The Droop Disagreement
07-10-2008, 12:18 PM
#31
And just a clarification I said 12th scale rocks. Not "nobody ever messes with the dampers, t-bar and springs".
Go ahead flame me... I am a die hard 12th scaler. I ran TC the past weekend... Mind you a TC3 with a crap load of torque steer and a crap set up and it was so easy to drive. No challenge... no fun.
IMO
07-10-2008, 12:27 PM
#32
Tech Adept
I do feel that you have contradicted yourself here, saying on the one hand that less droop increases grip and on the other hand that less droop decreases it.
I firmly believe that the phenomena of added grip that you are experiencing from your small adjustments are from something other than droop. Perhaps you are stopping the suspension from over extending and compromising the tyre contact patch. Droop adjustments alone will always tend to decrease grip as you approach the limit (which is the zero droop setting I mentioned).
But I don't want to get into a situation of argument and counter argument, if your way with droop "works" for you, go for it.
I firmly believe that the phenomena of added grip that you are experiencing from your small adjustments are from something other than droop. Perhaps you are stopping the suspension from over extending and compromising the tyre contact patch. Droop adjustments alone will always tend to decrease grip as you approach the limit (which is the zero droop setting I mentioned).
But I don't want to get into a situation of argument and counter argument, if your way with droop "works" for you, go for it.
But I do agree it isn't worth arguing over, it works for me and a lot of people I race with.
07-10-2008, 12:35 PM
#33
droop and transfer of wt.
We are not talking about transfering so much wt the tires come off the ground, only the amount of chassis wt allowed to throw around when braking and accel. that is why more droop on a end allows the wt to flow more in one direction, it also allows more momentum to flow in the direction before the rotation or roll of the car is stoped/slowed by the droop screws making contact with the chassis.
We are not talking about transfering so much wt the tires come off the ground, only the amount of chassis wt allowed to throw around when braking and accel. that is why more droop on a end allows the wt to flow more in one direction, it also allows more momentum to flow in the direction before the rotation or roll of the car is stoped/slowed by the droop screws making contact with the chassis.
07-10-2008, 12:41 PM
#34
Droop....Greek to me....
I always ran with this one setup in mind: When I setup the car, I adjusts the droop screws so that the drive axles nearly ran parallel to the chassis. Then I increased the spring rate to prevent the chassis from bottoming out and increased the oil in the shocks to eliminate rebound. Although it gave both my Evo III and RS4 Pro2 a wicked low CG, sometimes I was afraid to run it on certain surfaces. It handles great (in my book, haven't raced since 2003), it takes a lot of power to break traction in turns and in during transitions it is pretty smooth.
Like I said before, I haven't raced since 2003 and I am pretty sure there are far more better setups than what I do. That is why I am looking for clubs to race in; to further educate myself in suspension setups.
I always ran with this one setup in mind: When I setup the car, I adjusts the droop screws so that the drive axles nearly ran parallel to the chassis. Then I increased the spring rate to prevent the chassis from bottoming out and increased the oil in the shocks to eliminate rebound. Although it gave both my Evo III and RS4 Pro2 a wicked low CG, sometimes I was afraid to run it on certain surfaces. It handles great (in my book, haven't raced since 2003), it takes a lot of power to break traction in turns and in during transitions it is pretty smooth.
Like I said before, I haven't raced since 2003 and I am pretty sure there are far more better setups than what I do. That is why I am looking for clubs to race in; to further educate myself in suspension setups.
07-10-2008, 01:18 PM
#35
My personal method of measuring droop; Unscrew your droop screws, then set your ride height. Take your ride height gauge and slide it under the chassis to its ride height. Then push it in till you get to the amount of droop you want. For me, 5mm rh, 2mm droop, so I push it till it gets to 7mm. Then screw the droop screws in until the tires lift off the ground. Now take a piece of paper and slide it under the tire, unscrew the droop screw until the paper barely slides under the tire.
