markp27

If you measure the droop with another method as apposed to the droop gauge and block under the chassis, then of course this is true. The description above is only relevant when a) the droop was first set with "large" diameter tyres, b) the tyre are now worn and the ride height needs adjuting, and c) a droop guage is used.

goop

iTrader: (2)

no it is not, droop should always be used as part of your setup if someone gives you a setup with 2mm of droop over ride height with 60mm tires you can acheive the same droop with 56mm tires.

goop

iTrader: (2)

when your tires wear you have to first adjust ride height and then check droop this should be a standard practice to make sure your car is consistent

markp27

I think we are talking about two different things here - of course 2mm droop can be achieved with different diameters of tyres - I'm pointing out (rather poorly, I must admit, as I failed to mention using a droop guage in my first explination) that if you're using a droop guage, then when the gauge show 2mm it is only relevant for tyre sizes of 62mm or something. If you then use 58 mm tyres, then the droop shown on the droop guage has to be accomodated for by an extra 2mm - if you want the same level of droop as before

If you are using another method, where you measure the actual droop, you can setup the car without having to worry about this, as you are measuring actual droop - I'm just trying to point out that when measuring with a droop guage, then the droop shown has to be compensated as the tyres get smaller.

markp27

Also perfectly correct and this is what I was explaining to Tom G in my first posting on the subject, when he wondered why he should reset the droop as the tyres wear.

Michal101

iTrader: (13)

Great discussion here.

My question is that when you set droop on your car do you not use the "0" blocks (Hudy System) to measure it? So what would happen if now the "0" block is 3/4 of it's original size...ie, tires getting smaller due to wear? Wouldn't the droop setting now change as well?

Mike

Neil Rabara

You can place the chassis flat on the setting board and still set droop. Remember that droop is a measurement of downtravel. Don't confuse the droop setting with ride height.

markp27

*EDIT* Oops Thought this was an answer from Neil to one of my postings

Yep, as Neil says droop and ride height are different. What we are talking about is when you've set your droop for say your 63mm tyres and after a while you've 61mm diameter tyres. First you need to adjust your ride height to get back to your original ride height. But what you can't do is to put your car onto the hudy blocks and set your droop to the same value with the hudy droop gauge - you have to compensate for the smaller tyres.
This is because you have to use more pre-tension on the springs to acheive the same ride height as before and now due to this the suspension arms are forced down more to be able to bring up the chassis to the required ride height.
This being the case, the arms are now sitting lower relative to the chassis when the car is on the ground (with its wheels on of course). And when the car is lifted, there won't be as much downward movement on the suspension arms before the droop screws make contact with the chassis.

So, as goop has also stated, you have to also adjust the droop screws in order to get back to the same level of droop as before... but only after adjusting the ride height. Here is where you need to compensate when using the hudy droop gauges. The Xmm of droop now indicated on the droop gauge is no longer correct for the 61mm tyres - you have to take the difference between the two diameters (2mm in this case) and divide by two (as it is only the radius which counts) - this gives you the amount by which you need to compensate the droop gauge's measurement by.

Do you understand what I mean? Like goop says: ride height then droop setting - both have to be adjusted when the foam tyres wear,

markp27

The amount of droop (i.e. downward travel of the suspension) doesn't change until you adjust the ride height to compensate for the tyre wear.

The amount of down travel is the same even as the tyres wear - it is just that the chassis starts to get too low with respect to the track. Therefore you need to adjust the ride height.

I always use the 0 blocks from Hudy. But you have to take care in using the droop gauges as the tyres wear you have to compensate due to the diameter.

I think the gauges are set out for 62mm tyres. If you have +6 droop at the rear, for example (reading from the gauges) when your tyres wear to 60mm - you must do the following sum:

(62-60)/2 = 1mm

Now subtract this from the original +6 droop setting from the hudy gauge. So now due to the smaller tyre size (60mm) you have to adjust your droop screw until you have the droop on the +5 mark on the droop gauge.

