Friday, March 16, 2012

Playing In the Snow with Sherlock Holmes

The snow can both hide things and give clues.

The first picture shows a taxi on the sidewalk.  I thought it'd make a nice pic for my "naughty drivers" collection. Ok, taxis stop everywhere when they stop to pick or drop someone. Usually it's only temporary. But was that the case here?

What clues does this picture give? Two very obvious ones: no tyre marks in the snow means the snow came later, and huge snow free blot where the taxi was parked. Both mean that the taxi was here for a while. And because there was some snow on the roof but the windows were clean, the heat (and the engine) must have been on while the car was parked there. If there's no heat, the snow will freeze on the windows. So, parking in the sidewalk and idling the engine for who knows how long.

Well, Watson, what can we see in the picture below?

First, the snow banks on the sides are only knee high. That's because they've been pushed further away, under the trees. Looks like they've done it on both sides of the street, but it's more obvious on the left. We consider that as proof that the bikeway maintenance crew expects the snow melt this year, too.

Unfortunately I left my kneepads home, so I didn't examine the tyre tracks on the snow more closely. Therefore I can't tell you that ten minutes earlier a man weighing so-and-so many kilos rode south and returned  six minutes later after dropping of a letter at the post office. Why, there are sixteen new snowflakes on the tyre tracks, which gives the time difference. Also the tyre marks were 0,1 millimeter narrower on the back, so it's obvious he delivered something lightweight, under 50 grams, and the post office is in that direction.  Elementary, Watson!

Here the bikeway looks pretty smooth, and for the most part it is. There are just a little annoying things hidden under the snow. Old tyre marks left in the softened ice yesterday, and now they've frozen. The grooves here weren't very deep. Maybe an inch in the worst places. When they're up to four five inches in intersections where the snow plows fail to do the work properly, that's practically nothing.
Still, the grooves made the ride feel wobbly. It made me think I should go see if the studded tyres are on an end of icy season sale? Too early for that, yet. Maybe in June. Although the supermarkets have already started stocking their bike displays.

Part of the reason I felt so wobbly was very high pressure in the tyres. I have pumped them up to make the bike roll better. High pressure means smaller part of the tyres touch the ground, or ice in this case. The tyres aren't so elastic and will stay round, which means that they'll be more likely to get caught in the grooves instead of rolling over them. No, the tyre will actually seek the grooves.

So I decided to try if it would be better if I lowered the pressure. Here's a 'before' picture of the front wheel with approximately the right weight on the wheel. Leaning forward to take the picture changed the balance a bit but there's hardly any give in the tyre.
Watson, tell me what is that? --------^
There isn't an after picture, because after I deflated the tyres a little I had to re-inflate them again to stop the wall of the tyres touching the ground. Then I started riding, thinking I'd take the after picture if the pressure was right. Well, by the time I arrived at my destination I had forgotten about it. Sorry.

I wasn't so wobbly. It worked.

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