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Discussion Starter · #1 ·
I've posted about this before but now I have additional info.

Issue: Slow Speed Pulse while braking. (front only)

Stock rotors, caliper, BMC, buttons clean, rotor deglazed with scotch pad and fine sandpaper, EBC pads, lines bled annually, DOT 5.1.

Finally got a front wheel stand, spun the wheel, seems to spin freely, no drag or getting caught during the spin. Didn't check rotor warp properly because it spun freely.

What I did notice by eye is that my front wheel/tire wobbles a little?

I don't believe my rim is warped, but I suppose there's a chance the wheel is not balanced properly. The tires themselves have about 8,000km. Tread is good and even, they look good, gently ridden, road only.

If it is a poorly balanced tire, could this be causing the slow speed pulse on the brake? Or am I just trying to make stuff up and it is a warped rotor?

Thanks.
 

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Described sounds like a warped rotor. You could use Dykem to make the rotor front and back side (of the same rotor) and free spin. After the rotation if the Dykem is "spotted" on the rotor then there you go. Never seen an out of round wheel chatter during braking only. Hope this helps or at least clears an item.
 

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Described sounds like a warped rotor. You could use Dykem to make the rotor front and back side (of the same rotor) and free spin. After the rotation if the Dykem is "spotted" on the rotor then there you go. Never seen an out of round wheel chatter during braking only. Hope this helps or at least clears an item.
mark the rotor, not make the rotor
 

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Discussion Starter · #4 ·
Described sounds like a warped rotor. You could use Dykem to make the rotor front and back side (of the same rotor) and free spin. After the rotation if the Dykem is "spotted" on the rotor then there you go. Never seen an out of round wheel chatter during braking only. Hope this helps or at least clears an item.
Ok, since I've never done what you suggested, want to make sure I understand.

Use the dykem, make one mark on both sides of the rotor, spin the wheel, the brake pads should smear the dykem evenly but if there's a break in the smear "spots", means warped rotor?
 

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Ok, since I've never done what you suggested, want to make sure I understand.

Use the dykem, make one mark on both sides of the rotor, spin the wheel, the brake pads should smear the dykem evenly but if there's a break in the smear "spots", means warped rotor?
The Dykem is a marking dye that removes easily with brake cleaner. You will "paint" the rotor on both sides completely. Turn the wheel by hand, one revolution should be enough but two will not change it. The brake pad will mark the Dykem, but you will be looking for an area(s) where the area of Dykem removed more than what will be "normal" to what you see is the area of "warp."

So you apply the Dykem, rotate the wheel two (2) revolutions. Not spin the wheel but just by hand nice and easy. The Dykem will be removed by where the pad is in contact with the rotor. If the rotor is true then the Dykem "smear" will look the same all the way around. If the Dykem has been rubber off in a spot(s) then this shows you where the rotor is not true.

Dykem for me in the 48s is found at Lowe's and other hardware stores. The last bottle I purchased was from Amazon (not meant as any form of advertisement). If you are close to any type of machinist to tool seller, they should be able to sell you some. The Dykem will have a brush in the lid, simply paint it on the surface, it dries very quickly. Once dry, perform your test. When done spray brake cleaner into a rag and wipe off leftover.

Once again, this will only confirm there is an issue or not an issue with the rotor being true.
 

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Discussion Starter · #6 ·
The Dykem is a marking dye that removes easily with brake cleaner. You will "paint" the rotor on both sides completely. Turn the wheel by hand, one revolution should be enough but two will not change it. The brake pad will mark the Dykem, but you will be looking for an area(s) where the area of Dykem removed more than what will be "normal" to what you see is the area of "warp."

So you apply the Dykem, rotate the wheel two (2) revolutions. Not spin the wheel but just by hand nice and easy. The Dykem will be removed by where the pad is in contact with the rotor. If the rotor is true then the Dykem "smear" will look the same all the way around. If the Dykem has been rubber off in a spot(s) then this shows you where the rotor is not true.

Dykem for me in the 48s is found at Lowe's and other hardware stores. The last bottle I purchased was from Amazon (not meant as any form of advertisement). If you are close to any type of machinist to tool seller, they should be able to sell you some. The Dykem will have a brush in the lid, simply paint it on the surface, it dries very quickly. Once dry, perform your test. When done spray brake cleaner into a rag and wipe off leftover.

Once again, this will only confirm there is an issue or not an issue with the rotor being true.
Thank you.
 

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"What I did notice by eye is that my front wheel/tire wobbles a little?"
Don't like the sound of this. The wheel is probably OK. With the wheel up grab and try to wiggle about the axle. Any movement: wheel bearings.

Also could be the tire: poorly seated bead or just wear.

I don't think this relates to brake pulse, but worth looking at while the wheel is up. BTW, I've never had a disc brake that didn't pulse a little.
 

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Discussion Starter · #8 ·
BTW, I've never had a disc brake that didn't pulse a little
This is interesting, maybe this is what I am feeling?

I'll do as you suggested with the wheel up, to see if there's a wiggle about the axle. I've taken immaculate care of this bike since it came into my hands at 5,500km.

I'll report back.
 

