GT40 vs the Competition

It is interesting to note that the Lamborghini Countach had the same type of trailing arm suspension as the GT40.

Here the early Countach (LP400)





You can see that the upright has two pick-up points that merge into a single pick-up point on the chassis. Improvements then replaced this single link with a double link to provide more stiffness around the vertical axis.





The trailing arms were then deleted with the Diablo and the Murcielago which just featured two wishbones. These wishbones were not parallel, and featured a small amount of anti-dive. Virtually all modern sports cars do that now.



Here the C5/C6 Corvette suspension. Really simple, same upright on both front and rear.



Can you see the anti-dive they design in? The wishbones are not horizontal. In the front, the upper wishbone is angled upwards, in the rear, the lower wishbone is angled upwards. This is not easily possible with trailing link type suspensions and the reason why they no longer exist. Virtually all new suspensions I have seen are somewhat close to the C5/C6 suspension.



Do you have any more information here? Would love to learn more.

What information are you looking for?
One issue when discussing suspension geometry is that there are alot of different opinions and philisophies regarding how it is put together.
At the end of the day a car is a result of a large number of trade offs, one just have to choose what to prioritize.

turb00le said:

What information are you looking for?
One issue when discussing suspension geometry is that there are alot of different opinions and philisophies regarding how it is put together.
At the end of the day a car is a result of a large number of trade offs, one just have to choose what to prioritize.

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Yes, agree. Any insider information on suspension geometries and types that you cannot read-up on the web would be of interest for me.

Göran Malmberg, www.hemipanter.se
I think his book is available through speedlab.

Even after studying a bit it is difficult to conclude on anything. There are some rules of thumb but other than
that it is a matter of doing the most suitable trade offs.

THX, tried to purchase this book but not possible, at check-out it says "we dont ship to your country". Emailed them. This graph is great:

CTCH said:

THX, tried to purchase this book but not possible, at check-out it says "we dont ship to your country". Emailed them. This graph is great:

View attachment 139021

Click to expand...

I used Suspension Analyzer 2.4 by Performance Trends for my race car front & rear suspension design. The program is fairly intuitive and easy to use.

manta22 said:

I used Suspension Analyzer 2.4 by Performance Trends for my race car front & rear suspension design. The program is fairly intuitive and easy to use.

Click to expand...

That seems like a great software.

Do you guys remember the Garage Countach?

For sale here

Based on C4 suspension - love the engineering on that car.

VSusp is also useful.
Or just make a few sketches in solidworks or inventor and constrain them together.

Done that for this suspension.



What is a reasonable suspension travel? 50mm in and 50mm out?
I created this graph below directly from CAD for this unequal length double wishbone suspension above. You can see that it generates about 1deg of negative chamber when compressed 50mm. Chamber gain for negative suspension travel is almost flat.

The height of the upright and the knuckle is for sure one indicator for the stiffness and hence, also the performance of the suspension. The Granada uprights are a little on the small side. Here a comparison between Ford Granada, C4 and C5/6 Corvette:



I would argue that the stiffness is something like squared of the separation distance between the ball joints, so it would be fair to say that the C4 suspension is probably 2x as stiff than the Granada suspension. Blue is C4, green is Ford Granada, yellow is C5/6.

You can see the height of the upright with the original Countach, somewhere around 360mm?



Anyone have some images of the original front uprights of the GT40? Found this one, unsure if this was the original:

[A GT40 replica with a Granada suspension is a million times better than no replica (my situation) - I hope I am not offending anyone here with some of these statements. Second, the Granada suspension is good enough for 99% of the use cases. I have a C4 donor car that I got cheap and therefore I want to entertain that C4 suspension for my build]