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Old 03-21-2002, 01:11 PM   #1
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Default Droop and Preload questions

I've been working on gettting the ride height and droop set properly on my XXX-S and I had a few questions. I have the droop set at 3 in the front and 5 in the rear. I'm also running 4mm ride height front and rear. I have the short threaded shocks in front and the standard length threaded shocks in the rear and I'm running uncut proline foam tires.

The problem is that I had to run very little spring preload to get the proper ride height. Now when I pick the car up, the shocks do not extend fully to the droop screws. When I extend the suspension fully to the max droop, the spring is not under any preload. There is actually about a 1/8" gap from the top of the spring to the adjuster nut on the shocks. It seems that since the springs can not extend far enough to ever make contact with the droop scres, that the droop setting is meaningless.

If anyone could tell me if this is normal or what I need to do to correct it, it would be appreciated. I am assuming you would still want some amount of spring preload at full droop.

Thanks,
Rob
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Old 03-21-2002, 01:35 PM   #2
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Rob- you need to ask Losi questions on the XXX-S thread. You 'll find the guys that know a lot about that car in that thread.

To answer your question, that sounds about right. You didn't mention what height you had the droop set to, but at full extension, there should be no spring load on the shock. If you were to run your shocks preloaded, whick is where you have spring pressure on the shocks even when the suspension is fully extended, you would:

*have very little or no droop (down travel from static ride height after unloading the weight from the suspension)

have a car that is very hard to drive and waaaay to sensitive.

Hope this helps
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Old 03-21-2002, 01:50 PM   #3
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Ok,thanks. I'll ask my question in the xxx-s thread so you may delete this thread if you like.
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Old 03-21-2002, 06:19 PM   #4
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put some preloads in there til there's no gap
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Old 03-22-2002, 05:56 AM   #5
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Quote:
Originally posted by rctc3
put some preloads in there til there's no gap
But if I did that, then my ride height would be too high.....
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Old 03-22-2002, 11:00 AM   #6
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actually r andersen,
you are right on. a car should never have any preload. the idea is that the shocks compress under the static load of the car. as the car moves and the load on the tires increases even if just a little the shocks will compress accordingly. if you run preload, and in extreme cases to where the shocks don't compress at all when you set the car down, the shocks will be rigid until the dymamic force on them is enough to compress them. very inconsistent handling. the only way to have enough spring travel to accomodate your droop setting is to run a super soft one that will compress 5 mm untill the car is supported. right? well, that's certainly not the answer. short of dual rate springs, the shocks will always be unloaded at more than 2mm or so of droop. hpi actually has dual, or progressive, rate springs. but they aren't designed for this purpose. ideally the soft section of the spring would just compress completely under the three lbs of the vehicle. then it would only extend under droop conditions. the rest of the spring would be another spring constant and would act over the positive travel portion. wow. i smell a patent. yeah, right. the trouble with manufacturing this is the many different mounting locations and angles between each car. a neat idea though. come on hpi, where was your thinking cap? wow that was intense. gotta go.
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Old 03-23-2002, 03:04 AM   #7
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Here's what I've been doing lately... I set the car's ride height with the spring collars, and once the ride height is set I then adjust the droop screws to remove any gap between the spring and collar with the car off the wheels. I'll then measure the droop, just to ensure that it's the same from side to side. I don't eliminate the gap completely, I leave a tiny bit just to be sure I'm not preloading the springs.

That's been working pretty well for me so far. I don't want to take credit for this diea, I first found out about it at the Trinity race in Englishtown, NJ last summer when I asked Paul Lemieux about droop settings... he told me he set it that way.
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Old 03-23-2002, 03:57 AM   #8
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Default Re: Droop and Preload questions

Quote:
Originally posted by R_Andersen
I've been working on gettting the ride height and droop set properly on my XXX-S and I had a few questions. I have the droop set at 3 in the front and 5 in the rear. I'm also running 4mm ride height front and rear. I have the short threaded shocks in front and the standard length threaded shocks in the rear and I'm running uncut proline foam tires.

The problem is that I had to run very little spring preload to get the proper ride height. Now when I pick the car up, the shocks do not extend fully to the droop screws. When I extend the suspension fully to the max droop, the spring is not under any preload. There is actually about a 1/8" gap from the top of the spring to the adjuster nut on the shocks. It seems that since the springs can not extend far enough to ever make contact with the droop scres, that the droop setting is meaningless.

If anyone could tell me if this is normal or what I need to do to correct it, it would be appreciated. I am assuming you would still want some amount of spring preload at full droop.

Thanks,
Rob
I run on medium-bite pavement. I use droop 2 front. That is with stock roll center plates, 2 degree kickup, 0 degree castor blocks, no sway bars, stock camber link locations and stock shock shafts that were cut to .36. I use inside limiters to acheive 2 droop. Now with ride height, I can adjust my ride height anywhere from 3~6mm. I had to trim the front castor blocks because my springs were rubbing against them(If you mount the shocks on the outermost hole on the tower). I ditched them droop screws. Too-much flex in the bumper (caused by greater spring preload)which distorted my droop. If I set my car to have a ride height of 3mm, there is a little gap between my spring and my shock collar if I pick the car up and manually extend the shocks to their full length. I loose the gap at 4.5mm and up. Your case is normal and you could use a little less droop(higher number on droop gauge) especially if your running on a higher bite surface than the typical dusty parking lot. Dialing out some droop(higher number on gauge) will eliminate that gap between your springs and your collars. Sway bars will too!
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Old 03-23-2002, 03:58 AM   #9
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Quote:
Originally posted by rctc3
put some preloads in there til there's no gap
That will change the ride height.
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Old 03-23-2002, 07:56 AM   #10
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Default Re: Re: Droop and Preload questions

Quote:
Originally posted by proudwinner


I run on medium-bite pavement. I use droop 2 front. That is with stock roll center plates, 2 degree kickup, 0 degree castor blocks, no sway bars, stock camber link locations and stock shock shafts that were cut to .36. I use inside limiters to acheive 2 droop. Now with ride height, I can adjust my ride height anywhere from 3~6mm. I had to trim the front castor blocks because my springs were rubbing against them(If you mount the shocks on the outermost hole on the tower). I ditched them droop screws. Too-much flex in the bumper (caused by greater spring preload)which distorted my droop. If I set my car to have a ride height of 3mm, there is a little gap between my spring and my shock collar if I pick the car up and manually extend the shocks to their full length. I loose the gap at 4.5mm and up. Your case is normal and you could use a little less droop(higher number on droop gauge) especially if your running on a higher bite surface than the typical dusty parking lot. Dialing out some droop(higher number on gauge) will eliminate that gap between your springs and your collars. Sway bars will too!
now you need a tweekstation
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