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dirty trail dog
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601 Posts
Discussion Starter · #1 ·
I'm wondering about how the shock mounting location affects the feel and performance of a single-pivot bike. I am looking at the Ibex Atlas for example, and its forward shock mount on the downtube. Compare that to, say, a Heckler or Prophet, which has its forward shock mount on the top tube.

Is one position better than the other? Does it even matter? How does this affect all that "falling rate" stuff I've been reading about? Does it affect climbing?
 

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noMAD man
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12,227 Posts
I'll take a stab...but I'm not going over to the Ibex site to look at that bike. I'm too lazy, and you were too lazy to post a pic...LOL...just jabbing you. From your description I take it that the Atlas mounts the shock on the front downtube. So for equality let's compare it to a Bullit vs. Heckler setup. In reality the important issue is where all the "dots" of the suspension points are on a piece of paper that determines how the suspension rate or characteristics function. For this very general comparison, the Bullit's suspension rate is fairly linear with a slight falling rate...also depending on where you mount the shock in the shuttle...it has two positions. The Heckler has a very strong falling rate and is very sensitive to the type of shock it uses because of that. Most of these (I'll refer to them as Bullit clones) bikes with the front end of the shock mounted on the downtube are usually more linear while a design like the Heckler is more falling. This isn't always bad, as you can tell the Heckler is very popular and performs well.

Now, much of this generalization goes out the window as the pivot points change dramatically or you throw a linkage in there. There's no really straight answer here as to what's best or not. And if you're not familiar with falling, linear, or rising rate as it applies to the rear suspension, then that's another element altogether.
 

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2,029 Posts
TNC is spot on

here are some terms to think of, but only on a true single pivot like above and only a rough guide to seperate obvious falling from obvious progressive...

draw a line along the shock body, from one mount to the other.
now draw a line from the main pivot to the shock mount on the swingarm.
The angle between these lines and how they change is what you are lookin at.

essentialy at any time, as the suspension compresses, if the angle is tending toward 90*, the rate will be progressve in nature. If the angle is going away from 90*, the rate will be falling.

It is just simple trig...but remember the rear wheel moves around a circular path as well, so this also effects the rate....but that is another discussion (same math).
 
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