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Old 18th January 2013, 11:06   #61
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Default Re: Hyundai Accent, Steering and brake pedal shudders, when braking at speeds above 8

As others have said, I strongly suspect the brake discs are gone. Please replace them if you have not already. I faced similar problem on my Tucson - no vibrations/shudder while cruising at high speeds, but severe vibrations/shudder at the brake pedal and steering if I brake from high speeds. The front brake pads and discs were replaced and all is OK now.

BTW, rotors is just another name for brake discs or is it something else?
EDIT: OK, I see, brake discs are called rotors in American english (http://en.wikipedia.org/wiki/Disc_brake#Brake_disc). Oops .

Last edited by anandpadhye : 18th January 2013 at 11:09.
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Old 18th January 2013, 11:34   #62
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Default Re: Hyundai Accent, Steering and brake pedal shudders, when braking at speeds above 8

No need to change pads again, they are almost new. I suspect the rotors weren't skimmed when you changed the pads. Just try only skimming the rotors first, and sanding the pads lightly. If that doesn't work then look into other options.
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Old 19th January 2013, 01:20   #63
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Thanks a lot guys for the help. I'll be getting discs skimmed along with pads.

As my pads are almost new, just 1000 kms old.

Will update.

Thanks!
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Old 19th January 2013, 07:17   #64
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Default Re: Shuddering/Vibrations while braking! Need help!

Based on your description of the problem I would say the most likely culprit is indeed a warped rotor or disc. Even so, before you start replacing anything I would always try to diagnose to make sure. Otherwise it is just trial and error. And checking whether a rotor/disc is warped is pretty straight forward for any workshop and you could do it yourself as well.

Get the car on a jack, put a stand underneath (safety first), take the wheel of and spin the rotor/disk by hand, whilst you hold the point of a screwdriver very close (, 1mm) to the rotor/disc. Observe the space between rotor/disk and tip of your screwdriver. If you see the space opening up and contracting the rotor is warped! If you want to do this a little more professional invest in a little micrometer. Every car (see the workshop manual) has tolerances specified for how much rotorwrap is permissible. Trust me it is very little. Rule of thumb, if it shows up with just observing the gap, it’s warped.

Sometimes by just turning the rotor/disc by hand you can already feel that at certain positions the brake pads grip more and in other positions the brake pads grip less. Again that indicates warping.

But as stated above, best way is using a micrometer, see this youtube video:



Admittedly a motor bike brake, from the 5 minute mark on it show the micrometer and how you can exactly measure the amount of warping or throw as it sometimes called.

You really ought to do this measurement, as well as measure the overall thickness of the rotor/disc before you can decide you can actually skim it. Again, the workshop manual will tell you the exact specifications and when to replace or refurbish.

Finally, if you need to take the rotor/disc of, on most cars it is pretty straightforward job, with the only challenge being that they get really stuck!

Here’s a nice little trick how you can get them off without any fancy specials tools.



Just a bolt and some nuts. I replaced both front rotor/discs on my Jaguar XJR about six months ago. One of them came of no problem, just fell into my hands. The other one was completely stuck and I used the technique as in the video. Within 10-12 minutes I had it off.

Summary; always diagnose and measure first before you or your mechanic start swapping parts!

By the way, if you haven’t tried it out, you would be amazed how many DIY jobs on cars are out on you tube. Just type in “replacing brakes disc” and you’d be amazed.


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Old 20th January 2013, 21:59   #65
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Default Re: Shuddering/Vibrations while braking! Need help!

Slightly ,but since we are discussing about pads and rotors, i thought i can tell my problem here.

Yesterday when i gave my i20 for service, the front brake pads were changed and the brake fluid was bled and topped up. After service when they was the car, the rotors were all rusty(accepted since this is normal). But the problem is even after running 20 kms there is a ring of rust about a centimeter near the inner part of the rotor.This is the area where the pads are not getting in contact with the disk.And another strange observation is the same rust ring is present in the same location on the other front wheel too! The car has done 32K kms and i have no juddering/vibrations when braking at high speed! What could be the problem?And what should i do?
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Old 20th January 2013, 23:08   #66
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Quote:
Originally Posted by sagarpadaki View Post
Slightly ,but since we are discussing about pads and rotors, i thought i can tell my problem here.

But the problem is even after running 20 kms there is a ring of rust about a centimeter near the inner part of the rotor.This is the area where the pads are not getting in contact with the disk.And another strange observation is the same rust ring is present in the same location on the other front wheel too! What could be the problem?And what should i do?
The brake pads do not travel the entire length of the disc and therefore this "rust ring" is normal. The few mm of rust will be found on any car on the road which has Steel Discs. Leave it as it is.


Quote:
Originally Posted by asethi View Post
I faced a weird problem today morning while driving to office. The brakes suddenly started shuddering and I could feel the vibrations in the pedal, and they were quite strong to shake my leg. The brakes are functioning properly, with no loss in braking power, but just before the car comes to halt or is slowed down before crossing the hump, this shuddering/vibration starts. I don't doubt brake pads fading out, as they were changed just 4K kms back.
Any idea what it could be? Btw, the car is Swift diesel.
Normally if there is shuddering in the brakes it would mean there is a problem with the discs. The discs might have developed a warp or if the disc is unevenly worn out. If the disc is not evenly worn out then its best the caliper should be checked to make sure the pressure is linear accross the pad surface.

