Help w/ a Spooky Handling 56 Oval

[saggs]

Beetle alignment3072015.jpg

I got my 8 yr resto done finally on my oval, I pretty much replaced everything back to stock condition w/ the addition of a T4 motor, front disc brakes, adj beam (set at stock height) stock width. Rear suspension is one outer spline raised from stock height. I have BRM wheels w/ 175-70's up front and 205=65-15's in the rear. I added one caster shim under the front beam to try and help. I drove it daily last summer but the thing has pretty bad bump steer, like to follow troughs in the pavement, and gets kinda hairy over 60 mph. I brought it to a tire shop and had it aligned after I tried multi times. It's a little better but not much. I attached a copy of their printout showing before and after measurements. Can anyone see any glaring problems with this? The motor wants to GO but the car is spooky. If you click on the "alignment" link above you can see the measurements.
Thanks guys.

[Steve Arndt]

Make sure the rear end is not toed out at all at ride height. That will make it want to steer itself.

Caster shims go under the front beam to help stability. Camber compensator is a rear leaf spring to help prevent wheel tuck.

[saggs]

Youre right. Its the caster shims I have under the front beam. If you click on the other link you can see that I have about .12" of toe out on the rear. Not sure why that download didn't open on its own?
Thanks Steve

[aircooledtechguy]

I would begin by removing the caster shims. If you have everything at stock height, why add the shims?? Those shims are needed to restore caster angle on a front-end which has been lowered via an adjustable beam. Yours is stock height. . . By adding the shims, you've increased caster significantly which significantly effects the handling of a front-end.

As you lower the front-end via an adjustable front-end, you loose caster angle. This causes the front-end to get real twitchy. Adding those shims corrects that and helps to restore factory steering geometry. With those shims on your car, you have too much caster angle with is equally bad. Pull them out, drive it again and see if it improves.

[Marc]

I would begin by removing the caster shims..those shims are needed to restore caster angle on a front-end which has been lowered via an adjustable beam..

Caster is lost when the front is lowered more than the rear REGARDLESS of how it's accomplished -anything which changes the relationship of the beam to the horizon affects caster.
Even at 100% stock spring settings, just dropping the front tire diameter causes a loss of caster. It was commonplace 40+ years ago for German VW dealers to add caster shims for customers who desired increased autobahn stability...NO WAY would I start by removing them, you may even find that thicker ones are justified. I run 6mm caster shims on my Bug, which sits pretty level, and it tracks "one-finger" true at 90+ MPH. There's a slight penalty in added steering effort when parallel parking, but that's the only downside.
A major cause of "dartiness" is positive scrub radius, where the front tire contact patch is outboard of the kingpin axis. From your pics it doesn't look to me as though this is an issue, your front wheels don't appear to be severely short on backspace.
I cut my teeth driving swingaxles in the late `60s/early`70s but will never go back there - IRS is SO much better. To make a swingaxle handle forgivingly you must limit the wheel travel so that rear camber cannot go positive -that's where the evil behavior begins. Buttoned down to 2"- 2½" rear wheel travel, swingaxles handle nearly as well as IRS...until you exceed 9/10ths, anyway

[Piledriver]

Rear should not be toed out. At all. Ever(unless car is set for AX and you want the rear to come around at will)
0 at worst.

Also, tire pressures are critical, moreso on a SA. Thee factory recommended ~17F/28R is a good starting point.
(varies some, see the sticker inside of your glove box door for more details)

Tire shops will put 32-35 psi in all 4 tires, something ~guaranteed to make a beetle want to continually swap ends on the freeway. Not quite so bad with some stagger or IRS, but SA combined with toe out you are likely to see the fellow behind you a little too well.

This is easy to overlook... until you turn a corner or get on the freeway.

[Steve Arndt]

Agree with the above.

18 front and 28 rear is a pretty good tire pressure setup give or take a couple psi.

Get your rear axle tubes slid forward in the spring plates. That should make it zero or slightly toe in at the back.

[Marc]

Stock rear toe spec is pretty-much neutral (5' in plus or minus 10' for swingaxle IIRC) but the slightly-raised rear ride height has put you closer to positive camber (never a good thing on SA) so I'm with Steve here, slip those axles up a little in the springplates. Make little witness marks beforehand with a chisel so you can put them back to where you paid the alignment shop to put them. A simple tape-measure "driveway" alignment should suffice to see if more toe helps (odds are it will). Shoot for ~⅛" in.
Straight-line stability at speed is the issue at hand right now, but you may also want to consider adding some limiting straps in parallel with the rear shocks if you're experiencing "jacking" in hard corners.

