Droop

[Spetz83]

On an on road car on relatively smooth surfaces, should there be any suspension droop or not??

[SaxoChris]

Im running the TT-01 Chassis as a Drifter but the suspension arms are perfectly lined up with the bottom of the chassis, i mean the chassis is not higher than the arms i.e hard shocks or to low ie. soft shocks.

Hope this makes some sense.

SaxoChris

[94eg!]

If your suspension is running maxed out, then you will loose traction in EVERY instance. The suspension should always droop some. Now how you measure it is where the trick.

[retroman]

Best bet is to buy a droop guage, start with the kit recommended settings, and experiment from there. Normally you want the suspension arms dropping a little from dead horizontal. Droop can be a very powerful tool for setting up a touring car chassis, as it can help control weight transfer. One car I found quite sensitive to droop settings was the old Associated TC3. A friend was running one on carpet (rubber tyres) and it was kicking the rear end out wildly. We took some of the droop out the rear, and it was a different car!!

General rule of thumb I have always worked to is bumpy surface, more droop. smooth surface, less droop. Then play with the balance between front and rear to help get a neutral handling car. Always helps to get tips off a friendly racer for wheel, tyre, insert combinations, and spring and shock oil weights.

If you know anyone who runs an X-Ray, ask if you can borrow the set up book that comes with the kit. It pretty much explains all!

Hope this helps,

Rich :-)

[Spetz83]

I need gauges for droop?

I thought droop was basically the amount of downtravel the suspension has from it's resting state (with the cars weight on)

ie, when the car is on the ground, and you lift it off, the amount the suspension goes down by is the droop?

Or am I wrong?

[94eg!]

I need gauges for droop?

I thought droop was basically the amount of downtravel the suspension has from it's resting state (with the cars weight on)

ie, when the car is on the ground, and you lift it off, the amount the suspension goes down by is the droop?

Or am I wrong?

You are exactly right. That is what Droop is. The problem begins when you try to measure it. There are no kit recommendations anyways when it comes to Tamiya. And even if there were, the manual couldn't possibly explain how to measure it as they don't include a gauge with their kits anyways. Just make sure you have some droop, and that it's as equal side to side as you can make it. Don't bother with the gauge unless you are going racing, and really need to...

[retroman]

I agree with 94eg!, you don't really need guages unless you're going racing, but they do help you get it right. There are two ways you can measure droop. First, with the guage. The Guage has a flat part that sits under the chassis, then a rising scale that measures under the suspension arm, where the pin for the hub, or castor block goes in. The guage is simpy pushed in under the car until one of the steps on the guage just touches the arm. then read off the measurement

The second way doesn't need a guage. with the car sat on a flat surface, at running weight with wheels and tyres on, measure the ride height. then find the centre of the chassis, front or rear, then with say, a long thin screw driver, slowly lift that end of the car until the tyres are just about to leave the floor. Make a note of the measurement, then subtract the ride height from it, and this will give you the total droop, which will also factor in the give in the tyres under load.

All this only really applies if you're getting into racing. If you're just bashing, I would recommend that the arms are dropping the same amount side to side, and then experiment. It's all part of the fun.

If I get a mo later, I'll put one of my cars on the set up board, and take some piccy's so you can see.

[Spetz83]

So roughly what am I aiming for, something like 1mm droop?

I have an old TB-01 and when I built it to Tamiya specs (spacers etc) it had absolutely no droop whatsoever

The TGX (the car I am setting up now) has droop with the stock springs, but now I have the progressive spring set which the droop is mostly just the soft part of the spring

[retroman]

Ok Spetz, I'm not familliar with either of those cars, my only Tamiya touring cars are TL01's, which I use for bashing. I'll do some homework, and post later. :-)

[irenL]

basically, if the track is smooth as glass, then you can leave the suspension arms level in relation to the chassis, otherwise limits the down travel.

you can do this by installing O rings beneath the pistons in the dampers, or if the chassis facilitate it, by the grub screws in the arms.

This is best measured and set when the chassis is still fresh (flat). Set chassis on a flat glass top with wheels off, without dampers. Set ride height block under the outer hinge pin hole. Work the grub screw till desired setting is obtained.

There is not a single magic number that will work with all chassis with all track. You're best to experiment, taking out or adding droop from initial setting (usually arms level all around).

[retroman]

OK, here goes!!

The first picture shows setting droop by measuring height, rather than using a droop guage. The green guage under the chassis is a ride height guage, although you could use a rule.

