Front Droop

[sagero]

I installed some "aero" front shock brackets recently. With the new brackets the mounting points for the shocks are further apart. So with this setup and the shocks I want to run I have just about 1-1/4" of droop available from static ride height. Is this enough?

[Amon]

Sagero,

So you're saying the total amount of droop or shock compression is 1.25" with the change in mounting points? It would
depend on many factors such as ride height, bump stop used (if any) , cut front spring (?) and the type of shocks you're using.
If you can provide any photo's of your ride height in static and under compression/ rebound it would be helpful.

Mark

[sagero]

Sagero,

So you're saying the total amount of droop or shock compression is 1.25" with the change in mounting points? It would
depend on many factors such as ride height, bump stop used (if any) , cut front spring (?) and the type of shocks you're using.
If you can provide any photo's of your ride height in static and under compression/ rebound it would be helpful.

Mark

Hello Mark.
To clarify, I'm concerned about a fairly limited amount of shock extension available before they "top out". With the new setup the shocks are fully extended at about 1.25" of droop (from static ride height). I'm using the relatively standard Vee H-Beam front end with QA1 8252s (5" total travel).

[problemchild]

Assuming you are considering "static" ride height with driver on board then you have more than you need. Personally, I run my front at zero droop and add another 1/2" for wet conditions. Not everybody is so aggressive but certainly an inch is too much droop IMO.

[sagero]

Assuming you are considering "static" ride height with driver on board then you have more than you need. Personally, I run my front at zero droop and add another 1/2" for wet conditions. Not everybody is so aggressive but certainly an inch is too much droop IMO.

Thanks, Greg.

[mikehinkle]

The big question is are you in the car when measuring this?
My front end is soft and will droop about a inch when I get in.

[problemchild]

Whether you define droop by my terms or Mike's, 1 1/2" is more than enough.

[sagero]

Whether you define droop by my terms or Mike's, 1 1/2" is more than enough.

I did the measurement from a static position with drivers weight in. This stuff is new to me, but Mike, I think you're talking about "bump" travel. I'm asking about how much the wheel can FALL from static before limitation- in this case it's the extended length of my shocks.

Greg- I'm guessing the droop adjustment you mentioned is what you use on FF or other chassis(?) It is relevant but I'm also curious what other Vee preppers do or or don't do.

[problemchild]

Greg- I'm guessing the droop adjustment you mentioned is what you use on FF or other chassis(?) It is relevant but I'm also curious what other Vee preppers do or or don't do.

I like zero droop on the front of a FV or FST car. I tried to run an external adjuster so I could add droop in rain conditions. Some drivers (usually older FV drivers) prefer the car to roll more on corner entry, but I like a firm turn-in. I would leave a 1/4" of droop (measured at shock - not actual ride height) for some of my drivers. I see no need for more than 1/2" of droop per side.

As a side benefit, having minimal droop settings makes setting toe a lot easier, and therefore more accurate. Just jack it up! Spin the wheels .... no need to scribe tires or worry about straightness of wheels, etc.

[S Lathrop]

I found that you can tune the front of a FV by controlling droop. The car will respond positively to reducing droop. What Greg is recommending is perfectly reasonable but I would start testing and determine what you like best.

Zero droop is the point where full droop on the shock is exactly the point where the fully loaded car sits and the shock just slides on. You can preload the shock from this point as well. So you can set the car up with say 1/4 inch of droop, zero droop or pull the car down a 1/4 inch with the shock (this would be 1/4 inch preload). Again you need to test.

[sagero]

I found that you can tune the front of a FV by controlling droop. The car will respond positively to reducing droop. What Greg is recommending is perfectly reasonable but I would start testing and determine what you like best.

Zero droop is the point where full droop on the shock is exactly the point where the fully loaded car sits and the shock just slides on. You can preload the shock from this point as well. So you can set the car up with say 1/4 inch of droop, zero droop or pull the car down a 1/4 inch with the shock (this would be 1/4 inch preload). Again you need to test.

Very interesting. Thank you.
This discussion encouraged me to look around and I found this apex post by doing an outside search http://www.apexspeed.com/forums/show...ero-droop-quot

[enrikerace]

This is an interesting thread

I own a lynx car and i recently changed de front beam because of an accident.

The problem i see is that the suspension (with 4 torsion bars on top and the colroll on bottom) has its original drop.
How can i limit the travel and how much will be "acceptable".

I was thinking on making my shock absorber shorter but i dont think theyre built to limit the suspension.

The other way is that i can use a cable or nylon tie down but i havent seen this in any car.

Maybe I can use the height adjuster form empi on the center of the beam to control this.

Any help?

[Drake]

"I found that you can tune the front of a FV by controlling droop. The car will respond positively to reducing droop."

In what way? What are the characteristics of more or less droop?

As a side note, I have recently restored a 74 D13 and found that the front shocks were used to adjust ride height. The top of the shock has a threaded rod insert between the shock shaft and spherical bearing. A shorter threaded rod pulls the front down which also sets the suspension to zero droop. Don't have enough seat time to determine differences between lengths. Please elaborate on what you have found.

[grapefarmeral]

You can use a cable, it's been done in the past. You can also use a spacer inside the damper, between the piston and the bottom of the damper. They make droop limiters for the inside of the damper, but the last time I tried to buy a set at the track, the shock guy wouldn't sell them to me, but would provide and install for $75 per damper. We ended up making them from some PVC plumbing parts.

