Why are rear shocks longer than front shocks?

[Toolman]

You could never have identical shocks front & rear simply because the weight distribution of the car is not 50:50 front to back. If you did you would need to have different damping & spring rates.

The more I think about this the more I believe that aesthetics play a large part, a cars gotta look good to sell!

Tim.

 

[Lessen]

when I'm thinking about stuff like this I tend to break it down bit by bit. I ask myself the simplest questions. Let's play...

What is the basic effect of having a longer shock?
more shock travel. simple.

now there are two aspect of the shock travel. bound and rebound. We need to keep this in mind.

What is the advantage of having a longer bound? specifically at the rear.
longer bound "soaks up" the excess droop (because of more weight).
also allows the absorbance of more overall weight (important for landing)

What is the advantage of "soaking up" the extra droop?
no loss in the actual suspension stroke.

Ok, what about rebound..

What is the advantage of a longer rebound (at the rear)?
I find this one a bit harder to answer. The only thing I can come up with is that it helps kick up the rear end when jumping. so I continue...

How?
Since the rebound is longer the rear wheels are kept in contact with (pushing against) the lip of the jump for a longer period of time than the front wheels.

So?
It's like spring rates... Assuming 2 springs can hold the same amount of weight within a given measure of compression.. if one has a longer overall length is can hold a heavier overall load.

If the front and rear springs are of the same rate they both push off the lip of the jump with the same amount of force.. but the longer spring will push with the same force for a extended amount of time. This allows the rear end to catch up with the front.. in the end we have a more level takeoff

In a nutshell that's how I came up with my hypothesis. To me it seems to be the one solution to several design challenges.

 

[Claiwen]

I asked this question to Jamie Booth who is the distributor for Hong Nor (Jammin) in the UK and is a really really good driver!
His reply was as follows:-


Hi Tim,

I think you are on the trail, but I think the reason is much, much simpler.
Because the front wheels turn left and right it's often not possible to have the shocks mounted so far out on the wishbone as on the rear. If the shocks are moved in on the wishbone they need less movement for the same amount of travel, therefore having the same length of shocks on the front would A) make the car ugly and vulnerable to damage and B) it would be totally unnecessary.

Maybe I am wrong but I think it's as simple as that.

JB


So I think I pronounce that Myth Busted! – Tim.

THATS IT. YEAH DIFFERENT GEOMETRIES...

different effects on rear and front so you will need different geometries..

 

[iburnout]

Oh so so late to party, as usual, I am.
My non traxxas HBX 2995 has more travel on front than back as the back will bind up (axles and pins?) On the back with shocks that will just barely work for the front. So more possible travel to be had on the front. Stock shocks were same length all around.
So either the 2995 is just a physi s Fo PA(tx google) physics.
Looking to put softer springs on the car so my o resized epinion big bore shocks let the var compress u Der its own weight led me to this fine read. Tx