Brief Venting Moment about Brakes - PeachParts Mercedes-Benz Forum

VA-Merc · #1 01-30-2014, 04:22 PM

I am feeling pretty frustrated right now. I have been battling a brake vibration in the 87 for months now. I replaced my front rotors and pads last spring. No issue until last fall when this vibration popped up. I thought...well it's gotta be the rears since I just did the fronts. I replaced rear pads and rotors...did the proper bedding procedure etc. Still had a vibration although it felt a bit different. Then I thought well maybe the fronts warped again. I just dropped some $$ on some ATE rotors from Pelican this month...still have the same issue! Brake pins slide in and out freely....none of the wheels feel excessively hot after driving, no pulling, hubs are clean. I think I am going to pull the rear rotors (which have 2,000 miles on them) and have them resurfaced just to see if it gets rid of it (they were lower-quality centric rotors). Also I measured the bearing end-play with my dial indicator....still in spec.

Okay, just had to vent about it for a minute haha.

nelbur · #2 01-30-2014, 05:32 PM

Quote:

Originally Posted by VA-Merc

I am feeling pretty frustrated right now. I have been battling a brake vibration in the 87 for months now. I replaced my front rotors and pads last spring. No issue until last fall when this vibration popped up. I thought...well it's gotta be the rears since I just did the fronts. I replaced rear pads and rotors...did the proper bedding procedure etc. Still had a vibration although it felt a bit different. Then I thought well maybe the fronts warped again. I just dropped some $$ on some ATE rotors from Pelican this month...still have the same issue! Brake pins slide in and out freely....none of the wheels feel excessively hot after driving, no pulling, hubs are clean. I think I am going to pull the rear rotors (which have 2,000 miles on them) and have them resurfaced just to see if it gets rid of it (they were lower-quality centric rotors). Also I measured the bearing end-play with my dial indicator....still in spec.

Okay, just had to vent about it for a minute haha.

You don't mention the nature of the vibration. The only brake related vibration I am familiar with is a once per revolution pulsation from warped rotors, or more likely pad bits welded onto the rotors. If it is more of a rumble it is likely to be from a rough bearing or feathered tire tread. Just because you feel it when you brake doesn't mean it is a brake problem.

colincoon · #3 01-30-2014, 05:41 PM

Did you rebuild the calipers? If not then you probably should, or buy rebuilt units. This fixed my vibration issue.

Also brake lines fixed a separate vibration issue on another car. Try those first, they are cheaper than rebuilt calipers.

65aircooled · #4 01-30-2014, 06:38 PM

Does this vibration involve boobs shaking in any level?... sorry, couldn't help myself

sixto · #5 01-31-2014, 01:39 AM

I had an occasional brake pulsing that I traced to a worn LCA bushing.

Sixto
87 300D

VA-Merc · #6 01-31-2014, 08:41 AM

This is why I love this forum...came here mainly to vent for a minute and I walk away with lots of advice! It's sometimes good to look at it from a fresh perspective.

The nature of the vibration is a pulse I can feel with every revolution. At high speed...it is rapid and more noticeable. At low speeds you can feel the pulse still....it's just not as annoying. I did rotate the tires to see if that would change the feel at all....it did not. Also, I should mention that braking performance still feels really good...just comes with vibration. The steering wheel does not shake...I feel it in the floor (which is why I was thinking the rear end might be suspect at this point).

Someone mentioned wheel bearings. When I changed the rotors both times I pulled the bearings and re-packed them/adjusted with the dial indicator method. I also do not hear any noise or feel any looseness from them.

Someone also mentioned the calipers...I have not touched them or the hoses. The hoses do not have any bulges or cracks...but I guess it doesn't mean they aren't bad. I honestly just didn't think that the hydraulic side could cause this...but I have been known to be wrong plenty of times

.

Someone mentioned the boob test....haven't done that yet lol.

whunter · #7 01-31-2014, 10:06 AM

Quote:

Originally Posted by VA-Merc

This is why I love this forum...came here mainly to vent for a minute and I walk away with lots of advice! It's sometimes good to look at it from a fresh perspective.

The nature of the vibration is a pulse I can feel with every revolution. At high speed...it is rapid and more noticeable. At low speeds you can feel the pulse still....it's just not as annoying. I did rotate the tires to see if that would change the feel at all....it did not. Also, I should mention that braking performance still feels really good...just comes with vibration. The steering wheel does not shake...I feel it in the floor (which is why I was thinking the rear end might be suspect at this point).

Someone mentioned wheel bearings. When I changed the rotors both times I pulled the bearings and re-packed them/adjusted with the dial indicator method. I also do not hear any noise or feel any looseness from them.

Someone also mentioned the calipers...I have not touched them or the hoses. The hoses do not have any bulges or cracks...but I guess it doesn't mean they aren't bad. I honestly just didn't think that the hydraulic side could cause this...but I have been known to be wrong plenty of times

.

Someone mentioned the boob test....haven't done that yet lol.

It only takes one dragging brake piston to warp a rotor.
Brake:

Some Facts About Brake Hoses:
#1. The industry standard average safety life of a brake hose is six years. FYI data SAE: J1401, J1703, J1705, J1873, J1406, J1288, J1403, J1833, J1402.
#2. Brake hoses deteriorate from the inside as well as the outside.
#3. Moisture is absorbed into brake fluid systems through brake hoses.
#4. Contaminants in brake fluid act abrasively on the inner wall of brake hoses.
#5. The brake hose reinforcing fabric deteriorates through expansion and moisture.
#6. High operating temperatures contribute to the deterioration of hoses.
#7. Brake hoses swell with age and restrict flow.
#8. Generally all brake hoses on a vehicle deteriorate at the same rate, So all hoses should be replaced if one is found to be faulty!