Weight transfer and droop; First keep in mind that the distance from your roll center to the center of gravity has a big effect on the side to side weight transfer. Limiting droop in the rear of the car will limit the amount of weight being shifted to the front of the car during deceleration or braking and limiting the droop in the front of the car will limit the weight transfer to the rear during acceleration. This is always the case, however the problem arises that some will run little droop and low roll centers. When running a low roll center your car will roll more in the corner, when running little droop you can unspring the weight on one wheel during cornering, so the effect that this scenario gives off is that you are not transferring much weight to the front of the car while entering the corner, but because your rc is low your car will roll a lot, especially with more weight over the rear of the car and your uptravel on the inside tire is limited causing that tire to lift and loose traction. Because of this, a lot of people have misconceptions on the effects of roll center. Just do a search and you will see what I mean, some people think that lowering your roll center will loose traction, but this is only the case if your droop it too little, so long as you match your droop with your roll center you will gain traction by lowering your roll center, and hence the topic. However running too much droop will allow too much weight to be transferred, leaving you with little weight to roll with. Basically, to keep the rear end planted, you need the right amount of droop for the roll center you are using, if the roll center is high, you need less droop. If the roll center is low, you need more droop.
However I will say that this is only my experience, and such is open to interpretation and of course constructive criticism. But from what I have come to believe, it just goes to show you that any change you make will affect something else.
Weight transfer and droop; First keep in mind that the distance from your roll center to the center of gravity has a big effect on the side to side weight transfer. Limiting droop in the rear of the car will limit the amount of weight being shifted to the front of the car during deceleration or braking and limiting the droop in the front of the car will limit the weight transfer to the rear during acceleration. This is always the case, however the problem arises that some will run little droop and low roll centers. When running a low roll center your car will roll more in the corner, when running little droop you can unspring the weight on one wheel during cornering, so the effect that this scenario gives off is that you are not transferring much weight to the front of the car while entering the corner, but because your rc is low your car will roll a lot, especially with more weight over the rear of the car and your uptravel on the inside tire is limited causing that tire to lift and loose traction. Because of this, a lot of people have misconceptions on the effects of roll center. Just do a search and you will see what I mean, some people think that lowering your roll center will loose traction, but this is only the case if your droop it too little, so long as you match your droop with your roll center you will gain traction by lowering your roll center, and hence the topic. However running too much droop will allow too much weight to be transferred, leaving you with little weight to roll with. Basically, to keep the rear end planted, you need the right amount of droop for the roll center you are using, if the roll center is high, you need less droop. If the roll center is low, you need more droop.
However I will say that this is only my experience, and such is open to interpretation and of course constructive criticism. But from what I have come to believe, it just goes to show you that any change you make will affect something else.
07-10-2008, 01:34 PM
#36
You have to think about downstops (droop) both in terms of what it does under acceleration/deceleration and cornering.
While turning (no acceleration or deceleration):
When you turn, hitting a limiter moves the rollcenter to the inside of the car. Instantly I might add. For the sake of argument here the rollcenter is at the center of the inside tire (and at ground level).
The end of the car that hits the limiter first will force the other end to roll a little more. Less front droop in a turn will make the car oversteer more and less rear droop will cause the car to understeer more.
Droop ALWAYS reduces traction but it can be used to reduce one end of the car's traction more than the other (changing the balance).
Under acceleration/deceleration NOT TURNING:
No droop and the car wants to rotate around the CG (the suspension has an affect on this but bare with me). In the end, without droop the car wants to rotate around some point near the center of the car.
Remove droop in the front (less lift) and the car will hit the stops and suddenly it wants to rotate around the front end (under acceleration). This gives the feel of more rear bite. Both ends lose traction but the front loses more.
Less rear droop will do the same thing under deceleration but gives the feel of more front bite.
So, the affect of droop on pitch isn't the same as the affect it has on roll and they're happening at the same time.
While turning (no acceleration or deceleration):
When you turn, hitting a limiter moves the rollcenter to the inside of the car. Instantly I might add. For the sake of argument here the rollcenter is at the center of the inside tire (and at ground level).
The end of the car that hits the limiter first will force the other end to roll a little more. Less front droop in a turn will make the car oversteer more and less rear droop will cause the car to understeer more.
Droop ALWAYS reduces traction but it can be used to reduce one end of the car's traction more than the other (changing the balance).
Under acceleration/deceleration NOT TURNING:
No droop and the car wants to rotate around the CG (the suspension has an affect on this but bare with me). In the end, without droop the car wants to rotate around some point near the center of the car.
