Steering Wheel Vibration

[comicbook8@gmai]

HI ALL
JUST WONDERED IF ANY YOU GUYS HAD OPINION ON THIS,
when i brake at speed i get a strong vibration on steering wheel and a pulling to the left .my anti roll bar bushings need replacing could they effect it or am i in for something a little more interesting !!! . also anyone know the symptoms of a sticking caliper piston ? im getting a rattle noise from my left rear hub when i hit a bump or speed ramp and have uneven wear on the brake pad ,like the pad is loose in caliper and knocking off the hub
thanks guys !!

[Cking1975]

Warped Rotors

[mikepellegrini]

+1 Warped Rotors

[Spidey944]

replace the rotors, dont just have them resurfaced. The warpage will come back within 6 months in most scenarios.

If your pull contunues after this, have the alignment checked. If it's OK, take that car for a drive, get the brakes warmed up with some normal driving, then use an infrared thermometer to check the brake rotor temps. The hot one will more then likely have the issue. Could be a piston hanging up, or simply frozen hardware. You can slowly apply the ebrake while driving straight to eliminate the rear rotors as a poss. cause. If you get a shake while slowly applying the ebrake, then it's the rears.

[924Sman]

May as well have a look at the bearings too. If all this car is driven is on the street I kind of doubt the rotors are warped, takes a ton of heat to even warp one and street use is not going to get them that hot. Now having said that if the rotors on the rear got hot like on the track and you set the E brake then yes it is very possible one is warped. But your vibration is only upon braking and a warped rotor will vibrate at any speed not just at one. It would feel just as if the wheel was not true, constant vibration.

The pistons may have brake dust damage and or debrie sandwiched in the piston bore were the rubber seal is supposed to be around the piston.

Dal

[DSPTurtle]

Don't forget to check the tires. While the rotors is the most likely suspect, I once had a belt on a tire separate and it had the exact same symptoms.

[Cking1975]

I will have to disagree about the warped rotors and only street driving. Many factors lead to warped rotors and all cars can get them...even cars with a few thousand miles on them.

[flash968]

rotors almost never warp - this is an urban auto myth that continues to boggle my mind - what happens is uneven deposits on the rotors cause vibration - turn them and it is gone - unfortunately, many rotors cannot be turned and the result is the same as if they were indeed warped - they still have to be replaced - the most common cause of this is poor break in of pads and/or rotors, and very often people who do a pad slap and don't surface the rotors at the same time

there is a really good article explaining this at the stoptech site

my guess is that your problem is a control arm bushing

[924Sman]

Thanks Flash. Porsche rotors are pretty stout especially turbo rotors, they were designed to get red hot and maintain stopping ability. Now if one decided to take a dip in a puddle of water when hot that is another thing, but even then a crack would be more of an issue than warpage.
My thinking is the piston is hanging up on one side of the caliper causing uneven pressure on the pad which results in uneven wear. A good cleaning or rebuild may be the answer, trouble is finding a caliper rebuild kit.


Dal

[flash968]

calipers usually don't hang up just part of the time - they generally jam and stay that way

seriously, i would take a look at the suspension - i've been through this on another car with a similar design (bmw) and it is a common problem, especially if you have anything leaking down there

i'm betting on a castor block or control arm bushing - they are very well known for failing - remember, every original rubber component on the car has long since gone past its life expectancy - when you brake, you change the load on these, and it can easily result in both a vibration and a pull (castor is the adjustment for pulling) - it takes very little play to create this symptom

you can probably see signs of this in the tire wear - there should be some scrubbing on a corner

[comicbook8@gmai]

thanks for the input you guys.
i was quite fancying a new set of rotors, i will have 2 get busy on those bushings and the rest , would wd-40 be good for cleaning up that rear caliper ?
unfortunatly previous owner tracked her at mondello park in ireland , i came accross the pics on the porsche club ireland website red 944 s2 , looks good in action !!

[flash968]

do not use wd-40 - it contains a solvent that will dry up and eat rubber - use a brake cleaner

[924Sman]

By hanging up I mean the piston is not flush to the pad backing, one side is touching the other not touching, calipers don't do anything but hold it all together as it is fixed the float is in the pads/pins. Hope that makes my statement clearer.
Yes no doubt there are more issues on the suspension components that play into the problem.

One thing you want to check is the power steering hose from the tank, it is a known leaker and the fluid drips down on the passenger side swaybar bushing and it too eats up rubber. That I know to be true as it melted my bushing. But did not have the symptoms Flash mentioned on the braking or pulling, in my case it was all good, just a knock of the bar tapping the control arm and a big dip on a hard right hander. This not to disagree with Flash just in my case your symptoms did not occur....But heck I have a 924S and have no need for braking.

Dal

[flash968]

lol - i used to say that about the mgb

yeah, there are a couple of things that can cause pulling, but ruling out the brakes is easy - use a thermometer (no, not the one your mommy used when you felt icky) - one will be hotter than the other

[petrolhead611]

Holding the car on the footbrakes at a stoplight after really hard braking prevents the heat from disipating evenly from the rotors, hence warping.

[Lapponia]

+1 Dal. I would say if car is pulling to one side when breaking, a caliper piston is sticking in opposite side. One never knows when dirt and water will contaminate a piston/cylinder and make it to corrode and thereby jam the piston. A loose or damaged piston seal is not uncommon here. I would suggest to jack up the car in front, take off the wheels and pull out the brake pads. A piece of wood smaller than the brake pads are to be placed between piston and rotor, then operate the brake lever. If piston now presses the wood piece against rotor, this piston is OK. If one is not, it is jammed and probably cause of the issue I think. And it is wise to check movement of the caliper floating frame too
------------------------------------------
Lapponia

[924Sman]

If his swaybar rubber is shot I'll say the cylinder rubber is to and it also has to endure the heat from the brakes.

Dal

[flash968]

sway bar rubber is usually from leaks getting on them - yes, like anything rubber, age will deteriorate them, but when a caliper seal goes, it usually goes all at once - if a caliper hangs up, the car will usually really dive, not just pull, especially if it's the front

again, it should be easy to tell if you use a thermometer

[924Sman]

Flash wouldn't you agree that the best fix is to grab a wrench and start replacing the front end components, he is beyond a temp reading at this point... IMHO!

Dal

[flash968]

probably, but given the predominance of the "fix only what i have to, as cheaply as i can" that seems to accompany these cars, i presumed that an accurate diagnosis would be in line first

but yes, at this point, i would at least be looking long and hard at the front suspension - way too many cars are out there on old and tired components - people often continue drive on them because they don't know any better - once they are replaced, it's like a whole new car, and they kick themselves for not having done it sooner

clearly i am the other extreme, but i drive my car very hard - that's why i replace things BEFORE they need it - i want this car in top shape always