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Discussion Starter #1
If any of you are getting a grinding noise while braking together with bad brake fade and you can see no obvious reason for it (i.e. worn pads) you may like to look at the inside surface of your brake discs. If budget discs have been fitted in the past you can virtually guarantee they will be badly corroded on the inside even if the outside surface looks in good order. I`m not sure why this happens only on the inside but having a little knowledge of casting techniques, I think it may be because during the manufacturing process, the inferior metal used in these castings have a lot of contaminates in them which rise to the top of the casting while cooling, the inside surface of the disc would be the top of the cast. This corrosion happens regardless of whether the car has been in constant use or not, the friction surface of the disc literally starts to come away to a depth of about 1mm. Some of the cheap discs you get on a certain auction site are not worth getting even if they have a brand name, I have found to my cost that they can often be counterfeit parts and thus will not last or perform as they should. Some of these discs can have a life of just 12 months or less. Just a theory!
 

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Surely that means the pad isnt making contact?

Fade I would attribute to old brake fluid...
 

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If any of you are getting a grinding noise while braking together with bad brake fade and you can see no obvious reason for it (i.e. worn pads) you may like to look at the inside surface of your brake discs. If budget discs have been fitted in the past you can virtually guarantee they will be badly corroded on the inside even if the outside surface looks in good order. I`m not sure why this happens only on the inside but having a little knowledge of casting techniques, I think it may be because during the manufacturing process, the inferior metal used in these castings have a lot of contaminates in them which rise to the top of the casting while cooling, the inside surface of the disc would be the top of the cast. This corrosion happens regardless of whether the car has been in constant use or not, the friction surface of the disc literally starts to come away to a depth of about 1mm. Some of the cheap discs you get on a certain auction site are not worth getting even if they have a brand name, I have found to my cost that they can often be counterfeit parts and thus will not last or perform as they should. Some of these discs can have a life of just 12 months or less. Just a theory!
design of calipers tend to wear inside of disc before even though they float its the thrust side

as for brake fade ...i can cook standard pads easy even with quality brake fluid so thats why i run ds2500's
 

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Discussion Starter #4 (Edited)
design of calipers tend to wear inside of disc before even though they float its the thrust side

as for brake fade ...i can cook standard pads easy even with quality brake fluid so thats why i run ds2500's
Only telling of my experience after 35 years of motoring and 16 cars 9 of which Italian. You suggest that the thrust side of the disc is subjected to more pressure than the other and so will degrade more quickly than the opposite side. This is in fact not so; if it were the resulting unequal pressure on the disc would cause it to disintegrate under the load of braking. The floating brake calliper such as is fitted to the 156 and many other vehicles when well maintained, is designed in such a way as to exert equal pressure on both sides of the discs. For the sake of debate we can look at the definition of thrust as explained in the dictionary:
Thrust is when a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system.
Do you think Newton got it all wrong?
(Sorry for the lecture)
There are lots of reasons for brake fade, most if not all of which I am aware. What I describe is only one more that I have encountered.
 

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Only telling of my experience after 35 years of motoring and 16 cars 9 of which Italian. You suggest that the thrust side of the disc is subjected to more pressure than the other and so will degrade more quickly than the opposite side. This is in fact not so; if it were the resulting unequal pressure on the disc would cause it to disintegrate under the load of braking. The floating brake calliper such as is fitted to the 156 and many other vehicles when well maintained, is designed in such a way as to exert equal pressure on both sides of the discs. For the sake of debate we can look at the definition of thrust as explained in the dictionary:
Thrust is when a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system.
Do you think Newton got it all wrong?
(Sorry for the lecture)
There are lots of reasons for brake fade, most if not all of which I am aware. What I describe is only one more more that I have encountered.
tell you what ..when you buy new discs ..get your vernier out and get them on a calibrated block and measure ..then measure your old ones and compare ..........lecture over!
 

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You suggest that the thrust side of the disc is subjected to more pressure than the other and so will degrade more quickly than the opposite side. This is in fact not so; if it were the resulting unequal pressure on the disc would cause it to disintegrate under the load of braking.
Not more pressure, but on a sliding caliper the inner pad & disc face have more contact time than the outer. It is the contact of the inner pad & disc that makes the caliper slide and pull the outer pad into contact with the disc.
The inner pad is also the last to release when you come off of the brakes.

That is for a properly serviced caliper.

For a caliper that hasn't been serviced properly the slider sticks causing the outer pad to drag on the disc.
 

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Discussion Starter #7
design of calipers tend to wear inside of disc before even though they float its the thrust side

as for brake fade ...i can cook standard pads easy even with quality brake fluid so thats why i run ds2500's
Read my post again...I stated "corroded" not worn there is a definitive difference in this case!
 

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Discussion Starter #8
tell you what ..when you buy new discs ..get your vernier out and get them on a calibrated block and measure ..then measure your old ones and compare ..........lecture over!
See Dave C`s explanation for this, he puts it across better than I could.
 

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Also brake fade is nothing to do with old fluid. Or anything to do with the fluid at all - its all to do with overheating the pad itself. The pedal stays good, just the brakes don't work. It often accompanied with an awful smell of cooked pads as well!
 

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Correct rockhopper - brake fade happens when the pad material gets too hot and outgasses. Pedal stays where it is but you stop slowing down (if you know what I mean). If the fluid's no good it boils and the pedal goes soft.
 

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Brake fade can be due to pedal fade or pad fade, different issues...
I assume the OP is discussing fade during road, not track use, therefore I find it hard to believe that pad fade would be the factor in this case...
 
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It's easy to get pad fade on std brakes of most cars if pushing it a little on twisties.
 

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Fair enough, not something I've experienced on the road TBH...
 
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Obv not done an Italian tune up then :)

As Dave says hit brakes hard at 70 down to 30 get back to 70 quickly and do it again. you'll fund by time your getting to 30 the 2nd time they'll be struggling.

In fact this sort of treatment is the break in procedure for some makes of pad....
 

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Obv not done an Italian tune up then :)

As Dave says hit brakes hard at 70 down to 30 get back to 70 quickly and do it again. you'll fund by time your getting to 30 the 2nd time they'll be struggling.

In fact this sort of treatment is the break in procedure for some makes of pad....
yes ds2500's but they dont suffer fade though:D well on road mind;)
 
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