Wheel Bearing Contact Spring - PeachParts Mercedes-Benz Forum

tobybul · #1 05-01-2007, 12:12 PM

What is the purpose of the wheel bearing contact spring located in the dust cap??

Whiskeydan · #2 05-01-2007, 12:14 PM

Static discharge I believe.

Motorhead · #3 05-01-2007, 12:42 PM

It is to make sure the brake rotor is GROUNDED so your brake pad wear sensors will work.

Carson357 · #4 05-01-2007, 01:13 PM

Quote:

Originally Posted by Motorhead

It is to make sure the brake rotor is GROUNDED so your brake pad wear sensors will work.

those were installed on cars even before the brake pad sensors were used, i was told by a long time mercedes tech who assures me they do provide ground to reduce radio interference from static electricity. the ones on my car are long gone, and my radio is fine, maybe was for older technology electronics.

Motorhead · #5 05-01-2007, 03:03 PM

Quote:

Originally Posted by Carson357

those were installed on cars even before the brake pad sensors were used, i was told by a long time mercedes tech who assures me they do provide ground to reduce radio interference from static electricity. the ones on my car are long gone, and my radio is fine, maybe was for older technology electronics.

Cool... We learn something NEW every day. I was told that it was for the pad sensors. AM radio seems MORE static sensitive. Maybe that was what it was for.

rrgrassi · #6 05-01-2007, 03:06 PM

My car has them missing as well. No probs with radio reception, AM or FM.

Bajaman · #7 05-01-2007, 03:16 PM

I would tend to agree with the radio idea. The brake pad sensors are likely magnetic and don't need grounding.

rrgrassi · #8 05-01-2007, 03:36 PM

Quote:

Originally Posted by Bajaman

I would tend to agree with the radio idea. The brake pad sensors are likely magnetic and don't need grounding.

Acutally, the pad wear sensors both need to contact the rotor to complete the circuit. I used a jumper to connect the sensors to test the wiring since some $#%@ rodent decided it liked wires. The wear light came on each time.

Whiskeydan · #9 05-01-2007, 03:52 PM

Quote:

Originally Posted by Carson357

those were installed on cars even before the brake pad sensors were used, i was told by a long time mercedes tech who assures me they do provide ground to reduce radio interference from static electricity. the ones on my car are long gone, and my radio is fine, maybe was for older technology electronics.

Correct.
Tires on pavement generate a lot of static which could discharge thru the bearing grease causing noise on an AM radio. This little spring creates a path for the static to silence the noise.
An FM radio is somewhat immune since it is not detecting amplitude changes.
Could be the grease is more conductive these days.

toomany MBZ · #10 05-01-2007, 03:58 PM

[quote=Whiskeydan;1495368]Correct.

Agreed.

whunter · #11 05-01-2007, 05:04 PM

Quote:

Originally Posted by Whiskeydan

Static discharge I believe.

Car audio noise reduction.

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Have a great day.

Whiskeydan · #12 05-01-2007, 09:52 PM

QRM reduction.

73,
N5MRG

#13 05-02-2007, 12:10 AM

I have a CD with a bunch of .pdfs of W115 maintenance instructions, and I was just looking at the ones for wheel bearings. One of them mentions removing the radio spring (or clip or something) during dissasembly.