99 ls 400 137k

I've noticed it rides better with a full tank. When I let it go down to an 1/8 of a tank theres a noticeable wobble a higher speeds. And braking at higher speeds.also braking at low speeds just before a stop.

Any ideas?

 

there's something called a rear carrier bushing that can cause a wobble/shimmy at the rear

i've also noticed an ever so slight increase in ride quality in any car with more weight in the back, there's a reason jeremy clarkson filled his lorry truck with bricks to improve the ride quality during the burma special... and then proceeded to dump all the bricks into the road when the increased weight prevented him from being able to climb a relatively mild hill

idk just put something heavy in the trunk if you can't be bothered to properly track this down lol

 

So keep the sand in there year round? That works. Small MPG penalty, but to chase what the problem is is an unknown cost rabbit hole it could be a better option.

I'm surprised you can tell the difference to be honest. A full tank only weighs about 120 pounds. That's not much weight in the scheme of things.

Do a good inspection of the suspension to see if anything is obviously broken or really worn down?

 

Check your brake rotors, I got the same problem with my SC430. After I replaced the front rotors and pads everything is good. Good luck.

 

i'm sure it's more in my head than anything lol

 

Honestly I'm pretty sensitive to cars and weird noises\feelings, but I barely notice when I have a 200lb friend riding shotgun. Or a bunch of groceries and **** in the back.

The cars still a boat regardless of how much it's weighed down lol

 

Pretty good on the OP for being able to notice a difference and that it is correlated with fuel level.

A full tank should be a little over 160 lbs more than an empty one.

As a debugging step, I'd recommend to run the tank down to near empty, confirm the problem. Then load 150lb of weight in the trunk and see if the problem instantly changes. Not suggested as a permanent solution, just for test purposes.

The other possibly related thing is if you have the fuel pump inside the tank (mine is on my '91, not sure about other years) - there could be some sort of soft failure when it gets hot due to not being fully submersed with a near-empty tank. I know if that happened it would cause an engine performance issue, but maybe you feel it in the vehicle dynamics.

 

If your shocks are original, then i would suggest replacement. My 99 has 151k on it and its on original shocks. It feels like it noticeably dives and squats when accelerating and braking which gives me a very uneasy feeling. The shocks just feel very very soft but I don't think that they're blown.

As a contrast, I had a 97 that I had replaced the front shocks with KYBs and rears had been replaced with GR2s by previous owner. This car felt much tighter and confidence inspiring.

I'm trying to decide between putting H&R lowering springs with KYB ExcelG shocks or just replace the front shocks with Bilstein HD shocks to improve the ride control and body movement.

 

In the research I've done, putting lowering springs and stiffer shocks will ruin the "lexus plush" for lack of a better term. Yes the car handles a lot sharper and everything, but it's not setup to be that stiff and won't be as smooth as a car designed to be that stiff from the ground up.

I've been contemplating on doing the replacement as well. But I think personally I'd go with the Bilsteins because I want to stay as close to the OEM ride quality as possible.

 

yes the H&Rs definitely take out some of the lexus plushness, like you said it's still basically a squishy boat but now with quite a bit less suspension travel so bumps are all more harsh and noticeable, and everything is now out of calibration

stock really is just the best way, i'm so happy i'm back to it again... the lowered on 18s phase was fun and all but considering how much engineering went into making this actually be like the nicest riding car ever i couldn't take knowing i was undoing all the hard work of its designers

 

Thanks ,l`ll defiantly check the rear carrier bushing.

Is there a test procedure? You know like checking ball joints ie: putting a big bar under the wheel and checking for play.

As far as just keeping weight in the trunk. I`m too **** for that. Lol

 

Great idea! Thanks

I`m old school I drive older nice vehicles .pay cash for them and keep them going as long as possible. I can fix most thing on a car and am in tune with any noises or ride differences.

 

Yes, you can check it with a bar, or just your hands try wiggling each way. Also you can grab onto all the suspension arms and try to move them. Any play is no good. You will also be able to see if any of the rubber is badly dry rotted and cracked.
This is the carrier bushing he's talking about. http://www.lexls.com/tutorials/suspe...abushings.html

 

Ok, that's what I was worried about. Do you think with new Bilstein shocks the body diving and pitching will be noticeably less? Because there's a guy selling KYBs and H&Rs for 175 near me so i was considering it since it's basically plug and play on all 4 corners.

 

Stock everything or you will have poor ride!