Brake hose failure mode:

#A. Rupture (burst hose) = age, exercise (too many miles) or impact are the typical cause.

*B. Partial internal collapse = the inner ply becomes damaged/detached acting as a partial restriction and/or one way valve.

#C. Full internal Blockage = the inner ply becomes damaged/detached acting as a plug = brake pedal still feels good but there is no brake application.

.

nelbur · #8 01-31-2014, 02:10 PM

Quote:

Originally Posted by VA-Merc

This is why I love this forum...came here mainly to vent for a minute and I walk away with lots of advice! It's sometimes good to look at it from a fresh perspective.

The nature of the vibration is a pulse I can feel with every revolution. At high speed...it is rapid and more noticeable. At low speeds you can feel the pulse still....it's just not as annoying. I did rotate the tires to see if that would change the feel at all....it did not. Also, I should mention that braking performance still feels really good...just comes with vibration. The steering wheel does not shake...I feel it in the floor (which is why I was thinking the rear end might be suspect at this point).

Someone mentioned wheel bearings. When I changed the rotors both times I pulled the bearings and re-packed them/adjusted with the dial indicator method. I also do not hear any noise or feel any looseness from them.

Someone also mentioned the calipers...I have not touched them or the hoses. The hoses do not have any bulges or cracks...but I guess it doesn't mean they aren't bad. I honestly just didn't think that the hydraulic side could cause this...but I have been known to be wrong plenty of times

.

Someone mentioned the boob test....haven't done that yet lol.

A once per revolution pulse IS likely a brake issue. A warped rotor is easy to find as you can spin the rotor, with something setting on the ground nearly touching the rotor, so you can see the wobble. However, pulsing is not always due to warped rotors. You can develop a rough spot on a rotor, apparently cause by metal bits from the pad welding to the rotor. In this case the rotor will eventually wear smooth again, or you can sand it smooth if you can see the spot.

VA-Merc · #9 02-01-2014, 04:53 PM

Good thoughts...I guess I shouldn't just chalk it up to cheap rotors so quickly then. I can proactively replace the hoses...I don't think that should be a major job. I will try to figure out exactly which rotor is warped....that would really help me and has been kind of difficult to figure out. That was one reason I was going to get the rears turned...that way I could isolate if it was a rear or front issue before I throw parts at it. I'll try to see if I can visualize a warped rotor as someone suggested by putting an object on the ground near it.

Stretch · #10 02-01-2014, 05:25 PM

You've owned up to using a DTI to set your wheel bearings - use it to measure the run out (Luke)

Diesel911 · #11 02-01-2014, 07:30 PM

Quote:

Originally Posted by 65aircooled

Does this vibration involve boobs shaking in any level?... sorry, couldn't help myself

Does this vibration involve Male or Femal Boobs?...Sorry, couldn't help myself

Vibration effecting Male Boobs being more severe then; well you get the picture.

Chris W. · #12 02-01-2014, 09:38 PM

Not that you would, but don't ignore what Sixto said - it is one possible reason you are feeling the pulsing.

Rgds,
Chris W.
'95 E300D

vstech · #13 02-01-2014, 10:39 PM

at high speed, just BARELY touching the brakes, do you feel the pulse?

I think the caliper could easily be causing the pulse. if one piston is seized, it'll try to TWIST the caliper, and you will feel a pulse from all manner of parts of the car.

if the pads are new, check them all and see if any are thicker than their mate...

VA-Merc · #14 02-03-2014, 08:45 AM

Sorry guys didn't get a chance to check this all weekend...I don't know why I didn't think of using the dial gauge to measure run-out...seems pretty obvious. What amount of run-out would cause a noticeable vibration?

I will check the LCA bushings as Sixto mentioned. They are not completely cracked/falling apart...what is the preferred method for determining if they are worn enough to need replacing?

Also vstech, at high speed (55mph or above) just barely touching the brakes it is extremely noticeable. At lower speeds you notice it as the one pulse per revolution kind of feel but at higher speeds it is really obnoxious. After a drive none of the wheels feel hotter than the others. On the fronts the brake pad wear looked perfectly even when I changed the pads and rotors last week. I guess I should also mention that I do torque lug nuts to 80 ft. lbs (spec in my owner's manual) so uneven torque shouldn't be suspect either.

When this rain dies down I will check for rotor warpage with my dial indicator, pull the rear pads and check for uneven wear, and also look for suspect lca bushings. I probably won't be able to until Thursday with all the rain they are forecasting...oh well. Anything else I should be checking?

whunter · #15 02-03-2014, 09:44 AM

How much lateral runout can cause a detectable brake pulsation ?

Maximum total lateral runout: 0.12 mm = 0.004724395 inch.

In my experience, few drivers will notice until lateral runout is near 0.015 inch per side.

#########################

Typically this junks the rotor.
There is only "1" mm (0.03936996 inch) per side before minimum thickness.
* Subtract 0.02 inch per side for normal wear.
* Subtract 0.02 inch per side for lateral runout.

Brake lathe cutting the used rotors 0.02 inch per side for truing lateral runout.

Leaving each rotor face -0.00063004 inch per side, beyond the minimum (DISCARD) specification.

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