Body Roll/Twist

S

shadow191

Premium Member
Premium
Location
Atlanta, GA
Car
2007 FX35
So I've had an '07 FX35 AWD for about 3 weeks now and I'm still getting used to driving it. I've noticed that on rougher roads - potholes, cracked pavement, etc., the body and suspension seem to want to go in different directions. It's hard to describe; but it's as if the wheels are trying to go one way and the body another so its a twisting feeling. I've looked up threads discussing body roll, but those were always referencing cornering and it's not what I'm referring to.

My question is, what's the solution? Just lower the car? Get all the GT Spec bracing? Or will it always be there and is just how the FX drives? I've never owned a car this big nor this high off the ground so I have no prior experience. Any help is appreciated.
 
what tires and tire sizes are you running?

ive noticed what you said but after changing the stock good year RSAs to other tires (yoko parada spec-x), it made a big difference, but not gone completely. I still feel a lot of the bumps on the road

others have used gt-spec sway bars, stbs, but i think that might mainly be for body roll
 
you need to describe better..
do you mean the wheels are tracking? (kind of steering themselves) when you hit roughness? the suspension is stiff on the FX maybe you're just not used to it
 
Did you check your tire pressure? The suspension is stiff on the FX and sitting a bit higher up than normal it can feel like it is jumping (at least until you settle in). If everything checks out and the car is tight I would suggest to start with a set of springs and an STB and go from there. The GT-Spec braces will DEF stiffen everything up but its more of a cost issue and depends on what you are willing to invest.......
 
All of my previous cars were lowered significantly and had aftermarket wheels/low profile tires so I'm used to the wheels tracking uneven pavement. It's not that. The FX has stiff stock suspension, but it's not that stiff.

The best way that I can describe it is when I hit a pavement crack, the suspension compresses and then it feels as if the wheels want to go in one direction while the rest of the car wants to go in the opposite. Then the suspension pulls everything back together. It just feels like the suspension is twisting. I know this isn't a great explanation; but it's hard to describe.

It's very noticable to me. When it first happened, I thought it was just a one time occurence due to a specific road condition. But now I notice it happens quite frequently and seems to be the way the FX responds to uneven roads. It makes the car feel very heavy. The car doesn't feel like it's planted very well; it feels really unsettled in corners where the pavement is not smooth. Other than this though, it's a great car.

jbaker1121 said:
you need to describe better..
do you mean the wheels are tracking? (kind of steering themselves) when you hit roughness? the suspension is stiff on the FX maybe you're just not used to it
Click to expand...
 
this is something that all fx's suffer from. the rear of the fx wants to walk sideways in the bumpy stuff, which is that side to side feeling your discribing. I think I've narrowed this down to underdampened rear shocks as the culprit... I have not been able to eliminate this until I went to much higher dampening & compression rated rear shocks... the fx is designed to be a sporty ride, but they also did try to engineer some level of comfort too which is why I think they underdampened it to begin with... hard to say what your solution might be, I did a lot of suspension modifications myself to lower the center of gravity, increase front & rear spring rates & add much needed extra dampening in the rear & now my fx tracks straight even through the ruffest streets that nyc can dish out, even very bumpy higher speed turns don't unsettle it any more, of course by going this spporty it may not be quite as cushy as stock but still not harsh at all.

kinda hard for me to actually recommend that you revamp your whole suspension though at this point... but just want you to know that it's not a design flaw but more of a suspension tunning flaw...
 
Bingo, that's exactly what it feels like. So the only solution is to rework most of the suspension... I'm actually not against that idea. I'd gladly trade a little bit of cush for better tracking and a more planted feeling. Plus part of the reason I got the FX was because there are modifications for it. Back in the day, I had very heavily modified cars and then I did the grown up thing and sold them. Picked up an '06 IS350 which was great, but there was literally nothing I could do to it other than lower it and wheels/tires. Since that was all I could do, I got really agressive on the wheels with stretched tires and all that. Rubbing over every pothole gets old though. Unfortunately, that car was totalled last month and hence the FX. So I'm happy that there are actually aftermarket parts (albeit only a few) for the FX.

Since it looks like there aren't readily available off the shelf coilovers for the FX, is the only real solution to my issue to do what you did? Koni inserts with modified spring mounts? If the ride is still reasonable like you say, I'm definitely going to look into it. I just don't want it to be like my previous cars where they were so low we had to max out the damping on the coilovers to prevent scraping and bottoming out.

