Weight Distribution and Handling

[FJCamper]

ABOVE: Karmann Ghia chassis

Way back when, all the front engine car guys were certain the Porsche would come to no good as a sports car because the engine was in the wrong place ... hung out behind the rear axle.

This put 60% of the weight on the rear end, when other cars had much more even weight distribution, especially the front "mid engine" types that placed the engine even farther back in the chassis.

Yet, even with the wrong weight distribution, Porsche won races. So it really wasn't all that bad.

Of course, Porsche people worked as hard as they could to even up weight distribution. The spare tire, fuel tank, and battery were up front, and of course the driver and passenger were ahead of the engine, which gave about a 47%-53% weight split.

The theoretically perfect road racing weight situation is to have the same weight on all four tires, and with a Formula-type car with the driver in the center and the engine inside the wheel base (rear mid engine), you can actually accomplish this.

A street car can't quite do the same thing because the driver has to sit on one side of the chassis or the other. And that makes a difference. On a right-hand drive car, you can turn left faster than turn right, meaning with less suspension loading. Ask autocrossers.

In fact, even with the added weight of a passenger, autocrossers usually report that the car handles better overall.

What can you do for your street car to help the weight distribution? Well, battery relocation is the place to start. The Ghia came with its battery back in the engine compartment. At least move it within the wheel base by locating it behind the passenger seat, a la VW sedan style. Better yet, if you're hard core, move your battery to the bottom of the spare tire well and carry your spare laid flat on top of the gas tank.

If you're really hard core, you'll strip out everything you can from the rear end of the car, and replace that heavy glass rear window with a nice Lexan one.

If you're road racing, you can take a cue from the NASCAR boys and jack a little weight around. A one-inch forward rake (don't do more than this or strange suspension responses will emerge) will shift even more weight forward.

The general rule is always lighten up, but lighten up in the rear first.

Our 1970 Ghia 53 road racer (fuel and driver) tips the scales at 2000lbs, 1200 of which ride on the rear tires, although not exactly 600lbs per tire.

FJC

[raygreenwood]

Or...you can do it like my 412 and have the battery under the drivers seat where the factory put it. I have a battery under both driver and passengers seat.

A long time ago I read some information ...no recollection where....that the center of gravity (static) of the average beetle is right about at the middle to back 1/3 of the seat rails if you draw an imaginary line across the car.

Of course in theory....having perfect 50/50 weight distribution is desirable. In reality that would depend on what kind driving you plan to do.
Problem is that if you have a lot of quick braking you get lots of enertial shifts. The beetle was actually about 65/35 rear to front...with no load. That can change to 50/50 and even 40/60 rear front in hard braking.
Its in braking through a turn that the movement gets questionable. Ray

[sideshow]

Wow, never seen anyone mistake a ghia for a 412/wedge bus before? Good luck fitting a battery under the seat unless you are thinking a 6 volt spiral/sealed laid on the side. Of course you would need one on each side ala real old school 12 volt conversion.

Now I don't how this would go with tech inspection, but how about replacing the passenger footkick plate with a battery?

[FJCamper]

Hi Sideshow,

The Porsche 904's had the battery in the passenger footwell. Great place, actually.

Today, SCCA wants a enclosed battery box at minimum, and the battery well secured to the floor, if it is within the passenger compartment. On those classes where battery relocation is permitted, of course.

We put our battery in the Beetle position (behind the passenger seat) in our Pan-Am car, in a battery box, rigidly mounted to the floor. Our road-course NASA Ghia has the battery in the nose, on a specially constructed and strong-looking mount. Eye candy never hurts when it comes to tech.

FJC

[raygreenwood]

There is really not much less room under a ghia's front seats than a 412. The difference is a change to the height of the seat mounts. It also had a semi-nifty plastic cover to keep you from arcing against the seat bottom springs. A couple of times I neglected to put that cover back on...and about lit my backside on fire.
A spiral cell battery on its side...12 volt should fit as well.

So...are you insinuating that my 412 is in any way similar to a bus
Funny thing is...that there were NO stock ghias that beat the 411 or 412 in acceleration, top end, skid pad, braking or general handling....though they look sweet. Ray

[FJCamper]

Hi Ray,

I have no complaints with Type 4's.

The trouble with a battery below a Ghia seat is that there is little headroom wearing a racing helmet.

You want your driver sitting as high as possible to see, but not so much that dips or bumps will crash his helmet into the roof.

We use one of those tube steel generic slide-adjustable seat mounts sold by many of the VW parts vendors, but with the slide mechanism removed and almost two inches cut off the mount feet and the flat bolt plate welded back on.

