Drag Racing Suspension Setup and Tuning with Digital Video
Videotaping Your Race Car
A video camera may turn out to be one of your best performance investments if you use it to help diagnose what your car is doing. No matter how many buddy's you have watching your car launch, you're not likely going to get a very good idea of what the car is doing without video. You'll get 10 different opinions, and likely none of them will be correct.
While you may be a Pro at video taping, it's likely your new crew member that's trying to help you with this task isn't. Just like anything on a racing team, it can take some practice to get good recordings. Have your crew member review this article to help get them up to speed fast.
Safety on the Starting Line
The starting line at the drag strip isn't the safest place to be screwing around looking at the view finder of a video camera. If you're going to be the one doing this task, get familiar with how your video camera works before you go to the track. Learn how to turn the camera on, how to start and stop recording, how to operate the zoom button, etc. Practice so you don't have to attempt to find these controls on the line when you need to be playing very close attention to what is going on around you.
Stay out of the way of your car, and the car that is in the burnout box getting ready to do their burnout. Drivers expect you to know what you're doing if you're up on the line, so it's up to you to pay close attention and not get run over if a car gets sideways doing their burnout. Stay out of the way and be safe, remember these folks driving are NOT paying attention to what you are doing, you step out in front of the car and you're going to get hurt.
Tips for Taping the Launch
Since getting a car to hook good is one of the most important things to do in order to go fast, you'll likely want to film the car launching to see how the suspension is reacting. Here's a few tips for recording the launch.
- Use a shoe marker and paint a mark on the side of the rear tire so you can watch to see if the tire is spinning. You might also want to paint a thin mark all the way around the outside edge of the tire to help view the contact patch and tire distortion.
- If you have wheelie bars, coat the wheels with wheelie bar chalk. You can get the chalk from Jerry Bickle Race Cars (and probably Summit or Jegs), it's made by either VHT or Geddex and costs about $10 a can.
- Have the person shooting the video shoot the starting line after the pass so you can see the tire pattern laid down and what the chalk marks the wheelie bars made. Just remind them to get out of the way in a hurry as the next car will be doing it's burnout and you don't want to be in the way.
- Avoid shooting into the sun, try and choose the side of the car that will let you tape with the sun behind the camera if at all possible.
- Have the person video taping the car stand behind and to the side of the car. Ideally you want to capture the left front and rear of the car. Have them fill the screen as much as possible without zooming. This will mean they will have to stand most likely about 10-12 feet or so behind and to the left of the drivers door.
- Try to include the Christmas tree in the video, at least the top bulbs. Not only does it help you known when to start your video (assuming you're only wanting to film the launch itself), there are many situations where having that information is handy.
- Avoid using the zoom feature if possible, at least during the launch of the car. Zooming in tends to magnify hand movement and results in a really shaky video.
- Get the scoreboard in the video at the end of the run. This is not only handy for keeping track of which run it is, but hey you might have set a record and want to record it for proof!
- Use the highest FPS (Frames Per Second) setting your video camera is capable of. The higher the frame rate, the more information you can capture and the better your slow motion video will be. Even if you have to sacrifice your video resolution, is almost always better to have the higher speed. Example if you have to chose between 1080 at 30 FPS, or 640 at 120 FPS, use the 640 at 120 FPS - remember we're trying to capture data here not make a movie. If you're not sure how to set this in your Camera, consult the manual.
- Some teams use Go Pro Cameras mounted on a Tri-pod and just set the camera down near the car during launch to capture it in high speed. Go Pro Cameras have some very high FPS rates available, and very good video quality. They often have a 2nd camera to use for to watch what the car does down track.
- Don't have the money for a dedicated high speed video camera? Use your smartphone! Many of the newer Smartphones like the Galaxy G5, or iPhone 5s have the ability to record in high speed, and some pretty impressive video cameras built in.
What to Watch For...
There is a standard progression of events that occur as a doorslammer launches. Watching each of these events and at what point in time they occur gives you the clues you need to dial in your suspension. The key is to making these events all happen at the right "time" is your shock valving controls.
Mike Canter of Outlaw Pro-Mod fame had this jewel of a post years ago that I saved where he detailed the following sequence that you should watch for:
"This should be the sequence of events seen on the video. Right at launch the front should start to come up before any forward movement or the car.
The rear of the car with this added weight transferred from the rising front will lift very little but it should not go down (squat). An inch or two is normal and can be best seen by looking at the relationship between the top of the slicks and the rear fender lip.
This one or two inches of rise will indicate that the rear of the car is lifting and pushing harder on the tires while the front weight is being transferred (for every motion there is an equal and opposite motion).
If the front of the car does not rise first then the front shocks are too stiff or the rear shocks are not stiff enough.
If the rear of the car squats right away then the rear shocks are too loose.
