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Old 05-06-2009, 11:34 PM   #1021
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I see your point, but you only see one side of it. I use a Tamiya "Droop gauge" (AE, Yokomo, MM, many many companies make "droop" gauges too) and measure droop as you measure your downstops. They are one and the same. But there are many, many, many different ways to measure them, as well as different terms and how to use them.

So with that said... to translate my term droop to your term downstop.... I use 6F/5R downstop.
Well, you can call it a flying speghetti monster gauge if you like ... but it still doesn't measure droop. It measures the distance between the chassis, and the lowest part of the lower control arm, at its lowest positiong (downstops). Droop is how far the car rises before the tires leave the surface, which is affected by ride height.
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Old 05-07-2009, 12:02 AM   #1022
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I guess that's why Hudy calls it a Droop gauge. Look in the Hudy catalog that comes with the kit.
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Old 05-07-2009, 12:14 AM   #1023
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Okay, screw you... I'm running 26.5mm up front and 26mm in the rear. That's how Tamiya measures it...
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Old 05-07-2009, 01:32 AM   #1024
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I don't think the problem is terminology.

If you look at the car, there are three distances there. Ride height, droop and downstop, each with it's own significance. Let's say you have the car on the wheels, sitting on the ground. The distance between the ground and the outer edge of your suspension arm is now equal to RH (ride height) + DS (downstop) + a fraction of droop (DR). If you adjust spring tension in your shock to be really hard, the equation loses the droop term and becomes RH+DS. This means that as soon as you lift the car up, the wheels will lift off the ground. In other words, the suspension doesn't "sag" at all when the car is placed on the ground. This means that the car might not roll at all or if it does, it will lift the wheel off the ground straight away. The possible consequence of this situation is then either traction roll or drifting. The lower the center of gravity (and grip) the more likely you will be drifting. The higher the CG (and higher grip) the more likely you'll be traction rolling. Finding the midpoint then becomes a very difficult exercise and most likely any change in surface condition (grip level or smoothness) will throw the car out of balance. The "midpoint" is going to be indeed a point rather than a "band" of stability (i.e. like balancing a weight on a knife edge; you can do it, but it's very unstable).

Conversely, if you release spring tension and the car sags a lot when stationary on the ground then you will have a lot of droop and the equation above becomes again total distance to the arm (extreme outer point)=RH+DS+ a fraction of DR with the mention that this time the fraction of droop in there is much smaller. This means your car will have to lift a lot before the wheels leave the ground.

All this doesn't mean you should use soft spring tension. This only demonstrates that suspension needs to be analysed as a whole and droop, downstop and ride height are just part of it. In the example above, if there is no droop, your car can only roll (whilst still keeping all wheels on the ground) by compressing the outer spring. Now if this is too hard to compress or doesn't compress at all, then you're traction rolling or drifting as explained above. But you can find a setting that will allow the damper to be compressed and I have seen a lot of people are tuning their cars this way. I suppose on an open track this can be very effective. On a very tight track, these cars drive "point and shoot" style, i.e. go drifting through hairpins with a very quick twitch and then floor it on the straight hoping nothing will go wrong (i.e. throttle action is perfectly timed with turning). When it does, oh well, the crashes are indeed spectacular.

In my opinion, this tuning and riving style suits best very experienced drivers. Begginers are not that quick and well trained (experienced) to make good use of their setup and get the timing right with reliability.

Back to soft and smooth setting, if you run a lot of ride height and a lot of droop your car will be a lot more forgiving, but will not react that fast. You will need more room to turn around (depending on speed) which is again a disadvantage on twisty tracks which tend to be narrower too.

Then there are a lot of other factors that will help further tune the car to improve performance (read compensate for your DR/RH/DS balance) such as weight distribution, roll center position, camber, caster and what not. these are all part of the handling equation and inevitably they should be looked at when deciding what to do to improve your car's behaviour. Xray cars come with a little leaflet which suggests the order of adjustment operations in relation to the desired effect, but even that is just a very broad overview and should not be used to replace your personal experience at the track where you're racing.
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Last edited by niznai; 05-09-2009 at 05:47 AM.
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Old 05-07-2009, 01:43 AM   #1025
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I understand all that. But as I have said... my droop is his downstop. I run 6mm front and 5mm rear (using droop gauge) with rubber tire on asphalt and carpet. This may change +/- 1mm. But it's usually 6 and 5.

Welp, done rebuilding my shocks. I just switched from clickers to fixed pistons. Off to bed.
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Old 05-07-2009, 01:56 AM   #1026
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Downstop is a fixed quantity (and indeed the vertical distance between the bottom of the chassis and the bottom outer edge of the suspension arm) that is adjusted by the screw in the arm against the chassis therefore can not be changed by adjusting anything else.

Ride height and droop can both change when adjusting a number of things including downstop. Also, droop and ride height both change greatly when the car is moving (similar to the rollcentre which is changing position with the car in motion). Perhaps they should be called "dynamic" settings as opposed to settings which are fixed, therefore "static".
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Old 05-07-2009, 04:41 AM   #1027
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Well, you can call it a flying speghetti monster gauge if you like ... but it still doesn't measure droop. It measures the distance between the chassis, and the lowest part of the lower control arm, at its lowest positiong (downstops). Droop is how far the car rises before the tires leave the surface, which is affected by ride height.
Well, using a gauge to measure 'whatever you want to call it' between the chassis and the wishbone .

I had 5-3, it's currently down to 4-3 to try and provide better rear grip and better stability coming out of the corner.

I only ever race carpet occasionally, then I would use 6-5 ot 7-5 etc. I've found those sort of settings on asphalt make the car too twitchy and unstable.


These are all measured using a stepped guage
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Old 05-07-2009, 08:16 PM   #1028
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Anyone has a used differential that will like to sale? I have a 007 differential but one of the outdrives broke can i just replace the outdrive and use it on my 009?
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Old 05-08-2009, 11:11 PM   #1029
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Say Drew i need your help again in your carpet nationals setup sheet you are using 600 front and 450 rear shock oil, if i use let say AE shock oil which one will it be 30,35 40 weight?
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Old 05-09-2009, 06:02 AM   #1030
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Say Drew i need your help again in your carpet nationals setup sheet you are using 600 front and 450 rear shock oil, if i use let say AE shock oil which one will it be 30,35 40 weight?
Most of the AE oils have the CST value printed somewhere on the label
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Old 05-09-2009, 08:08 AM   #1031
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Say Drew i need your help again in your carpet nationals setup sheet you are using 600 front and 450 rear shock oil, if i use let say AE shock oil which one will it be 30,35 40 weight?
Here you go you will find this chart interesting!!!

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Old 05-09-2009, 08:19 AM   #1032
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Let's see if im getting this right. If i use the xray 400cst it will be losi's 32.5?
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Old 05-09-2009, 08:20 AM   #1033
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Yes, the CST oils from 350 to 600 is a span of 30wt to 35wt.

Here is a website you will be interested in also.

http://www.offroad-cult.org/Special/...wt_convert.php

After some research, the whole cSt and cPs thing goes like this:
cSt stands for CentiStokes and cPs stands for CentiPoise where both are equivalent measures of viscosity.
Units of Stoke and Poise are equivalent so any measure you see with either units will be equal.

450cSt = 450cPs
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Old 05-09-2009, 08:24 AM   #1034
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DODGE YOU ARE A BEAST! Thanks a lot for the help.
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Old 05-09-2009, 10:29 AM   #1035
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Anyone else find it suspicious that Xray's new oils are _exactly_ at their rating? Even the website you linked to has the new oils as being within a tolerance of their rating.
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