SEAT AND ALIGNMENT

[DENNISC020]

getting closer to getting the "rock" race ready,but I have two questions. What would be a good starting point for a front alignment . The second , currently my seat is mounted to the cage but I see alot of cars were the seat is mounted to the body.is one better than the other

[joeg]

Toe-out for the front (about 1/16+" total); as much negative camber as is feasible.

Don't mess with the caster angles or rear alignment for the time being--as long as the rear is straight.

[Bill Miller]

Originally posted by joeg@Aug 9 2005, 07:38 PM
Toe-out for the front (about 1/16+" total); as much negative camber as is feasible.

Don't mess with the caster angles or rear alignment for the time being--as long as the rear is straight.

The camber setting is a function of the tire you're running. Some like less camber than others.

[lateapex911]

The seat question raises an interesting point...

You state it is currrently mounted to the cage, which is the preferred method if you have the choice.

But..........here in IT, we are limited to 6 mounting points, plus the foot bars. So, it is very difficult to construct a cage structure to mount the seat to while observing the 6 point rule, without creating a hugely heavy structure.

Can you describe it, or, better yet, as the new site supports picture posting, do you have pics??

[Ryan Williams]

Originally posted by joeg@Aug 9 2005, 07:38 PM
Toe-out for the front (about 1/16+" total); as much negative camber as is feasible.

Don't mess with the caster angles or rear alignment for the time being--as long as the rear is straight.

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The rear trailing arms have one degree of negative camber built in. As the rear trailing arms are inclined upward as the car is lowered, the TOE setting of the rear wheels will be "TOED-IN".

Consequently, a rear alignment is required to get the TOE back to specs, using shims between the rear stub axles and their mounting plates on the trailing arms.

Cheers, Ryan.

[DENNISC020]

after looking closer it isn't mounted to the cage. Its mounted to the seat track, so it is mounted to the body. Good idea about pics' I will take some and post .

[DENNISC020]

after looking at my autopower cage I count eight mounting points -

[Bildon]

Originally posted by Ryan Williams@Aug 10 2005, 12:04 AM
the TOE setting of the rear wheels will be "TOED-IN".

Consequently, a rear alignment is required to get the TOE back to specs, using shims between the rear stub axles and their mounting plates on the trailing arms.

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But that's a static spec... and we don't race on skinny low grip street tires where we keep all 4 wheels on the ground.

OK ... I feel like giving today.
The rear axle is very flexible unless you make some modifications to prevent EXTREME toe changes under side loading. This is why VW used the toe correcting bushings in the rear axle beam chassis mounts. If you have switched to an aftermarket bushing or bearing and not stiffened your axle beam trailing arms you have just made this problem much worse.

So....
Pay special attention to the wear in the rear on the of the tire. If you see it wearing on the outside but you have pickup in the center, this doesn't necessarily mean you need more camber, it may mean you need to stop the axle flex, because what is happening is that the rear axles are also bending inward under cornering side loads. They will bend so much that even 1/2" of static toe in sometimes is not enough to compensate. Also the axle's trailing arm can twist allowing the tire to "fold under".
To visualize, imagine the car in a high grip corner, rolling over and generating maximum side load with a rear axle made from 1/2" thin walled tubing...what happens? It will fold all the way under the car, binding the shock/spring against the inner fender and creating a massive degree of toe out.

Thankfully, the installation of a rear axle locating device is spelled out in the rules. Also your rear swaybar design is free. A BIG BIG bar that resists bending under side loads will help immensely. Especially the rear mounted types that use the big splined Sprint Car type sway bar arms. (rear weight is an added bonus)

After you get the rear axles stiffened up you'll have MUCH better control over the rear toe, and will be able to run much less static toe. This will reduce the scrub in a straight line and allow you to motor by your opposition who will then start complaining that you have an illegal motor

Another edit note: Depending on your inital camber and toe settings you may see different patterns of wear that what is described above ... the point of this post is to be aware of the dynamic toe out change that is usually not taken into consideration by people not familiar with the VW axle beam suspension.

Happy Motoring

[lateapex911]

the 8 mounting points should be:

Rear shock area braces, roll bar feet, front hoop feet, and two stiffeners to the front floor/firewall, intended to provide front end crush resistance.