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Rear Brakes Pad Contact Area.


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#1 Andyeddie

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Posted 21 April 2017 - 11:43 AM

My rear pads only contact around half the area of the of the discs, they don't make contact with the outer area of the discs at all. I cannot figure this out, I have new discs, pads and reconditioned Calipers, I've carried out a full rear suspension rebuild with new bushes, ball joints, toe links and wheel bearings and had a gel done to ensure everything is hunky dory, but now I'm scratching my head.

This may be a common issue, appreciate any ideas as to what could be the problem, thanks in advance.

#2 james_ly

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Posted 21 April 2017 - 12:26 PM

Did your pads come with those spring spacer things in the hole on the edge? My Mintex pads had them (I took them off), but Pagid pads didn't have them at all.



#3 Edgeydt50

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Posted 21 April 2017 - 02:21 PM

I would say mine make less contact with the inner of the disc



#4 Ormes

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Posted 21 April 2017 - 05:04 PM

Sure the slider bar isn't bent/siezed?



#5 Nev

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Posted 21 April 2017 - 05:33 PM

I would imagine many VX calipers are like this, those rear unit are really cheap single piston jobbies so you can't expect even wear from them.

 

As a solution you could make a slighly tapered spacer, or else just let them bed in fully (so the pads make full contact) before driving very hard.

 

 

 

 


Edited by Nev, 21 April 2017 - 05:57 PM.


#6 Johnboyhgt

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Posted 21 April 2017 - 06:36 PM

Got a pic of the contact area Andy ?


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#7 Arno

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Posted 21 April 2017 - 07:00 PM

Sure the slider bar isn't bent/siezed?

 

This.. Or the top slider bar is not sitting flush/even in the upright cavity.

 

Or the upright has been damaged in the past and the 'ears' that the caliper bolts onto have been tweaked/bent.

 

Usually any caliper mis-alignment shows up in limited (initial) contact. Often it's swapped/mirrored on either side of the disc, so if the wheel side of the disc is not getting hit by the pad on the outer edge then the chassis side may show the opposite and lack contact nearer the hub.

 

 

Bye, Arno.



#8 ianrm

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Posted 21 April 2017 - 07:36 PM

How wide is the pad material compared the wear on the disc?



#9 Andyeddie

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Posted 21 April 2017 - 07:56 PM

Thanks for all your answers so far, as I said everything is either new or reconditioned, new Mintex pads with springy things, new Mintex discs, Calipers recon' d professionally, slider bolts free and straight, no damage on the uprights, geo didn't show any anomalies, I even put a run out dial indicator on the discs and they run true, so I'm totally baffled, I was thinking would it be possible for the Pistons to be slightly askew?? I've never heard of this and wouldn't imagine it possible??? But if it was it would have this effect I think???

#10 Andyeddie

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Posted 21 April 2017 - 08:00 PM

How wide is the pad material compared the wear on the disc?


Sorry Ian, I don't understand your question, the pad material is new, so are the discs, sorry if I'm being dense!

#11 ianrm

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Posted 21 April 2017 - 08:18 PM

Does the height of the pad material match the wear on the disc. i.e, from the centre of the disc to the outer edge, if that makes sense.



#12 Andyeddie

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Posted 22 April 2017 - 07:57 AM

Does the height of the pad material match the wear on the disc. i.e, from the centre of the disc to the outer edge, if that makes sense.


As both pads and discs are new their isn't any wear to speak of, but you can see that the outer half of the disc is not being contacted by the pads when the brakes are applied, because of the small amount of surface rust that is evident, In static mode the pads appear to be sitting equidistant from the discs and from what I can see, when the handbrake is applied the contact appears uniform across the disc and pad.

#13 oblomov

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Posted 22 April 2017 - 09:00 AM

Andy, my rear pads wear unevenly in similar fashion. I always thought it was a tads issue so I've never queried it. But it does mean I have to take the wheels off and take a really good look at both pad edges because one side can appear O.K. when the other is below an acceptable thickness when checking pad wear. However, I've never bothered to check pad wear and contact after new discs and pads, just allowing them to bed in, but I know you are a stickler for attention to detail. Having said all that, it does sound as if your problem may be due to a somewhat worse misalignment.
When the pad is in contact with the disc what size is the gap where there is no contact? I'll have a look later and see if I can find a set of old half worn pads to see what my front/rear wear bias is.

#14 ianrm

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Posted 22 April 2017 - 09:04 AM

Can you post a picture? They paint a thousand words.

 



#15 Andyeddie

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Posted 22 April 2017 - 09:30 AM

I'll get a picture posted soon, having just got home I find myself being dragged in all directions, none of which appear to be my garage, strange that! I guess that's family for you!!!




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