MattyMurdah

Hey Guys,

I purchased my first set of carbon clinchers from Competitive Cyclist in June of this year and I recently noticed there is some visible wear on the brake tracks. The wheelset is a set of Mercury M5's and I've only ever used Mercury's own brake pads, have never ridden in the rain, and I clean the bike almost religiously (every 50-100 miles tops).

Is this normal for wheels this new? Have any of you experienced similar wear like this?

I'm going to submit a warranty claim through CC to see if they can comment or possible replace but, being my first set of all-carbon wheels, I'm a little concerned and frustrated that they may already be breaking.

Thanks for any advice!

Dan Burkhart 

What brake pads are you using? You're aware carbon rims require a special pad compound?

SquidPuppet

That's pretty nasty. I'm curious to learn more.

Altimis

That's serious wears, did you brake hard a lot while descent or what?.

From what I read, this is your very first carbon rims? how you do braking on carbon and aluminum rims will not be the same practices.

Aluminum rims, you can do a lot long hard squeeze at you want without fear of rims wear but not carbon rims. With carbon rims, you want to "taps" multiple time to brake like "stop-release-stop-release", never long squeezing braking or else heat will built up quickly and may risking damaging carbon rims surfaces.

I never use stock brake pads even its came from their own brands, most of them are poor and cheap quality.

I never bought cheap one from store either, always use the highest modulation brake pads (often softest pads).

Next time you should try SwissStop Yellow or Black one carbon brake pads, quite expensive but worth every coins and your carbon rims will thanks you.

Anyway, your rims still hold though, just change the way how you brake and change the pads.

MattyMurdah

I've made sure to only use the Mercury branded pads that came with the set because I know that swapping them out will void the warranty. Braking has been a little spongy/sticky feeling at times but I thought it was just because of the new material and carbon-specific pads. I've definitely braked much more cautiously with these - always trying to be mindful of how long I squeeze the brakes and making sure to "pulse" on and off, sometimes alternating front and rear if I need to keep braking down a descent.

I've read that carbon brake tracks can wear more quickly than aluminum but I've been nothing but delicate with these wheels. I live in San Francisco and so occasionally ride climbs like Mt Tam which require some fairly consistent braking on the downhill, however nothing I would consider aggressive braking by any means. The wheels literally have less than 1500 miles on them, probably closer to 1000.

MattyMurdah

Yeah I have made sure to only use the Mercury branded pads that came with the set.

gsa103

The wear looks weirdly narrow. Do both rims show that or only the front?

Kimmo

Need better pics; multiple angles in daylight.

MattyMurdah

Both rims show the exact same wear pattern - it looks like two symmetrical streaks that run parallel on the brake tracks. For whatever reason, the back is showing more wear than the front.

I just swapped out the brake pads with some brand new Mercury ones hoping it might buy me some life on the wheels. Pictures of the old and new pads are attached - they look about 50% worn through but other than that nothing weird seems to be going on.

Wondering if the stock brake pads could literally be so bad that they are ruining the wheels? Will update you all when I get a response from CC :\.

MattyMurdah

I will snap some better ones tmrw morning and upload.

Andrew R Stewart 

No image of the pads' actual braking surfaces. Are there any bits of grit embedded into the pads' surfaces? This thread is one more reason that carbon isn't always the best choice... Andy

chorlton

My immediate thought as well. Recently my rear brakes on aluminium rims started making horrible noises and it turned out the right pad had a lump of shiny metal embedded in it. Naturally I was/am slightly concerned that it might have been chewed out of the rim itself but could not find a corresponding missing bit. However the right rim was scored in a way very similar to what the OP's pictures show.

I would guess that in the case of metal on metal the noise that alerted me to the problem might not be as obvious if something, metal or otherwise, embedded itself in the brake pad and was run against carbon fibre. It might be there for a while doing damage and then, when you notice the damage, it has already dropped out of the pad. You did not hear it you just saw the damage later.

Andrew R Stewart 

Pad surface embedded grit will act as a lathe turning tool bit and lightly gauge the rim's brake track. The AL rim will have a shallow cut but with the rim about 77" "long" the amount of Al shavings that get further trapped in the pad can be greater then any one section of rim might suggest.


Back in the day with relatively soft AL used for rims and the then pad compounds this was a common issue. I moved away from Campy pads for my NR calipers for this reason. The recently developer Scott Mathouser pads reduced this grinding of the rim a lot, but not completely. Andy

prj71

Disc brakes for the win!!

chorlton

Just in case I missed that, and I initially did. What you are saying is the lump of metal in my brake pad was an accumulation of metal scraped off the rim by what may have originally been a bit of grit. I can believe that and it is quite HorrorShow.

I should have saved the lump of metal for an analysis I do not have the tools to do. Maybe it is reported elsewhere but I have seen no references so it could be a 'project'.

The rim is an Alesa 622x14 from a 1990 bike... 77 inches and the track is that length. Originally black but that finish has been worn off. It was prior to the recent damage.

Interesting stuff.

chorlton

FTW!!!1!!!

Just don't ask any questions on the forum when yours go wrong.

MattyMurdah

I've definitely had this happen on my rims with alu braking surfaces which is why I constantly check the brake pad surfaces and pick out the metal shards or grit with a needle. However, I've not once seen anything embedded in these carbon pads :\.

The other thing that makes me think there's something bigger happening here is that BOTH front and back brake tracks have nearly the same wear pattern - two symmetrical streaks that run parallel with the track. The chances that there are undetectable shards of road grit lodged identically into both sides would seem impossible.

woodcraft

Looks like a defective set.

File the claim.

fietsbob

Save your Carbon wheels for the race, train on something less expensive.

Dan Burkhart 

The shop that I build a branded line of carbon wheels for used to get pads with the rims from the manufacturer, but after a lot of issues with delaminating brake tracks they now carry Swiss Stop carbon specific pads exclusively. There are a lot of crappy pads out there posing as carbon compatible.

MattyMurdah

That's interesting! Damned if you do, damned if you don't, I guess? Use the branded pads to keep warranty and ruin the wheels or use non branded pads and void warranty but hope for better wear?