Front/rear balance ratio

They vary by manufacturer and equipment.  Danny Piperato brought corner balancing scales to Carlisle a few years back and most of us weighed out cars.  Mine was a svelte 1700pounds and nicely corner balanced, but the weight distribution was 39% front/61% rear.  Yow! 

When the back-end of our cars starts to come around you'd better be REALLY fast (or lucky).

GR,

You didn't actually state it, but you seem to indicate that a 50/50 weight distribution is ideal.  If that is what you meant, you won't find many auto engineers agreeing.

The more commonly accepted ratio is 40-45 front, 55-60 rear.  This ratio is for rear wheel drive cars.  The rear weight bias helps in many ways: better braking, better accelleration, better corner entry and exit.

Suspension tuning is a critical component of preparation for track use, and includes corner weighing/balancing, and making sure the left and right sides of the car have the same weights in the front, and the same weights in the rear.  Wedge weighting is common for circle track cars that only turn one direction, but harmful for road or track cars.  It also is necessary to tune suspensions with the driver or equivalent weight in the driver's seat.  

There is lots of information on suspension tuning available on line.  The difficulty is in finding information on the physics of racing and suspension tuning that a non-scientist like me can understand.

Danny weighed just about every Speedster that attended Carlisle---he's definitely one of the 'good guys"!

My VS with 1/2 tanlk of gas (4 gal) weighed 1,763# with the front being 46% and the rear 54%.  I've never had it on any track and don't plan to do so but it drives great.

Basic... if you want to test different weights, set a few rocks on top of a towel next to the battery and test drive ...add or subtract until you get the best handling. Then weigh the rocks and replace with a piece of steel under the battery or affix to the axle beam...yup a bit basic but... it works.

Easy to add permanent weight to front.  Larger 16 gallon (think they are actually 14 gallons) adds 4 gallon over front axle for 35 #, spare tire/jack/tools add 40#, and large battery maybe exta 15#.  I remember repainting an early 1966 911 that I had only to find it had big OEM iron weights in each side of the front bumpers - it addition to 2 batteries in the front nose (L and R sides).   

G.R. You asked "Does anyone know what the approx. balance ratio of these cars is?"

For comparison, mine is a home-built (by me) CMC and was weighed by Danny at Carlisle (Thanks Danny!).  Total weight empty (not sure how full gas tank) was 1,596 pounds, 713 front, 883 rear.  Works out to approx 45% front and 55% rear.  

I am still aghast that a bunch of cars weighed at Carlisle came in well under 1,800 pounds (like Bruce's CMC) and my CMC weighed 2,002 pounds.  

I must have one hell of a lot of sound proofing in there......

or really, really heavy Nerf bars.

Very interesting Greg.  I read that the weights in the front bumper were a fix to counteract the heavier 911 motor as opposed to the 912/356 motor.  Cool you found that in yours.  Wish you still had it??

'66 was still SWB. I believe it.

Sold in '75 when I moved to DC so I could pay downpayment on TH.  Ah to be single again.  Put lots of $$$ in that car - always needed something costly.

^ NICE!!!! 

Most V-8 powered front engine drive cars ie: Corvette, Mustang, Charger/Challenger and Camaro are very nose heavy due to the engine weight and are longer wheelbased. And the weight I gave for the Cobra also included my weight(205). The Cobra only has a 90" wheelbase thus it can get 'loose' in the rear end very quickly due to lightweight, short wheelbase and the high HP and torque as the nose has a tendency to 'dive' into corners at speed. Having a 40/45 to 55/60 rear weight bias on this short wheelbased car compounds the problem.

I wanted to race my car on occasion so I learned what I could regarding suspension and tuning, weight balance bias, shock and A-arm tuning, Etc for a Cobra...I had the chance along with several other Cobra owners to talk at length with several of the original Shelby American mechanics, guys that were involved in setting up the team cars for the different race tracks, at a seminar on tuning and handling at a SAAC convention in Las Vegas. I took lots of notes and and suggestions and applied them to my car. One thing they all said was that with the 289 FIA SB the balance front/rear and HP to weight/wheelbase bias seemed ideal in the near 50/50 area...I figure these guys ought to know Remember I'm talking about a Cobra replica that is just about 200 hundred pounds heavier than the original aluminum bodied cars not about a conventional off the showroom floor, V-8 daily driver. This Cobra is a 'driver', you have to pay attention when driving it or it can get away from you in a hurry. 

You are right in that suspension/chassis tuning is a bit of 'engineering science' and can get uber technical to the point one would need to be an engineer to understand a lot of it.

When I raced I ran against Porsche's, vintage 911 or 912's usually, saw a few of end up going 'rounders' in corners when they entered a corner to fast and braked a little to hard then tried to power out...sometimes didn't work so well and they headed for the infield...BB block 427 Cobras often had the same issue as the back end got real loose and trying to power out often led to spin off. The 427's are somewhere in the 55/60 front to 40/45rear weight balance.

My Cobra isn't a perfect track car as it wasn't built strictly for the track yet it is very tunable with front and rear adjustable A-arms for camber, adjustable coil overs on all four corners, tuneable suspension hiem joints. I have a book that I recorded every change made to the suspension for certain track/track layouts this enabled me to tune the car the next time I ran there.

Anyway I was just curious of what to expect in this Speedster...Thanks to all