[saggs]

Thats good advice. I added the caster shims early on and it did seem to help. Do you think the offset on the BRM's will adversly affect handling? I'll get the rear end squatting a bit and get the toe out changed to zero or toe in on the rear axle. I've noticed that the front end doesnt seem to rebound back up very well after you push down on the bumper. Would a stiff front suspension, stiff xle tube bushings, or a bent torsion arm adversly affect handling? I do have OEM style shocks , no gas or anything special??

[buildabiggerboxer]

Hmm, sound to me like it has bump steer, its likely the steering box has been removed more than a few times just due to the age process, there is an installed angle for the pitman arm that we used on our r.h drive ovals, there was no locators on the axle tube as on the b/j cars, for correct register, I can neither remember or find it in my old notes, so old Skool eyeball checks will have to be done, start by just jacking the front and eyeball for toe change, then if you can't see too much change, you will need to carry out more detailed checks, measure off a standard Dunlop toe gauge set too wide will give you a starting point, if it toe changes, try differing angular adjustments by rotating the 'box on the axle, then you will see how tetchy the pitman angle is, it's time consuming to get bang on, once it's come good, weld a locator lug onto the axle so that the 'box goes back at exactly the right angle and centred dead ahead so the steering angle is not off set.

[Marc]

Between the disc brakes and the BRMs you've got a greater scrub radius than stock, but it doesn't look obscene. That makes steering at low speeds easier since the contact patch rolls about the kingpin axis, but does make the steering react more to pavement irregularities. If the suspension/steering's binding, the increased scrub radius could also aggravate the effect when it "unsticks".
At stock ride height you shouldn't need to rotate the steering box away from its normal location by much - but when the beam is tilted out by the caster shims it does cause misalignment between the box and the steering column. That puts excess strain on the "rag joint" which will shorten its life...you may also feel a slight binding every ¼ turn of the wheel - if the coupler happens to be close to one of those "flexed" locations when you're driving straight, it'll want to twist away from that spot. You may need to actually file out the notch in the clamp a bit (and/or trim the nub on the beam - Brazilian beams are notorious for those being misplaced). Note that there are two notches on the clamp half, the "14" notch rotates the box down slightly because 'Ghias' columns are more horizontal - so sometimes all you need to do is flip the clamp around. Have an assistant crank the steering hard in both directions while you observe the coupler where it clamps around the shafts of the column and box. There are fine splines on the shafts which are supposed to resist any slippage, but if the parts are worn, relative motion can develop that'll have you chasing your tail on alignment for a good while
While you're checking for suspension bind (I'd disconnect the shocks temporarily to see if there's any problem there; it's rare but possible) take a good look at the "phasing" of the tierod ends. One would hope that the alignment shop paid attention to this, but if it was overlooked it'll need to be corrected.
Both ends on each tierod should be parallel so that it can "roll" through full travel - if they aren't the steering can bind (hard on the ends, too).
The driver's side inner tierod end has a slight downward angle built into it since at stock ride height the tierod points downward from the Pitman arm to the spindle. It's not a lot, but if the tierod gets installed backwards, so that end is outboard, you can experience travel limitations.

[Steve Arndt]

Do you have urethane bushings in the front beam, and what shocks are you running? Tight fitting bushings and gas shocks will make it stiff.

[Bruce.m]

Some photos with the tank out might help. For example, the steering box itself should be mid travel at exactly straight ahead to minimise play in the box when driving straight.

[Marc]

There're two centering procedures depending upon whether the box is the original Porsche design or the c1961-up type - I have a vintage manual back home that goes into detail but simply splitting the difference usually gets you very close. If it's off by very much you'll need to start by disconnecting the tierods (or drop the Pitman arm) in order to get to full lock on one side.
Also check that the cover bolts are snug, the late boxes in particular can have a problem with them working loose. I didn't see any mention of a steering damper (those weren't stock until c1959, and aren't desperately needed, but they can improve the highway-driving experience) - does this beam have a perch to attach one?

Bob Hoover wrote up this nice article on front end/steering; be sure to read the part about how to properly adjust the steering box. http://bobhooversblog.blogspot.com/2006 ... t-ten.html

[saggs]

Ok, so that's a lot of info and much appreciated. I put a new beam in it w/ the oem style bushings for the torsion arms. It was a very tight fit and I've had to ream them a few times to loosen them up. They may still be too tight? I have standard oem type shocks, I put a new later model steering box on it, added a steering damper, and a new rag joint on the steering box. I will remove the tank to look at the alignment of everything and check the tie rod angle at resting height. If I remove the shocks the car should spring right back up after hard downward force correct? Is there anyway to tell if a torsion arm is slightly bent other than comparing it to another one?