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Not a duplicate of this one I think, circumstances are different.

My bike has rim brakes. The last two day I have cycled on snowy ground, and at the end of the rides the brake pads where covered in dirty snow.

Now I have noticed that when I use the rear brakes, I immediately smell a peculiar odor, even with light braking like the last 10 meters before a traffic light. The closest odor I can relate to it is the one of a used rifle shell few days after it was shot.

Is this normal?

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  • If you use your nose and smell the brakes up close, is the odour coming from the brakes? Or is it coming from the snow on the brakes?
    – Criggie ♦
    Dec 13, 2017 at 9:11
  • That sounds like a hot (or rather heated) metal smell, but it's odd that you immediately smell the rear brakes, which are behind you into a headwind
    – Chris H
    Dec 13, 2017 at 9:47
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    The key here is that the snow was dirty. Usually that means things spread from cars like particles from exhaust, oil and metal and rubber dust.
    – ojs
    Dec 13, 2017 at 9:51

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Generally no - smell would be an indication of heat and vaporisation of something. In a brake it would be the pad turning to smoke with overheating.

If your pad is that hot then your rims are about as hot, and will be very noticeable to the touch. This level of heating normally requires hundreds of metres of fast descent, combined with hard braking.

Snow on the brakes would pretty much make overheating impossible.

I suspect the snow has an odour. Its also possible your location salts the roads in times of snow, and this may be close enough to trigger your nose-memory.

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    Melting the snow may release the odour (so it just about could be coming from the wheels), as may slowing down at a spot where it's been melted by others. I suspect the latter is more likely
    – Chris H
    Dec 13, 2017 at 9:49
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    It's also dirty road snow that'll be full of tiny pieces of ground-up road and ground-up car. (See, for example, the Cody's lab episode where he manages to extract visible amounts of precious metals from road dust, presumably from cars' catalytic converters. He estimates that road dust contains about 7g/ton of platinum, for instance.)
    – David Richerby
    Dec 13, 2017 at 9:59
  • "Snow on the brakes would pretty much make overheating impossible." Not really.
    – Acccumulation
    Jan 30, 2018 at 22:00
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    @Acccumulation a flat denial offers no evidence. Feel free to add your own answer with more info. If your brakes have snow on/in them they can't overheat without melting the snow. So then you have wet brakes which are also somewhat hard to overheat. So they dry and then you have dry brakes which can totally overheat. But you don't have snow on overheating brakes.
    – Criggie ♦
    Jan 31, 2018 at 0:05
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I'd say it's not normal ... most people do not sniff their brake pads.:-) I suspect something was picked up on the rims & pads. Clean the pads (or replace) removing any embedded bits & clean the rims.

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