I have found through slow motion video tape that if the rear shocks are too loose the rear tire actually bounces on the initial hit and will break loose almost right away. I stood next to the car pointing the camera right at the rear tire. It was amazing to watch. I kept on tightening the rear shocks until it stopped which was just below mid point of the adjustment. From all that I have seen the rear shocks should never be adjusted less that half way because of rear squat and tire bounce."
Pat Musi's Tips On Adjusting Wheelie Bars & Reading Chalk Marks
- There are two different heights, measuring center-to-center, from the back to the ground. The first is the cold tire pressure height, You should always be on the flattest ground you can find, so if you're setting them with the tires cold, you know where you want to be. "Every driver, every crew knows where they want to be at what we call cold tire pressure."
- The second is the height after the burnout. When the tires get hotter, they grow and the height changes. So, after the burnout they see how much the wheelie bar moves up. "We have a measurement that we use and we'll go up or down on one or both, it just depends. We're talking very slight adjustments at that point. Generally we know where we want to be within an eighth of an inch."
- "We read many things by the chalk. Chalk is used for two reasons. You'll have two strikes. You're going to strike them immediately, and then the car is going to get up on the tire. It'll come off them, the front end will start to come up, and it gets on them again. So, we're looking at the distance of those two marks. The first strike is very short. We run stagger. You have to run the driver's side 1/4 inch higher, typically, than the passenger side because that's the side that is going to hit first."
- "You can also tell by the width of the chalk how hard they struck. If the chalk is wide, meaning you hit hard, you'll want to raise them up a little bit. Also, you can control the car from going left to right, I mean you shouldn't steer the car with the wheelie bars, that should be done with the suspension, but if the wheelie bars are off left to right, you have to adjust them."
Slow Motion Video
Let's take a look at this video of one of a launch and see how much more information you can see when the video is slowed down. This video was slowed down substantially using Microsoft Movie Maker "Half Speed" effect.
Notice how much more detail you can observe when you have time to observe everything going on? Would you like to venture a guess at what is causing this car to unload? Watch the car strike the tire then bounce back up.
The higher the Frames Per Second your video camera can record, the smoother your slow motion video will be and quite possibly you may see something in a frame that would be missed by a slower camera. A video camera with at least a 60 FPS capability would be great, the higher FPS the better. Note that some cameras can be set for a higher FPS setting but will require a lower resolution in order to run that fast. Check your manual on your camera for the settings to chose the fastest one for these types of shots.
Studying Video at the Track
Many teams now play back their video on a laptop between rounds to see what the car is doing. Video Cameras that use an SD Card are awesome for this, you just pop the card out of the camera and into the laptop to watch it on the bigger monitor. However time is limited between rounds making it difficult to slow the video down with software for close examination, nobody's got time to mess around with software slowing a video down unless you've got a team member to do that task.
This is where using Apple's QuickTime Video Player can be VERY handy. It allows you to move frame by frame in the video just by pushing the arrow key. Just start the video, then pause it. When paused the arrow keys on your keyboard allow you to move forward and backward frame by frame. Hold the arrow key down to advance or rewind at regular speed.
Many other video players like Microsoft's don't do this very well, but QuickTime works great for this purpose. You can download it for free at www.apple.com/quicktime/download/.
On Board Video Cams
Mounting a camera under the car can reveal some very good information. For example on my car years ago, I was trying to figure out what was causing "camel humps" in the accelerometer data in first gear. I knew it was spinning a little bit, but it appeared to be a cyclic pattern to the spin. So I decided to try and video tape what was going on under the car. Here's what we found after recording a launch with a make shift video camera... Today's GoPro's would have been a vast improvement, but this was all we had at the time.
These were QA1 single adjustable shocks, and the valving was way too soft for this car. Even at full tight, they could not control the axle and ran out of travel. When the shock ran out of travel so fast, it upset the tire and it would spin.
Look at the other details we noticed - we also found A) Shock Bracket almost hitting the shock B) Upper mount is flexing. This was many years ago on my Nova, since then we've switched to Santhuff shocks, an anti-roll bar and many other changes. These problems have been solved, but this old video is a good example of the things you can discover with chassis mounted video cameras.
Now this is a real old video, before Go Pro's were available so understand the video quality isn't that great but it did the job. Now almost everyone and their brother has a Go Pro or similar video camera that can generate far better video at a much higher resolution. Not to mention there are a lot of different mounts to use to attach it anywhere on the car. Make use of modern technology to enhance your program!
In Car Camera Roll Bar Mounts
If you want to mount the camera in-car so you can see what the driver is doing, watch gauges or just for fun there are a lot of ways to mount the camera. One of the first roll bar mounts I used was this mount, one of those quicky things I made in a few minutes that's nothing more than a couple muffler clamps with a piece of steel strap welded between them. It worked pretty good, but had limited adjustability.
After playing around with this mount for a while, I can see where you could mount it in a lot of different positions in the car - you could even rig it up to point out the window so you can catch yourself passing the competition!
If you want to buy a mount, most modern action camera manufacturers offer many different styles of mounts to stick your camera/s any where you want on the car.