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Question about brake pads and rim wear indicator grooves

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Question about brake pads and rim wear indicator grooves

Old 03-02-14, 01:09 AM
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Question about brake pads and rim wear indicator grooves

Hi newbie here...

So a few months ago I got a new bike (Giant Escape 1) that I use for commuting and I've put about 500mi on it. Today while cleaning, I noticed that the brake pads contact the rims on a groove in the rims which I deduced is probably a wear indicator for the rims (pic 1). Then I took off the pads and saw that there is a raised ridge on the pads which aligns to where they contact the groove on the rim (pic 2).

So, I have a few questions: Is this normal that the brake pads contact the rims right on the groove? I'm not sure where they started when the bike was new, but the contact surface may have moved down as they wore down. Should I leave them in this position, or move them up a little higher on the rim so they don't contact the groove? When re-installing the pads, should I sand down the ridge on them or just not worry about it?

One reason I'm wondering about this is because my brakes don't have what I would consider a lot of stopping power. For instance I cannot lockup the rear wheel even if I pull on the brake lever as hard as I can.

I would think that you would not want the brake pad to contact the groove because the rim is pretty wide and you would lose about about 10-20% of the brake-rim contact surface. On the other hand if you are not wearing the rim around the groove then it can't really function as a wear indicator, right?


Pic 1. The black line is the groove in the rim and it is maybe a few mm deep.


Pic 2. Notice raised ridge on the pads
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Old 03-02-14, 04:11 AM
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IME, i've never seen bike brake pads that were manufactured with raised ridges, but then again i usually just use those old-fashioned black ones that haven't changed for the last 75 years of so....

OTOH, that mark around the rim looks like typical rim wear that i've seen plenty of. it's usually a result of a bit of debris getting caught between the pad and rim for a while, causing a groove. it may eventually wear away.

it's hard to see from the pic how deep it is. IME they don't get very deep in as much as there is a telltale accompanying noise that let's me know that there is a problem.

Last edited by hueyhoolihan; 03-02-14 at 04:14 AM.
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Old 03-02-14, 08:29 AM
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Of course it doesnt address your question, but the increased use of disc brakes will render problems like yours moot.
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Old 03-02-14, 08:48 AM
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I don't worry about rim-wear indicator grooves. When your brake pads were new, they were smooth. The "tenon" you are looking at is where the pad has worn to match the rim. I don't worry about that either.

The PROBLEM you have described is poor brake performance. If it was my bike the first thing that I would do would be to take a fingernail emery board and dress up the surface of your brake pads to knock down any glaze that has formed. If that doesn't work (my bet) I'd treat myself to a set of Kool Stop salmon brake pads.
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Old 03-02-14, 08:51 AM
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Nothing to worry about, but I noticed that your brake shoes may not be setup the correct way in relation to the rim. Maybe that is the reason for not much stopping power. https://sheldonbrown.com/canti-direct.html

Last edited by lopek77; 03-02-14 at 08:55 AM.
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Old 03-02-14, 09:05 AM
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Are your brake cables adjusted properly? Even with hard pads, squeezing the brake lever as hard as you can should get some lock-up.

I don't run my pads exactly parallel to the braking surface of the rim, I install them with a slight skew (nose slightly up on the front side) so they cover more of the braking surface on the rim, giving more stopping power.
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Old 03-02-14, 11:12 AM
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Originally Posted by 02Giant
Are your brake cables adjusted properly? Even with hard pads, squeezing the brake lever as hard as you can should get some lock-up.

I don't run my pads exactly parallel to the braking surface of the rim, I install them with a slight skew (nose slightly up on the front side) so they cover more of the braking surface on the rim, giving more stopping power.
i doubt it, but i could be wrong. the surface area of a brake pad doesn't increase when rotated.
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Old 03-02-14, 11:18 AM
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Originally Posted by Retro Grouch
I don't worry about rim-wear indicator grooves. When your brake pads were new, they were smooth. The "tenon" you are looking at is where the pad has worn to match the rim. I don't worry about that either.

