5600

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If you stick with hockey pucks buy on of these.

20210111_184504.jpg


Just one flat washer and sink the head flush.

20180831_222010.jpg
 

fuse

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So the only thing not connected is the sway bar, springs, and shocks depending on if you are checking them at the time?
Keep the shocks connected when you check your bump stops. As the rest of the thread shows, shocks limit travel in both directions.
 

pc1p

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Do the LCoG builds emphasize down travel while limiting up travel? In other words, is the shock 2/3+ of the way compressed at ride height?

If so, that would seem to be counterproductive to utilizing the shocks’ full travel.
It depends on who is doing the build and what their understanding of how the entire suspension system will work together. The LCOG term and philosophy has been bastardized a bit - it's basically the "overlanding" equivalent of a crawler. For a long time, the 1/3-up and 2/3-down travel split has been a very solid target for a "Jack of All Trades" build, with the notable exception of a high-speed, desert running rig.

There are a few issues with this - particularly in the constraints of the TJ - as others have pointed out. The biggest issue is the diminished amount of uptravel when compared to stock (which is generally accepted to be 4-4.5"), which causes chassis lift when going over obstacles. This causes tipping and general unstable balance through obstacles, rather than allowing your suspension to work for you.

The other big issue is lack of contact pressure. I was talking about this very topic not too long ago with someone who's very experienced and knowledgable on the topic (and who's been on Ultimate Adventure a few times and is a KOH regular). He said there is no hard answer but a good rule of thumb is that residual spring pressure should equal to tire weight. I haven't seen this mentioned in other resources but he noted that the entire build world is moving towards a more balanced travel setup and getting away from the RTI/flex shows.

**Edit for clarity**
By "residual spring pressure", it was described to me as follows - it is the amount of force the spring is able to apply downward due to the amount of compression on the spring. For example, if you have a 200#/in spring and your tire/wheel combination weights 100#, you want roughly 1/2" of compression at the end of suspension travel. If you have 175#/in springs and your tire/wheel combo weights 75#, you want roughly 7/16" of spring compression.
 
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pc1p

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That sounds like a coilover thing.
The conversation actually got there in a sort of twisted way. I was reading some opinions and theory on limiting straps and how/why/when to set suspension limits (other than to prevent catastrophic bind), which is what I was asking his opinion on. As we got into the conversation, he mentioned the importance of contact pressure and very similar to what was discussed earlier in this thread, explained why flexing a tire to the point when the spring is dangling in the bucket looks cool but does very little for performance. This is where he mentioned the information I noted in my comment earlier. I asked if there were any differences between coil types/rates or with coilovers and he said "nope - springs pressure is spring pressure", which at least on the surface makes sense. The next time I see him, I'll ask him some more questions now that I've had some time to mull the theory over.

**EDIT** After reading my original comment over - I have clarified it some.
 

jjvw

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The conversation actually got there in a sort of twisted way. I was reading some opinions and theory on limiting straps and how/why/when to set suspension limits (other than to prevent catastrophic bind), which is what I was asking his opinion on. As we got into the conversation, he mentioned the importance of contact pressure and very similar to what was discussed earlier in this thread, explained why flexing a tire to the point when the spring is dangling in the bucket looks cool but does very little for performance. This is where he mentioned the information I noted in my comment earlier. I asked if there were any differences between coil types/rates or with coilovers and he said "nope - springs pressure is spring pressure", which at least on the surface makes sense. The next time I see him, I'll ask him some more questions now that I've had some time to mull the theory over.

**EDIT** After reading my original comment over - I have clarified it some.

Sounds like a complicated way to describe maintaining sufficient free length to keep the springs seated at full shock extension.
 
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pc1p

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Sounds like a complicated way to describe maintaining sufficient free length to keep the springs seated at full shock extension.
I think there’s slightly more to it than that - arguably you could keep the spring seated with almost 0# of spring pressure... what he is telling me is that there is value is retaining some compression for the sake of contact pressure.

I can’t speak to the efficacy of it as I haven’t experimented with enough setups to say, but it is something I would explore based on his success.
 
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jjvw

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I think there’s slightly more to it than that - arguably you could keep the spring seated with almost 0# of spring pressure... what he is telling me is that there is value is retaining some compression for the sake of contact pressure.

I can’t speak to the efficacy of it as I haven’t experimented with enough setups to say, but it is something I would explore based on his success.

Once the shock is fully extended, the spring can't provide any additional down force. Beyond that, the down force cannot at any point of the shock travel exceed the weight of the vehicle. Usually it is far less than that.
 
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pc1p

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Once the shock is fully extended, the spring can't provide any additional down force.
Perhaps I’m butchering the explanation, but I wasn’t suggesting otherwise.

At the point of full shock extension, is it not possible to have spring force pushing down on the axle/wheel?


Beyond that, the down force cannot at any point of the shock travel exceed the weight of the vehicle. Usually it is far less than that.
Same as above, I’m probably explaining it poorly. I don’t believe I said or suggested the spring force should exceed the weight of the vehicle though. How it was explained to me was that the remaining spring compressive force should equal the weight of the tire. In a typical TJ, that would be ~1/2” of compression at the end of travel (be it limited by shock or strap) .
 

jjvw

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Perhaps I’m butchering the explanation, but I wasn’t suggesting otherwise.

At the point of full shock extension, is it not possible to have spring force pushing down on the axle/wheel?



....

Vehicle weight is all that matters. The spring is only transfering that force to the axle to the tire to the ground.

If the spring becomes unseated, then the only down force comes from the weight of the axle and tires.

The moment the tire lifts off the ground, it doesn't matter the amount of spring pressure there is against the upper and lower spring seats. It could be a million pounds. There is no force being transferred to the ground.
 

jjvw

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Been a long time since I did some Newtonian formulas, but wouldn’t force on the strap/shock be the same as on the tire?

Not necessarily. And when it is, the window where both are equal is very narrow.
 
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Impact LJ

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Alright, here's the finished product of the bump stops.
IMG_0575.jpeg


I had to extend the top by 1.5" and added 3" to the bottom. Not happy with it but it keeps the tires out of the fenders for now, until I add the Savvy body lift.

There is about 2 inches of shock left up top which I plan to fix with either a spacer or longer shock. Either of them will make the brake lines too short at full droop.
 

jjvw

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Alright, here's the finished product of the bump stops.
View attachment 217692

I had to extend the top by 1.5" and added 3" to the bottom. Not happy with it but it keeps the tires out of the fenders for now, until I add the Savvy body lift.

There is about 2 inches of shock left up top which I plan to fix with either a spacer or longer shock. Either of them will make the brake lines too short at full droop.

That's a lot of extension. When I had 33s, I never had more than 1.5" extension.
 
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jjvw

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Total. I had a 3" diameter nylon body lift puck that I cut down to about 1.5" and bolted down to the axle pad. It matched my first set of front shocks. Then when I changed to slightly longer shocks, I raised to upper shock mount rather than add more bump. The most mine would ever have is about 3".