Koni front ??

[slayer61]

So as I mentioned in my build topic... viewtopic.php?t=152439 ... the buggy is tagged, titled and insured and on the road, for now and I'm pretty happy with it over all... but.


I'm just not really happy nor satisfied with the way it handles. It's "OK", but it's just not great, know what I mean? For the record, it has new ball joints, new tie rods and tie rod ends, new Koni shocks front and rear, new pitman arm, new (German) rag joint, VW steering box reconditioned by one of the leading suppliers of air cooled parts & services, new sway bar and bushings in the front and a camber compensator in the rear. I suppose I still have rear torsion grommets to put in, but when I was re-indexing the torsion bars, the donuts were in excellent shape with no deterioration at all.

Back in the day, as they say, I used to have a Datsun 510 with just lowering springs on it that handled like a go-cart. I was expecting AT LEAST that kind of response.

What am I missing? Why doesn't my short wheel based, freshly built buggy feel "sharp" or responsive? Any ideas?

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[Ol'fogasaurus]

What did you re-set the torsion bars at? Stock is in the 19 degree set but you can reset it a bit higher.

For off-road my opinion (I run in the dunes) is about 26 degrees max and that would be if you are playing hard with it. I'm not running blade type of paddles anymore so the short run-on asphalt isn't that bad and it works good on the dunes.

To get it above the rear tires and running on the street or light duty off-road, maybe try 22 or 23 degrees and I would think that might be max but you have to test drive it before you go higher or lower. I did have mine set very high once (30 degrees on bad advice) and holy cow, was that not a good idea. An opinion.

Lee

[slayer61]

As always,
Thanks for the reply Lee.
Based on some info I gleaned off the interwebs about Manx FG buggies on the street, my rear torsion, or spring plates were set at 15 degrees. The rear wheels show only slight negative camber as it sits right now. IF I was to change it, it would only be a couple of degrees, 17 MAX. to straighten up the rear end.

Before: (even without the motor)




After:

[Ol'fogasaurus]

If I remember correctly a stock VW bug's rear torsion setting is something like 19 - 20 degrees as I already have said.

17 degrees allows the pan to sit lower giving the change in angle. The body and interior goodies weigh a lot hence the change. Before you get too busy with changing the torsion bar settings wait (no pun intended) until your body, interior and other stuff is installed before you reset the torsion bar. The change in weight and use may change things they may need to be changed (liked dropped trailing arms... if they are still available anyway.

Remember, a FG glass buggy body is much lighter than a stock VW and and because so, not necessarily as strong. Also, it the pan is shortened to match the body there is more of a weight change. Don't use a single hoop as they are laid back and can be bent so structurally not doing much work. A cage done properly will protect you front and rear and additional things can be added to it to make it stronger and help pass loading around.

I also would make a body lift similar to mine and that, again, is for more pan strength.

There are things you can do to the front suspension also to give a better and smoother ride. You have a BJ front beam so I would also do some mods that way. When it is time, we can show stuff but my new computer (where most of my pix on this stuff is or look at my black buggy string as my new computer is not readily accessible to me right now).

Lee

[Ian Godfrey]

A few thoughts. Broadly it might be too stiff. What size rear torsions are you running? and what size is front sway bar? The Koni's might be a bit stiff even on full soft. My road race Ghia with Koni's ran well just a few clicks of full soft.
Next, what tyre pressures are you running front and rear, and what size are the front tyres?
Then I'd be thinking what are your castor/camber/toe setting at the front? and toe/camber at the rear.
My feeling is the front might be plowing (understeer), so at the front a bit more neg camber (-1 to -2) and a bit more caster (5 - 6 deg) and less sway bar, or no sway bar? and less tyre pressure... even as low as 16lb? 14lb? 12lb?, you need to experiment, just go lower and see if it gets better. Factory beetle is roughly 18 front 26 rear and you are a lot lighter in the front. A REALLY soft front tyre would help too.
One of the great feelings is a car is responsive turn in, when it just goes where you point it.
I only have Ghia experience but I'm sure you car can be 'smartened up'

[Ol'fogasaurus]

A few thoughts. Broadly it might be too stiff. What size rear torsions are you running? and what size is front sway bar? The Koni's might be a bit stiff even on full soft. My road race Ghia with Koni's ran well just a few clicks of full soft.
Next, what tyre pressures are you running front and rear, and what size are the front tyres?
Then I'd be thinking what are your castor/camber/toe setting at the front? and toe/camber at the rear.
My feeling is the front might be plowing (understeer), so at the front a bit more neg camber (-1 to -2) and a bit more caster (5 - 6 deg) and less sway bar, or no sway bar? and less tyre pressure... even as low as 16lb? 14lb? 12lb?, you need to experiment, just go lower and see if it gets better. Factory beetle is roughly 18 front 26 rear and you are a lot lighter in the front. A REALLY soft front tyre would help too.
One of the great feelings is a car is responsive turn in, when it just goes where you point it.
I only have Ghia experience but I'm sure you car can be 'smartened up'

Some good points.