The PROBLEM you have described is poor brake performance. If it was my bike the first thing that I would do would be to take a fingernail emery board and dress up the surface of your brake pads to knock down any glaze that has formed. If that doesn't work (my bet) I'd treat myself to a set of Kool Stop salmon brake pads.
+1

The pads shown look like Shimano and these eat rims as we know.
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Old 03-02-14, 11:23 AM
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Originally Posted by Retro Grouch
I'd treat myself to a set of Kool Stop salmon brake pads.
Just skip straight to this. Much more better. You're welcome
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Old 03-02-14, 11:25 AM
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Originally Posted by rydabent
Of course it doesnt address your question, but the increased use of disc brakes will render problems like yours moot.
well, it will just be reworded with disk replacing rim, won't it?

like this:

Hi newbie here...

So a few months ago I got a new bike (Giant Escape 1) that I use for commuting and I've put about 500mi on it. Today while cleaning, I noticed that the brake pads contact the disk on a groove in the disk which I deduced is probably a wear indicator for the disk (pic 1). Then I took off the pads and saw that there is a raised ridge on the pads which aligns to where they contact the groove on the disk (pic 2).

So, I have a few questions: Is this normal that the brake pads contact the disk right on the groove? I'm not sure where they started when the bike was new, but the contact surface may have moved down as they wore down. Should I leave them in this position, or move them up a little higher on the disk so they don't contact the groove? When re-installing the pads, should I sand down the ridge on them or just not worry about it?

One reason I'm wondering about this is because my brakes don't have what I would consider a lot of stopping power. For instance I cannot lockup the rear wheel even if I pull on the brake lever as hard as I can.

I would think that you would not want the brake pad to contact the groove because the disk is pretty wide and you would lose about about 10-20% of the brake-disk contact surface. On the other hand if you are not wearing the disk around the groove then it can't really function as a wear indicator, right?

if only it were true.



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Old 03-02-14, 11:30 AM
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NB As the brake pad is thinner.. the way it contacts the rim changes *
and the contact of the pad moves towards the pivot axis of the brake caliper

with cantilevers that is towards the inside of the rim.. pivot on frame being below the rim..
* so that wear ridge matching the indicator groove in the rim, will go away
and/or be shifted in its location.. as seen, temporarily, on the pad..

when U brakes were popular, installed on the underside of the chainstays,
the brake pad contact veered off the outside of the rim and wore in to the tire sidewall

as you may expect, the tire blows out when there was a hole in the casing.


One reason I'm wondering about this is because my brakes don't have what I would consider a lot of stopping power.
For instance I cannot lockup the rear wheel even if I pull on the brake lever as hard as I can.
not able to critique the way you adjust your brakes , by remote sensing..
rear-wheel skidding is not a good practice, none the less.. flat spotting the tire..

but I am among the many riders using Kool Stop's Salmon compound pads, and find them quite satisfactory ,
in a cantilever caliper brake. properly adjusted ..

Last edited by fietsbob; 03-02-14 at 11:41 AM.
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Old 03-02-14, 12:08 PM
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[QUOTE=hueyhoolihan;16541062]well, it will just be reworded with disk replacing rim, won't it?[QUOTE]

Yeah, but it's a lot easier to replace a disc than it is to replace a rim. Cheaper too.
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Old 03-02-14, 12:20 PM
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Yes, it is a wear indicator groove. You get a corresponding raised ridge in the pad because the areas to either side, while the ridge didn't.

This is normal and I wouldn't sweat it either way as it really won't change anything. In any case brake pad movement is in an arc, and as the pad wears, the ridge will hit the rim in a different place and get shave off as a new ridge forms in a new place.
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Old 03-02-14, 02:41 PM
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Originally Posted by hueyhoolihan
i doubt it, but i could be wrong. the surface area of a brake pad doesn't increase when rotated.
Yea...I don't know what was on my mind, covers more rim area but doesn't increase surface area.
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