FLATTOP

What would happen . . .. .
if I were to widen the front track on my 911 ('72 chassis) race car by 6" ? The car is powered by a supercharged 964 motor with 550 rwhp and has a 993 6 speed box. Front tire width 10" and rear 14". Spring stiffness front is 130 N/mm and rear 220 N/mm (sorry I don't know the lb/inch conversion). Weight in the region of 2100 lb.

M758

Just the front?

FLATTOP

Yes.

Gasser

Cervelli set my 993 up and told me to get the track out as far as I could front and rear but keep the front the same or less then the rear, not more or wider.

I have no science behind it but everything he does for me is spot on so I trust him.

Move your front out to be just under or match your rear track IMO.

Larry Herman

Time out guys. Exactly how do you plan to widen the track?

onefastviking

Might as well ask why while you are at it Larry.
Or better yet, what is the condition that you are trying to correct for by increasing the track ?

Seth Thomas

5.7 is the conversion rate for the springs.

claykos

Widening the track and lowering center of gravity are the only ways to reduce total weight transfer while cornering (despite what some people will tell you about changing springs). Widening the front track will in general increase oversteer. Depending on how it is done it can have adverse effects on suspension geometry (most likely scrub radius) which will increase steering effort (an issue if you have no power steering) and kickback through the wheel.

FLATTOP

Thank you all for your for your comments. I have already implimented the wider track to the car and the attached pictures show the results. The assesment that oversteer is induced by the wider track (especially in slow corners) is absolutely correct. In the original configuration I found that under acceleration out of slow corners the car would just understeer and the only remedy would be to lift off and allow the car to turn, then to get back on the throttle.

With the dramatic increase in front track you will notice from the pictures that the shock towers now are on the outside of the body and are accessed through an opening on the top of the fender.

The bottom suspension arm was turned from 7075 aluminium and is shown in the pictures. To effect all of these changes to the car it was needed to jig the car and the work was then done on the jig. This allowed for the chassis to retain its flatness - this coupled with the extremely stiff suspension is of course critical.

From my experience with this there were only positive results to be gained from the mod.

SundayDriver

Very cool.

For those who think this is strange, almost all Formula Cars and Sports Racers have a wider front track than rear and similar weight distribution as a 911.

FLATTOP

For the astute observer you will also notice in this picture how the spindle was raised and the bracket that was put in place to allow for bump steer adjustments.

For what its worth I also include a picture as the car is sitting on the grid at the Kyalami racing circuit in South Africa.

RickBetterley

That is darned impressive. Well done and very interesting.

analogmike

Nice work!

I think the front track on my '73 is wider than the rear as I run 930 8x15s on the front. Seems to work well!

FLATTOP

Rick. Thank you too for your kind words. I do not want to hijack my own thread but I will end by showing you a picture of how this car looked in 2003 when I bought it. From then it went through, as you can understand, dramatic changes - including a complete stip down and sandblasting of the chassis before rebuilding it with carbon body panels etc. etc.

The ONLY things that remain from the original car is the shell, the steering box and the rear banana arms. Believe me, and I have thought of this many times, is from the original car you see below. Not the door latches, not any of the wiring, not any of the brake pipes, not the brakes, not the seat, not even the steering boss is the same. I suppose you can say that I would have been better off starting with just a naked chassis. One day, on another thread, I'll show detailed photos of the transformation. Johan.

Lane

Cool !! Now this is what this site is about. Cars and racing!