kaikai114

I just came back from Barnes and Nobles and was reading this magazine called Sport Compacts. They mentioned 3 things: Center Gravity, Roll Center and Roll Couple. The part that got me interested the most is that they said overlowering your car may actually reduce the handling aspect of your car, it may seem to reduce body roll, but at the limits, handling performance decreases if you have too much Roll Couple. On average 2-5 inches from the ground to the bottom of your car is the ideal drop they said... That seems pretty broad to me. They mentioned that Nissan Sentra R should only be lowered no more than 1" to get the most performance out of the suspension since it's a MacPherson strut. Can someone provide detail info to what is the perfect balance drop for our TSX in terms of performance and also the 3 terms above?

-KC

BlackAc036

I'm installing my TIEN Basic Coilovers tommorow morning, I intend to drop the car 1.8 front and 1.5 rear. That is .1 inches higher than the Eibach Sportline. I'll post pics, but before I do it (is there anything wrong with this drop?) If the first question can be answered I might change the drop...

jlukja

Wow, this is technical but a quick Google Search found this on roll center.

jlukja, who would love to see more discussion on this.

vwong

Here is a good book on suspension stuffs. It's called "How to Make Your Car Handle" by Fred Puhn. I have this book, I read it but didn't absorb everything from it though. I'll probably have to read to book again to refresh my memory.

xizor

SCC has done an excellent series on suspension dynamics (this one is the 3rd part). The problem with MacPherson strut (and why its inferior to our double wishbone) is that as the McP Strut compresses the toe of the wheel/tire changes. I haven't read the article on roll change, but I think its safe to say our suspension does not have the problem that the Sentra or any McP Strut car does. For double wishbone as it compresses, camber increases which is the best possible scenario.

moda_way

If you see what RTR did to their RSXs via the search on Mid-Ohio, you notice that they cut the strut tower and replaced it with a new piece of metal that has cuts where the top of the strut bolts onto the tower. This means they can significantly adjust tow as well as camber.

kaikai114

it was kinda hard for me to digest all those info first time reading it. so is it true that overlowering on our double wish bone suspension will actually increase roll couple and decrease handling capabilities? in the SCC article part 3, they mentions the car will be within the roll couple range if the car is 2-5 inches from the ground. That seems to be a very broad range to me though, so basically in order for our car to have too much roll couple, we'd have to lower it to kiss the ground?

//JDMTSX//

look at realtime's car its slammed.... so what does that mean???? do they know what their doing?

Dan Martin

It means they've invested over $30,000 in suspension alone. It's completely different than a stock TSX.

kaikai114

RTR TSX isnt that slammed. It looks slammed because they've added extension ground kits making the car look lower than it actually is.

kaikai114

Dan,

RTR TSX has the Eibach springs doesnt it? What is the main difference on just the springs/struts/shocks compared with stock?

Dan Martin

It's a full moton damper system with eibach springs used on the coil-overs. The arms have been replaced with fully adjustable tubular units that allow a million different settings for toe, camber, and caster.

Dan Martin

I asked them about ride height and they said that depending on the track, they can lower it up to a half inch lower than it was at Mid-Ohio when I took this pic: http://www.flickr.com/photo_zoom.gne...-409183&size=l

SWRT

Roll Couple is the moment created by the distance between your centre of gravity and your instantaneous roll centre.

Think of your roll centre as a stuck bolt, and your CG as your hand on a wrench. The further away from the bolt that you grab the wrench, the more torque you put into the bolt.

The further your CG is from your roll centre, the more rolling moment your car will experience, and untimately... the more roll angle you will see when cornering.

When you lower your car, you are lowering your CG, but you do not necessarly know where your roll centre is going. Generally your roll centre will fall faster than your CG as your suspension is compressed, so the theory behind overlowering is to not start off with a greater roll couple than you already have by OEM design.

That said, a good suspension design has minimal roll centre migration, so a modest drop should show decent gains in CG height with minimal change in roll centre. Keep in mind that roll centre moves side to side too, that is why it is improtant to make sure your suspension geometry and ride height is symetrical... or close too it... your CG isn't really centred anyways.

-SWRT

peter_bigblock

That's an exactly right explanation of the three concepts. What I have found as a good rule of thumb is to not let your lower suspension arms/links go beyond parallel to the ground as you lower a car. In other words, you want the inboard mounting point at least as as far off the ground as your outboard mounting point.

It's when you go beyond parallel (to the ground) that your roll center really starts to dive and roll couple increases dramatically.

A short level with a magnet can help, or simply measure the distance from the ground of your suspension pickup points with stock suspension. The difference between the inboard and outboard points distance to the ground is the max you want to lower your car. Rule of thumb.

sho0z

interesting, i will follow this when i get my tein flex's. peter_bigblock, i wish i would of known of a fellow a'ziner with a tsx...ssm, 6mt, no nav. lol i JUST moved from there a couple months ago.

peter_bigblock

Too bad, I'll bet I've seen your car in WDM before. Where'd you live?

HI OFECR

Good read ill have to pick that up