[enrikerace]

The shock can be damaged because it will be bottoming out arround the track several times. Or are they strong enought?

[S Lathrop]

There are many shocks that are designed to be"topped out". These are popular on off road vehicles.

Penske has many shocks that have provisions to be topped out. You ca add this feature to many of their shocks.

There is no magical setting for droop limiting. You will have to do a lot of testing. What you will fine is that over a large range, droop limiting has no noticeable effect. But at some point the car will become very sensitive to the amount of droop you allow. My guess is that if you limit you car to 1 inch of droop below loaded ride height, nothing will change. But if you limit droop to say 3/4" you might feel something and at say 5/8 inch the car is not very nice. At some point you will be find that the car is very sensitive to changes in preload. As an example I have found that I calculate preload as spring forces and that a change of 15 pounds in the preload is very significant.

[Hardingfv32]

Or are they strong enought?

They only force they are seeing is what is provides by front spring in rebound…. maybe 25-40 lb if you consider the motion ratio.

Brian

[Daryl DeArman]

They only force they are seeing is what is provides by front spring in rebound…. maybe 25-40 lb if you consider the motion ratio.

Brian

That would certainly depend on how much preload, if any, you have in the front end.

[Hardingfv32]

1) Point of interest: Exactly what is the purpose of preload.. created by a droop limiter.. in a FV front suspension? By what means does it change the balance of the car?

2) In rebound shock is controlling only the spring force and movement is slowed by the shock rebound valving. This is not like the sometimes high velocity of the compression movement. I can not imagine that any front preload is going to exceed 200-300 lb. Again do not forget the motion ratio. The shock's motion is half of the wheel's.

Brian

[S Lathrop]

1) Point of interest: Exactly what is the purpose of preload.. created by a droop limiter.. in a FV front suspension? By what means does it change the balance of the car? Brian

As you corner, the inside front wheel goes to full droop. For the front to roll any more, the front end of the car has to go down on both sides. This changes the weight transfer between all four wheels a lot. Collectively the changes work well or not depending on how much you limit the droop travel.

[BLS]

Just to make sure I am understanding the pre load...

By pre load, it means you have limited droop, then adjust the spring to push against this limit? And this would then mean that the droop limit must/should be set to the normal level ride height of the car?

Thanks

[Drake]

Would this have a similar effect as a sway-bar? I can imagine a situation where you would have a sway-bar of one rate until the weight transfer rolled the car enough to hit the inside droop stop which would increase the rate exponentially. Could this explain a car with understear?

[S Lathrop]

Would this have a similar effect as a sway-bar? I can imagine a situation where you would have a sway-bar of one rate until the weight transfer rolled the car enough to hit the inside droop stop which would increase the rate exponentially. Could this explain a car with understear?

No. A sway bar controls roll by adding a second spring that only works as the car rolls. In roll the spring rate of the out side wheel increases by the spring rate of the swaybar. Droop limiting does not change the spring rate of the outside wheel in roll. It limits roll by stopping the inside wheel from going down For the outside front tire to go up and that side of the car to go down, as it does in roll, the entire front of the car must move down.

Understeer can be caused by 2 different effects, a tire that does not grip the track and simply slides across the surface, like a way too stiff spring or way too much air pressure. Or understeer can be a simple case of getting to the cornering limit of the front tire and not calling upon the rear tire to get into the cornering game. To correct a push condition, you must decide which situation you are dealing with.

[Drake]

So a front droop limit can be used to limit roll and therefore allow a lower rate sway-bar: correct?

[S Lathrop]

So a front droop limit can be used to limit roll and therefore allow a lower rate sway-bar: correct?

Droop limiting is a way to over come other suspension issues. In a FV, you are limited on the spring rate you can get because of design limits. When you need to use a soft spring for various reasons, droop limiting allows you to get the ride height you want with a soft spring that can not support the car at the ride height you want. With a FV, you want the lower trainling arms close to level. Droop limiting is a good way to achieve that.

One characteristic of the FV front is you have a rising rate suspension when the trailing arms get to an extreme angle as it would in a high roll position. You are limited on the spring rate you can build in a VW beam. So droop limiting solves a bunch of problems that in a FF you would not have.

For my FF and FC cars I never set them up with preload in front suspension. But with that car I am not stuck with the VW front suspension. I have always been able to get the handling I want without going to droop limiting. But VD as general use preload front springs as a normal practice. And they make it work very well. For a FV, I would build in the ability to droop limit the front end.

I have built a FV front end with a cockpit adjustable front sway bar and droop limiting both. I think it is the way to really get the optimum setup.

[Daryl DeArman]

Just to make sure I am understanding the pre load...

By pre load, it means you have limited droop, then adjust the spring to push against this limit?

Yes

And this would then mean that the droop limit must/should be set to the normal level ride height of the car?

If you subscribe to the practice of zero droop, then yes. However, I'm sure that most run some amount of droop.

You could, for example, have 50# of preload at 1/2" of droop, but when you set the car on the ground it is going to compress some amount because the amount of static weight on the front end is enough to overcome the preload.

[BLS]

Thanks Daryl.