Weight transfer and the effect of shocks

[Echoshill]

I wanted to throw a topic out her for conversation, hope that is alright, regarding the effect of shock absorbers on weight transfer. I will share first my school of thought which will hopefully result in affirmation and/or gentile correction.

Understanding that shocks do not control the amount of weight transferred in any form acceleration, as track width, WB, CoG and total vehicle weight are the only true factors there, the best that one can hope for is to effect the rate at which the weights moves. In a very general sense, increasing the stiffness of the shock, whether it is in bound or rebound, increases rate at which the available weight transfers on (bounce) or off (rebound) the wheels(s). Would you all agree with this and if so, what is the point of diminishing return? In other words, one could argue that the shock be so soft in bounce that, besides the time it takes for the shock to compress, that the weight transfers as fast as if there was no shock at all or the shock was a rigid member.

Would some of you folks chime in and offer your thoughts on this?

Thanks in advance.

 

[evelrod]

From my experience...Looks like you have a pretty good handle on the theory. Practical application involves a lot of voodoo and a bit of luck. I was present at the old RIR back in the mid 80's when some GM types were doing some work on a prototype Corvette (an 85/86, I think). One of the sessions involved setting the car up and taking lap times then removing all the shocks and comparing lap times. I was personally amazed as the lap times were NOT all that different! I was outside T-2 and later in the paddock at the "dogleg" and T-9 and what I saw was very little difference in roll or pitch. It changed my approach to the point that I now use as little damping as is needed to keep the car from bouncing or pitching down under braking in a corner. Shocks are the last thing I tinker with in setup. I use GAZ on my Mini and Koni on my Lotus Cortina both at relatively soft settings. My spring rates are on the high side from what I see in other vintage racers.

Rod

 

[Echoshill]

Thank you. I thought I did too. But have you ever had one of those day's where the data you were seeing was making you doubt everything you thought you knew?

That was my yesterday.

M

 

[evelrod]

That's the voodoo part. I only do vintage now, but, yes, I still have those days.

I spent a month assembling a Lotus twincam to have it crack the cylinder head on the first dyno run. Fast forward...Got the new head (Omnitech Engr.) last week and spent yesterday setting cam timing only to discover that now I have ZERO intake valve clearance to the pistons...It took me a week to lovingly assemble that bottom end and now I gotta un assemble it!!!

That was MY yesterday!

Rod

 

[GregLocock]

I like the corvette story. All that heat in the shocks has to come from the crankshaft.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[evelrod]

My question at the time was "why". Why make the handling more difficult even if short term lap times are close. From my view point it may have seemed smooth...I'll bet a pint of panther p*** to a pasted doughnut that it wasn't that smooth to the driver!

Rod