Short wheel Base/ Long wheel base 2.244 inches

[flycut]

My Local Porsche Guru Guy told me that my 1969 Long Wheel base Porsche Handles Better Than Short wheel Base Models.
My Question is Why? Is it based on 2.244 Inches? Or just His personal Opinion??

[Chris Pomares]

I own a SWB 1967 912. The 1969 and later cars as you point out have a wheel base about 2 1/4 inches longer toward the rear. This gives the LWB cars a slightly more favorable, ( more even ) front to rear weight balance as in not too over weighted to the rear. That being said it is less of a issue in the 912's. They have a engine that is over 100 pounds lighter than the 6 cylinder 911. I've had 356's, a 914, and a 914-6. I've driven many but never owned a 911. So I don't have enough road time in a LWB car to be a good judge of the difference. All I can say is I love the way my car handles and prefer it to the other Porsches I've owned. Your fellow 911 owners on this site can probably give you their personal experiences.

[edmayo]

I have both, LWB and SWB, for higher speed track events I prefer the LWB, but for autocross I much prefer the SWB car. The SWB car handles more like a 914, that is the turn -in is much quicker, the ability to change direction quickly is better, which is to say it is more "twitchy" which can be an advantage in certain situations, but twitchy isn't necessarily what you want in faster corners, so in that regard the LWB car is easier to drive. I instructed someone in a PanAmera at the last autocross. Now there is a car that likes to maintain whatever course it is on! The difference in those two extremes is that in the PanAmera my arms are totally crossed over to negotiate turns, in the SWB you barely turn the wheel, the rest is done with throttle control. If you drove both examples it would be very clear to you.

[chris_seven]

I think there are some issues with LWB cars on 'bumpy' tarmac.

The 'line' projected through the rear trailing arm mounting on a SWB car passes through the centre of the torsion bar/Spring plate.

On the LWB car this line misses the centre of the torsion bar/spring plate by a significant margin and this must affect the way the arm articulates.

The RSR with the short rear arm and the extended trailing arm mounting is identical to the SWB car and the line passes through the centre of the torsion bar spring plate.

I am not sure what this really means but I think it is an interesting observation and I have always preferred a SWB car on bumpy Asphalt such as the Isle of Man on Tarmac Rallies.

In general I do prefer SWB cars as they do seem to steer much more sharply.

[Flunder]

Chris: That is an interesting observation that I have never seen in any of the usual sources including the 911 performance books. I wonder if sharper turn-in and better characteristics on bumpy tarmac can be accounted for in the original design plotted for the rear suspension geometry of the SWB chassis. I wonder if this can be traced to a difference in relative toe-gain or some other geometry through the arc of suspension travel on the rear arm on LWB v SWB?

[Flieger]

I cannot understand exactly what Chris means without a diagram, but the RSR had the shorter arms to have more (favorable) camber change in roll so that they could run less static camber with the increasingly huge tires they were running on them. Perhaps that is also present with the SWB geometry, just with a longer wheelbase?

I am not sure exactly how toe is affected on with the different changes but because the toe is set relative to the arm like the camber I imagine there is more toe change along with more camber change. The toe change would be towards toe out if the front view line between the bushings is horizontal. With raised inner pickup points there should be less toe out or even toe in change in bump, but worse in droop. So I would say that raising the outer pickup point like on the 935 would be necessary, and raise it more than the inner. That way you get toe out on bump and toe in on droop.

[Reza]

I like early 911s. To OP, donf matter which theyre all great.

You can always vic elford levels of caster on the front for sharper turns.

[chris_seven]

SWB




LWB

[Chris Pomares]

Help me out here. I'm confused, ( my normal state of being). I thought the 2 1/4 inch increase in wheelbase was to lengthen the trailing arms and spring plates to the rear. I assumed the change in body panel where the hole for the torsen bar was, was because they changed the rear quarter panel. Your pictures of the SWB and LWB cars show the relation of the pick up points for the trailing arms at the torsion tube and the spring plate to torsion bar to be quite different. Explain please what really happened here.
Thanks, Chris

[Flieger]

Thanks for the diagrams. Those pictures look to be the same diagram but with different red lines drawn for illustration purposes. Are those line drawings actually the SWB and LWB geometry?

The way I see it, the important thing is the line between the centers of the two pivots, not the angle of the one bushing. This is because of the compliance of the rubber or the spherical bearings that some place in the inner bushing position. The kinematics are not determined by those angles as much as they are the x,y,z relative coordinates of the different points of attachment to the chassis.

Anyway, angling the axis of the trailing arm like that should mean more camber change for the LWB. At least that is how it appears to me.