Here is something to get your mind chewing on as we head towards the winter rebuild months.
I’ve heard of people working with cambered and toed rear ends for years, but my recent association with Strange Engineering rekindled my thought process on this.
They do pay me to write articles describing their products and how to use them.
Of course, we all know cambering tires can increase tire grip. So, naturally if you can camber a right rear tire you will increase side bite. Strange does make some quality drive flanges and axles to help you accomplish this.
Incase you are not familiar with how cambering a rear end can add traction, I’ll run through the basic principles to make sure we are on the same page.
Putting camber in a tire adds side bite traction. We really only need to put camber in tires because we put air in tires. On a solid sidewall tire like a tricycle tire, you don’t nearly need as much camber, if any at all. The air in the tire makes all the difference.
Push a tire sideways that is sitting flat on the floor. You’ll notice the outside sidewall will fold under and the inside sidewall will create a bulge.
The treaded portion of the tire on the inside with the bulge will not have as much downward pressure on it and consequently, will have less traction than the outside edge.
Now, if you take the tire and tilt the tire top inward. Then give it a push.
The bulge will be located more directly under the tire and the pressure will have more equal pressure across the tread of the tire.
So technically, we are not adding traction to the tire we are just restoring the traction potential to the tire that would normally be lost by the side loading.
But, what I was thinking more about is axle tube flex and how this affects the handling of your car. I personally deal with a lot of late models which are running aluminum axle tube quick change rear ends, but all the
principles will apply no matter what type of car you are running or solid axle rear end your car has in it.
We are not always as scientific as we should be in the dirt track community. A lot of the experimenting and figuring we do is by trial and error instead of with a calculator. So, I’m going to explain what I’m thinking just as we would be experimenting with it.
In my last article we talked about how much torque is going through our drivetrain. It’s enough torque, in fact, to twist an axle like a candy cane. Now lets think about how this torque can actually flex and bend our rear end housings and axle tubes.
We apply a thrusting torque at the tire contact patch. The fore and aft locating links transfer that torque to the frame and the car moves forward.
Since the tire wants to move forward and the locating links want to resist that, there will be a tendency for the tires to toe in under sever load as you accelerate your car. Under severe braking would have the opposite effect.
I believe the place of the most flex on the axle tube will be between the hub and the place where the locating links are positioned.
Or, to tell the truth, I believe side bells on quick change rear ends flex a bunch also.
There will be some inboard of the locating links, but not nearly as much. It makes sense then that the distance between the inner hub bearing and the trailing arm position (or the birdcage position) makes a difference as to how much flex toe you are going to get.
Now lets think about axle bind. The axle basically floats inside the axle tube. It’s attached to the spool on the inside and the drive flange on the outside. any misalignment will naturally start to wear the spool or drive flange faster. This is where I think Strange comes to the rescue once again. They offer drive train options designed for cambered rear ends.
It’s not the perfect solution, but I believe they do take a little bind out and extend the life of the parts.
You know, toe is just camber in a different direction.
In a true cambered rear end, the axle snouts are either welded or machined off center. With a balled drive axle end and a properly designed drive flange, just about all the bind is removed.
That where I say the Strange set up will help some when the tube flexes, but it is not a perfect cure all solution.
Their axles and flanges are designed to run square through the axle tube with the ends welded offset to create a true cambered rear end. The ball and socket end will on prevent a little wear.
What is the best solution?
This is where my thoughts are at on this.
First, I would use the Strange Oval system and put about 2 degrees of camber in the right rear tire.
Then, I would install axle tube struts to support the axle from toeing under acceleration and braking. There are several companies that make kits you can bolt on the center section and run to somewhere close to inside the birdcage.
Because of the birdcage or trailing arm mounts, I don’t believe you can get the mounted all the way to the spindle snouts. If you can, that would be best.
Anything you can do to strengthen the axle tube as far out as possible the better.
Just make sure the strut tubes clear all suspension components and don’t add any bind to the car.
If you are running Ford 9” rear ends you may need to weld tabs to the center section to bolt the struts. Quick change rear ends will have brackets that bolt to the center section then a clamp collar to bolt to the tube.
Hopefully I’ve planted a seed of thought. Something to chew on a little through the winter months.
That’s the nice thing about a long rebuild season off. It gives us time to think about things rather that just getting to the next race.
If you are interested in learning more on what Strange Oval has to offer, here is a link to their website: http://www.strangeoval.com.
Til next time, Kevin