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I was wondering which you'd expect to wear faster: wheel rims or brake blocks.

The reason I ask is that my mileage has shot up the last couple of years so I'm seeing a lot of wear on things I never knew could wear.

I'm told that chain, cassette and front chain rings should generally be replaced together. As per comments and answers I won't be using that cycle shop again. Luckily it didn't cost me too much cash.

I was wondering if the same applied wheel rims or if or if wheel rims are expected to last much longer than brake blocks?


Edit

So here's what prompted the question... I have some "Mavic Open Pro" rims bought two years ago. I've burned through less than 2 sets of brake blocks since. This last month I've started hearing about rims wearing and the existence of markers. Here's where I get stuck. I can't find any markers.

So although the above seems a stupid question I'm trying to figure out if it ever had them? I'm presuming not because I would have thought I'd notice and I shouldn't have worn them smooth yet judging from comments. I'm also trying to figure out if I don't have them what the sign would be if they need replacing.

By the sound of it I wont need to worry for a while, I've got a few brake pad changes left in them yet... but for piece of mind I wonder if there's a way to know if they're out of tolerance without markers?

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    The chain should be replaced when it's stretched, the cassette and rings when they're worn. If you service each appropriately you will get maybe 2-3 chains per cassette and 2-3 cassettes per large ring. (But if you replace a cassette you should usually replace the chain at the same time.) And you should be able to get several standard brake block sets per rim. – Daniel R Hicks Nov 24 '14 at 12:43
  • New pads on really old rims will take some time to wear into the grooves and give you full stopping power. This is also why really worn rims wear out your brake pads faster. It's really important to properly adjust your brakes so that you get even wear, and better preserve your rims. – ShemSeger Nov 24 '14 at 16:16
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    @superluminary Even though the brake blocks are rubber, dirt and grit gets between the brake block and the rim, causing wear every time you brake. – Johnny Nov 24 '14 at 18:20
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    Regarding the edit, not all rims have wear markers. Generally the wear markers are a ridge (replace when disappear), or a dimple (replace when appear). It seems that the Open Pro's don't have any wear markers so you need to use a caliper and measure the maximum wear of the rim (Mavic says 0.4 mm). – Batman Nov 25 '14 at 17:30
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    I've never worn out a rim, but a couple of images of failed rims have been posted here, and in those cases it was obvious that the rim was worn out -- there were essentially holes worn through it. I don't know if this is always the case, but I suspect it is fairly normal. – Daniel R Hicks Nov 26 '14 at 1:59
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Rims last a lot longer than brake pads. It's difficult to put a number, as it depends on so many parameters, but personally I change brake pads roughly once a year (2-3'000km), and I haven't ever changed a rim due to it wearing out. (There has always been other reasons to change them.)

On many rims there's a tiny groove in the middle of the braking surface. You're supposed to change the rim when the bulk of the rim has worn down to that level. (But as I said, it hasn't happened to me yet.)

Regarding your other advice, 'replacing cassette, chain ring and chain together', it's not the most common of advice, to put it bluntly. The advice you're likely to get is to change the chain when it's starting to wear (you have to measure the length of it, either with a special chain-tool, or with a tape measure. If it's increased by 1% it's time to change.) If you don't change the chain it will start to wear down the cassette, and eventually the chain ring - but that takes a lot longer.)

  • +1 Wearing out a pad is pretty unequivocal. Wearing out a rim is a little more subjective. A worn rim will crack more easily than a new one, but will be fine until then. – goldilocks Nov 24 '14 at 20:43
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Typically it's the brake pads that wear faster as they are the softer material. However, under certain (but rather special) conditions it can be the other way round.

If you ride in an area where there's lots of dust from hard and sharp materials in the air (something like granite dust or dust from volcanic rock) and it is in addition often rainy, you might get some grinding paste like debris onto your brake pads that could grind down your rims in no time. But luckily that is a rather rare occasion and normally rims should last for several sets of brake pads.

Also both have normally indicators that tell you when they need replacement. For the brake pads you should replace them by the latest when they are worn down so much that the notches – that are to better remove water and debris from their surface – are no longer existent. Rims have for some years now also a notch (often differently colored) in their braking surface. If the surface is worn down so much that the notch is gone, they should be also be replaced. In this case it's also a safety thing as the structural integrity of the rim might get affected if you use it above that point.

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I would expect brake blocks to wear out, to the point of needing replacement, much faster than rims. However, the rims may look gouged or a little rough, long before that.

Both will wear out faster if you are riding in dirty/gritty conditions.

The rate of wear can also depend on the kind of rim blocks you use. In my experience it's worth investing in good brake blocks to preserve your much more expensive rims.

When choosing blocks, there is also a bit of a trade-off between braking power and wear on the rims. Several people I know who do very high mileage recommend Swisstop Green, which are apparently kind to the rims and provide reasonable stopping power in all conditions. Others swear by Koolstop Salmon for their stopping power, although they may wear the rims a bit more.

Whatever you use it's a good idea to remove any bits of grit/metal from the blocks regularly as this will wear the rims much faster than any block.

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Checking Mavics for wear:

Not all Mavic rims have the wear indicating groove along the rim.

Some rims, including a pair of Mavic Ksyrium I currently ride, have a small circular wear indicator on each side, located on the rim brake surface exactly opposite to the valve location. Such wear indicators do not wear away, like the groove, but rather a small hole will appear as the rim is almost worn out.

I cannot find if your OpenPro's have this, but if they lack a wear indicating groove chances are they do. Please check the Mavic documentation to make sure.

Note that it is possible under strong light to see the indicators, even if the rim is not worn out. You will only need to replace the rim as soon as you can clearly see the hole (unfortunately I don't have a photo but it is pretty obvious)

  • Very helpful. Thanks! I'll have a look and check. – Philip Couling Nov 26 '14 at 14:20
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Rims last much longer than brake blocks. If you are biking in gritty conditions (in my case slushy snow with sand mixed in) then you will wear out rims a little faster.

I've had two rims wear out, and the failure mode was not catastrophic, but it showed up as a thump wile braking. Don't worry about lack of wear markers.

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I takes a lot of miles to wear out rims. A cheap bike with really cheap rims will wear out faster.

Often there will be wear bar and when you wear through that the rim is at the end of its life. If not you could use calipers.

If you don't have a wear bar what will typically fail first is the seam where rim joins. When you see it start to separate then it is time for a new rim.

You take it to the shop to have it straightened and they tell you the rim will just not true and you need a new one.

Then the choice is to put new rim and spokes on the existing hub or buy a new complete wheel. Unless you have a high end hub that is designed to last multiple rims you should get a complete wheel.

If it is a bike you plan to keep then consider getting a new wheel before it is gone all the way to have spare.

Also is it a wheel that would work as a spare if you bought a new bike. Like a 26" on a mountain bike then don't spend much as the new bikes are 29" disc.

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