If the shock absorbers are very weak you could get shuddering while breaking but it should also happen while speeding over a bad bump.

If a tire has a broken radial or a collaped side wall you would get a shuddering that would always be present in the steering wheel and this will also have pulling to one side.

You need to systematically run through a cycle of tests and eleminate probable problems one by one. Good luck!

Last edited by aah78 : 21st January 2013 at 00:00. Reason: Posts merged.
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Old 21st January 2013, 00:01   #67
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Arrow Re: Shuddering/Vibrations while braking! Need help!

Quote:
Originally Posted by noelravin View Post
Steel Discs.
Brake discs are made from iron, not steel.
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Old 10th February 2013, 12:34   #68
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Default Re: Shuddering/Vibrations while braking! Need help!

Hello guys, I am facing this vibration issue in my sx4 from sometime.
Basically, the braking is butter smooth in the city and at normal usage scenarios. However, once on the highway, after a few rounds of hard braking, the brakes start to judder. Once the brakes heat up, this becomes very prominent and the judder is felt in the brake pedal. Once the brakes are cool enough, the problem disappears. What could be the issue? Brake pads are just 7k kms old and the car has run 22k kms till date. If the rotors are uneven, wont the judder be prominent at all times? I say this as my neighbour's verna had this problem of uneven discs. In his case, judder existed both in cold as well as hot conditions. But in my case it starts after driving on the highway for.a while.

Also, another doubt. Do the brake pads remain in contact with the disc even when brakes are released? Or do they maintain a visible gap? Recently the front tyre was removed and I found that there is no gap between the disc and pad. Is it okay? My car was serviced by the dealer just a month back. Brake fluid was changed and the lines were bled.
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Old 10th February 2013, 17:30   #69
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Default Re: Shuddering/Vibrations while braking! Need help!

Quote:
Originally Posted by audioholic View Post
Hello guys, I am facing this vibration issue in my sx4 from sometime.
Basically, the braking is butter smooth in the city and at normal usage scenarios. However, once on the highway, after a few rounds of hard braking, the brakes start to judder. Once the brakes heat up, this becomes very prominent and the judder is felt in the brake pedal. Once the brakes are cool enough, the problem disappears. What could be the issue? Brake pads are just 7k kms old and the car has run 22k kms till date. If the rotors are uneven, wont the judder be prominent at all times? I say this as my neighbour's verna had this problem of uneven discs. In his case, judder existed both in cold as well as hot conditions. But in my case it starts after driving on the highway for.a while.

Also, another doubt. Do the brake pads remain in contact with the disc even when brakes are released? Or do they maintain a visible gap? Recently the front tyre was removed and I found that there is no gap between the disc and pad. Is it okay? My car was serviced by the dealer just a month back. Brake fluid was changed and the lines were bled.

Lets start with the easy one first; when the brakes are released the brake pads should be barely touching the rotor. But you'd be very hard pressed to find/see a gap. On most calliperit's the seal on the brake cilinder is designed in such a way that as you release the brake pressure in the cilinder it's actually the seal that rotates the pistion inwards. It;s only a fraction, but sufficient to release the pad from the rotor.

the If the brakes don't release well, you'll notice pretty quickly because you're bound to heat up the pads very quickly indeed!
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Old 10th February 2013, 17:43   #70
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Default Re: Shuddering/Vibrations while braking! Need help!

The wheel does rotate freely without any noise when brake is released. Also there is no problems with respect to braking power. It is excellent at all speeds and conditions. However, juddering is my concern. Also, how do I know whether the brakes are overheating? There has been no brake fade or as such. Only I observed that on hard driving, the discs become burning hot.
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Old 10th February 2013, 18:18   #71
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Default Re: Shuddering/Vibrations while braking! Need help!

Quote:
Originally Posted by audioholic View Post
The wheel does rotate freely without any noise when brake is released. Also there is no problems with respect to braking power. It is excellent at all speeds and conditions. However, juddering is my concern. Also, how do I know whether the brakes are overheating? There has been no brake fade or as such. Only I observed that on hard driving, the discs become burning hot.

Its normal for the brakes and even the rims to get hot when braking. But try and drive a stretch of several kilometers with very little or just moderate driving. Feel all four rims / brakes. If you haven't braked much, all four rims/brakes should be maybe warm but you should be able to put your hand on them.

I have a little infrared thermometer that is extremely handy to quickly measure the temperature of the brakes and compare. As long as they're all about the same temperature, probably nothing really amiss, But if one or two are noticeable higher there might be a problem.

Sometimes an odd combination of pads/rotors might cause what you're experiencing. Maybe the pads are glazed? Any problems with the brakes that you don't trust and can't solve yourself, go and see a specialist immediately.

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Old 10th February 2013, 19:46   #72
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Default Re: Shuddering/Vibrations while braking! Need help!

