I have been noticing that alot of track set-ups use a heavier front spring.


18k 16k or 16k 14k

what is the advantage? disadvantage...

 

I think it's to counter that giant weight in the front...ya know...the engine...

 

that is what I figured, but most set ups I see all have heavier rear springs.

I was just thinking there might be another reason.

 

This has been discussed to death in several forums (searching the archives will reveal more than you ever wanted to know on the subject). The quick answer is that street AND racing setups may use front-heavy or rear-heavy suspensions. The placement of the motor is not the reason. A well balanced and corner-weighted suspension may still be rear-heavy on a FF car. The setup that ends up being the fastest is the one that is designed around the whole car (tires, suspension, alignment, track, driver, etc.) so don't accept any single answer as correct. The only generalization that I will make is that many street setups are front-heavy as they tend to promote understeer in an otherwise unmodified car. This is considered safer on the streets than oversteer because the corrections necessary for oversteer are counter to what most people do in emergency situations (slam on the brake).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by travis &raquo;</TD></TR><TR><TD CLASS="quote">...This is considered safer on the streets than oversteer because the corrections necessary for oversteer are counter to what most people do in emergency situations (slam on the brake).</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">A well balanced and corner-weighted suspension may still be rear-heavy on a FF car.</TD></TR></TABLE>

Huh?! Static weight distribution can only be changed by physically moving the weight placement of parts in the vehicle. Corner weighting wont change static weight distribution. So how is a FF car ever rear heavy?

Spring rate bias front to rear coincides with static weight bias front to rear, with some added rear rate to cause steady state oversteer. In other words, the front to rear weight bias is 60/40% or 3/2, so the spring rate should be 3/2 with a little bit added to the rear as needed.

Basically you increase the front spring rate until the front is safe from bottoming out, then you choose a rear rate according to the weight bias ratio, then you increase the rear rate in small increments to get the handling balance you want (or use the adjustment on the rear sway.) Swaybars are then used to control body roll, except in high powered 2WD cars where the springs and sway on the drivewheels share the task of controlling body roll at that end.

 

I think he means heavy as in heavier spring rates.

I've never really thought about it too much before but I guess it would be correct that you could only affect the cross weights and not the F/R distribution.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by shaundrake &raquo;</TD></TR><TR><TD CLASS="quote">

Huh?! Static weight distribution can only be changed by physically moving the weight placement of parts in the vehicle. Corner weighting wont change static weight distribution. So how is a FF car ever rear heavy?

Spring rate bias front to rear coincides with static weight bias front to rear, with some added rear rate to cause steady state oversteer. In other words, the front to rear weight bias is 60/40% or 3/2, so the spring rate should be 3/2 with a little bit added to the rear as needed.

Basically you increase the front spring rate until the front is safe from bottoming out, then you choose a rear rate according to the weight bias ratio, then you increase the rear rate in small increments to get the handling balance you want (or use the adjustment on the rear sway.) Swaybars are then used to control body roll, except in high powered 2WD cars where the springs and sway on the drivewheels share the task of controlling body roll at that end.</TD></TR></TABLE>

Sorry for the confusion. SoloCivic had it right, mine was a sloppy reference to higher and lower spring rates, not static weight distribution. I'll admit is was a poor choice of words given the discussion of corner weights