Addressing front roll stiffness with droop limiters / preload?

Currently, one of the biggest problems, as I see it, with the handling of my '86 Ford Escort dual engine crapcan racer is not enough front roll stiffness. The suspension up front is pretty much stock with a coil and a half lopped off the springs. With weight taken out of the front and larger tires on the car, the ride height is actually very nearly stock. One of the problems that comes from cutting the springs even more to lower and stiffen is that every time I jack up the car, or even get it kinda airborne the spring may become unseated. So I was going to weld myself up a droop limiting device, basically a rod with a nut and a washer that will only let the strut open up to the point that the spring is just barely loaded. I then got to thinking about what effect it might have to use the same device to add preload to the springs more than necessary to just keep the spring seated. When I Google this all the examples are open wheel cars, and while it seems like a reasonable idea for stiffening the front end essentially for free ($2013 Challenge and Chumpcar dictates that I basically have to do this for free) I've got to think there's a really good reason not to do it, or else it would be more common place.

Yes, preload would mean that until the dynamic forces exceed the preload amount the suspension will be essentially like a go-kart, that is to say, nonexistent. So, I would want to use this sparingly, but just wondering if anyone had any first hand experience with how preload and droop limiting practically affects cornering performance in a production based car.

No first-hand experience, but I thought I would point out one phase of limit/preload that I don't think you mentioned (though you may have considered it).

At full droop, the spring is unseated.

At full spring droop with a droop limiter, the spring is not preloaded at all, but kept seated.

There is a phase wherein the droop limiter preloads the spring less than the weight of the car would. (this is the unmentioned phase).

Then there is a phase where the droop limiter preloads the spring more than the weight of the car would (this is what you mention above with go-kart-until-dynamic-load-exceeds-static-load).

I have a couple of other thoughts, but they are not based on any first hand experience, and get into theorizing how things might work rather than just observations about what you're describing, so I'll keep my trap shut for now...

ransom wrote: There is a phase wherein the droop limiter preloads the spring *less* than the weight of the car would. (this is the unmentioned phase).

True, good point. And I would presume that preload in this range still has some effect, like to not push the car over in the corner, and the proper amount of preload is probably somewhere between this and the point where you exceed the static load of the car. (Just a guess)

I think you're looking for limit straps. You could probably DIY for $free with some old seatbelts.

look around online for a used set of ground control collars that will clear your shocks, get some cheap springs, both your seating, droop, ride height, and stiffness problems can all be solved for around $50. The most complicated part is getting the right top hats, but most will work as is with maybe some slight 'adjustment'

^^Beaten. Offroad limiting straps. Old seatbelts are the ghetto option for them.

It's an interesting thought. Seems like the best way to go is to try it. I would probably Use chain though. To get adjustability I would weld/bolt the chain to the suspension and then put a hole on the chassis somewhere. I would use a ~3/8-1/2" Eye bolt with 4" or so of threading and put a Locknut on that. I would set the whole thing up so at the longest point it's just where your limiting droop to keep your springs in place. You can then mess with adding more and more pre-load by tightening the eyebolt.

nocones wrote: It's an interesting thought. Seems like the best way to go is to try it. I would probably Use chain though. To get adjustability I would weld/bolt the chain to the suspension and then put a hole on the chassis somewhere. I would use a ~3/8-1/2" Eye bolt with 4" or so of threading and put a Locknut on that. I would set the whole thing up so at the longest point it's just where your limiting droop to keep your springs in place. You can then mess with adding more and more pre-load by tightening the eyebolt.

In the offroad world they always use some kind of strap, not a chain, there's probably a good reason for that, the potential for chassis damage with an unyielding chain being the one that stands out to me. A chain with bushings on one end would at least be safer.

And more on-topic, limiting straps should be used to hold your suspension together, not to affect handling. Running a stock-spec shocks with cut springs is about the most ghetto "performance" suspension setup possible, sometimes it can work well but when it doesn't, you gotta pony up and do things right.

Go easy on limiting droop unless you also control body roll by stiffening the suspension even more, from personal experience that can cause the inside tires to lift and thus spin like crazy under power. If you don't want to stiffen the suspension any more, see if you can tie strap or otherwise attach the spring to the upper hat or mount, then use PVC or similar to make an alignment sleeve for the shock so the spring has no chioce but to go back onto its seat.

You might also look into dropping some motorcycle springs inside the main spring to stiffen things up.

^That reminds me of another offroad technology, tender springs. They are short and very soft springs that only work to keep the primary and/or secondary springs from unseating, once a meaningful amount of weight is on them they collapse flat. Something similar could work for this car but you won't find anything with the diameter of a stock spring off-the-shelf.

I have tenders on the rear of the Jensenator, they are completely flat until the spring comes off its seat. They then push the spring up, keeping it in contact with the upper hat. This setup needs a divider to keep the tender sprng aligned.

sporqster wrote:

ransom wrote: There is a phase wherein the droop limiter preloads the spring *less* than the weight of the car would. (this is the unmentioned phase).

True, good point. And I would presume that preload in this range still has some effect, like to not push the car over in the corner, and the proper amount of preload is probably somewhere between this and the point where you exceed the static load of the car. (Just a guess)

At rest, droop-limit preload less than that caused by the weight of the car has no effect. It's only when enough load is transfered off of that wheel to reach the limiter that any effect would occur. Until that point, the limiter is a floppy piece of strap sitting next to the spring.

The idea makes me uneasy, and I think that comes down to having a point in the corner where the car's suspension's characteristics change suddenly. It seems like one of those things where if it can be made to work, it definitely increases the number of considerations involved in making the car not do crazy things.

There's an interesting discussion here.

Off roaders probably use straps because of the rate and number of times you go from fully loaded to 0 load and back again. Agreed that in this situation chains probably cause problems that a slightly spongy strap aleiviate. His situation shouldn't experience that sort of thing.

What's the Deal with calling the lower cost fab it yourself option (Seatbelts) ghetto? Unless Ghetto now means awesome it sounds like your saying DIY options are bad.

nocones wrote: What's the Deal with calling the lower cost fab it yourself option (Seatbelts) ghetto? Unless Ghetto now means awesome it sounds like your saying DIY options are bad.

Not necessarily. Ghetto is the gray area between really cheap and stupid In the case of seatbelt limiting straps it's safely on the "really cheap" side.