Coil Binding: a seemingly untouched realm

[Belisario93]

Pre-post note: I do not consider myself a tuning expert at all (in fact I think I suck pretty bad at tuning), so what you're about to see is possibly going to suck horribly and/or not work for you at all. I mostly posted this to bounce ideas off everybody. Please, if you're going to criticize, provide some constructive thoughts on why it doesn't work or how I can do things better. If you have any questions that haven't been answered by this post, please ask and I will answer when I can.

I've been wanting to do some testing on coil binding for a long time now (ever since I started hearing about coil binding when watching NASCAR on TV), but I've been scared of diving into the dark art of tuning. Since summer break started for me a couple weeks ago, I started learning more and more about tuning in GT4, and now I think I have a small grasp on how things work (although I still have much to learn).

What is "Coil Binding"?
Coil Binding, which used to be used in NASCAR by just about everyone until it was banned, is essentially when the front springs are set to be very soft as needed to allow the springs to bind all the way until the front tires are acting as the shock absorbers.

I've read multiple articles on this, and each of them explained the benefits in a different way. The way I see it, is that it causes the weight distribution to move to where it is most needed. My assumption is since braking causes weight to move to the front due to inertia, softer front springs will allow it to push down on the tires even more than stiffer ones, giving the front tires more grip and allowing the car to turn better. Then, when the driver gets on the gas, the front springs will move back to their normal position and the weight will shift backwards (again due to inertia). Depending on the way the rest of the suspension settings are set up, this can cause the rear tires to have more grip, improving acceleration in RWD cars and possibly AWD cars (testing on AWD cars coming soon).

These are the pros and cons that I foresee in using coil binding in GT4:
Pros:

• allows for better turning abilities
• allows for better corner exit acceleration
• allows car to make the most out of its power
• can help reduce corner exit wheelspin

Cons:

• makes high speed corners more difficult
• requires a very specific driving style
• can be understeery on corner exit
• can be unstable on corner entry

Testing
Test Cars used so far:

• Amuse CarbonR (FR)
• Lancia Stratos (MR)

I have some more cars lined up for testing. I will do the tomorrow, and post my results as soon as I can. They involve different types of drivetrains and engine placements (although you won't see me trying this on FF cars, of course).

The Set-ups:
Note: these are works in progress, and are nowhere near finished. I have a lot of fine tuning to do on these. Currently all they are here to do is give you a general idea of what I'm rambling on about in this post. I also still have yet to learn how to effectively tune things like brake bias and camber. If you're having trouble reading the set-up image let me know and I'll provide an image that doesn't have the background.

Amuse CarbonR GT1 '04
Amuse CarbonR GT1 '04 Setup (png file, 725px x 687px, ~272kb)
Notes:
I tried with the Stage 4 Turbo installed, but it was hard for me to control wheelspin exiting corners. However I'm sure wheel users would be able to use the stage 4 turbo much more effectively.

Lancia Stratos R '73
Lancia Stratos R '73 Setup (png file, 725px x 675px, ~225kb)
Notes:
At first I tried using S3 tires, but found that they do not have enough grip to make this useful (at least not with this car). Also tried R1s, and while they provided enough grip to work, it was pretty subtle.
Some issues that I ran into after that involved stability, so I put a wing on it. I decided that front downforce would remove a lot of the point of this set-up, and found that too much rear downforce does that as well.

The basic principles of tuning this way:
As you can see on the set-ups so far, there are some similarities in how they are tuned:

• the front Spring rate is very low. You wouldn't get the effect if the front rate wasn't low.
• the front ride height is slightly higher than the rear. This allows the weight to be on the rear tires when the car gets on the gas. A similar effect could probably be done with a low rear spring rate, but I haven't tested that yet. The amount of front height over rear has important effects when coil binding.
• Bound settings are very low. Front bound definitely needs to be low in order to make this work. Otherwise the nose won't dive under braking quickly enough.
• Rear Toe is negative. This helps the car turn better, especially on exiting the turn where the car is likely getting understeer.

Driving a Coil Bind set-up:
Basically you want to take as much advantage of your horsepower as you can. A later turn-in combined with getting on the gas earlier is important, and in theory is made easier with a coil bind set-up.

Based on this research so far coil binding works best with:

• Cars with a decent amount of power per kilogram* (I figure that if the car doesn't have enough power to take advantage of, this won't help much)
• Cars with easily controlled wheelspin on corner exit (even better if no wheelspin is present)
• Tracks with few high speed corners (harder to turn when you aren't using brakes)
• Tracks with more banked corners (banked corners help keep the nose down and allow for more normal racing lines)
• Racing Slicks (in small sports tire tests I have found that even S3's don't seem to provide enough grip to do this right; more testing on this will be done soon)

* denotes theories

Whew *whipes forehead* that was a lot of work. And there's still more ahead. Watch this space.

 

[Leonidae@MFT]

You know, Stratos was probably too light for experimenting on this matter. Perhaps Lotus Esprit or such would had worked better?

 

[Belisario93]

You know, Stratos was probably too light for experimenting on this matter. Perhaps Lotus Esprit or such would had worked better?

You're probably right. I did get it so that the nose was able to dive down, however look how soft I had to make the front in order to get that to happen. That's probably where those stability issues that I mentioned came from.

I'll look for a new MR car to add to my list for testing today as well. More testing can only help, right?

EDIT: I've been doing the testing on and off today, and found out some important stuff, like the use of downforce and what it does with these kinds of set-ups. I'm also learning a decent amount on how well this works with 4WD cars.

Here are some cars that you can expect to see in this thread sometime soon:

• Lotus Esprit V8 '02
• Subaru Impreza WRX STi '02

 

[nomis3613]

Hi Belisario, I've never heard of "Coil Binding" before now, but if I may throw in my 2 cents.

- designing a car to sit on the bump stops regularly sure is an...ahem... unusual tuning strategy. I reckon it's just a way to exploit a loophole in the very restrictive Nascar rule book, and not a tuning strategy to be used in more normal situations). So I'd be doubtful if GT4 models this effect.

- however these suspension settings would move the weight distribution rearward, which could help FR cars (improving power-down, reducing braking understeer, etc) so you might notice improvements because of this. MR cars could develop some RR traits (lift-off oversteer, improved power-down, power understeer).

- the spring and damper rates will be very compromised when it comes to dealing with bumps, so you could be in for some interesting times on bumpy tracks!

Good luck for the testing. It's great that you've got a theory and are testing it, if nothing else you'll learn heaps about how GT4 tuning works in general.

Simon