If I remember right the Icon truck runs stock springs, do they recommend sticking with stock with these shocks and bumps or will they work just as well or better with aftermarket springs and if so do they have a preference?
ICON Bumpstop Kit Install Write-up
- Thread starter BIRDMAN
- Start date
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There have been several discussions on the topic. I'll give you both versions.
1. My GF has told me that I'm a generous lover and as such I didn't feel it necessary to compensate for anything with unnecessarily large bumstops.
2.
An air bump is hybrid of a shock and an air spring. They can have some very odd characteristics however due to the fact that they are emulsion (gas and oil not separated), they are not connected to the axle, and the current impact partially depends on the previous impact(non linear).
As an air spring its characteristics are based on: shaft dia, stroke, initial pressure and compression ratio. The graph ramps up drastically at the end and how drastically is based on the compression ratio. We set it up for very high compression ratios and sometimes close to infinite or hydraulically locked. Here's the catch.....the shape of the graph is ALWAYS the same if set up this way regardless of size. See attached
The problem with an air spring of this nature is it doesn't really do much till the end of its travel so there isn't really that much energy to be stored. What we do is force it to develop some extra force earlier in its stroke with the valving on the piston. It is also velocity sensitive so the faster it hits the more it ramps the pressure up. This combined with a reasonable initial charge makes it so that first contact is mild and if it's a small hit doesn't upset the attitude or stability of the vehicle or its occupants but when hit hard will create(and dissipate) more energy earlier in the stroke and lift the chassis over the obstacle.
Does size mater? Yes at some point, but not because of heat or performance. It's relative to shaft size more than body size. At some point the pressures get hard to deal with and a larger shaft diameter is called for.
This dyno graph shows some of the characteristics of an air bump.
The blue line is very slow so the hydraulic part is not influencing it very much and the shape is very close to just an air spring
The red line is at 10 inches per second and shows the hydraulic effect add additional force. You can also see that there is a flat spot at the lower left corner. This is because due to the rate of impact as its cycled on the dyno the shaft has not had time to fully extend before the next impact.
The green line is at 30 inches per second and shows how it can develop forces much higher than just those due to nitrogen pressure and shaft diameter. This is being cycled much faster than the random bumps you would encounter in the field yet still returns to 60% of its travel.
The energy that is being absorbed is based on the area under the curve. So you can see that at low speed there is less energy to use the majority travel available and at high speed more energy is absorbed.
Note it is also important to tune the rebound correctly to not kick back but also not overdo it so that it extends to slowly. This is especially bad as it will pack up the bump on the first hit and the second one will slam extremely hard because there is no travel left. This pack up situation can be dangerous and is common when a large air bump is run at low pressure to reduce the initial contact force.
It is not uncommon to see wheel speeds over 100 in/sec
---------- Post added at 12:22 PM ---------- Previous post was at 12:18 PM ----------
IconREP gave me the impression that the kit will work with either because I did express my intention of upgrading springs at some point.
bstoner59
does it come in shmedium?
I just made a scene spit out a full mouth of my food and coffee at breakfast when I read Bird's response...
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So is a bump stop kit only needed for those OH Sh*t moments or does it aid the shocks in everyday use as well, and how about if you load your truck up with stuff or tow a trailer does it aid in anyway in those situations?
I don't know about towing because I never have and probably never will tow anything with my truck but as for the every day use you don't gain or lose anything on the street from any bump stop kit from what I can tell. They have only hit once so far while not deliberately off roading and I was pulling on to a steep embankment to park on the side of the road. Off road they will aid in the rear end control through the last 35-40% of shock up travel and obviously within that includes the oh shit moments too.
BlueSVT
FRF Addict
Nice write up, as always... looks good. Now go beat on it, so we can see what sort of abuse it takes!
Havoc in the Hills will be the test
Bird will take one lap at havoc before anyone gets there and will then proceed to park his purdy white truck for the remainder of the weekend. Pfff... Testing?
"These ICONs do feel really good" -Brian Stoner TRR13
bstoner59
does it come in shmedium?
#whatareicons
I was just trying to pump up your ego after your website was called "little"
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I was just trying to pump up your ego after your website was called "little"
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