Front Disk Rotor - Embedded Particles?

Paul Sutton

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I have been having trouble with my front brakes constantly squeaking. This noise only goes away when the brakes are applied heavily or lightly. Decided to take the caliper off and have yet another close look. I was surprised to see that the pads are not wearing smoothly, in fact they are being gouged with well defined tracks and the pad flaking away between gouge marks:
Disk Pad.jpg


I have examined the rotor and by rotating it between my fingers I can feel many raised pin spots. Their position on the rotor matches with the tracks on the pads:
Disk1.jpg

Below the wheel size marking and on the rotor there is a silver track just below the center line of the wear area and it terminates to the left of the photo's vertical center line. I have attempted to photograph the head of this line but was unsuccessful. Under a magnifier the silver track is actually a tear in the metal that terminated with a raised head. I cannot confirm if there is an embedded particle in the head. Each track on the pads corresponds to one of these features.

Has anyone seen this behaviour before on a brake rotor and is there a remedy?

Thank you for any advice offered - Much appreciated.

Edit - I spelt Disc wrong, again!
 
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That pad may be an original which I think were semi-metallic. They did have little metal bits embedded in them. If you drill the disc and leave the holes sharp edged, most of that grooving will eventually polish itself out.
 
Hi Paul,
they all do that to a certain extent although yours is an extreme example.
What mostly works is to drill the disk full of holes. 3/8" or 10mm drill bit is a good choice.
Lotsa holes is better than less, the pattern don't matter so long as it's symmetrical.
Slotted disk off a late model XS11 is a straight swap and saves you all that drilling.
(The XS650 brake disk material is tougher than old boots, I had to use Cobalt steel
drill bits and flood cooling to drill mine.)
 
Thank you Guys. I have not seen wear this bad. The pads were new last August and only have about 200 miles on then. The pads do have what appears to be brass metal chips in them. I could hand grind the rotor surface to remove the bits that stick up and get new pads?? What pad material should I be looking for???

Thank you.

Edit: Forgot to mention that I am exploring the XS11 disc option as suggested. Drilling may happen once I determine my mates grinding and drilling capabilities.
 
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I have just been tracing my brake pads, they are from EBC and are called FA034. These are Organic pads with Kevlar fibre. I have probed them with my Ohm meter and the shiny brass looking bits have a significant resistance so must be non-metal. This leads me to agree with 5twins' comment that the previous pads must have had metal in them and that is what attacked the disc. I noticed that a couple of spots had rust stain around them and it was common once to put iron dust in pads.

I will keep the pads and in the first instance polish/grind the disc to remove any high spots. I must also check to see how many models used the same disc as the 81. Fred's comment about the XS11 is very interesting, I looked them up and they look really fab with the slots. I am very tempted Fred!

Thank you.
 
Long ago I bought into the metallic pads "longer lasting" scheme, for my cars and trucks. They may last longer, but at the expense of chewing into the discs. Nowadays I'll only run organic pads, and save the discs...
 
:agree:
I replaced my stock calipers (front and back), on my 78 SE, with Brembo 4 piston calipers, a few years ago. I continued to use my stock discs. I soon found that the semi-metallic pads, that came with the Brembo calipers, were causing too much wear on my stock discs.
They gave extremely strong braking, but were chewing up my discs.

I then bought some Organic Galfer green G1532 pads. I have been using them for 4 seasons now, and find they are much more gentle on my discs, yet they still give very strong braking. I really like the organic pads!
 
Update: I removed the disc and hand ground both sides to remove the high spots and embedded material. I used an oil stone with plenty of oil and rotated the disc approximately 30 degrees after every 2 rubs. The left-hand side of the disc was the more difficult due to the convex nature of the disc's centre. I spent 45 minutes non-stop and then finished off with the fine side of the oil stone. The right-hand side was easier to work on but took 1 and 1/2 hours to remove most of the high areas. I took great care not to work any area for too long or with too much pressure. I checked my progress with a micrometer and surprisingly I was able to keep the disc thickness to within +/- 0.01mm.

After thorough degreasing I refitted the disc and the organic pads. I have now done 1 hour of riding with regular heavy braking and the disc has remained smooth to the touch. I have examined the pads and they appear to be wearing more smoothly but I will know this for sure after a couple of months. It is my opinion that the damage to the disc and embedded particles originated from the brake pads fitted by the previous owner. I did notice that a couple of embedded particles had rust stain around then suggesting the damage was caused by steel/iron in the previous pads. Hopefully this issue is now put to rest!

Thank you for all advice given.

Note: I have traced the constant squeal from the front brakes to the shim that sits under the two pads - It is the one that kind of looks like a giraffe that has slipped over ice skating. I straightened it out a bit and the squeal has decreased a lot - must replace it.
 
Noting the hardness of the XS rotors, I am curious as to whether it would be easier to mill shallow narrow slots such as XS11 discs rather than drilling through ? Seems to me a 1/16 carbide endmill may cut very appealing slots and this machining may even be easier ? -RT
 
I've drilled a couple of these stock discs already and didn't find it that difficult. I used a good quality high speed steel drill bit and a drop of oil on each hole. Granted, smaller holes are easier and quicker to drill than larger ones, but neither is that hard. I use smaller holes now (3/16") on the pattern I favor. This follows the theory of not making the hole sizes any bigger than the disc is thick so you don't lose surface area. 3/16" is about 4.76mm so can be used on both 5mm and 7mm thick discs.



I'm pretty happy with the pattern I came up with, so much so I went ahead and transferred it from paper to sheet metal and made a more permanent template .....

DiscPattern3.jpg


DiscPattern6.jpg


DiscPattern.jpg
 
5twins.................great job on making the template! It could be a money maker. Charge maybe $25 plus shipping cost to send out the template to others:umm:
I agree, that anyone that has trouble drilling stock discs, must have dull drill bits. With a sharp bit, they are easy to drill.
 
I must say that is one of the best drilled discs I have seen 5twins, Well Done!!! aesthetically pleasing to the eye! Did you do all 128 holes on 1 good quality drill or did it take a couple? Does the disc metal drill best with a high load on the drill bit or a low loading?
 
Actually, it's 120 holes (15 "swirls" w/ 8 holes each) and I'm able to get several discs out of one bit. I'd say I use medium hard pressure, add more oil if it starts squealing. You kinda get a feel for how hard to push as you're doing it. I do them on my $49 HF drill press, by no means a high quality unit, but good enough for stuff like this. I figure it's paid for itself many times over what with all the holes I've drilled with it. I do clutch screws on it too .....

ScrewHolder.jpg


ScrewHolder2.jpg


ScrewsDrilled.jpg
 
Apologies for the miscount 5twins ......

Thank you very much for the info - I have that type of drill press too and some good Bosch HSS drill bits so this job is within my capability. I have found in the past that you have to keep the drill bit cutting on stainless. Let it squeal and the bit burns up!

I must get brave and try this .......
 
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