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Are my discs buggered?

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Wafer_Thin_Ham
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PostPosted: 18:03 - 05 Jun 2016    Post subject: Are my discs buggered? Reply with quote
They look like this, and it seems to have penetrated the full depth of the discs. I've never seen anything like it.

It doesn't seem to rub off when the brake is applied. It's been in the same place for ages.
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Suntan Sid
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PostPosted: 18:15 - 05 Jun 2016    Post subject: Reply with quote
Looks like the bike was parked up for a long time and the disc corroded behind the brake pad!
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Commuter_Tim
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PostPosted: 18:25 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Wafer_Thin_Ham wrote:
They look like this, and it seems to have penetrated the full depth of the discs. I've never seen anything like it.

It doesn't seem to rub off when the brake is applied. It's been in the same place for ages.


How many times does the wheel free spin when you throw it around?
Any audible brake rubbing at that spot?
I cant imagine that rust would change the disc runout to throw it past the service limit tbh, and if it did, I rode on a disc with massive runout before I realised how bad it was.
Put my dial caliper on it, 3 times the service limit.
Even then it just went WAHP WAHP WAHP at slow speeds and had slightly reduced efficiency, no potato.
I highly doubt its the entire depth of the disc, I imagine your pads wouldn't last so long though.
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Wafer_Thin_Ham
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PostPosted: 18:29 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Commuter_Tim wrote:

How many times does the wheel free spin when you throw it around?
Any audible brake rubbing at that spot?
I cant imagine that rust would change the disc runout to throw it past the service limit tbh, and if it did, I rode on a disc with massive runout before I realised how bad it was, put my dial caliper on it, 3 times the service limit.
Even then it just went WAP WAP WAP at slow speeds and had slightly reduced efficiency, no potato.
I highly doubt its the entire depth of the disc, I imagine your pads wouldn't last so long though.


Haven't tried to be honest. You can feel it a little through the lever, but it wasn't noticeable on the dial when it was MOTed.

It's not noticeably harder than other bikes to push around.
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jaffa90
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PostPosted: 18:29 - 05 Jun 2016    Post subject: Reply with quote
I would replace it / them.
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Wafer_Thin_Ham
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PostPosted: 18:30 - 05 Jun 2016    Post subject: Reply with quote
Suntan Sid wrote:
Looks like the bike was parked up for a long time and the disc corroded behind the brake pad!


Agreed (it has something similar on the other disc). There is also a few spots in another place that again seem to have penetrated the whole disc (or is has spots in exactly the same place on the opposite face of the disc).
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Commuter_Tim
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PostPosted: 18:39 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Wafer_Thin_Ham wrote:

Haven't tried to be honest. You can feel it a little through the lever, but it wasn't noticeable on the dial when it was MOTed.

It's not noticeably harder than other bikes to push around.


I didn't get any warnings for mine 3 times the limit, through 2 different MOT shops, don't trust mechanics.

If it was going to be a problem you would only notice it at that one point of the rotation that the pads touch anyway, and the noise it makes when rubbing is rather noticeable.

Anyway this is your punishment for being a fair weather rider. Razz
You could always take some 0000 wire wool to it and see if it comes off?
0000 isn't going to cut into the discs really but it should reduce the rust down to just pitting.

What are you afraid of happening here? reduced braking efficiency and increased pad wear is about all you can expect, try a few Emergency Stops?
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Wafer_Thin_Ham
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PostPosted: 18:45 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Commuter_Tim wrote:

I didn't get any warnings for mine 3 times the limit, through 2 different MOT shops, don't trust mechanics.

If it was going to be a problem you would only notice it at that one point of the rotation that the pads touch anyway, and the noise it makes when rubbing is rather noticeable.

Anyway this is your punishment for being a fair weather rider. Razz
You could always take some 0000 wire wool to it and see if it comes off?
0000 isn't going to cut into the discs really but it should reduce the rust down to just pitting.


