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Graham NZ

Front brake disc replacement

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Graham NZ

Has anyone here needed to replace the front brake disc?  My bike looks to have been dropped before I got it and the disc may be damaged.  I'm about to check it for runout and thickness but the online manual doesn't seem to give runout tolerance.  It's a fixed disc so very little runout can be tolerated.

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outrunner

Most discs have the thickness wear limit stamped on them somewhere but I have never seen one with runout tolerance marked. If it has any runout on it at all it should probably be replaced as a matter of course in the interest of safety.

 

Andy.

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usabikes

Hi Graham,

I had to replace my front disc due to runout. Fortunately it scraped in under warrantee when my friendly local Honda dealer went to bat for me and i got a free replacement.

 

Maybe you'll find yours measures poorly, but unless you can feel it pulsing when you brake it doesn't seem to me to be an issue. If it does measure poorly but you still can't feel it pulsing then ignore it IMHO.

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pjm

Is every biker called Graham in New Zealand😄

  • Haha 3

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machinman

Because of the holes, i struggled to measure run out accurately on a rear disc

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ste7ios

For the NC700XD (2012):

 

BRAKE DISC INSPECTION
Visually inspect the brake discs for damage or crack.

 

Measure the brake disc thickness using a micrometer.


SERVICE LIMITS:
Front: 4.0 mm (0.16 in)

Rear: 4.0 mm (0.16 in)


Replace the brake disc if the smallest measurement is less than the service limit.

 

Measure the brake discs warpage using a dial indicator.

 

SERVICE LIMITS:
Front: 0.30 mm (0.012 in)

Rear: 0.30 mm (0.012 in)


Check the wheel bearings for excessive play, if the warpage exceeds the service limit.


Replace the brake disc if the wheel bearings are normal.

 

 

I guess it will be the same on newer models but check it on the service manual of your model...

 

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Graham NZ
13 hours ago, pjm said:

Is every biker called Graham in New Zealand😄

 

No.  Just the two members on this forum and Graeme Crosby.

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Graham NZ

No thickness variation found.

Could not find anywhere appropriate to get a dial gauge to run near the rim of the disc.  Touche, Stuart.

The amount of pulsing is very little but compared with the perfect feel on my 'other bike', it is noticeable.

Next I will remove the caliper and make sure that it is sliding freely.  Even slight disc runout and a reluctant-to-slide caliper would be a bad combination.

Quoted $NZ 550 for a Honda disc and less than half that for one from China via the usual sellers.

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machinman
35 minutes ago, Graham NZ said:

No thickness variation found.

Could not find anywhere appropriate to get a dial gauge to run near the rim of the disc.  Touche, Stuart.

The amount of pulsing is very little but compared with the perfect feel on my 'other bike', it is noticeable.

Next I will remove the caliper and make sure that it is sliding freely.  Even slight disc runout and a reluctant-to-slide caliper would be a bad combination.

Quoted $NZ 550 for a Honda disc and less than half that for one from China via the usual sellers.

My scenario is quite strange. I replaced the rear disc due to a slight pulsing through the pedal. As i said, the runout was impossible to measure due to the pattern of the holes.

With the new disc the pulsing returned after a 1000 mile or so. Caliper is free and well maintained, so decided to live with it as i cant find a logical explanation.

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Graham NZ
43 minutes ago, machinman said:

With the new disc the pulsing returned after a 1000 mile or so. Caliper is free and well maintained, so decided to live with it as i cant find a logical explanation.

 

Stuart, that strikes me as the sensible thing to do.

 

My rear brake is perfectly smooth. The front isn't quite as good but nowhere near as bad as the front brakes on my two Guzzis where the problem was cured by freeing the mounting bobbins.  The NCs have fixed discs which must make it more likely for even a little runout to be felt, let alone the runout limits quoted by Stelios.

 

With the front wheel off the ground I applied the brake progressively by means of a cable tie over the twist grip and lever.  As the pads started to contact there was barely discernible differential resistance as the wheel was rotated slowly.  That is normally a fair indicator of runout but seemingly not in my case.

 

I'll get a wise old mate to ride the bike and get his opinion on the brake feel. As I said earlier I noticed the pulsing only because there is none on my other bike.

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klrman

Just a thought. Are there any brake pad shaped witness marks/pitting on the disc ? Evidence of medium to long term damp storage with no wheel movement 

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Graham NZ

No, Julian, the bike is kept in a dry garage and the only marks on the disc are from brake application.  The bike had had a hard 4,500km on it before I got it and it's now on only 12,000km so not really well worn.  The pads are original I suspect and nowhere near worn out.  I've had the wheel out a few times, so had the caliper off but never removed the pads.  The pistons are nice and free.  I changed the fluid as soon as I got the bike.

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skorpion

Hi Graham.

 

Iv'e had this problem before and found in my case that it wasn't a warped disc, but uneven brake pad residue coating the disc, that was causing the pulsing.

 

If you clean the disc with 240 grit wet & dry paper and fit new pads this is maybe the cure, or try a few emergency stops from a good speed using that brake only, could clean up the disc &  pads.

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embee

I've had it to some extent on my 2012 Integra, but it comes and goes depending on use. I've fitted a new set of OE pads before, although the originals weren't worn out. I feel the replacement pads seem to have some sort of abrasive layer which makes them quite aggressive for a few miles, I wonder if this is to ensure cleaning of the disc and good braking performance from the start, just guessing.

I have done a few tours to the mountains, Alps and Pyrenees, and the brakes get a reasonably hard use coming down the passes with sequences of hairpins, and it definitely affects the pulsing depending on how hard they've been used though not always predictably. Sometimes it will get worse, sometimes it more or less goes away.

I clean the discs regularly with brake cleaner, which also alters the effect to a slight extent.

Since it hasn't got unacceptable at any stage I've come to the conclusion it's just something I have to live with on this NC, as scorpion I suspect it's the way the surfaces behave/react. Alternative pad manufacture might give a different behaviour.

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machinman
2 hours ago, skorpion said:

Hi Graham.

 

Iv'e had this problem before and found in my case that it wasn't a warped disc, but uneven brake pad residue coating the disc, that was causing the pulsing.

 

If you clean the disc with 240 grit wet & dry paper and fit new pads this is maybe the cure, or try a few emergency stops from a good speed using that brake only, could clean up the disc &  pads.

Thanks, il try that.

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Graham NZ

Thanks for the disc cleaning advice, which I will follow as well as checking the caliper over.

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usabikes
On 10/11/2018 at 18:45, pjm said:

Is every biker called Graham in New Zealand😄

 

Only the good ones ;)

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Graham NZ

I've now removed the caliper and pads, lubed the sliding pins, sanded the pads on a flat sanding surface, rubbed the disc with wet and dry paper and cleaned it with brake cleaner.  Brake feel does seem smoother but more high speed testing is needed.

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