Wednesday 28 March 2007

Slippery when wet

We had a spot of rain last week, which meant I got wet coming home for the first time in a long time. It was nice to ride in the rain, given that the air temp was in the high 20's or low 30's, so the rain went a long way to taking the edge off the thermometer.

It's been so long since I've been in the wet that I'd forgotten the impact it has on the brakes. With a car, it takes longer to pull up in the wet, but at least you have a lot more rubber making contact with the road, and the brake pads tend to grip on the brake disks as soon as you pump the brake pedal.

Not so with the treadly. I was ambling along and needed to slow down, so I gave the brake levers the usual amount of squeeze.

Nothing happened for a few seconds, which is how long it took the wheels to do several revolutions.

So I squeezed harder. The pads started to grip a bit, but it was only enough for them to go "squeak, squeak, squeak", and not enough to actually retard my forward motion.

So I gave them everything I had, which involved pretty much trying to force the levers and the handle bars to fuse together, and I finally started to slow down. I thought I was about to go into the back of a hire car when everything finally worked and I came to a halt.

In the wet, after you squeeze, the first revolution of the wheel simply wipes off he excess water from the wheel rim. The second revolution dries the rim out a bit (assuming it is not bucketing down and replenishing the rim with wetness faster than it can be rubbed off). The third revolution is when the pads start to bite.

Now the average bike wheel is a lot bigger in diameter than your car wheel, so three revolutions takes you a long way. I can't figure out the maths but it has something to do with pi and it seems to boil down to this....."aaaaarrrrggghhhhh!", which is the sound you make when you suddenly find that your bike has all the braking potential of a greased humpback whale being pushed down a playground slide.

One day, there will be a revolution in the braking systems fitted to road bikes.

I hope I live to see it.

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