To be honest I can get replacement discs cheaply, I just wanted to see if they were knackered. If so, it's an excuse for some trick ones. As said you can feel pulsing through the lever. And fair weather rider, wash your mouth out with soap! It was like that that I got it. It's not happened during my ownership. Wink The discs have always pulsed I've just not been too bothered to look into it until now.
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Commuter_Tim
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PostPosted: 19:15 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Wafer_Thin_Ham wrote:

To be honest I can get replacement discs cheaply, I just wanted to see if they were knackered. If so, it's an excuse for some trick ones. As said you can feel pulsing through the lever. And fair weather rider, wash your mouth out with soap! It was like that that I got it. It's not happened during my ownership. Wink The discs have always pulsed I've just not been too bothered to look into it until now.


Gotcha, if you have the cash it's worth it, not dangerous but there can be a difference in noticable stopping distance.
I guess I was so used to shitty drum brakes that I just learned to increase the gaps in front.
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mentalboy
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PostPosted: 20:27 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Commuter_Tim wrote:
Wafer_Thin_Ham wrote:

...you can feel pulsing through the lever. The discs have always pulsed I've just not been too bothered to look into it until now.


Gotcha, if you have the cash it's worth it, not dangerous but there can be a difference in noticable stopping distance.


I doubt if:
a) your stopping distance would be noticeably different once you've actually gotten out and ridden the beast a few times to remove the spotting (I think it'd have to be fairly grim to make a noticeable difference);
b) the spotting is causing the pulsing.

I would, however, endeavour to replace pulsing discs at the earliest opportune moment, best to replace the pads at the same time and give your calipers a good service whilst you're at it.
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Commuter_Tim
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PostPosted: 20:45 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
mentalboy wrote:

I doubt if:
a) your stopping distance would be noticeably different once you've actually gotten out and ridden the beast a few times to remove the spotting (I think it'd have to be fairly grim to make a noticeable difference);
b) the spotting is causing the pulsing.

I would, however, endeavour to replace pulsing discs at the earliest opportune moment, best to replace the pads at the same time and give your calipers a good service whilst you're at it.


I don't disagree with you, but perhaps I was unclear before, pulsing can effect the stopping distance, as it's a sure sign the brakes are working in a stop/start manner.

I wasn't entirely convinced the pulsing was caused by the rust either, rubbing sure but doesn't seem like enough rust to actually pulse the brakes, and he said its been there "ages", but he reported pulsing ergo reduced stopping distance.
If it's warped too however. Thinking

Good call on the caliper service/seal replacement though, if someone left it sitting long enough for that, who knows when it was last cleaned.
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Snod Blatter
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PostPosted: 21:09 - 05 Jun 2016    Post subject: Reply with quote
Sintered (i.e. metal) pads can cause this if the bike is left out in the wet and stood still for a long time, though it's much less common with stainless discs. Perhaps something in the pad ate away at it?

I'd just use it, the K100s discs seemed to sort themselves out (wear past the depth of the pits) eventually.
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mentalboy
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PostPosted: 22:15 - 05 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
Commuter_Tim wrote:


Good call on the caliper service/seal replacement though, if someone left it sitting long enough for that, who knows when it was last cleaned.


I'd always do a caliper service (not necessarily replace seals) if changing out the discs, I'd be inclined to do a thorough caliper clean up as a very minimum when pads are being changed. British roads are dirty places and it never hurts cleaning all the crap out of what are probably the most essential moving parts on a bike.
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Commuter_Tim
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PostPosted: 14:00 - 06 Jun 2016    Post subject: Re: Are my discs buggered? Reply with quote
mentalboy wrote:
Commuter_Tim wrote:


Good call on the caliper service/seal replacement though, if someone left it sitting long enough for that, who knows when it was last cleaned.


I'd always do a caliper service (not necessarily replace seals) if changing out the discs, I'd be inclined to do a thorough caliper clean up as a very minimum when pads are being changed. British roads are dirty places and it never hurts cleaning all the crap out of what are probably the most essential moving parts on a bike.


I'm lazy so I just spray the brakes down with brake cleaner extremely frequently, and change fluid by service intervals or if things start to bind.
It appears to work rather well but damned expensive. Smile
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