Brakes damaging rims?

class5700

Hi,

First post but I have lurked for quite a while now.

I have a new Trek 1.2 with just 150km on it. Recently I had a problem with grinding on my rear brakes, which came on at the bottom of a long descent. I dismantled the brakes and found metal pieces lodged in the brake block, which I removed. Problem apparently solved for the next ride or two.

Today I had the same problem occur again (bizarrely, at the end of exactly the same descent!)

The metal is obviously coming from the rim and as far as I can see I have set up the brakes correctly.

I have read that this can happen, but not why it can happen or how concerning it is.

So I am wondering:

Is the problem likely to be the brakes or some manufacturing fault with the rim?

I will of course take it back to the shop for them to have a look, but want to learn a bit more first.

Thanks for your help.

nigelgos

I doubt it's a fault. Which brake pads are you using? I found since switching out my 105 pads for some Kool Stop ones that they picked up less derbies and gave greater stopping power. Swisstops seem to get a mention as good ones from lots of people too.

class5700

they are just the unbranded stock ones that come with the bike. I had read that the brakes were a weak point before purchasing it though. been thinking about upgrading but not if the same problem is likely to come up.

the thing is that the braking efficiency reduces dramatically when this grinding has happened. luckily both times were at the bottom of the final hill up to my house. not sure I would trust them for another descent and if it had happened earlier I would probably still be walking home now!

ugo.santalucia

metal shavings in the pads are normal... yes brake pads damage the rims, you can say that

dodgy

Yes perfectly normal, I have to pick alloy shards out of my brake blocks often, and it's the reason why I'll never buy another rim braked bike again.

Bring on the discs.

kajjal

I use swisstop greens which don't seem to do much damage to the rims.

lapavoni10

Yes, a problem with all older brake blocks, and some cheaper ones.

I have used Campag ones for many years now and have never had the same issue.
No need to ditch the brakes, just get some decent blocks and you should be ready to rock and roll.

class5700

wow, that is not what I was expecting to hear! I guess that is good news. I assume this is then all part of 'breaking in' the bike?

I'll try changing the blocks and see how it goes.

ugo.santalucia

It's not the pad that grids the rim as clearly in a hardness experiment rubber cannot scratch aluminium, but debris that gets stuck in the pad and grinds the rim... you can believe in magic potions and rubber that is gentle to your rims, but in my experience any pad will do that (including the Campagnolo mentioned above). Keep them clean, clean them more... or throw money at it for the latest green/yellow/blue/red wonder rubber... your choice

keezx

Koolstop Salmon.

class5700

ugo.santalucia wrote:

It's not the pad that grids the rim as clearly in a hardness experiment rubber cannot scratch aluminium, but debris that gets stuck in the pad and grinds the rim... you can believe in magic potions and rubber that is gentle to your rims, but in my experience any pad will do that (including the Campagnolo mentioned above). Keep them clean, clean them more... or throw money at it for the latest green/yellow/blue/red wonder rubber... your choice

ha ha ha. ok, point taken (I'm new to this, in case it was not obvious)

earthvspace4XTuUWcX

I partly disagree with Ugo, better quality and softer pads (I like the Koolstop Salmons too) seem to be less prone at picking up debris/bits of aluminium or whatever than cheap hard pads, they also improve the overall braking feel/performance, so for the sake of a few quid are worth it.

lapavoni10

Yes, cheaper/older pads I believe are more prone to pick up debris, whether its the compound or the pattern on the pads. Have not had issues for years now, and although rim material has probably got harder, I think its down to pad compound.
I am not clinical when cleaning my bikes but do wash the brakes and rims thoroughly.

class5700

great. thanks for all your replies.

dodgy

xdoc wrote:

I partly disagree with Ugo, better quality and softer pads (I like the Koolstop Salmons too) seem to be less prone at picking up debris/bits of aluminium or whatever than cheap hard pads, they also improve the overall braking feel/performance, so for the sake of a few quid are worth it.

That's counter intuitive, you'd expect a softer pad to more easily allow bits of alloy and grit to become embedded into the pad.

earthvspace4XTuUWcX

dodgy wrote:

xdoc wrote:

I partly disagree with Ugo, better quality and softer pads (I like the Koolstop Salmons too) seem to be less prone at picking up debris/bits of aluminium or whatever than cheap hard pads, they also improve the overall braking feel/performance, so for the sake of a few quid are worth it.

That's counter intuitive, you'd expect a softer pad to more easily allow bits of alloy and grit to become embedded into the pad.