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Originally Posted by audioholic View Post
Basically, the braking is butter smooth in the city and at normal usage scenarios. However, once on the highway, after a few rounds of hard braking, the brakes start to judder. Once the brakes heat up, this becomes very prominent and the judder is felt in the brake pedal. Once the brakes are cool enough, the problem disappears. What could be the issue? Brake pads are just 7k kms old and the car has run 22k kms till date.

Brake fluid was changed and the lines were bled.
Some questions first:

1. Why were your brake pads changed at 15k km? Is it because of wearing out, or some other reason? What brand of brake pads was put in? Were the discs faced/changed when the pads were changed?

2. Why did you have your brake fluid changed at 15k km as well? How old is the car? Was bleeding done from all 4 wheels? Did you watch and make sure? I would suggest another round of bleeding from all 4 wheels.

3. When the juddering starts, if you continue to maintain moderate pressure on the brake pedal, do you feel the juddering reduce gradually as the vehicle slows down, or does it disappear all of a sudden?

4. Are you sure this is not the ABS kicking in? Ask your service centre to check for ABS system error codes, even though the ABS light is not glowing in normal usage.

5. Does the SX4 come with a proportioning valve for the front and rear brakes? Ask your service centre to check if the valve is fine.

Last edited by SS-Traveller : 10th February 2013 at 19:48.
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Old 10th February 2013, 19:58   #73
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Default Re: Shuddering/Vibrations while braking! Need help!

I had a same issue on my Octavia. If braking was done smoothly there were a hell lot of vibrations on brake pedal and on steering wheel too. Also while braking there was some serious noise from the discs. (I might have made some bus/truck drivers jealous from the noise) After a long trials and errors got the solution on this problem. The Skoda engineers advised me a list of parts to be changed.
1. Front brake discs,
2. Front and rear brake pads.
3. Brake booster. (I was like on seeing this item)
In short they advised me to change whole brake system exluding the rear drums on my skoda.

After this beautiful advice, I made a trial and error diagnosis on my own. I was confident the problem was with front discs. So overhauled the front brakes. The brake pads were very good but still changed them and took the car for spin. Still the problem was there.
So now, I attacked the discs. Removed them and machined them on lathe machine. Before machining them I checked them with a micrometer. There was an unever wear on the disc.
Assembled them and YES... The vibrations were gone and the braking noise was gone too.
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Old 10th February 2013, 20:08   #74
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Default Re: Shuddering/Vibrations while braking! Need help!

1. The brake pads were changed at the dealer. I was not present in station and they convinced my dad that they were worn out and replaced. As it was related to the brakes and the cost was not much, less than 2k my father agreed and got them changed. Unfortunately, the old pads were not even half thin as the new ones and as usual the SA played a trick. However, the new ones were replaced in the prescence of my father. The discs were fine as per the SA and also taking into account it was a trick, I dont think the discs were bad. The replacement were sealed MGP pads.

2. The brake fluid was topped up and brakes were bled when the pads were changed. However, a month back, at 22k kms the brake fluid was changed and bled as per routine maintenance. At that time too, the SA did not find a problem with the pads and discs.

3. The juddering is clearly felt at the brake pedal. It continues and the frequency reduces as the speed drops, until zero. This clearly points out that the brakes engage and disengage until the end.

4. Havent experienced what ABS kicking means, so pardon my innocence. From what I read, ABS kicks in several times a second, but is it really so prominent?

5. Yes it does. Regarding the braking efficiency, till date I havent faced a problem.

Also, on a drive about 80kms recently, from Kanchipuram to Mahabalipuram, I drove the stretch in a relaxed manner, and the problem did not show up. On the return journey, my father drove the car a bit hard, ie sudden accelaration and rapid braking. That time, the problem showed up. Again left the car for a one hour lunch break after which I took on again, and no problem.


Does hard driving cause this? My car is routinely maintained by MASS, with all necessary works done(except those add-ons) well in time. The car has completed four years.
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Old 10th February 2013, 20:37   #75
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Default Re: Shuddering/Vibrations while braking! Need help!

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Originally Posted by audioholic View Post
...discs were fine as per the SA...
...22k kms the brake fluid was changed and bled...
3. The juddering is clearly felt at the brake pedal. It continues and the frequency reduces as the speed drops, until zero.
...ABS kicks in several times a second, but is it really so prominent?
...drove the car a bit hard, ie sudden accelaration and rapid braking. That time, the problem showed up. Again left the car for a one hour lunch break after which I took on again, and no problem.
The car has completed four years.
Based on what you've said, get the following done, and check if the problem goes away:
1. Check the discs for "runout", preferably with a dial gauge / on a lathe - the usual max. acceptable amount of runout is 0.1mm IIRC. If more, have the discs faced.

2. Bleed the hydraulic system at all 4 wheels. Check that the rear wheel cylinders are getting free flow of brake oil when tested on the car lift - otherwise the proportioning valve may need replacement/adjustment.

3. Change and grease the front brake calliper pins.

If the problem still persists, you need to change both discs and pads together as a set.
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