I appreciate your help.

turbocad6 said:
this is something that all fx's suffer from. the rear of the fx wants to walk sideways in the bumpy stuff, which is that side to side feeling your discribing. I think I've narrowed this down to underdampened rear shocks as the culprit... I have not been able to eliminate this until I went to much higher dampening & compression rated rear shocks... the fx is designed to be a sporty ride, but they also did try to engineer some level of comfort too which is why I think they underdampened it to begin with... hard to say what your solution might be, I did a lot of suspension modifications myself to lower the center of gravity, increase front & rear spring rates & add much needed extra dampening in the rear & now my fx tracks straight even through the ruffest streets that nyc can dish out, even very bumpy higher speed turns don't unsettle it any more, of course by going this spporty it may not be quite as cushy as stock but still not harsh at all.

kinda hard for me to actually recommend that you revamp your whole suspension though at this point... but just want you to know that it's not a design flaw but more of a suspension tunning flaw...
Click to expand...
 
you don't need to do front koni inserts... I'm doing that for an even more agressive tunability factor & full adjustabilty but not necissary really. the main culprit in the situation your discribing is from the rear, but of course if your going to lower & do other stuff then you'll still want the rear to match the fronts for the right balance...

to me the best thing I would recommend for those that want a great ride & a lower more agressive stance & a really nice suspension is the way I have my fx set up right now, before the coilovers I'm building & the koni inserts & stuff.

my goal with the coil overs I'm building & the koni inserts is to just hopefully at least get it to be as good as it actually is right now, & then give me the adjustability to tweek from there, it's that good right now.


as it sits now includes a modification to the front struts for a bit more drop, removing 1/2 coil for the front H&R springs, modifying the rear lower arms for more drop & adding off the shelf monroe "coilovers" which are nothing more than a load leveling shock they designed for a cargo van for extra load carrying capacity, they also will increase the rear spring rate to match that of the cut front H&R & they have much higher rebound & compression dampening which the fx really needs & really likes... then substituting a rear lower spring seat for the upper rear. modifying the rear lower arm for more drop that will be pretty much made up for with the rear monroe coilovers... I'd say the only real defficency in my setup right now is dialing in the exact amount of drop needed to add the the rear lower arm mod as it can vary depending on static hieght & this is because of the non adjustability of the monroe coilover preload...

I also highly recommend the geometry change I have made in the rear too if your going to go pretty low but many may be a bit leary about doing that I guess because it involves redrilling the upper rear control arm mounting points, but this has went a long way in correcting the excessive rear camber & excessive rear camber ramp up on compression too & I am able to get a pefect alignment out of it with just the stock camber/toe bolts even at this much lowered stance...

ideally it would be great if I could make the cheap monroe load handling rear shocks adjustable for you guys for preload & dialing in the best height ratio to the front which is pretty much fixed height, but predicatable fixed height at least... I may play around with trying to get another set of the monroe rear load leveling shocks & attempt to make the coil over portion of it adjustable... if I can do that then that will def be THE suspension to have for most.... big difference between where I'm at now & stock in the handling & stability, especially over the rough stuff...
 
Dr.2K said:
It is not so bad once you know this is the way the FX was built.
Click to expand...

And once you get used to it, though the "FX hop" never feels right, it doesn't happen that often - unless you live where the streets are just rough.

Personally, I hope you and Turbocad both figure out two totally different, but equally performing suspension setups. Maybe tuned for a particular style of driving, or adjustable. That way I can totally take advantage of your stellar write-up with illustrative photos! :biggrin:
 
in nyc we have some pretty screwed up roads... there always fixing them & there still always chopped up. there are some places through longer sweeping turns that are just so friggin choppy that the fx just felt so unstable & almost scary at times & def would cause me to slow down through those sections & I hated it, nothing worse than the feeling of not being in total control or feeling like control is slipping away from you... it almost felt like if the road was rough enough that you were going to wind up in the next lane or into the guard rail. maybe it wasn't quite that unstable but it certainly felt like it at times...

now I look for those sections & gun it even harder, the stability is just there now, I can take these situations harder now even in the rain than I could before in even dry weather, I think there is a big difference, but if your in a place where the roads are all not bad at all or if you just like slowing down for rough sections then I guess this is less of an issue too, I really like the stability that I feel now though, big big difference....
 
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