Remove droop in the front (less lift) and the car will hit the stops and suddenly it wants to rotate around the front end (under acceleration). This gives the feel of more rear bite. Both ends lose traction but the front loses more.
Less rear droop will do the same thing under deceleration but gives the feel of more front bite.
So, the affect of droop on pitch isn't the same as the affect it has on roll and they're happening at the same time.
07-10-2008, 02:07 PM
#37
You'd need super stiff springs and that would compromise the handling... unless you run on foams but then again setting a car up on foams is a different philosophy...
07-10-2008, 02:26 PM
#38
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You don't know greek?
wtf is wrong with you!
I measure droop with the wheels off on a setup board with the chassis either flat on the board or elevated off of it (depending on if the arms sink below the base of the chassis) and then i use calipers to measure the distance from the axle to the platform of the setup board. It easy enough for me, and i can adjust droop in extremely small increments. The only problem with this is when someone asks you about downtravel they get an odd look on their face when you tell them you're running 19.5 mm.
I usually run a little more front droop than rear so i have more on power back traction but it doesn't feel as "lazy" through on and off power turns.
07-11-2008, 02:26 AM
#39
Some more reading to add to the topic... 
http://www.losi.com/Products/HintsAn...rodID=LOSA0251
How applicable is this info for using foams with a stock motor?
Slightly off topic (sorry) but I like running foam and know tyre rotation is important to keep the wear even, but I do find understanding droop for this type of tyre difficult to understand
http://www.losi.com/Products/HintsAn...rodID=LOSA0251
How applicable is this info for using foams with a stock motor?
Slightly off topic (sorry) but I like running foam and know tyre rotation is important to keep the wear even, but I do find understanding droop for this type of tyre difficult to understand
07-11-2008, 06:17 AM
#40
Some more reading to add to the topic...
http://www.losi.com/Products/HintsAn...rodID=LOSA0251
How applicable is this info for using foams with a stock motor?
Slightly off topic (sorry) but I like running foam and know tyre rotation is important to keep the wear even, but I do find understanding droop for this type of tyre difficult to understand
http://www.losi.com/Products/HintsAn...rodID=LOSA0251
How applicable is this info for using foams with a stock motor?
Slightly off topic (sorry) but I like running foam and know tyre rotation is important to keep the wear even, but I do find understanding droop for this type of tyre difficult to understand
It is as applicable for foams and a stock motor as it is for rubbers and a mod and for flux-capacitors on parking lots!
I don't know why people get the idea in their heads that setups work differently for different surfaces. The physics is exactly the same.
As for droop and foams - this is why I hate foams! What the 12th racers do is have a box of them and run each one only once a day, that way your rollout is hardly affected during a meeting, and all your tyres stay at roughly the same diameter as each other. I don't know if serious 10th racers do the same.
If you are just trying to get the longest life out of a set (like most club racers do), make sure that your car is capable of having enough droop at the smallest diameter, and keep readjusting your droop and gearing and ride height to compensate for the wear. A real nuisance but if you don't do it your car will not handle consistently and at worst you will run out of droop at some point.
07-11-2008, 06:36 AM
#41
Thanks, I thought things were getting a little overcomplicated in here and I havn't used foams for ages, hence I thought I would ask (racing tonight)...
Obviously the tyre structure is different to rubber so there are setup differences, maybe some people think droop is one of them but it's not...
But I do know that when foams grip, they grip just as well as a rubber tyre!
Thanks again
Obviously the tyre structure is different to rubber so there are setup differences, maybe some people think droop is one of them but it's not...
But I do know that when foams grip, they grip just as well as a rubber tyre!
Thanks again
07-11-2008, 07:01 AM
#42
07-11-2008, 07:07 AM
#43
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one of my favorite comments over the years is that foam tires racers try to "shed grip". lol. newsflash: grip = cornerspeed . that's why the tire durometer has been going down and the wheel diameter going up, folks. i suppose we're always welcome to run shock oil as tire sauce, if the current tires have too much grip. (it's odorless, too!)
07-11-2008, 07:11 AM
#44
yes, that's a gem too. 
07-11-2008, 07:23 AM
#45