vibration when braking hard
 

Noob question, but when I brake from higher speeds (like 45-55) and a good amount of pressure on the pedal I get some pretty bad vibration throughout the car.

I got new front brake pads almost a year ago, put on by a local shop here, but they didn't mention the rotors needing replaced.

I have just had a lot of work done recently so I want to not take it back, but can I assume I have a warped rotor, or worn down rotor... is there any other thing that it could be....

when I softly apply the brakes I get no vibration...

I can get the rotors for about $50 shipped, but is this a job a novice can handle. I have only done brakes once with my Dad, but I have a friend who is more experienced than I am....

Sounds like rotors to me. They are quite easy to replace.

I would also check the brake calipers. I have the same symptom and it is caused by the caliper on the driver front. It has a corroded piston and a torn boot. Thus the piston is not functioning properly causing the shimmy. I have a rebuild kit and will repair this weekend.

Thanks
 

With the wheel off, can I visually see a problem if it is the rotors warped, or worn out, or do I have to take them off and have them measured, machined, etc...

Honestly for $50 in parts, if I can do it myself I will probably change them, and if it is not the problem, look at the calipers, right?

well- the way to check your rotors is w/ a ball ended caliper(measuring device) and check for disc thickness variation. the rotor will wear thinner in some areas than others, causing the shudder. they really dont "warp"

could also be worn bushings. worn tie rod. worn ball joint, etc.

get the front end up on good jackstands and push,pry,pull the front steering/ suspension bits. look at the stay rod bushings that are on the bottom of the firewall. they have a rod going out to the lower control arm.

there are many things that will give a shimmy while braking. dont just start throwing parts at it, your brakes could be fine.

I'm not following how the lack of proper piston function can cause any vibration on the front end? The loss of a piston will cause a severe pull away from the side of the frozen piston, however, I don't see any scenario that will cause front end vibration.

I had a similar problem with a sticky caliper. The brakes would shudder after driving a while a speed. Apprently the rotor would get wavy once it was hot. Jack up the wheel(s) and see how hard they are to turn by hand after applying the brakes and releasing. The same symptoms can be caused by a collapsed rubber brake line, but there the brake is released by opening the bleeder screw.

While worn suspension components can possibly cause a shimmy on braking, it would be more likely to observe such a shimmy at higher speeds when not braking. The act of braking loads the components on the front end and prevents oscillation in most cases. However, when the disc is loaded, it will immediately display a vibration at most speeds above 40 mph if it's got any runout in it's faces.

I will confirm the results following the caliper repair this weekend.

Often times it is cheaper to replace the rotors, as you have found out, a bit involved replacing the fronts, new/and or repacked bearings. Yet a DIY. MB requests not turning. See if there is any rust spots on the caliper cylinder walls.
You can use the old pads, as long as they measure 2mm, might as well, just swapping those out, very simple. If you replace, get new sensors too, only on front.

Check the bushings I showed in this picture. I had both these bearing ware out on me and when they are warn they will feel solid while driving, but when you step on the breaks if puts force directly on that rod. and if the bushings on ether end are warn out the whole assembly will vibrate.

I don't disagree that such a condition can exist. It's simply far more common for the rotor to have runout than for the guide rod bushings to be worn to just the level where there is oscillation in the rod on braking.

Vibration on braking!
 

Your rotors are warped. That's where the vibration comes in. If they are too thin to turn, it's time to replace them!:headshot:

FWIW, youy can get rotors from checker/shucks/kragen for $18. turning is prolly $15.

Yes, but turning has a effect you dont often find in new rotors.;)
Braking performance is enhanced by turning those rotors! :thumbsup:
Those rotors from checker/schucks/kragen are made in CHINA :headshot:and reliability with chinese made auto parts keeps them off ANY of my vehicles! :eek:
Chinese parts use weaker and less costly pot metals in their castings! :(With something as important as brakes, I'm going to get what should be on their in the first place, Febi, Lemforder or Goetts rotors!!:thumbsup: :D Genuine MB parts, that's where it's at!:thumbsup: Turning is $10.00.;)

MB recommends no turning - MB rotors are relatively thin and this makes the rotor to thin and dangerous

If they are really warped, I'd be hesitant to do so, but if the thickness is within specs, then this is ok.:thumbsup: (Totally German Auto, Phoenix.) Any reputable shop will tell you if these are to thin to turn anyway. ;)I'd still get genuine or approved replacement parts and Chinese rotors are neither! The only thing they are guaranteed to do is fit.:headshot:

Brakes are safety items - don't cheap out on them. OEM rotors are NOT expensive. Buy new rotors, end of story. They're a whopping $28 each for Balo rotors at ***************, or $34/ea here at MBShop (link at top of page). They're a PITA to replace on the front of a W123, though. Use the OE/dealer neon-green wheel bearing grease if possible (it's not expensive), and do NOT mix grease types. Don't forget to order new grease seals, and use a dial indicator to set the wheel bearing end play (the spec is stupidly tight, 0.01-0.02mm, or something like that.)

Another option is to upgrade to 560SEL brakes, which are vented... the 123 has solid front rotors, which are a little undersized for the weight of the car.

:o

Interesting about the 560 SEL brakes. what would be necessary for an exchange and retrofit? Just putting these on in place of the originals?

I have not done this myself, but I believe it's pretty close to a straight bolt-on, with the W126 calipers & rotors. I know some other forum mebers have done this. Maybe they could chime in? I know W124 brake upgrade options forwards, backwards, and upside down... but I've never investigated 123 stuff.

:o

Rears?
 

Check the rear brakes and rotors. I recently replaced the front pads and rotors on mine which helped alot, but still have some vibration and oscillation apparently caused by the rear rotors.:mad:
In my case, it can be seen on the rotors in the form of heavy rust pitting from a combination of the car sitting alot and the calipers being partially setup. The rotor surface is visibly worn unevenly and varies from smooth to rough on it's faces. Normally though, it's not very obvious when they are "warped".:thumbsup:

front
 

I swear it is coming from the front passenger side....

I just feel it like that....

easy or hard
 

Some people say easy job, some say hard.

I'll probably do a lookup here unless someone can elaborate?

They're a PITA on a 123 because you have to mess with the bearings. On a 124, 129, 201, etc the rotor pops off the front of hub, no need to touch the bearings. It's a 10-minute job on those cars. On the 123, plan on several hours. Huge nuisance. Maybe not hard, just annoying...

;)

I'll pay someone
 

Ok,

I will probably pay someone then.

***update*****
 

The vibration nearly goes away when the brakes are hot.

In my 45 minute commute at around the 40 minute mark the vibration is nearly gone!!!!


Are the rotors are warmed up at that point and more pliable???

It was a warped Rotor
 

It turned out to be a warped rotor, and so they are replacing the front two....

$150 labor! JC.

I understand it is a little different on a W123 (more labor) to change the rotors, so I will be happy with a smooth braking experience today on my ride home.

Merry Christmas to me.

soooooooooo smooth
 

Got my baby back, and the braking is oh so smooth.

Two new rotors, new seals, and labor around $200.:(:(:(:(:(:(