If you went on to measure the droop using calipers (i.e. one reading with the car with the wheels on the ground and one reading with the suspension arms resting on the droop screws) you would still find that the downtravel would be the +6mm which you want.

Tom G

I get what you're saying.

But droop, by techinal settings are set against the chasis, thus, making tire wear not a coefficient. Tire wear certainly impacts ride height and I can agree that it has an impact on static settings regaridng spring compression and the wanton to maintan the same tension [which may bring up the question of linear spring and their advantages/disadvantages, but we'll leave that for later]

I guess I'm going to continue reading on, take everything in and then put in onto the track [or set-up] and see the effects/non-effects of both sides.

I'm surprised this discussion actually started in a nitro thread, since I usually apply the logic of "if the set-up ain't working, I'll plow through it or back-off a little" I'm glad I brough it in here, since I'm able to see & hear the "technical theories" of it quite a bit better [and there seems to be a lot more response as well, as I expected too!].

So long as we have a "clean fight and no hitting below the belt".

Although I'm usually a believer in "'till the last man standing", it's ok to "agree to disagree".

<fight bell rings>

HEWITT

iTrader: (14)

i finally ordered the xray fk off of rc mushroom..i got tired waiting for the xrays to be in till like end of september....hopefully rc mushroom has them in stock

markp27

Swoosh *duck* Hey, I'm a nitro guy always ready to plow through it

I see what you're saying, but this droop measurement is only a measurement of how far above the chassis the arms will stop moving.
The real droop (please correct me here if I'm wrong) is how far the arms move down from the "in-the-springs" position (car on the ground with its wheels on) and the postion of the arms when the droop screws hit the chassis.
So if you setup your car from 62mm tyres and had a 6mm droop, then decided to changed to 60mm tyres and adjusted the ride height to be equal to that with the 62mm tyres, then now the suspension arms wouldn't move down so far between the "in-the-springs" position and the position where the droop screws hit the chassis. Therefore the droop screw has to be back out a little to allow the same downtravel as before. If you see what I mean?

ding, ding!

theisgroup

iTrader: (10)

mark,

this may help. As your tire gets smaller, to maintain the same ride height. the droop screw will need to be backed out to maintain the same amount of chassis up travel. It is true that the droop setting is basically how much the arm will travel below the plane of the chassis, but we are talking about how much up travel the chassis will have will definatly change. And to maintain the same up travel is critical in maintaining the amount to weight transfer there is in the car. So as the tires get smaller the arm will have more of an angle to maintain ride height. And that angle reduces up travel.

So basically, Droop will not change with ride height, but chassis up travel will. But I think droop is not the critical setting we should be looking at. Chassis up travel is. As this does change with ride height and must be check every run. And this does affect performance of the car, because weight transfer is affected

Tom G

I'm with ya except for the "in the springs" position.

Droop, the downward travel of the suspension arm, is set with "0" blocks beneath the chasis and the guage beneath the hub [some even argue whether the shocks should even be on or in place when setting the droop].

Does the upstop [I realize most don't actually use this or it's a setting that most set as "free"] change with the tire diameter as well? Again, the measurement is made against the chasis.

What I've started doing is setting up & down stops without the shocks, note it and then make a note of the travel distances with the shocks in place. I use it more as a comaparison between runs, giving me a quick reference with the gauge while keepign the shocks in place. If I note a difference, then I know to slap on the the set-up station plates and all the other tools we use to se what changed and hopefully figure out why [usually a plastic-molded piece that allows a a screw/set-screw to back out or go in].

But what I'm I talking about? It's an Xray, settings never change unless I launch myself out of the track, in which case, I'll have bigger problems.

I'll check the settings with different tires diameters and see if I notice a change in up/down stops and report back to ya!<saluting with a commanding "Sir" coming out of the mouth>

^5

Tom G

I gotcha. This I can mentally see and will try to physically see it as well [soon as I get of this thing and actually make it to the pit table!].

^5