I'm wondering since I'm running stock ITR springs and shocks, and looking to upgrade the shocks in the future, would it be better to have a shock like the illuminas that increase compression along with rebound? The reason I'm asking is, I know if you increase rebound too much on a given spring, it can cause the suspension to crank down to the point that its resting on the bump stops until its given a chance to recover. Would an increase in compression help? I'm trying to get away without running an ITR rear sway as well. The car is an LS. Thanks for any input.

 

it is a debatable thing.

Personally i wouldn't want it, and i don't think it is good for performance.

 

what exactly are you trying to get at?

carroll smith says: [this is all rwd advice]

corner entry understee: car initialy points in and then washes out

-excessive front toe-in or toe-out (car is usually darty)
-insufficient front droop
-incorrectly adjusted packers
-insufficient front damper bump resistance (similar feel to roll stiffness example)
-insufficient front roll stiffness
-non linear lateral load transfer due to spring and or bar geometry or to non optimum lateral rollaxis inclination

mid corner understeer is not a function of the shocks. so im not listing those. lateral grip shouldnt be the issue in corner exit either.

<U>transitions</U>
understeer in, snap oversteer on power application [again this is RWD advice]
-increase front bar and/or spring and/or front damper low piston speed bump force. stiffening the bar will also transfer some load on the inside rear tire on acceleration.
-if suggestion above cures the understeer but the car still snaps, the culprit is almost always the car falling over on the outside rear tire on longitudinal plus lateral load transfer. add rear bar or psirng. bar will transfer load away from inside rear tire. spring will not. spring will, however, decrease traction over exit bumps while bar will not.
-loose antiroll bar linkage.


its the weekend.... i have time to type.

i recommend illuminas.

 

well it is good to have a philosophy to go by, but a book isn't going to have the correct answers.

I have spent a bit of time around race cars, most of which have compression and rebound adjusters separate.

I can't remember a time when we increased compression and increased rebound, or decreased compression and decreased rebound.

Most of the time we fought a tight car, but depending on many things the adjustment was different, and we never changed two things at once. Well we did but only when it was a last ditch effort.

Like going into the race after qualifying and having a car that pushes bad and will kill front tires. Then we might make more then one change.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18LS &raquo;</TD></TR><TR><TD CLASS="quote">I'm wondering since I'm running stock ITR springs and shocks, and looking to upgrade the shocks in the future, would it be better to have a shock like the illuminas that increase compression along with rebound? The reason I'm asking is, I know if you increase rebound too much on a given spring, it can cause the suspension to crank down to the point that its resting on the bump stops until its given a chance to recover. Would an increase in compression help? I'm trying to get away without running an ITR rear sway as well. The car is an LS. Thanks for any input.</TD></TR></TABLE>

Adjustable compression could benefit those who know how to use it, and hurt those who don't. If plan to use it to keep the car from jacking down, then you don't need it.

Generally, increasing rear compression can also help counter corner entry understeer.

 

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

Adjustable compression could benefit those who know how to use it, and hurt those who don't. If plan to use it to keep the car from jacking down, then you don't need it.

Generally, increasing rear compression can also help counter corner entry understeer.</TD></TR></TABLE>

i think he was talking about a shock with one adjuster that adjusts both compression and rebound at the same time

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slammed_93_hatch &raquo;</TD></TR><TR><TD CLASS="quote">

i think he was talking about a shock with one adjuster that adjusts both compression and rebound at the same time</TD></TR></TABLE>

Yeah that is closer to what I was asking, but I think its been answered. Im getting that a shock like the illuminas would help correct understeer more than one that just adjusts rebound. I think it would be more corner entry though, because they will still allow the body to roll and take a set, once the car has initally turned it. Blah. This stuff can drive you mad. I'm running ITR LCA's now, so I was thinking either bilstein sp or illuminas. The adjustability of the illuminas is great, but Ive heard the bilteins are magic. We'll see/ Thanks fot the help.

 

another opinion. (he's been around racecars too.)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mark Ortiz &raquo;</TD></TR><TR><TD CLASS="quote">
Regarding whether to add or reduce damping on compression or extension, and at high velocited or low, some widely repeated advice would have us set compression damping to control sprung mass motion, and set extension damping to control unsprung mass motion. In my opinion, this is incorrect. At some time it may have served as simple advice to racers faced with setting the earliest double-adjustable shocks, but now we have revalaveable and four-way adjustable shocks, and reasonably good shock dynos. My advice nowadays is:

1) Use low-speed damping, in both extension and compression, to manage transient weight transfer and sprung mass motion. Do not expect this to work unless the surface is smooth enough so that sprung mass motion is the main cause of suspension movement. Use the springs and bars as your main means of managing weight transfer.

2) Use damping properties at velocities above 2 in/sec to manage sprung and unsprung mass behavior over road irregularites. Again, both compression and extension matter.

3) Keep compression and extension damping in reasonable proportion to each other. At most absolute velocities, extension damping should be at least a little stiffer than compression damping, but not more than twice as stiff and never more than three times as stiff unless you are deliberately trying to make the car jack down.
</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tyson &raquo;</TD></TR><TR><TD CLASS="quote">another opinion. (he's been around racecars too.)

</TD></TR></TABLE>NICE, thats a good writeup. Thanks. I've always liked konis, but figure there was an advantage to being able to adjust compression/

 

I see what Mark Ortiz is getting at, but I'm not sure who is saying that compression damping should control the sprung mass and rebound damping should control the unsprung mass. I haven't heard anyone saying this (except maybe some people using Advance Design dampers, but I couldn't comprehend their tuning strategy at all anyway ), and I agree that it is incorrect.

In fact, I've read the exact opposite: Compression should control the unsprung mass, and rebound should control the sprung mass. I agree with this. In practice, it has worked for me, and thinking of it this way also somehow helps my brain to better comprehend the different actions at each corner of the car through all phases of the turn. It also negates my need for a compression adjustment that I'd have no idea how to adjust correctly, because I pretty much never make changes to my car's unsprung weight anyway.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Targa250R &raquo;</TD></TR><TR><TD CLASS="quote">I haven't heard anyone saying this ...., and I agree that it is incorrect.</TD></TR></TABLE>

actually youre right, i think mark ortiz is quoting the opposing point of view incorrectly, in reverse (maybe i transposed it incorrectly). never the less, it is staunchly defended by koni, among others.

https://honda-tech.com/zerothread?id=1455741