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When in wet conditions and usually going downhill on my (Road Bike with 25c tires) but even at a shallow downhill, when I am braking my rear wheel starts to slide, I am applying both my brakes but it still happens, I thought it may have been my technique but my son does the same but never skids even if he tries! Is this a tire problem? Thanks Also this happens when I am going straight down a road as well as round a corner just to be clear.

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  • How much do you weigh? To what air pressure are your tyres inflated ?
    – Criggie
    Jul 29 at 3:14
  • And what model of tyres are you using? Some tyres are well known to grip poorly in wet conditions.
    – Andy P
    Jul 29 at 8:03
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This is to be expected.

Bicycles have most of their weight on rear wheel on flat land, so some amount of braking using the rear brake is possible. Braking tends to skew the weight distribution towards front, so a rear brake is never as powerful as a front brake. Thus, most experienced cyclists, if riding on pavement, only use ever the front brake and never use the rear brake. An exception to this is maybe hard cornering -- if you need to brake during hard cornering, you have only very little braking power available since hard braking would lose traction and make you crash, so it might be beneficial to equally apply very lightly both the front and the rear brake during hard cornering.

When going downhill, the weight distribution is even more skewed towards the front. Even without braking, on a downhill you might have more weight on the front than on the rear. Brake a little and the weight distribution becomes even more front-heavy.

So, the rear tire has very little weight on it during braking. In wet conditions, the coefficient of friction is worse so that makes it even more problematic to use the rear brake on downhills.

Learn how to use the front brake. Note that unlike rear where skid is recoverable, when using the front brake you can raise your rear wheel (recoverable) or skid the front wheel (not recoverable). Front skidding can happen when there's sand on the road (acting like little ball bearing balls), or if riding on the wet over manhole covers or painted lane markings or other road markings. Also do note that the tar patches used to patch cracked pavement are very slippery in the wet.

Basically, sand is slippery and in fact, everything except normal pavement is slippery when wet.

Even on wet downhills, I would not touch the rear brake at all, unless the front brake fails in which case you have no other option than to skid the rear wheel. Every lane/road marking, tar patch, sandy portion and manhole cover should be a location where you temporarily stop braking.


And an addendum, some time ago it used to be fashionable to fit road bikes with colored tires. Those tires can't have carbon black in the compound, because that would always make the tire black. So they had to use silica instead of carbon black to make coloring the tire possible. Not all of these silica tires were colored, in fact some were black (although may be a slightly different shade of black than that in carbon black tires). Silica has very poor traction when wet, so if you have a silica tire you might want to replace it with carbon black tire. Also tires age so ten-year old tires should be discarded even if they have enough tread depth available.

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  • 3
    And it should be noted that posture affects weight distribution - If you're leaning forward on the handlebars you place more weight on the front. This may have something to do with the difference between you and your son. Jul 28 at 21:52
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    I don’t see why it is necessary to completely avoid using the rear brake, especially if you are able to move your body position around. Also, silica technology has improved dramatically, although I’m not sure if bike tires have caught up to automotive etc silica tech yet.
    – MaplePanda
    Jul 28 at 22:38
  • I'd really expect that brands that have both car and bicycle tires don't keep secrets between product lines. But I could be wrong.
    – ojs
    Jul 29 at 6:56
  • I'd hang my weight back behind the saddle, and take up the slack in the back brake, maybe a little more, as @MaplePanda hints. Also load (panniers, child seat etc) affects weight distribution and can hold the back down
    – Chris H
    Jul 29 at 9:39
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    Would there be a source for the 'experienced cyclists never use the rear brake'? Even though the front brake is the go-to one, adding a bit of rear will make you decelerate faster, more so the closer it comes to the point of skidding, so in occasions where that matters wouldn't the experienced rider aim for that exactly?
    – stijn
    Jul 29 at 17:50

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