I think few would argue against that old cars have more character and are simply cooler than modern cars; but the performance of modern cars is undeniable even though they are bigger and weigh more than ever. So how is it that all of these modern sports cars (and many non-sports cars) that tip the scales at 3500lbs+ (even over 4000lbs!) drive and handle so much better than light cars of the past?
A perfectly timed shot – the car was doing close to 100mph in this photo.
It is true that engines are more powerful and chassis are much stiffer than in the past. But, if you were going to race an old car, those things can be fixed with adding a cage and tuning the engine. But often, even though a set-up and tuned older car might make modern power and have a reinforced chassis that surpasses anything you can get today, they can be difficult to make handle as well as something you can go find in the show room now.
The biggest factor of this is suspension geometry. Old cars simply do not have a suspension as well engineered as today’s cars. Often, the roll centers of old cars can be very low and they can lack anti-dive. When roll centers are low, they tend to induce body roll which we all know makes a car less stable, slower to respond, and causes inefficient use of the tires. To the driver, body roll makes any car feel heavier regardless of the actual weight.
A lack of anti-dive can also be a performance limiting factor. Some early Macpherson strut setups lacked anti-dive due to harness it would transmit to the chassis over road imperfections; the result is of course lots of dive while braking. If whatever car you are racing has these geometric shortcomings, making the chassis perform to a modern level can be quite difficult.
Furthermore, when the ride height of a car is lowered, as many people do in order to lower the CG, the roll centers can move even lower, often below the ground which increases body roll even further. One can try to counter this by adding enormous spring rates, but that places a lot of stress on control arms and other suspension components. Not to mention that these huge spring rates will also need shocks custom valved to be able to damp them, which means the shock will now be doing a lot more work and probably wont last as long.
Sometimes, companies offer dropped spindles (redesigned uprights) so the car can be lowered and maintain better suspension geometry. This is probably the best solution for a race car, but there is another way to do this which is more common with race teams – that is to cut suspension mounting points off and to raise them up higher on the chassis. The effect of both of these is the same, but dropped spindles are much easier to install.
It is possible to make anything handle well and many people have created examples as proof. But, unless you have a strong attachment to certain old car, often the price of modding it will exceed its value on resale; so this is a another factor to consider.