One rotor much hotter than other 3 - cause of vibrations? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

rexcramer · 12-09-2018, 05:54 PM

Have you measured the rotors for thickness? If the rotors are warped, you should feel it at almost any speed with your foot on the brake. Does it pull that way, when you step on the brakes? I don't remember from previous posts, what is your brake service history?

thom4782 · 12-09-2018, 06:28 PM

Here's a question...does the frequency of the vibration increase as the speed of the car increases. Asking b/c as the rotational speed of the wheel increases the time between the peaks and valleys of a warped rotor passing by the brake pads should decrease thereby leading to an increase in the frequency of the vibration.

Just a guess on my part of how the physics of a warped rotor translates into the feel in the steering wheel. My experience with an unbalanced tire suggests things could be more complicated in that I've felt stronger vibrations at speed.

356Guy · 12-09-2018, 06:49 PM

I like the idea of the rolling road test. Also, have you checked the front wheel bearings? My $0.02

911monty · 12-09-2018, 08:04 PM

You have been extremely patient over this, good on ya! The hot rotor is interesting. Don't know what year or system you have, but the ABS can activate either brake independently on the front on all years if a difference in rotational speed is detected and is usually a series of pulsations.. You might want to inspect your wheel speed sensors.

speedyspaghetti · 12-09-2018, 08:10 PM

Quote:

Originally Posted by 356Guy

I like the idea of the rolling road test. Also, have you checked the front wheel bearings? My $0.02

I replaced the front wheel bearings about 500 miles ago - did not make much of a difference. Haven't checked the rear bearings with the rotor off, but the wheels do not move at all at both 9&3 and 12&6. Can you explain what you mean by rolling road test?

911monty · 12-09-2018, 08:25 PM

Quote:

Originally Posted by speedyspaghetti

I replace the front wheel bearings about 500 miles ago - did not make much of a difference. Haven't checked the rear bearings with the rotor off, but the wheels do not move at all at both 9&3 and 12&6. Can you explain what you mean by rolling road test?

Again don't know what model or year you have, but the wheel bearings on some years have the speed sender as part of the bearing and need to be installed correctly.

speedyspaghetti · 12-09-2018, 08:37 PM

Quote:

Originally Posted by 911monty

Again don't know what model or year you have, but the wheel bearings on some years have the speed sender as part of the bearing and need to be installed correctly.

It's a 2002 S - it does not have PASM or TC, so I don't know if that has anything to do with it.

In regards to your other reply - thanks haha... it has been quite the journey. There have been times when I have wanted to just sell the car and maybe move onto a 60s Mustang to restore or an S2000 as an alternative to the Boxster... but I just love this car too much and I know how amazing it is when it is functioning properly... I don't want to give up on it yet.

As for the speed sensor - what could be tripping the ABS come on so frequently? Is there a way to check the speed sensor? When I replace the bearings, I did not notice any sort of sensor attached to them.

911monty · 12-09-2018, 08:49 PM

On your front and rear uprights there are two connectors, one is the brake pad wear sensor. The other is the speed sensor. You remove one bolt and pull the sensor out. make sure the hole the sensor inserts into is clean and you can see the reluctor rotating inside as you rotate the wheel. Also the sensor is magnetic and can become fouled by ferrous particles. Attached has the speed sensor. Usually recommended to remove while doing wheel bearings.

https://www.pelicanparts.com/catalog/SuperCat/1050/POR_1050_BRKHYD_pg4.htm#item17

speedyspaghetti · 12-09-2018, 08:09 PM

Quote:

Originally Posted by thom4782

Here's a question...does the frequency of the vibration increase as the speed of the car increases. Asking b/c as the rotational speed of the wheel increases the time between the peaks and valleys of a warped rotor passing by the brake pads should decrease thereby leading to an increase in the frequency of the vibration.

Just a guess on my part of how the physics of a warped rotor translates into the feel in the steering wheel. My experience with an unbalanced tire suggests things could be more complicated in that I've felt stronger vibrations at speed.

Yes, the vibration does the worse at speed - I took her up to 85 or so on my way home today and the vibration was at a higher frequency. Thank you again!

speedyspaghetti · 12-09-2018, 08:04 PM

Quote:

Originally Posted by rexcramer

Have you measured the rotors for thickness? If the rotors are warped, you should feel it at almost any speed with your foot on the brake. Does it pull that way, when you step on the brakes? I don't remember from previous posts, what is your brake service history?

I have not measure the rotors yet, but that is on my list now. It does not vibrate any more when I touch the brake, but the car does pull to the left when I accelerate at a low speed or even letting the car roll on a decline.

I bought the car at 76k and it is at 88k, I have not done anything to the brakes during that time.