Suspension Droop

[spetz]

Does anyone know how much droop is good for a fast street/track used car?
I noticed that with some coilovers (eg, BC Racing) you set the preload and the height is adjusted via lowering the shock body which gives very little droop.
And in other coilovers (eg. Tein SS) height is adjusted via preload basically, and these have a huge amount of droop when at a pretty low levels.

[DreadAngel]

The best amount of lowering usually means that your roll centre isn't out of whack, suspension arms aren't at ridiculous angles, the spring and shocks are correctly adjusted matched to account for the lowered height otherwise you may bottom out. There is no set height as different cars have different setups and preferences.

Street however, usually you want enough height clearance for both speed hump and irregular road clearance [steep V shaped inclines are fun in slammed cars], so personally I like to lower mine just enough so you know its lowered but I can still clear all humps and its lowered enough so I can physically feel the lowered centre of gravity working nicely.

[PHO]

If you can get over a bunning speedhump. You're not low enough.

[spetz]

Thanks guys for the responses, however I was asking about suspension droop and not ride height/lowering (I assume maybe you guys thought I misspelled "drop")

[curtis265]

If by droop you mean sag, It's normal and you should just adjust the ride height after it's settled.

[mugen_ctr]

Most ppl are missing the point here... his talking about when the car is on a certain angle or when jacked out, the amount of suspension travel there is... in this case, droop refers to when the suspension is at max down travel

IMO its best to find out ur self, what works for someone may not work for some one else... imo droop is least of most ppls worries on here due to 9/10 ppl including me running coilovers which have a lower body for height adjustment and a spring perch adjustability, which have little, 1/3 of the oem suspension travel.

Droop u would worry more if u were off-roading or rally, on track, its pointless as the car isnt traveling on uneven surfaces as much, which is why coilovers have very little droop, most ppl tend to just refer to what ever the coilover is preset to, or the preload settings... IMO for teins SS, just leave it as it is from the factory as i believe they are setup for the optimum performance for the car.

[spetz]

Thanks Mugen_ctr,
The issue with the Teins is that they do not have preload adjustment.
So, at least the theory is that the inside of the car will lift much more because of the large amounts of droop, which raises the center of gravity and also reduces the tire contact patch on the outside wheels.
I don't know if in the real world this would happen, as cars have swaybars etc, but it seems to me that you can run softer springs/swaybars and achieve less roll if you have little droop.

[chargeR]

I've heard numbers of 2/3 bump travel to 1/3 droop travel thrown around. I think if you stay somewhere around there you won't have problems, assuming your shocks have adequate overall stroke. I have come across the same issue you mention, that if you set coilovers that have separate height and "preload" adjustment with the spring perches just snugged up against the spring you end up with bugger all droop travel. This issue is exacerbated with stiff springs. After thinking about it for a while I lowered the spring perches on my car until the springs were just a bit loose at full droop, if I had room I'd probably fit a helper spring and lower the spring perches more but that isn't an option at the moment. I found a perceptible difference in performance over bumps once I had that little more droop travel.

I would advise against trying to limit roll by limiting inside suspension droop, I've read of this being used in extreme situations with open wheelers etc. Imagine what happens when one end of the car hits the droop limit, that tyre will be suddenly unloaded and all that load must transfer to other tyres. Bad/unpredictable handling will ensue IMO. Also as you mention above I have no idea if a car will even hit droop limit on the inside shocks considering our cars generally have decent sized sway bars.

[mugen_ctr]

correct, but as u pointed out, due to the nature of cars with swaybars, this effect would b limited to the swaybar design and thickness, material, hollow or solid etc etc...

But not necessarily u can run softer spring because u got smaller droop, when cornering, u would need stiffer springs as if u have a smaller droop u limit the suspension travel, than the shock would have less time to react, an how the car would react etc etc, alot to think about, im not expert but thats my understanding

One of the main problems ive seen with tein ss, is when its lowered beyond the point where the spring is no longer preloaded on the base of the spring perch to the top of the strut, when at full droop, it has the potential to unseat the spring.... BUT i havent seen or heard of such cases as 9/10 times the cars weight will always keep the spring seated.

I believe to counter-act the problem with tein ss is to run a helper spring to always keep the spring preloaded at all times, especially when at full droop, an allow you to go for a lower ride height.

[spetz]

ChargeR, did you ever drive your car with little droop?

Mugen, I think with the Teins for the helper spring to no longer be trapped, the ride height has to be so low that the primary objective is looks and handling is no longer that much of a consideration.

Does anyone know if the dampers rebound rate has much of an affect with droop? ie, will it stop the suspension from drooping, or is it just a matter of slowing down the drooping?

[chargeR]

ChargeR, did you ever drive your car with little droop?

Mugen, I think with the Teins for the helper spring to no longer be trapped, the ride height has to be so low that the primary objective is looks and handling is no longer that much of a consideration.

Does anyone know if the dampers rebound rate has much of an affect with droop? ie, will it stop the suspension from drooping, or is it just a matter of slowing down the drooping?

Yes I drove the car at quite a few track days with the springs lightly preloaded at full droop (a 150mm spring compressed to maybe 147-148mm) which resulted in bugger all droop travel with the 14 and 28 kg/mm rates I was using. Bump compliance over big bumps where the suspension rebounds heavily off the bump and risks topping out seemed better after I reduced bump travel and increased droop.

Damper rebound will definitely affect the amount of droop you use up over transients ie. fast direction changes or bumps. Won't do much in a steady state corner.