na9ase

Hi all,

I have been doing my fair share of research on this but I have yet to come to a conclusive answer. For the most part, I can find scenarios similar to what I am experiencing but not exactly.

I drive a 2000 LS400 with 235xxx miles. My car has had this very annoying wobbling issue since I purchased it last year. When I am at highway speeds, the steering wheel gets very wobbly when I begin to brake. The shaking reduces the harder that I apply the brakes and disappears under about 50mph or so - the car becomes super smooth and no issues under braking whatsoever. I recently changed the brake pads and checked the rotors - they are not the issue. I also replaced the lower transmission mount to solve a shudder feeling in the drive train which did eliminate that vibration but did nothing to solve this wobbling. I am convinced that this is suspension related based on other posts and research. I have seen some posts about vibrations or wobbling but most are either constant wobbling or happen under braking but at all speeds. This only occurs for me above a certain speed threshold and the shaking weakens the harder I brake.

My thoughts are leaning towards the strut rod bushing BUT I am not so sure that I experience any knocking sounds like people describe in posts regarding the strut rod bushing. My alignment feels good and the car does not pull in any direction out of the ordinary. Are there any other telltale signs of bad strut rod bushings? I would assume that regardless of apparent issues, many of these old bushings are not in good shape but I am not looking to replace everything at once here. I have noticed the problem getting worse over time but it is a very slow increase if anything. Who knows - I might have just not given any thought to it originally because I chalked it up to brakes or was still enjoying the overall comfort of the car. But now this is becoming extremely annoying and I am going on a road trip in about a month and this does concern me.

Any help or ideas would be greatly appreciated. Cheers

djamps

Your front brake rotors are warped. Get new ones or have the old ones machined if there is enough material left.

na9ase

I really do not see how this could possibly be the rotors... If it were the rotors 1.) Would it not be a feeling in the pedal as well? Like the brakes are pulsing. I feel nothing unusual in the pedal at all. 2.) Wouldn't it happen at slower speeds too then?

Also - the rotors were not warped when I inspected them. Nothing major enough to be noticeable. (obviously I did not check it with any machines but visual and touch) I have seen much worse rotors.

djamps

Mine had the exact same issue, a pair or cryo treated rotors at rock auto (reused the existing pads since they had plenty of meat) and problem gone.

Mine weren't noticably warped (with the bare eye) either... they would have to be really, really bad before you see it with the bare eye...that's the point where you get it at all speeds and in the pedal, ect.

bradland

Can you elaborate on the details of the recent brake pad replacement ? I say this because I don't consider pad replacement to be a sufficient brake job. Especially on a car with over 200K miles...
Rotors may look ok but they need to be resurfaced when replacing pads. I always replace calipers as well when doing front brakes since they get approx 70% of the braking load. It just doesn't make sense to take shortcuts where brakes and safety are concerned. Those calipers experience EXTREME heat cycling and with 2 pistons per side that's just more moving parts and seals potentially compromised. Old brake fluid can easily take on a little moisture which results in corrosion inside the caliper and all of a sudden one caliper piston doesn't move in unison with the others and the caliper starts sticking slightly at certain speeds. When servicing brakes be as thorough as possible.

Almost every LS400 on the road today needs strut rod bushings. I think this problem would be much more prevalent if that was the culprit...

djamps

The front LS calipers are oversized one-peice units designed to last the life of the car... replacing them on routine brake jobs without due cause would be overkill and very damaging to your checkbook.

na9ase

Do you remember which brand of rotors you got? Centric, Bendix, Dura-go, Beck Arnley. There are lots of options here for pricing - not interested in drilled rotors here. For what it's worth I got the Akebono brake pads.

As far as the brake job - I know doing the rotors at the same times is standard procedure but personally I find replacing the calipers every time the pads need replacing to be pretty overkill. But nothing to elaborate on here - just got pads and was hoping to get away without new rotors/machining mine because they looked alright. I guess looks can be deceiving.

djamps

I used the centric cryo's on every car I own, never had one warp prematurely even on cars with known issues with this (my QX56 eats 'standard' rotors for lunch).

na9ase

Thanks for the help I will order those up and report back if the wobble is still here.

djamps

Another thing I like about these rotors is they all have black anti-rust paint... small details go a long way in the looks department and reduce the likelyhood you'll have to bang them off with a sledge hammer down the road.

billydpowe

iTrader: (1)

my 99 was doing this and I ordered this (Front Kit 2 OE Replacement Optimum Series Brake Rotors 4 Ceramic Brake Pad 5Lugs) for 68.00 put them on and now it is smooth... this was last week..213k miles

na9ase

Back in as a follow up - you were all wrong hahahahaha!

Well yes and no.

I ended up replacing my strut rod(bar) bushings by buying brand new OE bars with the bushings in them. (I did not want PU bushings and I found a good deal on the bars) Those bushings turned out to be the real culprit behind the serious vibration and wobbling in the steering wheel. Now that I have replaced those I do feel a slight vibration (under braking only) that is indeed the rotors. BUT the nastier symptoms that I was experiencing were due to the strut bar bushings being shot. After I replaced them, the car no longer had vibrations at slower speed braking, the steering wheel shudder was gone under braking, and the cruising vibrations at highway speed were eradicated.

For anybody dealing with this issue in the future - it is hard to explain the different sensations until you start replacing parts and discover what is causing each feeling. I was mistaken in thinking that all of the vibrations, wobbles, and sounds were caused by the same thing. The best advice I can give is that if your strut bar bushings are shot, you will feel some serious wobbling in the steering wheel and the whole experience feels like the front end is a bit unstable. With that issue corrected - the rotor issue is much easier to determine. If it's simply a vibration feeling under braking with little to no vibrations while cruising and minimal steering wheel shudder then it is most likely just your rotors.

Replacing the strut bars was fairly easy - some of the bolts are tough to get out. You may need to anchor your back against a wall or another car and use your foot to loosen them. Overall it was about a 3 - 4 hour job and I did get an alignment afterwards just to be sure things were not messed up during installation.

dabrook

I still had the problem after doing a front brake overhaul, but then I got the tires rotated and balanced and the problem was solved.