My current setup is an '06 IS350 on BCR Coilovers 10kg Front/8kg with both F-Sport front and rear sway bars. I'm riding about 1.25" lower than stock up front and 1.00" lower in the rear.

Since installing coilovers, I have noticed the inside rear tire lifting and causing VDIM to kick on while accelerating out of corners. I'm talking even mild corners too where I'm barely pushing it. This tendency to lift is very annoying and makes it very difficult for me to have any fun. With this inside tire lifting, I've had the car oversteer pretty back at higher speeds around turns simply because that tire lost all traction.

I added the front F-Sport sway to help reduce front end sway to see if it would counteract the problem, but it definitely didn't help. I suspect the rear BCR coilovers being about 1.5-2" shorter than stock rear assemblies playing a role in this greatly since it's not allowing the inside rear tire to droop down and maintain traction during cornering. I know that I could induce this scenario as well when I had a bone stock suspension with simply the F-Sport rear sway bar installed, but it wasn't nearly as bad and prevalent. Another thought is that since I'm riding slightly lower in front than in the rear, I'm upsetting the balance and weight distribution and making it nose heavy.

Anyone have any ideas on how I can cure this problem? I'm going to try and increase the dampening on the front coils from near soft to medium tomorrow to see if that changes anything. Then go from there. I'm even thinking about swapping out the rear suspension to the Sport Package rear suspension if I can't resolve this issue. That way I can get rid of the clunk noises over bumps back there as well.

 

Looks like your rear is set too stiff and the clunking is from incorrectly set preload on the coil overs. Give as much travel as you can nd soften the shock setting.

 

I've reset the pre-load a couple of times and have tried many settings from no pre-load to 2-4mm pre-load to my current 8-10mm pre-load. I played with this to see if it would eliminate the clunking. I've removed these coils from the car 4-5 times now and swapped them right to left too. I even added a Tein spring silencer at one point and removed them. I'll probably reset the pre-load back to default 2-4mm this weekend. Everything has been torqued tight including the top hat nuts. BC also sent me 1 replacement shock back in June 2011. That did nothing to resolve the clunk problem either. Before it was only 1 side clunking. Now both sides are clunking.

Anyhow back to the main topic about droop - another thought I had was possibly raising the shock at the lower perch to increase total assembly length at the expense of damper travel using helper springs above the BCR springs.

This morning, I increased the front coils from 9 clicks to 20 clicks towards hard setting and it definitely helped out a little as the car doesn't lean as much into corners allowing me to put more throttle out of turns without lifting the inside tire as much. Needless to say, I still got rear lift at relatively low speeds (~15mph) causing the VDIM to cut the power. The rear is currently set around 4-5 clicks from full soft.

 

remove the rear sway bar or revert to stock size.

The F-sport swaybars were most likely designed to be used with F-sport springs and shocks

My rx7 track car I completely removed the rear bar, was experiencing the same thing with the coilovers. the sway bar limits your rear wheel travel/droop. you could go back to the stock rear or figure out away to get more droop with the suspension.

Or you can increase front stiffness, by a) increase dampening, b) stiffer front bar c) more front preload

and the for the clunking see if the sway bars are installed properly the rear could be binding on something making the clunk and lifting the rear tire

 

Tell me, have you gotten an alignment after any of the suspension adjustments you have made? After I added my BCRs and my alignment I could tell with the added negative camber that I lost alot of streetable traction off the line. I can spin without a problem...where as before with my OE sport pkg springs/shocks it would only lose traction in a corner, never off the line. Alot of factors are at work here : wheels, tires, tire psi, spring stiffness, shock stiffness, chassis height, sways, entry speed. Try adjusting other factors to see what can help.

*My tires are BFG KDWs at normal operating temp.

 

Thanks for starting this thread. Something I'll need to keep into consideration, as I have just ordered BCR coilovers AND f-sport front and rear sway bars. Even with a mild drop you experience these issues, which is concerning

 

Alignment won't affect a rear tire lifting, It's a suspension preload, dampening, sway bar issue

pdpgps; from a performance stand point I wouldn't upgrade the rear sway bar+ coilovers RWD front stiffness= Good FWD rear stiffness= good

 

Alignment was done a few times now over last 6 months. Most recent was done in back in December 2011. That's interesting you mention the breaking traction off the line after installing BCR - that's exactly what I noticed too. Since I'm lowered only an inch at most in the back, I'm not quite sure that an added half degree to one degree of negative camber takes away that much straight line traction, but I can see how a combination of stiffer rear sway bar and stiffer rear springs can cause decrease in straight line traction. Before the coils on the non sport oem suspension, I would slip and get some wheel hop only when it was really wet out off the line in a straight. With the coilovers, I will started breaking traction on dry pavement unless I carefully modulate the gas pedal to keep tires from spinning.

 

Thanks - I'll have to try disconnecting the rear sway bar and seeing if this helps alleviates the problem as one of my tests. As I mentioned originally, the first time I experienced tire lift around a corner was when I first installed the Rear F-Sport sway bar onto the stock non-sport suspension. Increasing the firmness of front damper definitely helped after driving to and from work today. It's also a heck of a lot firmer at 20 clicks compared to the 9 clicks, but the front end is much more composed. I might try to increase the rear damper firmness as well. It's very well possible that the rear springs aren't being dampened enough causing the outside rear wheel to compress too much and allowing the stiff sway bar to pull the inside rear wheel upwards with it. This may also reduce the traction issues off the line if the dampers are controlling the action back there at WOT. Anyhow, I'll play around and will update later this weekend.

 

Might have to play around with raising/lowering the front and rear of your car to determine if unbalanced roll centers could be causing excessive body roll in turns. I had to raise my rear slightly to reduce the roll. I ride on BC coilovers 12k/10k and fsport sways front and rear.

 

How does this impact AWD systems? I have the is250 AWD

 

the 250 /350 are still rwd with front wheel drive assist basically

ya disconnecting the rear bar will help you can at least do it easily

I wouldn't stiffen the rear shocks it will limit how fast the wheel can travel and cost you traction+droop

Id also look into if the right springs are on the right ends 10k up front and 8k in the rear

 

I mentioned an alignment purely to ensure the OP is properly maintainng his vehicle. Alot of people don't even consider getting an alignment done after messing with their suspension and they wonder why their tires do this or that and why they have this or that noise.

Regarding straight, off the line accelration and wheel hop...I messed ALOT with my FWD drag Civic and it's damper setups. Best place to hook...4 clicks from it's lowest setting on 12k fronts. If you want to help with accelrating off the line, look to drop the rear setting lower. Not sure what effect that will have on your "tire lifting" issue...but it's worth looking into.

 

Did you check the endlinks bolts for the clunk. I to had a clunk and it was the endlinks bolts not being tight enough.

 

Yeah I triple checked end link and sway bar bracket bolts. I even used locktite on them last month.