About Flex

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Flex-Frame™ technology.
Everything else is just a waste of tubing.

Flex-Frame™

What is flex? There are a lot of misconceptions about how and where a pulling tractor frame twists and moves during a pull. It seems to be a buzzword that everyone considers to be an important feature when buying a new chassis, even a major buying point for some, but few people seem to know the how and whys. Some builders advertise flexibility, but are clueless as to where and how much movement actually exists. Just because it is made out of chrome-moly does not automatically make it flexible. Simply making some 'trick' motor mount does not make one flexible.

Just because a builder it says it is flexible does not make it so.

What about motor cradles? Do they help protect the block?

I will answer that with another question: How many twd trucks have motor cradles? Do they have block issues? If a chassis is designed correctly, the frame rails are the cradle. Dont let someone sell you (for extra money of course) a second frame inside a frame to "eliminate torque" or "protect the block", which will only needlessly add more weight and expense. The frame rails are all you need, the flex just needs to be controlled properly

How to know if your chassis flexes? The simplest way is to jack up one corner of the frame until one front tire comes off the ground. If both tires come off the ground at the same time, it would be considered a 'stiff' chassis. If the weight of the tractor itself will not cause the frame to flex, you can bet that the torque of the motor will not either. I'm sure you have seen a tractor being pulled thru the pits and go over an uneven surface, and one front wheel will come completely off the ground. This is stiffness. I'm not saying this is a bad thing, because there are some very stiff tractors out that do perform well, but if you want to tap the maximum potential of having a full length frame, this concept is the only safe way to get it done.

picture of frame flex on a pulling tractor

There is a trend to make the frame out of thinner or smaller diameter tubing, which will cause the tractor to flex. This is dangerous for three reasons:

1. Because of the reduced load carrying capacity. Why compromise safety for performance?

2. It places undue stress on the driveline components. Movement takes place in 2 planes instead of only one.

3. It limits the number of cycles that the frame can be moved and brought back to its original shape. Do you really want to invest your money in a weak, disposable frame ?

Advantages: The biggest factor would be the ability to keep the rear tires planted longer.

Disadvantages: cost. Everything, including the motor, turbos, fuel tanks, tranny, etc. has to be able to move with the frame, and takes a little planning to make it happen.

It will add some labor cost over a basic chassis.

it is time to use your chassis for something besides an engine stand.