You can over shock a vehicle very un-intendedly. While I don't think you have done it, I also recommend not using the type of "air-shock" you can change the settings on it by adding or removing air to them by an air fitting. Several safety reasons for that.

Resetting the rear torsion bar for more rear tire clearance does/can make the ride stiffer and also changes the camber angle at the front end (6-degrees or something like that is stock. Adding a "rake" to your toy does change that.

I am not sure that the 26-degree rear torsion setting is correct, as I remember it is more in the 19-degree setting but check it before you change it. Swing axle settings might be different, I haven't played with them so this is a guess. I run 26-degree setting in the rear but then my tire pressure is something like 9-pounds too (paddle tires on the sand) while my front "steering tires" pressures are at 26-degrees (I ride in the buggy on the sand only now).

Tires also can be too large or too stiff for a lightweight dune buggy vehicle.

Also, there are ways to soften the ride in the front which takes some work on the front beam by adding adjusters (I recommend doing the top one first then trying it out before doing the bottom one also. Also, since you have a BJ beam there are a couple of other tricks out there, but I think using "adjusters" are a better and safer way to go.

Remember the weight of a full fuel tank is involved in this also especially if it is still in the front of the car so the front beam must be balanced for that too.

Your cage design looks like it could/can add some stiffness and load transfer to the pan now that the Bug body, and its duties, is gone.

If you haven't already done it have the front end formally checked. It could be a distance thing in the photo, but the driver's side front tire looks a bit off.

Lee

[slayer61]

Thanks Ian. I always appreciate your input.
right now the front suspension is "tape measured" to about 1 degree of negative camber & I'm not sure about castor, but I have 2 sets of shims installed right now. It also has a 3/4" (19mm?) sway bar on the front & camber comp in the rear. My notes say I had 14 psig in the fronts on the last outing.

My training has taught me to change no more than 1 thing at a time... so next outing will be with lower tire pressure & maybe after without the sway bar.

I'll let you know.

[Ol'fogasaurus]

Thanks Ian. I always appreciate your input.
right now the front suspension is "tape measured" to about 1 degree of negative camber & I'm not sure about castor, but I have 2 sets of shims installed right now. It also has a 3/4" (19mm?) sway bar on the front & camber comp in the rear. My notes say I had 14 psig in the fronts on the last outing.

My training has taught me to change no more than 1 thing at a time... so next outing will be with lower tire pressure & maybe after without the sway bar.

I'll let you know.

That is a good idea but can move the finishing of your buggy out a way's further. Better to be safe than sorry though.

Not sure just how many shims can be added to the beam and still be safe. The shimming will be at the bottom of the beam mounts to tilt the beam to the rear. As I remember my blue buggy's beam is shimmed out too, but it was so long ago I don't remember just how much shimming I had to do.

Assuming that your pan is straight try this: measure your body tilt using the pan as an angle check. For a stock vehicle use, mount he required angle for the beam is already built into the beams mount so if the angle is a negative measurement from flat then one would think that that is going to take away from the beams needed angle. As I remember the less positive angle the beam has the "twitchier" the steering can be.

Lee

[Ian Godfrey]

2 castor shims should be plenty, it looks like there is not a lot of downward rake. 1 deg neg sounds good too.
so I think less air and / or less sway bar (a stock bar or nothing) will be good to try. A 3/4 bar is pretty stiff.

[Ol'fogasaurus]

It is often hard to tell from pix what there is rake wise which is why I mentioned the checking things out. Big and littles also make things look different than they really are.

Lee

[Piledriver]

Probably has been covered but a light buggy is almost always oversprung...
...and what works in the dirt is almost never what is needed if you want it to handle on pavement, exception being a nice stiff tube frame.

