Dune buggy all over the road

[oprn]

My Buggy is put away for the winter now and apart from ice racing in February will not see the road again until it warms up in the spring. It's -11 here today with a -24 wind chill.
I definitely have the installation of those shims on my to do list this winter. And I will put a set of stock rims on the front to see what that does.


The rear tires by the way should be toed out not in. Toeing them in will make matters worse not better.

[dustymojave]

Rear toe-out will render the car quick to change direction. Good for autocross and slalom. NOT good for highway, desert offroad or circle track racing. At speed it makes a car sketchy to drive.

Rear toe-in, if moderate, will induce a stable condition. Substantial toe-in will also render the car sketchy to drive.

Spec according to my "Without Guesswork" Factory Service book is -5' +/- 10' for swingaxle. Which is VERY SLIGHTLY toed out to very slightly toed in.

Spec for IRS is 0° +/- 15'.

With 15" wheels, 10' (10 minutes, a minute being 1/60th of a degree) = 1.2mm measured. That's just over 1/16".

Basically stated in layman's terms, that means the factory spec for rear toe is pretty damned close to zero for either swing axle or IRS. Straight ahead for the rear wheels!
_________________
Richard
Offroading VW based cars since 1965
Tech Inspection 1963 - 2012 SCCA/SCORE/HDRA/MORE/MDR +
Retired from building Bajas, Fiberglass Buggies and Rails in the Mojave Desert. Also Sprints & Midgets, Dry Lakes, Road Race cars. All types New and Vintage
SoCalBajas Member
Kicked Cancer's A$$...1st and 2nd round...Fight ain't over yet.

[oprn]

[slalombuggy]

Setting the rear toe should also take into account what bushings you are using.

If you are using factory bushings I would toe it out 1/16" or 10' due to the fact that the softer rubber allows the spring plates to move more and the toe under load is more apt to drive inwards closer to zero. This is more pronounced in IRS rear ends

If you are using urethane, or bronze bushings or rod ends, I would set it at zero as there is little to no movement and the toe does not change under load.

On my street buggy with 6* caster, 1/8" toe, -.5* camber in front and zero toe, -.75* camber in rear the car is very stable at highway speeds and even up to 100+mph with 165/45/15 tires in front at 30psi and 215/65/15 tires in rear at 35psi.

The race car has very similar settings and feels like it's on rails at 130mph

brad

[hillmotorsports]

Brad
Is your street buggy swing axle or IRS?

Paul
_________________
Rosemarie and Paul Hill
Morrisburg, Ontario

(With way more projects than spare time!)

[andk5591]

[slalombuggy]

Paul - My street buggy is IRS.

andk - You have it partially correct, however, you toe them out so that they come closer to zero toe as they are forced inwards under load. If you were to start out toed in they would toe in even more wearing the tires on the outside edge. Toe in is very stable, I have seen guys come in with over a half inch of toe in and say the car drove really well, but the tires take a severe beating.

Drive wheels always want to push the front of the tire inwards towards the center of the car, so you start zero toe or with a very slight toe out to account for this.

Non driven wheels have a tendency to have the fronts of the tires pulled outwards from the center of the car or a toed out alignment, so we set them with toe in so that when they are travelling down the rad they are close to zero toe.

VW suspension is rather loose and floppy so I have always set things on the high side of spec, unless the car has urethane bushings in the back then I set things in the back as close to the preffered spec as possible. But on front ends I still set them to max toe in and camber.

brad

[andk5591]

Duuhhhh - you are right....Slight toe out for swing....been long days LOL
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[PhilKo]

My final fix was;
Four caster shims, two on each side and I installed a steering damper.
Turns out the pan is a 56.

Steers great now!

Thank you all again for your advice!!

[oprn]

Good to hear, I did install 2 castor shims but the Buggy is down right now for some ignition system changes. As soon as it is running again I will try it out and report back.

One thing that has not been mentioned in regard for the need to start with toe out on the rear is tire tread deflection/distortion. As the power comes on not only does it push the axle ahead, the tread on the tire takes on a slight "S" shape in the same direction the amount depending on tire construction and compound. This increases the need for a bit of toe out. There is a similar phenomena that occurs to on the front tires in a hard turn. A distortion of the tread that actually causes the car to turn in a larger radius that the wheel angle would dictate. A slight understeer effect.

[modok]

Seems like for me, every time I tried front wheels with less backspace, or a wider beam, it was worse.
Wants to be wide track in the back and skinny in the front, I guess it wants to be a trike

[oprn]

I just got the Buggy running again and had it out on the highway at 70 mph for a few miles. Feeling pretty solid on the steering now. I would say the camber shims did the trick big time!

I like it!