I agree dodgy, but in practice, in my experience, that does not appear to be the case.

ugo.santalucia

Here's a class society explanation: Grit and dirt are clearly working class, if you buy proper upper middle class pads (>35 quid for the set), the grit doesn't want to stick to them.... simple...

mamba80

I think what happens is the harder compound pad still picks up the grit etc and then, because the pad doesn't wear as quickly, it then has far longer to wear away at the rim, picking up lots of alloy shards along the way.
a softer pad wears down quickly and the offending debris get removed faster, unless you constantly ride in the wet that is.
Shimano pads (which r not cheap) seem particularly prone this, where as, say halo gooey pads, which are dirt cheap, very soft, do not hold onto the crxp and are great in wet and dry and in mho far better than the expensive sets.

John.T

Been using Koolstop Salmon for years. They hardly ever take chunks out of the rims but, as with all pads, they still wear the rims especially in winter. They are not expensive, I paid £6 a pair last time. One set will last all winter on the rear and 2 on the front. They seem to last for ever on the summer bike. I had forgotten how bad some pads are until I got a warranty Madone frame recently with Bonty direct mount brakes. The noise and damage was horrible. A set of Koolstops soon sorted that out. No noise, better power and modulation.
If you have one piece pads and shoes get the Koolstop pad and shoe set. £16 for 2 shoes and 4 pads. From then on just pads needed.

class5700

John.T wrote:

Been using Koolstop Salmon for years. They hardly ever take chunks out of the rims but, as with all pads, they still wear the rims especially in winter. They are not expensive, I paid £6 a pair last time. One set will last all winter on the rear and 2 on the front. They seem to last for ever on the summer bike. I had forgotten how bad some pads are until I got a warranty Madone frame recently with Bonty direct mount brakes. The noise and damage was horrible. A set of Koolstops soon sorted that out. No noise, better power and modulation.
If you have one piece pads and shoes get the Koolstop pad and shoe set. £16 for 2 shoes and 4 pads. From then on just pads needed.

thanks for this. trouble is, I've been looking for the pad and shoe set, as you and other have suggested, for Kool Stop pads (I believe it is the Campy 2000 I'm after), but no one seems to sell them any more...nothing on ebay, amazon, through all the distributor sites, not to mention all the main online shops of course. I wonder if they have been replaced with something else...

John.T

I think your Trek will have Shimano brakes. These will fit fine.
http://www.bicyclehero.com/gb/kool-stop-dura-set-dual-pads-salmon.html?gclid=CjwKEAjwyYCgBRCMmbWl5beV_RQSJABESqHAqFh9wwNA38llSewiqw_ljlxM_-QsxttvPUfuvHILzxoCc4Xw_wcB#.VADDrcVdWrY
From then you will only need these.
http://www.spacycles.co.uk/products.php?plid=m2b0s104p822
I can recommend the Salmon ones for general use.

class5700

^^^cool. thanks. that site had some enormous shipping so I went for some shimano blocks with salmon replacements from wiggle. looking forward to braking with confidence, and expanding my routes to some steeper gradients as a result.

andrew_s

I used to get bits of metal in my brake blocks, and also wear the rims out in 5 or 6000 miles.
I swapped from Shimano to Koolstop pads (salmon or salmon/black dual compound), and things have been OK since.

meanredspider

3 years on the Volagi in all weathers and absolutely zero wear on the rims - I use cheap pads too - and I stop just great in the wet 8)

class5700

well I can report that I have just been out with my new brake blocks (shimano with the kool stop salmon inserts).

what a difference!!! I went out for a 50k ride with lots of sharp gradients and they are just night and day from the rubbish stock ones. quiet, powerful, excellent! and being a bit of a geek I found them to weigh 40g less. 8)

anyone who finds this thread: throw away the unbranded blocks asap. pretty sure anything would be better, but the salmons are a great improvement.

thanks to those who responded.

pinarellokid

I bought swissstop greens for my Sunday bike and was I sung them on Campag zonda wheels,
I was shocked at how quickly the filings collected in the rubber pads, you can clean them out fine but what I didn't like was the fact the rims were being worn down so quickly. I don't like the idea of wearing my nice rims away. Swapping g the pads back to Campag ones has sorted my issue.. I don't find filings in the pads now. All I can assume is the rims are made of a sorter alloy, on the zonda's. Probably to save weight as they are very light wheels. I now use the green Swiss stop pads on my winter wheels which are Khamsins and they don't pick up filings, I assume the rims are harder and don't allow the pads to wear into them.

holiver

Yeah my Khamsins appear extremely hard wearing too.