PCCB scraping sound
Thread Starter
Nordschleife Master
Joined: Nov 2010
Posts: 7,804
Likes: 193
From: Bay Area
Macster,
Once again, thanks! Based on your description, would you agree that the areas circled in the below pictures are the areas that appear to be glazed? It did feel as though the brakes did not grip quite as hard as they have in the past during my last track day. I wonder if this is glazing.
Once again, thanks! Based on your description, would you agree that the areas circled in the below pictures are the areas that appear to be glazed? It did feel as though the brakes did not grip quite as hard as they have in the past during my last track day. I wonder if this is glazing.
The consensus there was to get new pads.
Race Director
Joined: Sep 2006
Posts: 19,035
Likes: 269
From: Bentonville, AR
Then I'd suggest you listen and get new pads.
The braking performance may be down due to glazing, but the glazing arises from the pads losing material (which of course is natural, brake pad wear) and suffering from elevated temperature because of it.
This elevated temperature can overheat the brake fluid. If the fluid is not fresh any moisture in the fluid can turn to steam and braking performance will be affected.
PCCBs are the ultimate in high performance brakes. They are being asked to perform at a level far above other brakes. They can do this and do this reliably but the entire braking system must be in top form.
Sincerely,
Macster.
The braking performance may be down due to glazing, but the glazing arises from the pads losing material (which of course is natural, brake pad wear) and suffering from elevated temperature because of it.
This elevated temperature can overheat the brake fluid. If the fluid is not fresh any moisture in the fluid can turn to steam and braking performance will be affected.
PCCBs are the ultimate in high performance brakes. They are being asked to perform at a level far above other brakes. They can do this and do this reliably but the entire braking system must be in top form.
Sincerely,
Macster.
Race Director
Joined: Sep 2006
Posts: 19,035
Likes: 269
From: Bentonville, AR
There appears to some sign of glazing. In this case I think it really requires hands on confirmation.
(Just as aside, and which has been covered in another post, really if you suspect the pads are glazed or unsuitable for continued use you should replace them. New pads is cheaper than hosing one or more rotors or worse.)
Another 'trick' to spot glazed areas when visually the evidence is inconclusive is to use a carbide tipped scribe and with a straight edge draw the scribe across the surface. I've never had any reason though to try this with brakes. I've only used this trick to confirm the presence of hard spots on flywheels.
Anyhow, when the carbide tip comes to a harder area the scribe's mark will grow faint. At the same time you'll feel the resistance diminish as the scribe tip's bite is reduced.
You're not looking to gouge grooves in the material -- though the tip will probably leave some sign of its passing (a shallow 'scratch'), but if it doesn't the material is harder then the scribe tip and this 'trick' is useless in this situation) -- what you are seeking is to identify relatively large areas with a harder surface. The harder areas with the harder surface is possibly due to glazing.
The brake pad material is assumed to homogenous and encountering an irregularly shaped area with a length/width of something larger than a dime or quarter is a sign of localized glazing. Chances are if there is any glazing the area size will be larger than this.
Sincerely,
Macster.
(Just as aside, and which has been covered in another post, really if you suspect the pads are glazed or unsuitable for continued use you should replace them. New pads is cheaper than hosing one or more rotors or worse.)
Another 'trick' to spot glazed areas when visually the evidence is inconclusive is to use a carbide tipped scribe and with a straight edge draw the scribe across the surface. I've never had any reason though to try this with brakes. I've only used this trick to confirm the presence of hard spots on flywheels.
Anyhow, when the carbide tip comes to a harder area the scribe's mark will grow faint. At the same time you'll feel the resistance diminish as the scribe tip's bite is reduced.
You're not looking to gouge grooves in the material -- though the tip will probably leave some sign of its passing (a shallow 'scratch'), but if it doesn't the material is harder then the scribe tip and this 'trick' is useless in this situation) -- what you are seeking is to identify relatively large areas with a harder surface. The harder areas with the harder surface is possibly due to glazing.
The brake pad material is assumed to homogenous and encountering an irregularly shaped area with a length/width of something larger than a dime or quarter is a sign of localized glazing. Chances are if there is any glazing the area size will be larger than this.
Sincerely,
Macster.
Thread Starter
Nordschleife Master
Joined: Nov 2010
Posts: 7,804
Likes: 193
From: Bay Area
If the pads are glazed, there's no harm to the rotors if I still used the glazed pads?
The reason I ask is, I am considering continuing to use the glazed pads on the street since they work/sound just fine for street use. I was going to put in the new pads for my next track day.
The reason I ask is, I am considering continuing to use the glazed pads on the street since they work/sound just fine for street use. I was going to put in the new pads for my next track day.
