Since pulling vehicles have no adjustable suspension like drag cars, there is a challenge of canceling motor torque.  The rotationg force of the engine in it's most basic form, is trying to rotate the chassis around the centerline of the crankshaft.
If a high horsepower motor is in a chassis that has no flexibility, it tries to lift one rear wheel off the ground, depending on direction of crankshaft rotation.
The two wheel drive trucks have the advantage of having a longer distance between the motor and rearend, allowing more distance for the frame to absorb some of the torque. 
If you watch closely as they get hooked to the track, one front wheel will lift off the ground a considerable distance before the other side.
Therefore, the chassis itself becomes like a huge spring, absorbing the force before it affects the rear wheels.
  Tractors, on the other hand, have about half that distance absorb the same, if not more, rotational force. You hear a lot of talk about flex in a component chassis, but how does one measure exactly how much movement is actually taking place? You can have someone video from the side or the front as they go down the track, and at times it does appear to lift one front wheel before the other, even on an ag type tractor. How can an ag type tractor flex? It doesn't. What you are seeing is tire squat. One rear tire is flattening out more than the other, tilting the whole chassis due to the torque of the engine.  Even component tractors, which are made from sheet metal or tubing, do the same thing. How do I know? Cameras and lasers. By attaching a laser and a video camera to the hitch, the laser beam projects a horizontal line across the front of the vehicle, and the camera records any measurable movement between the front and rear. It might surprise you how much some chassis move. (or not)
Ace has tested several trucks and tractors using this technology, and specific results will not be made public, but a general statement can be made about component tractors. None of the four tractor chassis tested had any amount of measurable flex. (Trucks are a different story) Testing was done on a wedge chassis, one mild steel, and two different moly frames.
picture of under a pulling tractor marty chandler deeply hooked showing frame and chassis flex
What does this mean? It means there is still a lot of room for improvement in chassis design.
picture of frame flex on a pulling tractor
If a chassis flexes, does it mean its better? Only if it wins.
There are some problems involved in designing a flexible chassis.
1. The simplest way to allow more flexibility is to drop down in tubing diameter or wall thickness or both. This makes the frame weaker, and depending on the material, will not allow for many cycles before permanent fatigue or failure. A chassis that is too limber is just as bad (or worse) as one that is too stiff.  One that has reached the limit of its capacity to return to its original shape is useless.
2.  Removing vertical bracing. Not recommended
3. The short distance between motor and rearend in tractors does not allow for many variations. Also the weight involved dictates a stiff, strong  material to handle the load.
4. Finding a driver who is willing to try something new, versus playing 'follow the leader'.  It takes a big investment in time and money to experiment.  Someone dedicated enough to work thru the glitches that arise.  Someone with patience, a passion for the sport, and always looking for a place to hook....
Marty Chandler and his new IH 3088 light/heavy  super stock aptly named 'Deeply Hooked'
tractor specs: 505 ci. three charger alcohol with 3 speed Profab, steel chunk, cast iron head, Engler mag planetaries, 30.5 8 plys, unique front axle, front weight rack, and a few other trade secrets.
total weight:  4625#
the lightest, most flexible component super stock ever produced.
This is a work in progress, and updates will follow as the vehicle progresses
Debut in Shelbyville, Tn
after working feverishly all week to try and seal leaks in the rims, Marty made the decision to put tubes in the tires. After all the late nights, many trips to the hardware store,
last minute problems that always seem to multiply the closer it gets to time to pull, a quick test drive, a mad rush to get there and get inspected, registered and weighed, the results were disappointing.
The clutch was not locking up and only rolled the tire about 1/4 of a turn.
The next week will allow time to see what the problem with that is and finish up some cosmetic details.
April 26th Murray, Ky
With new clutch discs the power went to the ground, but lasted only a few seconds before the motor asked for more fuel and refused to go any more.
Maybe this is the last of the cold weather pulls for a while.  With a two week break, we can get the computer working right, and machine bigger fuel nozzles.
