Every time when I am driving like 90 or 100 MPH and start applying the brakes the steering wheel starts to vibrated a lot till I let go of the pedal. Could these be dangerous? what´s wrong?

 

Could what be dangerous? The fact that you are going 100mph, or the vibration???


Seriously, you probably have a warped rotor or two.

 

Yes, sounds like a warped rotor.

Should be an easy fix at the dealer though. :smile:

 

bought new wheels

balance it is good, tested twice already after two weeks.
vibration during driving more then 50mph.
vibration during braking.
what could it be?
Is it the same issue?

 

If the centerbore of your new wheels is larger than OEM wheels (56.1mm), you need to get centering rings.

 

i have got it on there.

maybe it is too small? but it fit ok thou!

 

I would go to another tire place and have them rebalanced using a Hunter.

 

Chris, I bet you've got those crappy plastic hubcentric rings, don't you?

Get some metal rings and the problem will go away, assuming (as was stated above) the wheels/tires are properly balanced. Here's a good source:

http://www.discounttiredirect.com/di...501717191!NONE

 

If this vibration occured wile accelerating coatsing and braking - I'd be thinking hub centricity - not the case - only during braking.

Rotors usualy dont warp - the common misconception. The pad material your using sometimes gets applied unevenly, this causes the pusation under braking. Ususally a good threshold stop from 50 mph can correct mild cases.

For the bad ones - I've used 130 grit garnet paper on pad firepath and rotor firepath to cut the glaze, and re-bed the pads - alot of work, but is cheaper than new rotors.

Alex

 

>Rotors usualy dont warp - the common misconception.

Reaaally... I guess resurfacing was just to get the clean
metal look back...

 

Grooving isn't really warping though, they can be deeply grooved and still not warped

 

Ken - exactly - so you have a clean fresh pure cast iron firepath , onto wich you'll transfer your new friction compound. It can take 4-5 times longer to burnish,and bed if the old compound is still present.

Alex

 

I see...

So the misconception is that we are feeling the vibrations from the
"grooving" (as mentioned by minimort) and not 'warping'... (?)

The grooving can be eliminated by resurfacing too, right?

 

As Alex said a lot of people think they warped their rotors when in reality, they just have some pad residue built up unevenly on the rotor surface. Think if you have some maple syrup on a granite countertop then try wiping it off with one quick pass of a dry paper towel. You end up with raised points from the syrup residue above the countertop. On your car, these raised portions come into contact with the pad instead of the smooth rotor and you get vibration.

It's just like when you transition from a smooth to bumpy road you start getting lots of vibration once you are on the bumpy one.

Like Alex said, a lot of times 1-2 good stops from 50-60mph usually will burn this off. Offramps from freeways are great to do this.

One other thing I have found prevents this to a great extent for me is limiting how much time I spend on the brake pedal. A lot of people do long easy stops. Then hold their foot on the brake for a while after they stop. If you stop faster, and don't just hold your foot on the brake once done, for some reason you see less of this buildup occuring.

 

>Like Alex said, a lot of times 1-2 good stops from 50-60mph usually will burn this off. Offramps from freeways are great to do this.



This wasn't the case on my other car that had the rotor resurfaced.
I no longer have the car, but it was defined as a 'warped' rotor being
the problem and was resurfaced. but I am thinking it was more of a
groove than really wabbly warped.

 

This is the key - everything we're ever taught about smooth and comfortable braking, is exactly what causes this. Threshold braking is the best exercise for brake component health.

Alex

 

So to summarize, if you have pulsating brakes....

First try 50-60mph to zero hard braking a few times to see if you can
burn off the gunk off the rotors. If this fixes the pulsation, great.
Prevent by using more brake force with shorter braking distance.


If not, take the car into the dealer or brakeshop to have it looked at.

It could be:

a. Grooving - needs to be resurfaced to clean-off gunk buildup and
flatten rotor.

b. "Warping" (possibly sever grooving) - needs to be resurfaced
to flatten the rotor, remove all gunk, or replace rotor.

c. more sever problem with rotor and pads.


yes? :smile:

 

thanks for all your help I will try all the steps and then tell you what happened

 

Further explanation on the warped rotor myth can be found at: http://www.stoptech.com/whitepapers/...otors_myth.htm

 

took it to the brake shop and in fact it was a warped rotor. it runs smooth now.