Street suspension.(Swing axle)

[Garrick Clark]

Hi Guys.
I have a 67 swing axle chassiis bug with a turbo type 4 motor.
Now the motor is running good its making the driving experience a bit scary.
I feel my suspension is set up wrong for fast street driving.
I'm looking for some advice on how to make this bug a better/safer drive on the street.
My suspension is like this.
2" narrowed beam
drop spindles.
the front wheels are set zero camber.
1 pair of caster shims
No front sway bar
standard shocks.
front is lower than rear.

Rear set up is
28 torsion bars.
Short rear axles
heavy duty spring plates.
rear wheels zero camber.
Standard shocks
145 front tyres
205-70 rear tyres.

[modnrod]

185/65r15 front, 205/65r15 rear, something decent. Wheels can be stock front if you want or 5.5s, 5.5s work on the rear or 6s.
Front sway bar, a little one. The clamp-on ones are better than nothing, but proper links work better.
Rear camber bar, just barely preloaded on the rubbers at rest. If your torsion bars are bigger than 28mm it will skip and bounce on the rear and not follow the road properly.
1mm-2mm front toe-in (what gives you the best confidence), with 1/2deg positive camber (bend stuff if needed), and only just enough castor to make it straight at 100mph.
No rear toe at all up to 1mm max (it'll be a bit twitchy, but progressive, set to your confidence), 1deg positive camber at rest (3/4deg on the road centre wheel if the road is heavily crowned).
Get the front down to match the rear height with 1/2 tank of fuel, preferably without reducing suspension tension or adding unsprung weight. The ride height is set by the rear suspension settings and your tyre height, if you want it lower then you need to find lightweight 14s and 205/55 Advans to start getting serious. 
Don't reduce track width. Stick the rubber right out on the guard edges.
The best shocks you can afford. Double-acting gas are too stiff and will make the car bounce and skip, hydraulic are better for this.

Others will have their preference settings no doubt, but these settings are the ones I like to "potter about" in (with maybe a bit less toe-in).

Try it out, it might work for you too maybe.
Go beat up some Porsches......   

[Garrick Clark]

Hey thanks modnrod, some good info there. looks like I've got a fair few adjustments to make. along with new tyres etc. Its looking like my 28 bars are causing a lot of the no confidence  feeling I'm having. Its does feel like its  bouncing on the tyres at the back. Its hard to tell what's going on while all my concentration is on the road.   

[baz]

Stock shocks are probably struggling to control the 28mm bars

[Garrick Clark]

I've got some KYB gas adjust shocks. Would putting them on help. There a lot stiffer than standard.
I adjusted the rear torsion bars today.Outer splines adjusted only.  Got rid of the rake. The bug is now sitting level. The exhaust is now a bit too close to the road.
. 3 inch clearance. Can't win can ya. I'll test drive it see if it improves stability. I think it probably will. If it does I'll have to re do the header.

[baz]

I know when I bought my 28mm bars I was concerned about the ride skipping about at the back, I asked when I bought them and was reassured the konis I have would control the stiff bars.
Can't say if it works as I've yet to drive it   

[Garrick Clark]

I adjusted the rear torsion bars today. Just the outer splines.
1 outer spline adjusted the height 2 inches, which is strange. As standard bars/plates adjust 1 inch up or down. I'm hoping to adjust the inners to lift the rear 1 inch. The bug does now sit level though. I put a spirit level on the sill to check it.

[Richierich56]

Hey Garrick, check you've not got some toe-out at the rear. I've just adjusted mine up as the car felt pretty dangerous when you really got on it. The difference now is night and day

[Garrick Clark]

Richie. Can the toe out be checked at home. DIY style.

[Garrick Clark]

I also noticed but gave no thought to it till now, the 3 bolt holes in the spring plate on one of the plates might possibly be in a different place to other one. It looks like the passenger axle fits further into the spring plate Cup.
Think I'll take off both plates, put them side by side and see if the bolt holes are a match.

[Richierich56]

Richie. Can the toe out be checked at home. DIY style.

Yes - it can, i just use some string and straight edges though its probably not the most accurate method. Does it feel like the rear end of the car is trying to overtake the front end?

[Garrick Clark]

Yeah. Like it's trying to over take me.

[Richierich56]

Yeah. Like it's trying to over take me.

Yep - that's exactly what mine was doing - damn scary. I reckon you've got a good amount of toe-out at the rear for sure. Can you post a photo of how the rear wheel sits in the arch - taken from the side?