The second picture with the rear wheels removed from the car show a droop guage. Start with the arms near horizontal for smooth surfaces, and dropping down slightly for bumpy surfaces

[Spetz83]

The chassis does have the grub screws for the droop but the way I was going to add/subtract any droop was by adding or taking away some spacers on the shocks

The ride height is 17mm off the ground which considering imperfections in the parking lot I run it at seems to be pretty good

As far as droop, the problem is I read contradicting articles

Some say that it's best not to have droop, as through corners the inside side rises a bit (by the amount of droop present for example) and hence raising the effective CG

And at the same time during lift off throttle the rear rises again causing excessive lift off oversteer

I guess for on road on smooth tracks droop isn't necessary, but on bumpier tracks it keeps the wheels on the ground and prevents skipping

[irenL]

The chassis does have the grub screws for the droop but the way I was going to add/subtract any droop was by adding or taking away some spacers on the shocks

The ride height is 17mm off the ground which considering imperfections in the parking lot I run it at seems to be pretty good

As far as droop, the problem is I read contradicting articles

Some say that it's best not to have droop, as through corners the inside side rises a bit (by the amount of droop present for example) and hence raising the effective CG

And at the same time during lift off throttle the rear rises again causing excessive lift off oversteer

I guess for on road on smooth tracks droop isn't necessary, but on bumpier tracks it keeps the wheels on the ground and prevents skipping

adding/taking spacers on the shocks only alter the ride height.

adding/taking spacers/o-rings inside the shocks alters droop.

for some chassis, the plastic are just too soft to hold any good droop setting. The TGX got too soft an arms. the TT01 got too soft a chassis ear.

[Spetz83]

When you take out the spacers the car does sit a bit lower but it adds droop as there is less preload on the springs (if your springs are fairly soft that is)

[irenL]

When you take out the spacers the car does sit a bit lower but it adds droop as there is less preload on the springs (if your springs are fairly soft that is)

me think you may have a misconception of what a 'droop' is. IMHO, it's the set maximum amount of suspension down travel, and this article supports it:

http://www.rctek.com/handling/suspension_droop.html

so, the thing that you've been doing with the spring spacers is simply lowering the ride height. this does not affect droop.

which is why I said, if you want to play around with it, and the chassis doesn' t originally facilitate such alteration, you're better off varying the amount of spacers 'inside' the shocks themselves. this would be the next best option to actually having the droop set on the chassis itself.

i generally set the rear end for a bit more droop (1-2mm) compared to the front end. This dictates a chassis that's stable off throttle into corner (even with 2, 1-ways), stable part throttle mid-corner, and understeers slightly out of corner under throttle.. until you hit the biggest bump on asphalt.

[Spetz83]

My understanding of droop:

When your car is sitting on the ground, and then you lift it off the ground, droop is the amount of mm the suspension extends out before the wheels come off the ground. ie, it's the amount that the springs have sagged from the weight of the car

Is this a correct definition?

[hedge]

My understanding of droop:

When your car is sitting on the ground, and then you lift it off the ground, droop is the amount of mm the suspension extends out before the wheels come off the ground.

Correct and can be limited by using the droop screws if your chassis has them. The easist way to measure is using a droop guage with your car sat on blocks (same height as 0 on the droop guage) with the shock absorbers detached.

[terry.sc]

me think you may have a misconception of what a 'droop' is. IMHO, it's the set maximum amount of suspension down travel, and this article supports it:

http://www.rctek.com/handling/suspension_droop.html

Spetz83 is right. Droop is the difference between normal ride height and maximum downward travel. Just removing spacers on the shocks without moving the shocks themselves (assuming the springs aren't preloaded and have some movement) will lower the ride height, so increasing the difference between normal ride height and maximum downward travel of the suspension.

On that link it also states that droop is the amount of downward suspension movement, not the amount of travel.

If the chassis has adjustable droop screws or if you use spacers in the shocks but the springs are preloaded, increasing the amount of suspension down travel will increase the ride height and it will still have no droop at all as there is still no difference between maximum down travel and normal ride height.

The idea of droop is to let the chassis rise above normal ride height when that end is unloaded, so the rear lifts when braking and the front lifts when accelerating to give more weight transfer between each end of the car.

Having lots of rear droop means under braking the rear lifts and transfers a lot of weight to the front of the chassis to load up the front suspension and give you more turn in. If the problem is lift off oversteer reducing the amount of droop will stop the forward weight transfer. If the problem is excessive the best solution is to start with harder front springs and/or thicker shock oil as the original setup is causing the front end to dive under braking, then adjusting rear droop to balance it out. If the springs are right elsewhere, such as high speed corners, then thicker damper oil in the front will slow down the weight transfer. You don't want to run with no droop at all though as it will prevent the wheels dropping into dips in the ground.

[Spetz83]

Thanks Terry that was pretty much my understanding as well as far as lift off oversteer etc is concerned

But droop would have an affect not only forward/rear weight transfer but side to side

So disregarding braking and acceleration, is droop good for cornering?

I understand it might offer more weight transfer, hence more traction but I read that at the same time that "droop" and lift of the other side effectively raises the CG, so in a way on smooth tracks you don't want droop so you keep CG as low as possible

I have been having lift off oversteer issues though and I do have substantial rear droop. I guess I need to take some out