elle88

like many of you i worked hard on my 69 suspensions to get a good street behaviour. i report a test done recently about unsprung weight effects

same turn , low speed. in the middle of the turn there's an asphalt junction and related little bump, really little
3 cars : Porsche Boxster, my Corvette 69 with total overhaul of suspension but stock , a friend's modern Mustang ( solid axle no positraction)

front suspension : good , same behaviour on the 3 cars

rear suspension when you hit the bump in the middle of the turn:

- Boxster : perfect , no issues
-Corvette : just little sliding of the rear. nothing serious but it's there
-Mustang : scary, the rear slides out a couple of inches

i suppose this is due to the heavier rear mass of suspension that hit the bump and floats , not immediately following the road . i don't know if the effect on the Mustang is also because it misses the limited slip diff

thoughts?

i did the test to indirectly evaluate the street behaviour of a solid axle car ( thinking to buy a 69 camaro or fastback Mustang)
I must say that these issues are on the street only. on the smooth asphalt of a race track all the issues go away: i tested on the same racetrack the Boxster and the Corvette and both super handling. I believe that a semi-race prepped camaro or mustang would do well too.

Note:
my 69 Corvette has F41 suspensions ( so 7 leaf rear spring ) , adjustable QA1 aluminum shocks, aluminum Minilite wheels ( 6lbs lighter than rally wheels)

shocks are setted very firm now. i want to do a test on the same turn with a softer setting on the rear and see if it helps. Bu definitively i don't like the bouncing behaviour of the Vette with soft shocks so... let's see

fiberglass spring : i didn't had a good experience with that on another Vette but it should work actually : less unsprung weight and faster reaction after hitting the bump

Aldo

cv67

Porcsche engineers have a formula for figuring unsprung weight gains in 1/4 mi at least. Have to find the link but if I remember it was almost worth zilch in comparison to what we think it may be.
Read about it on a Chevelle site go figure.
Guess it all adds up in the end though..

gingerbreadman1977

The less weight hanging from the suspension components, the easier it is for the mass of the wheels to stop and accelerate in the opposite direction.

When you put your car on a weight-reduction plan, it is important that you remember the 6-to-1 rule. It is said that a *1-pound reduction in unsprung weight is equal to a 6-pound reduction in sprung weight. Thus, if you’re going to spend money on lightweight hardware, concentrate on unsprung weight.

TheSkunkWorks

Yep. Reducing unsprung weight can definitely yield significant improvement in managing the tire contact patch when encountering upsets. As for the 'glass spring, every little bit helps, but less than half of its overall weight savings is unsprung, and despite its lighter weight many a hard charger has ultimately opted to stay with steel. FWIW, the wheels themselves and brake calipers would be where I'd look to minimize unsprung weight first. My $.02

elle88

TSW
that's the confirm that i was waiting for : that not the whole weight of springs is unsprung.

gingerbreadman1977

My $.02 is agreeing as well.... Springs, shocks, etc are neither sprung nor un-sprung. It is called Hybrid weight and is split 50/50 between sprung and unsprung.