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Able to get a clear answer? I've tried to think of things that would give you this feeling. I've seen and felt untrue tires, but it felt more like a hop and did it the entire time. Bearings is interesting but would be easy to tell while the wheel is up. I'd think not on this but weird things happen so it's worth chasing.
Hope your able to find an answer.
 

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Discussion Starter · #10 ·
Rotor is warped. Took another look, with a light, while the bike was up and saw the rotor moving back and forth and heard it grind against the pads unevenly.

Might buy the Galfer but it's $500CND after taxes etc, so I'll have to see...
 

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Rotor is warped. Took another look, with a light, while the bike was up and saw the rotor moving back and forth and heard it grind against the pads unevenly.

Might buy the Galfer but it's $500CND after taxes etc, so I'll have to see...
Something that's free to try before committing to buying stuff.

Put a nut and bolt through the bobbins and lightly tighten (don't crush) Then use a spanner on the bolt and rotate the bobbins back and fore. It is possible (should be) to turn the bobbin using finger and thumb pressure but you'll get a sore hand after a few.
The bobbins are meant to be free to move without rattling to allow the disc to self centre. If one or two are stuck then the disc can appear to be out of true.
DO NOT spray them with WD etc as the centrifugal force will make it flow out across the braking surface and is not required anyway.
 

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Discussion Starter · #12 ·
Something that's free to try before committing to buying stuff.

Put a nut and bolt through the bobbins and lightly tighten (don't crush) Then use a spanner on the bolt and rotate the bobbins back and fore. It is possible (should be) to turn the bobbin using finger and thumb pressure but you'll get a sore hand after a few.
The bobbins are meant to be free to move without rattling to allow the disc to self centre. If one or two are stuck then the disc can appear to be out of true.
DO NOT spray them with WD etc as the centrifugal force will make it flow out across the braking surface and is not required anyway.
I do this every season. Thanks for the tip.

I ordered the Galfer :)
 

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Possibly check your brake line as well?? air bubble in the brake line can cause the pulsing. It can also occur when your brake line is bent. SO CHECK THAT BEFORE ANYTHING.
 

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Possibly check your brake line as well?? air bubble in the brake line can cause the pulsing. It can also occur when your brake line is bent. SO CHECK THAT BEFORE ANYTHING.
Never found that before, how would air or bent hose cause pulsing ? JUST CURIOUS.
Pulling the lever in will tell you if there's air in the system, or at least it always did in the past, how and where would you suggest the line managed to get bent or kinked.
 

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Never found that before, how would air or bent hose cause pulsing ? JUST CURIOUS.
Pulling the lever in will tell you if there's air in the system, or at least it always did in the past, how and where would you suggest the line managed to get bent or kinked.
It happen, to me, I was adjusting my handle bars and some how it creates air in the line. Have like a pulse like issue with the front breaks. Looking at the scrambler you see from the front break line is quite curve. I was adjusting it somehow screw it. But mechanics flushed it out. All good now.
 

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It happen, to me, I was adjusting my handle bars and some how it creates air in the line. Have like a pulse like issue with the front breaks. Looking at the scrambler you see from the front break line is quite curve. I was adjusting it somehow screw it. But mechanics flushed it out. All good now.
Something's maybe wrong with my eyes because I can't see how air in the 'brake' line can cause 'brakes' to pulse.
If you 'break' the seal at the banjo when adjusting handlebars etc. you can easily introduce air into the system and need to bleed them then but never have I come across a pulsing brake due to this.

No matter, you got it sorted, all good and I'm glad you posted here and shared, because you never know.
 

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Discussion Starter · #17 ·
Possibly check your brake line as well?? air bubble in the brake line can cause the pulsing. It can also occur when your brake line is bent. SO CHECK THAT BEFORE ANYTHING.
I bleed the lines every season. As for the curve, I don't think that would cause a pulse. Also, though I appreciate the input from everyone. I did post that I confirmed the rotor being not "true". I can hear it and see it. Hear it by intermittent pad to rotor contact as I spin the wheel, and see...well, see the rotor moving laterally as I spin the wheel.
 

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I bleed the lines every season. As for the curve, I don't think that would cause a pulse. Also, though I appreciate the input from everyone. I did post that I confirmed the rotor being not "true". I can hear it and see it. Hear it by intermittent pad to rotor contact as I spin the wheel, and see...well, see the rotor moving laterally as I spin the wheel.
Right, and that could be caused by the bobbins, or little silver rings, attaching the rotor ring, (big silver ring) to the hub, (black spider shape piece in the middle) to be jammed up, so before you replacing anything, do as Hui suggested and make sure every single bobbin is rotating freely and not jamming up, causing your rotor to be off-center.
 

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Discussion Starter · #19 ·
Right, and that could be caused by the bobbins, or little silver rings, attaching the rotor ring, (big silver ring) to the hub, (black spider shape piece in the middle) to be jammed up, so before you replacing anything, do as Hui suggested and make sure every single bobbin is rotating freely and not jamming up, causing your rotor to be off-center.
If it is the buttons, then they are just really bad quality. I've cleaned them several times, they spin freely when I do the method I described above, touch of brake cleaner and let it spin. I even physically manipulated the rotor at each button to see if it allows for flex, and it does, yet the rotor is still not "true" and hence it's being replaced.
 
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