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  #1  
Old 08-16-2003, 05:32 AM
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Join Date: Feb 2003
Location: London, UK
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Front Brake Pad off resistance W126

What road wheel turning resistance should a 1990 420se have withe wheels clear of ground, brakes off and wheels rotated by hand. I was under the impression wheels should spin freely without resistance to rotation. Mine have a constant resistance to rotation. Calipers are Bendix and seals were replaced 5000 miles ago.

Thank you for any help.

Bill
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  #2  
Old 08-16-2003, 12:30 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
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Depending on the grease and wheel bearing setting, you will have some resistance. If the wheel won't turn easily with light hand pressure, the wheel bearings are bad or too tight, but it won't spin very long after you give it a good twirl even in perfect condition.

Any roughness in rotation, growling, grinding, binding, or ratcheting is a sign of bad wheel bearings.

Peter
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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #3  
Old 08-16-2003, 02:40 PM
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Thank you Peter for you reply.

Wheel bearings are fine, MB grease, set with dial gauge.

The pads rub on the discs when brakes are not applied. Is this normal and if so what is an acceptable turning resistance.

Bill
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  #4  
Old 08-16-2003, 05:16 PM
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Location: Evansville, Indiana
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If there is a significant difference between the drag with the pads in (after pressing and releasing the brake) and with the pads out, suspect old tired piston seals in the calipers.

A gently push should eaily turn the wheel, but dont' expect it to keep spinning more than half a turn or so, if that. You should be able to turn the wheel with you palm flat on the tire without pressing down more than a tiny bit.

There is always some noise from the pads brushing the rotors, they never move very far away, but it should only be a hissing noise that doesn't add any drag to speak of.

If stepping on the brake and then releasing it makes the wheel very hard to turn, one or more pistons is sticking in the bore.

Peter
__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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  #5  
Old 08-18-2003, 01:13 AM
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Join Date: Jan 2003
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Calipers or Hoses

I agree with the previous post, the caliper may not be releasing properly, which maybe due to the piston, but also check the emergency brake cable to ensure it is releasing properly. Also, the brake hose, attached to the caliper maybe rotting on the inside, and restricting the fluid flow. Have you ever flushed your entire brake system? The MB manual recommends replacing brake fluid annually.
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