..from memory, the front upper torsion leaves should be gone at least... it's quite easy & cheap to grab some small circle track Bilsteins and convert them to take-aparts, and then convert them to coil overs.
I even repurposed the old KYBs to be remote reservoirs, as that allowed the exact length and stroke I needed for my squareback.
(I still have the torsion bars F&R but they are set at rest, so act similar to the old "4 way shocks" resisting any motion away from neutral)

There are plenty of circle-track race (not necessarily "speed") shops that can help you out with valving/springs etc.
I got my new Bilstein pistons and valving parts from Day Motorsports in Tyler, Texas, YMMV.
My local race shop (Smileys) has a roving "shock guy" and dyno with very reasonable rates, although you will likely have to leave them and wait, run in batches.
(I got my initial shock/spring curves using the excellent online calculator at http://farnorthracing.com/autocross_secrets16.html )

After taking the KYBs apart and seeing how they are built there's absolutely no way I will ever use them for shocks again.
(they are also not rebuildable/repairable/revalveable like most bilsteins I have seen so far. Tweaking actual take apart shocks is really pretty simple)

[Ol'fogasaurus]

Pile, even with the light style of driving I do on the sand I, more than once, have hit a shallow "no-see-m" aka" WTFs" before. Once hard enough for the shocks (especially the driver's side shock) to jam/lock in a fully collapsed state. It too 3 of us with longer than normal tools quite a while to break the shock piston loose from its jammed/collapsed locked-in-place situation and this was before the body lift and cage were added to a stock, shortened, otherwise F-Glass VW bug pan.

Mine is a BJ front beam so the top torsion stack, if removed would still have to have a locking pole of some kind to connect the upper arms or a locking device in the middle of the beam to lock each arm to (I don't recommend this but others have gotten away with it. Beam adjusters can work allowing some of the spring rate to be lessened ir added, but... again, there is the "no-see-ums" one can occasionally run into.

K&L beams I have also seen badly damaged but they do have some advantages over BJ but the mounting of them is different so there is work there.

Good shocks can slow down the collapse rate but still give a good ride in rough situations.

Also, one type of shock is not necessarily good for several types of use; they can be and they can't be and that is definately for sure. After watching the guys I know go through the "shock thing" on their old and new rails plus also spend a lot of money changing things (and not only the shocks themselves) plus the way of mounting them front and rear.

I have spent a lof of time talking to supposed experts on this and this is more or less what I have come up with.
Lee

[Piledriver]

Discover good bump stops.
Shocks are not bump stops.
His buggy does not appear destined for off road use.
this is not the off-road forum

A jacked up stiffly sprung buggy is not going to handle like a go cart on asphalt as desired.

That requires the correct spring rate and damping, as well as reasonable chassis stiffness.
Spring rate and damping required can be determined from the link I posted and a little effort.
(at least as a very good starting point, , setup like that actually provides a supple but well damped ride that can swallow potholes)

A Manx buggies weight etc is not like any production car, ever.
Setting up some custom shocks with appropriate damping and springs is easily and reasonably doable if you have it done by a race shop or diy with their assistance.

I'd post my setup but my car is a full steel bodied 73 squareback, so it would be wrong for the buggy, or probably somewhat off even for a T1.

[Ol'fogasaurus]

At the time I had the almost "endo problem" (back to front almost rollover) and the shock problem I just talked about my buggy was still fully street legal and in WA that was hard to do then, and it got worse. Not sure what the limitations for them are now but I think I heard that if they didn't have "plates" and title already it had to go through the inspection. The old way of keeping the stock bug title for the buggy (like mine is), I have heard might require an inspection for a different title (not positive on this but a State Patroller made this statement when making a fun look at the buggy on a trailer (it still had WA "plates" on it and noticed the turning brakes and a couple of other things.

The stock rubber front bump stocks did not stop the shock loading it got when I hit the "no-see-um".

I've made a lot of suspension changes to my "blue buggy" since the "no-see-um" thing and the almost endo.

leebuggy-12 copy.jpg

This is pretty much as it is now and there have been a lot of updates even since this was taken.

On the "black buggy" Thing front suspension is going to be added mostly for lower BJ safety.

Lee

[Piledriver]

Sadly the T1 lower balljoint orientation makes a proper bumpstop harder to do, as if it contacts the lower arm, it tries to disassemble the lower ball joint, just as if you use the shock as the bump stop. For serious off road use it's a bad idea. This is not the off road forum

Some sort of limiting strap or other setup on the upper arm is required.

(T3s have the ball joints and bump stops designed properly, sadly not suitable to swap)

Should not be an issue for a 500 kg asphalt only go kart.