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TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

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Old May 31st, 2020, 06:00   #1
JohnPaulJones
Newbie
 
Join Date: Feb 2020
Location: Denmark
TDI(s): Golf MK4 TDI
Default New Brake rotors and pads, 50% active???

Hi TDI Club.

So i put new rotors and pads on the rear of my MK4. I went driving in it for a while and regularly stop to check the wear pattern on the new rotors. So on the visible side of the right rotor it is clear that only half of the pad rubs against the rotor. That would be the half part closest to the caliber. (I hope that is explained well...)

I jacked up the car again and made sure nothing was wrong. I cleaned the slidepins and lubed them. I lubed all contact faces again.
So the manuel for the pads says to bed the pads for the first 200-300 km / 120-190 miles. Break softly etc.
I have only driven for like 100km / 60 miles at this point.
So do you guys think that the pad will eventually get contact with the whole rotor face or is something very wrong?

I only have this problem on this one pad.

Also another question: Is it normal for the rubber boot on the slidepin to create a vacuum, so that when you push it in it wont slide out again by itself? Thanks in advance guys!
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Old May 31st, 2020, 06:56   #2
Mongler98
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Join Date: Mar 2011
Location: Northern MD
Fuel Economy: Race: 12mpg, Gandma:65mpg
Default

sounds like a defective pad it happens.
and yes they will act like a vacuum if pulled and pushed like that. they never move that much, ever, in application so its not an issue. you don't want water getting in there do you?

also bedding in pads are 1 of 2 schools
1: bindex uses a blue compound on the pad to make it bed in under normal driving. AWESOME. others do this as well .
2: go drive it and do a 90% stop from 40 mph to about 10 with as much braking force as you can with out locking the tires, do this about 5 to 6 times and the brakes will feel like mush, go drive for 10 minutes with no braking action like on a highway at night to let them cool, no full stop allowed.

i would check the face of the pad to the backing plate to see if its parallel. i bet you its not!. I had 2 similar issues with Hawks pads a while ago.

Last edited by Mongler98; May 31st, 2020 at 06:59.
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Old May 31st, 2020, 07:03   #3
Dh4276
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Join Date: Jul 2019
Location: South Carolina
Default

As for the wear pattern, that does not sound normal, you should have even wear across the whole pad, especially with new pads and rotors!

Did the piston slide in easily when you pushed it in? I have seen on some cars (not on VW) where the is a lip that can get caught on the piston when pressed on the way is causing it to hang. If the bottom is sticking it could be causing the piston to not come out in an even flat position thus causing this odd wear pattern. Can you tell if the wear is gradually less as it moves towards the hub?

As for the slide boots, I have seen this many times caused by the grease in the boots! Seen it on many different vehicles including VW.


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Old May 31st, 2020, 07:06   #4
Dh4276
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Join Date: Jul 2019
Location: South Carolina
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Quote:
Originally Posted by Mongler98 View Post
sounds like a defective pad it happens.
and yes they will act like a vacuum if pulled and pushed like that. they never move that much, ever, in application so its not an issue. you don't want water getting in there do you?

also bedding in pads are 1 of 2 schools
1: bindex uses a blue compound on the pad to make it bed in under normal driving. AWESOME. others do this as well .
2: go drive it and do a 90% stop from 40 mph to about 10 with as much braking force as you can with out locking the tires, do this about 5 to 6 times and the brakes will feel like mush, go drive for 10 minutes with no braking action like on a highway at night to let them cool, no full stop allowed.

i would check the face of the pad to the backing plate to see if its parallel. i bet you its not!. I had 2 similar issues with Hawks pads a while ago.

I have always used the second break-in option, has always worked great for me!

On the pad issue, that is also another possibility, Iíve never had it but I donít think it is out of the question, just didnít think about it!


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Old May 31st, 2020, 09:47   #5
JohnPaulJones
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Join Date: Feb 2020
Location: Denmark
TDI(s): Golf MK4 TDI
Default

Thank you guys. So you confirmed for me that this could not be normal behavior.
I took a nap and thought about it.
If there would be grime and dirt in the caliber where the pad is sitting, that would account for the wear pattern because the back part of the pad would be slightly farther out because of said grime and dirt.
And sure enough, i had not given the the old metal wire brush to the caliber. I took apart both brakes and cleaned them.
I now seems to have a much more normal wear across the whole rotor.
You can write this off as another weekend mechanic, not doing the job right the first time
Thanks again. Cheers from Denmark
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Old May 31st, 2020, 16:48   #6
Mongler98
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Join Date: Mar 2011
Location: Northern MD
Fuel Economy: Race: 12mpg, Gandma:65mpg
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That's got to be a lot of crap behind the pad!
Makes sense though. Big step is to clean all the mating surfaces and grease them.
Glad its sorted
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Old June 5th, 2020, 07:35   #7
jetta ,97
 
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Location: Dallas (McKinney) ,TX ,USA
Fuel Economy: Very good
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It depend of Brand. Some brands takes a while to brake in and never do brake job as quality brand does.


What brand of pads and rotors you got?
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Old June 5th, 2020, 09:03   #8
BobnOH
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Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
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If you've been very gentle with the brakes, I would take it out and do some hard braking.
But yea, excess rust and crap on the mating surface will do that.
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