steering wheel shimmy - 986 Forum - The Community for Porsche Boxster & Cayman Owners

jiggysubman · 12-02-2005, 07:10 AM

I've got a pretty bad steering wheel shimmy starting at about 50mph, and getting worse as speed increases. What are possible causes/fixes for this? Any help would be appeciated.

RandallNeighbour · 12-02-2005, 07:21 AM

wheel balancing is your culprit. I've got it too after FIVE trips to discount tire, last of which was a "road force balance" job on all four wheels, which is what you should find.

If you can find a local speed shop that specializes in balancing wheels on cars that are driven over 100 mph, that's where you should take it.

Boxsters seem to have this problem frequently and keeping the wheel from jiggling is going to be one of those things you'll work on a lot. You'll also learn to determine the difference between road feel and shimmy due to an unbalanced wheel.

Brucelee · 12-02-2005, 07:34 AM

Randall is dead on. Find a first class shop.

12-02-2005, 07:49 AM

Hey jiggysubman, when you get this problem resolved, you might need to change your screen name! Maybe to....smoothsubman!

prOk · 12-02-2005, 04:43 PM

Heh.. I had the same problem. I took it to all the usual tire places and had their 'best' balancing job done and could never get rid of the shimmy. Wound up finally breaking down and took it to the dealer. Their tire guy balanced them smooth as silk, I mean, zero shimmy. 49 bucks well spent in my opinion.

/b

deliriousga · 12-02-2005, 05:21 PM

Quote:

Originally Posted by jiggysubman

I've got a pretty bad steering wheel shimmy starting at about 50mph, and getting worse as speed increases. What are possible causes/fixes for this? Any help would be appeciated.

For future reference, if it starts at lower speeds and/or in the steering wheel is usually the front tires. Higher speeds and/or in the seat is usually the rear tires.

How many miles do you have on her? If balancing doesn't take care of it and you have a pretty good amount of mileage, check the ABS sensors to make sure they're not caked up with metal brake flecks. That keeps them from feeling the wheels moving then they think "holy cow, he's doing 90 and the wheel is locked up" and start fluttering to release the pressure. That one gets violent when the speed gets up there.

jiggysubman · 12-03-2005, 12:45 PM

Quote:

Originally Posted by deliriousga

How many miles do you have on her? If balancing doesn't take care of it and you have a pretty good amount of mileage, check the ABS sensors to make sure they're not caked up with metal brake flecks. That keeps them from feeling the wheels moving then they think "holy cow, he's doing 90 and the wheel is locked up" and start fluttering to release the pressure. That one gets violent when the speed gets up there.

i've got 81k on my 97. Perhaps i should look intot this being the problem as well. The drivers side of the car shakes as well starting around 80. Can you tell exactly where to look for these metal brake flecks?

deliriousga · 12-03-2005, 08:40 PM

Quote:

Originally Posted by jiggysubman

i've got 81k on my 97. Perhaps i should look intot this being the problem as well. The drivers side of the car shakes as well starting around 80. Can you tell exactly where to look for these metal brake flecks?

When you take the wheel off, there is a sensor for the ABS that plugs into the top of the steering knuckle. It is held in with one screw. The sensor goes through the knuckle with the bottom exposed just above the teeth on the axel. The sensor uses a magnet to sense those teeth moving past it. Since brake pads are "semi-metalic", some of the brake dust collects on the magnetic end of the sensor. Over time it can cover it with dust so the magnet in the sensor feels the dust sitting still and can't feel the teeth moving through that dust.

Unscrew the sensor and twist it lightly to slide it out. Be careful not to twist it too hard because you can break the sensor (I had a mechanic do this once and found out when the brakes let go.

) When you put it back in, put some anti-sieze on the sides of the sensor, but make sure you don't get it on the end where the magnetic feeler is.

jiggysubman · 12-04-2005, 08:30 AM

Quote:

Originally Posted by deliriousga

When you take the wheel off, there is a sensor for the ABS that plugs into the top of the steering knuckle. It is held in with one screw. The sensor goes through the knuckle with the bottom exposed just above the teeth on the axel. The sensor uses a magnet to sense those teeth moving past it. Since brake pads are "semi-metalic", some of the brake dust collects on the magnetic end of the sensor. Over time it can cover it with dust so the magnet in the sensor feels the dust sitting still and can't feel the teeth moving through that dust.

Unscrew the sensor and twist it lightly to slide it out. Be careful not to twist it too hard because you can break the sensor (I had a mechanic do this once and found out when the brakes let go.

) When you put it back in, put some anti-sieze on the sides of the sensor, but make sure you don't get it on the end where the magnetic feeler is.

this may be asking a lot but does anyone have a picture that points to this sensor, or shows the general area? I'm looking at taking off the wheel today.

12-04-2005, 08:31 AM

Tools Pants will probably be sending a picture any minute now!

deliriousga · 12-04-2005, 12:43 PM

Here's a layout of the different components. The sensors are in section #4:

jiggysubman · 12-04-2005, 06:10 PM

well i found them, however upon trying to remove the bolt that holds it in place, the head stripped right off. these must not have come out since they were put in. urgh, so now i have to get my hands on a tap set to remove those bolts. This is become more of a project than i thought it would.

deliriousga · 12-04-2005, 07:32 PM

That stinks. Sorry to hear about the screw head stripping.

Have you tried the re-balancing yet? If not, try that before you continue working on the sensors. I usually try balancing, then check the bearings and ball joints for play and go to the sensors if those aren't the cause. I clean the sensors at each pad change so that's usually not a problem for me any more.

As you said, the sensors have probably never been removed. With the other screws, put the allen wrench (sockets are better) in the screw and take a hammer and smack it with medium force several times to break up the rust that has formed on the threads. That gives it an impact wrench effect. Also, make sure the allen receptical in the screw is completely cleaned out and the allen wrench goes in all the way.

jiggysubman · 12-04-2005, 07:45 PM

actually mine arn't allens, they are nuts, 11mm to be exact
working on the submarine that i call home 5 months out of the year, we use a kind of rust buster spray on parts that are exposed to sea and get rusted out. I'll try some of that on the other nuts before trying to remove them.
But you're right, I suppose the next step is trying a balance before getting that deep into the sensor job.

deliriousga · 12-05-2005, 03:44 PM

You might want to look around back and see if you can spray some brake cleaner from the behind to clean them off a little. Hopefully the balancing will take care of the problem.

jiggysubman · 12-18-2005, 06:04 AM

took the car to the dealership yesterday to have the tires balanced. Not only that, but they did it for free! On top of that, they gave me one of those alum crush ring seals for oil plug for free as well. And I got to sit in a CaymanS. A very fruitful day indeed!

12-18-2005, 09:39 AM

Being a true hero for the USA, you deserve it!

jiggysubman · 12-18-2005, 11:19 PM

Quote:

Originally Posted by bmussatti

Being a true hero for the USA, you deserve it!

hey thanks. everyone has a job to do. Mine is going to sea to protect you guys. I take pride in it.