[Garrick Clark]

Well I'm hoping that the axle holes are drilled wrong in the plates.
The very end of the spring plate on the Nearside is flush with the axle flange . The off side spring plate is an 1/4" past the edge of the axle flange .
 When I lowered it yesterday the adjustment slots aren't that big really.
Once the bolts are in place there isn't much forward/backward  adjustment. After lowering it I just positioned the axles in the same place it was prior to lowering. Its probably been wrong since I bought it.

[Garrick Clark]

double post

[Garrick Clark]

.

[baz]

You should be able to measure wheelbase each side, if it's a quarter inch out it will show up easily.

Going back to the torsion bars, there's a chart somewhere that shows the spring rate increases with each step up in diameter. 28mm bars have something like 3 times the rate of 22mm bars. You couldn't expect a stock shock to keep that under control.

[Martin S.]

Lanner told me to set the axles all the way back for a regular set up and to grind even more for a lowered car to get some toe-out at the rear.
Then I went to an alignment shop and had the front toe in adjusted. They will give you a measurement of the rear toe so you can check if it is even with that.
I did those changes, and as well added Koni's all the way around, plus a Koni steering damper and it made the car much more stable at speed.
I still don't like the slight bouncing feeling in the rear end that comes with big heavy tires, in combination of the insanely heavy cheap disk brake kit I put on.

[Garrick Clark]

Just taken the spring plates off,I have them side by side and the bolt holes are nowhere near square.

[Richierich56]

Just taken the spring plates off,I have them side by side and the bolt holes are nowhere near square.

As in the plates are different lengths? Pics?

[Martin S.]

How are you guys checking the rear toe? String method? 

[Martin S.]

After messing around with the string the ONLY method I trust now is the alignment shop.
Here is my report after pushing the axles all the way back on my 68 long axle bug.
Note that the right is 1/16" and the left is 1/32" (close to zero) toe out.
Ideally I should grind some on the left and get the 1/16" toe out to match the right.

The operator adjusted my front end perfectly!

[Garrick Clark]

Sorry Guys.
I'M  not good at putting pics up on web sites.
What i have done today is grind out the bolt slots in the plates so both plates match. (They didn't before).Passenger plate was WAY OUT/ must of been toeing in on passenger wheel making it feel unstable at speed.
Refitted them and pulled them right back .Now the wheels should be in  the SAME position, maybe not to what the book says  but i now at least have enough adjustment to play with.
I set the rear wheels with a bit of neg camber.
32 psi on the rear tires
Fitted the white gas adjust rear shocks
hopefully i should now have rear end running in a straight line.
Thanks for the input guys.

Front end next.
Double caster shims.
And  add  some camber.
Currently there isn't any camber at all.
 I do have the extra adjustment eccentric nuts fitted allready.
I'll try 3 degees camber  and an 1/8" toe in and see how it goes.

[Martin S.]

If you're a risk taker, try the string method. Basically run the string from front to back and pull it tight and see how the front and rear of the wheel compare to each other.
This is shade tree and I would NOT trust it unless you don't value your life much (YOLO).
3 degrees camber at the front eh? That sounds like what autocrossers would like. If you look at mine it is very near zero which is factory spec.
The rear on a SA car is the most important to get right. Gene Berg has a good blue book article on it. When he got the rear toe where he liked it, he made a piece of metal that went from the rear of the door frame to the axle tip so it could be re-set easily anytime. Cool idea.

[leec]

I have my oval professionally aligned. For sake of £50 I wouldn't bother trying to do it with string etc.

[Martin S.]

Cool. Can you share your car's alignment spec sheet?

[Neil Davies]

I have my oval professionally aligned. For sake of £50 I wouldn't bother trying to do it with string etc.

I had my car aligned when it was first restored in 1999, but it's not been done since. I do have my own alignment gauge tho, so I could (and probably should) do it myself.

Garrick, I'd leave the front (other than alignment) until the back is right. You don't want to change too much at once.

[Garrick Clark]

I'll leave the front alone for now.
I will try the string way tomorrow just to see if I DO have the rears at least as straight and equal as possible . then pay some cash to get some suspension geometry numbers.
 

[leec]

Cool. Can you share your car's alignment spec sheet?

Will do, if I can find it. House moves are always good for hiding paperwork.
Lee

[Martin S.]

That's why I take a pic as soon as I can. I use Apple Photos app and set up the tags so each pic relating to my car hobby has a tag of which car it pertains to. Then, when I hit search for 'white 68', I see only the pics of that car. Makes it easy to find the pic I want.
This is what we have plenty of time to do in Canada when it is 30 below outside