We barely have room to roll a soda pop can under the front of our seats.

Forward vision is one thing. Rearward is another! We had to be careful how high our ducktail stood.

FJC

[petew]

I've moved my battery as far forward as possible for exactly these sorts of reasons. It's now hard up against the front wall of the passenger footwell. The other thing I'd tried to do is remove as much weight from the rear of the car as possible. The rear cage has been trimmed as much as possible...and will get further trimming. Between that and a new subframe and engine mounts, I'd guess the rear of the car weighs about 20kg lighter. Doesn't sound like much, but the difference is palpable. The front of the car is a different story, while the back is full of racing holes, I don't hold back on the metal if I need to make something for the front of the car. I don't know exactly what the weight distribution is now, but it used to be about 30/70 front to rear. I guess it would be more like 35/65 now. I still want it to be better, but what's been done so far has made a huge difference. The car is now predictable and almost neutral to drive on dirt.

[Wally]

Great post FJC!

I'am with Ray on the 412 though
What many don't realize is that in the 412, the entire engine/tranny is relocated forward so much that the driveshafts are angled forward to a considerable degree (at least the manual cars are).
I can only imagine this was done for better weight distribution. Or the factory wanted extra room for an anticipated 6-cylinder...

In my race bug I have the battery and the dry-sump tank and oil cooler relocated up front, exactly for the same reasons FJC mentions. Still will do the rear windows in lexan probably

[FJCamper]

Weight distribution is not just front to rear, but low to high.

The VW-Porsche design has the advantage of a low placement of mass, meaning the heavy stuff is mostly right down there at the axle level. Today, Formula cars are designed like this. We get it gratis from Dr. Porsche's 1930's P-Wagen Auto Union formula car.

In this drawing, you see our fuel tank is still high. It could be moved into the passenger compartment, on the floor where the passenger seat used to be, and inside a firewall box for safety.

FJC

[raygreenwood]

Yes....thats very true. Heavy weights placed up high tend to generate body roll through enertial changes. Braking through a curve generates forces in more than one axis. This roll behavior will also tend to twist the body magnifying the problem.
Forhot about racing seat and brain bucket. Not much room there.

You know...it would be a great product for someone like Optima is to make 12 volt spiral cell batteris that are not grouped in pairs like a six pack....but spread out flat in one cell layer. In this way it could simply be the 3.5 inch thick trunk mat up front.
That helps too. If you can take something that is a large dead weight like the fuel tank,....even if it has to remain up high for some reason.....if you can spread its weight out across and on both sides of the centerline axis you get less of the pendulum effect. Ray

[helowrench]

That helps too. If you can take something that is a large dead weight like the fuel tank,....even if it has to remain up high for some reason.....if you can spread its weight out across and on both sides of the centerline axis you get less of the pendulum effect. Ray

Only if the fuel tank is baffled.......

[raygreenwood]

Yep...or else you are just "slinging" weight from side to side.....or front to back. Ray

[FJCamper]

Gentlemen,

We do use fuel cell foam blocks squeezed into our custom-made tank. It sops up the gas and stops slosh.

These foam blocks work, but when aging over several years, sometimes break up a little and clog fuel filters. They are not for street use.

Fuel is heavy. 10 gallons weighs over 60lbs.

FJC

[sideshow]

I don't mind that just about every car made from say late 1960 can handle and accelerate better than a stock ghia, big deal. The list of better looking ones is rather curt. I never knew a 41x had a battery under the seat, figured that was a wedge bus thing.

Also never fond of the beetle rear seat hole or for that matter the ghia in the engine compartment.

My solution is an optima under the back window above the starter, run a bulkhead fitting in the firewall. Through bolt the battery tray to the floor and then the front tranny mount. Sure it kills some storage but to me seems like the least of three evils

[raygreenwood]

The battery under the front seat of at least somewhere in the cab had a distinct advantage. It warmed up faster and stayed warmer.

The bus battery was actually more of a pain to reach when necessary to work on it. The location in the 411/412 has never been a problem for me.
Yes...most of the cars after the late 60's and early 70's did not look as good.

the 411 and 412 were actually decent looking cars. Really much more volks-wagonesque than they appear from a distance...espcially when you starting driving one. Definately in the same family as the bug, type 2 and type 3. The one main killer that actually tips the 411/412 into the ugly category....is the stance as delivered from the factory...nose high, gappy wheel wells and skinny tires.
Judicious and careful lowering not only really improved teh looks...it greatly improves handling. Ray