With 150# more weight on the left side, it lifted evenly and looked great from the camera mounted underneath.
picture from underneath camera on a pulling tractor
May 10th Lawrenceburg, Tn
After some tuning, modifications, and installation of a 'PPS valve', the motor sounded better than ever.
With an average 50 ft gain in distance each week, Marty should reach 400 ft. very soon! At this point, we may see a blonde driver take over??
May 31st- Viola, Tn
Several things have changed over the last two weeks. One of the two fuel pumps was not operating at all, and now with both pumps working, it is going to be a gradual process of taking fuel away till that 'lean-n-mean' point is reached.  A combination of too much fuel, and a non-working computer will make it a guessing game. Tonight was the first time Marty had ever run the 8000# class, and drew first hook.  "I pulled as far as I could, drove off the track, and back to the trailer, so I'm happy!"
Marty spent more than one late night re-assembling everything after powder coating the chassis and repainting the sheet metal. Well worth the effort for the results, a totally different look...
photo courtesy of Chris Carlisle
June 20-21 Hazel Green, Al
A nice straight pass brings it up 1/2 inch shy of first place in the light class. Clutch problems in the heavy class send them back to the trailer. The computer is working finally, and some tuning can take place.
Words can't do this run justice, just watch the video...
Thanks Tim, wish I coulda  been there
June 28 Springfield, Tn
After some controversy at the scales over moveable weight in the light class,  Marty asked when it was his turn if the 300 had to come off the back rack or the front? No problem
The starter mount broke in the heavy class and since Possum was the only one who had electrical tape in his pocket, he automatically became the volunteer to tape the hot lead and hold it in place to get the motor cranked, then laid it on the front axle while we all hoped it didn't die.
He hit the weight just right in both classes and made two very respectable passes, wishing a few more horses were under the hood.
July 4-5 Hoptown, Ky
Well, it was a bad weekend. After a 2 1/2 hour rain delay, and wading thru mud to get to the track, the hopes of placing in the top 3 were gone about 3 seconds into the first hook of the night. The track was decent, considering all the effort made to rework it after the rain, and the tractor hooked up immediately, but erupted in a giant fireball when a rod broke and opened two huge holes on both sides of the block. Thanks to all the pullers who had fire extiguishers and showed the volunteer firemen how to put out a alcohol fire.
picture of rod sticking out of engine block
Aug 31 - Franklin, Ky
After all the efforts to get the motor running for Martys hometown pull, it just wasn't meant to be. It started and ran, but had a knock. Time just ran out as the event that he promoted this weekend demanded more and more of his attention.  We got to the pull a little early, and Marty was all smiles. "I got me a ride" he said, as soon as he saw us. He told us that another puller had signed him up to drive his tractor, and insisted he drive tonight. And he did... And he won...
There are a lot of examples of selfishness and greed, and it is rare to hear or see anything different, especially in motorsports.  This is one of those instances where the competitive attitude is overshadowed, and the spotlight turns to someone else. An example of true sportsmanship. It comes at a critical time when some political and personal issues are starting to rob the fun out of the sport for a lot of pullers in the association.
When something was mentioned about competing with Don in the future, Marty said, "Oh, I don't wanna beat him, I'll just stand off to the side and wave blue pom-poms".
So will all of us, Don. Thank you
picture of don head heads up pulling tractor
Marty driving Don Heads tractor 'Heads Up' at Franklin, Ky 8-31-08
Sept 27 - Manchester, Tn
After a few tuning passes on a fresh motor, this tractor got an amazing performance upgrade. Here we can see Marty attempting to install...
but it would not stay put. Well, at least till the tractor got down to 318'.  As soon as the tractor stopped, it came off. Sometimes changing one little thing on a vehicle will make a huge difference, and maybe we can figure out a way to get this one to stay on it more next year...
picture of melissa chandler
Congratulations Melissa Chandler !
Everything else is just a waste of tubing.
Thanks to all the pullers who agreed to let us use the lasers to collect information. Hopefully it will be useful to you in the near future.
Don't be afraid to give up the good to go for the great.
John D. Rockefeller