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Old 12-26-2006, 08:02 PM   #1
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Default Xray (fk05) downstop / droop measuring question

I'm trying to set the droop and downstop on an FK05 and I need some help.

1) The Xray setup sheet says that on the rear, measure downstop "under block". On the Xray FAQ, it says for the rear of an Fk05, measure "under the rear upright". Does that mean I measure from beneath the large boss into which the set screw goes under the rear hub? Or do I measure from the bottom of the hub, but not beneath the set screw boss which sticks out approx 1 or 2mm beneath it? Or???

2) The factory setups only refer to downstop, not droop. Downstop, as best I can understand it, refers to how far above or below the bottom of the chassis the specified measuring point is when the suspension is unloaded and against the downstops. Is my head screwed on straight here?

3) Are the values stated on the setup sheets positive, ie, above the chassis, or negative, below the chassis when they simply say downstop front=2mm rear =6mm?

4) Seems to me that downstop only specifies droop if you know both ride height and tire height, otherwise we don't know where the chassis sits at rest. Different ride heights will produce different droop, and same ride height will produce different droop depending on the tire height. Why aren't droop values shown on the xray sheets? Or do I just follow everything to a T, downstop plus specified ride height and tire diameter to get the droop they had?

5) Do you put some grease on the downstop screws? Its really had to adjust owing to the difficulty of moving the screw smoothly. The thread is so tight that it only moves in snaps as it brakes loose under great torque from a wrench?
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Old 12-27-2006, 05:16 AM   #2
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Personally, I rarely ever check "downstop". I measure droop above ride height every run. Get your ride height square. Settle the car and lift up on the shock tower until the tires just start to lift from your board. Measure with a ride height gauge and there's your droop. That should answer part of one of your questions.

P.S.- The droop screws should be tight so they can hold their setting. A pain, but worth it, none-the-less.
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Old 12-27-2006, 09:55 AM   #3
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Thanks Stampede. I would however like to know how the factory guys measure downstop at the rear.
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Old 12-27-2006, 05:51 PM   #4
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I set downstep / droop once on my FK05, and it's been by feel from there on in. I must be doing something right because if I'm driving ok, I can keep up and threaten the T2's and T2 007's I race against!
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Old 12-27-2006, 10:43 PM   #5
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Iceracer

4>>> Droop (Downstop in XRAY -speak) is how far down the arms are physically allowed to move. In terms of adjustment, it should be done with shocks and wheels removed. In saying this, it may be that when the shocks are then put back on the chassis, that the shocks/springs don't allow for full down travel - that is to say that the shocks may prevent the droop screws from contacting the chassis and limiting travel. If that is the way a particular setup is, then that's how it is supposed to be. Droop is an absolute and you measure it with shocks and wheels removed.

5 >>> If you possibly can, leave them tight to prevent them moving in a race. I know this sounds impossible but I have seen it happen.

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Quote:
Originally Posted by Iceracer
I'm trying to set the droop and downstop on an FK05 and I need some help.

4) Seems to me that downstop only specifies droop if you know both ride height and tire height, otherwise we don't know where the chassis sits at rest. Different ride heights will produce different droop, and same ride height will produce different droop depending on the tire height. Why aren't droop values shown on the xray sheets? Or do I just follow everything to a T, downstop plus specified ride height and tire diameter to get the droop they had?

5) Do you put some grease on the downstop screws? Its really had to adjust owing to the difficulty of moving the screw smoothly. The thread is so tight that it only moves in snaps as it brakes loose under great torque from a wrench?
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Old 12-28-2006, 05:11 AM   #6
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If your measuring with the shocks and tires off, all your getting is downstop measurements which is basically to start on on even field. You can't measure true "droop" without the tires or shocks. If your shocks are binding and hindering suspension travel, you have bigger problems than droop.
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Old 12-28-2006, 12:41 PM   #7
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Yeah you don't run your car on the track with no tires or shocks do you? Get the car exactly as if you were going to put it on the track, minus the body, then do as stampede said. I set droop with a droop guage just to make sure the arms are equal, then I set droop over ride height to get it exactly where I want it.
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