Collapsed rim

I managed to crash on a bike during a group ride (no one at fault besides myself). I could not reconstruct, what exactly happened: looks like my front wheel got suddenly turned aside and collapsed. The guy riding behind me told that my foot somehow mangled with the wheel, but I cannot understand how that could take place. Fortunately, the speed at that moment was very low, so the only damage I suffered is torn clothes and the pictured front wheel.

collapsedRim-1
collapsedRim-2
collapsedRim-0

Just recently I had to replace the rear wheel from this set because the rim did not withstand the spoke tension. That time, it was obviously the product’s inability to hold the applied load, which is a tradeoff for the ultralight weight. Now, with the front wheel, I do not have an indication that the ultralightness is at fault, as I do not exactly know what had happened.

Ultralight rim failure

I had to replace a rear wheel before leaving for a longer group ride:
crack-1
Drive-side spokes were tightened to 100Kg, which was just barely enough for non-drive side not to go slack.
crack-2
That was the most prominant crack, but not the only one – in fact, all drive-side sockets have developed smaller or bigger slits:
crack-4
This was an ultralight-class wheel with 24 spokes and under 400g rim. Weight-limited to 80kg, which I fit in, but without any reserve, has served me for some 10K kilometers. So I have decided not to send any claims to a vendor, but also not save on spoke number the next time – or use more meaningful 16/8 spokes.

754g, that is with stick-on rim tape.

754g, that is with stick-on rim tape.

Update: In just two weeks the pair front wheel collapsed in a small crash, so this ultralight wheelset does not serve me any more.

Probability of being caught in own loops

Suppose you are wondering randomly on a chessboard, starting from a corner, making one step up, down, left or right every time. You are not allowed to step on cells which you have already visited earlier. What are the chances that at some point you’ll not be able to go anywhere, i.e. you get caught in a dead end made by your own previous steps?

I got no idea how to solve this “purely”. Out of curiosity, I calculated the probabilities programmatically for 8×8 board for any path length (up to 63, naturally). Blue line shows the probability of being stuck at given path length or earlier, yellow line – 10 x probability of being stuck exactly at this path length.

Probabilities

Graphs do not show anything unexpected, except – what happens at points 48 and 49? I have no idea.

The calculation was straightforward by “first thought” without any optimizations. For each path length, I did 10^6 runs; with this amount, dispersion in the results between runs was by far under 1%, and run time acceptable (I do not indicate the units of the right Y-axis 🙂 )

Surprisingly I was not able to profile the run with gprof; looks like MacOS default C compiler and/or libraries just do not do it.

Still interested in a general solution, if there exists one.

SRAM ESP ~ Shimano Dyna-Sys

I have got a report that these two types of rear deraileurs have the same mechanical advantage:

  • Shimano Dyna-Sys (which are marketed only as “10-speed”)
  • SRAM E.S.P (which are marketed only as “9-speed”

Sram ESP and Shimano Dyna-Sys rear derailleurs have same mechanical advantage

Both take 35mm of cable to go over the whole cassette. Picture shows SRAM X.9 and Shimano XT, but any other derailleurs of the mentioned types would be interchangeable.

This means that either one can be replaced with another (provided that it can handle your biggest cog). I have not verified this myself. Remember that “SRAM 10-speed” deraileurs have different mechanical advantage, as do “Shimano 9-speed” ones, and there are no other pairs which are not designed for each other but work.

Maybe not a really useful finding in practice, but certainly an interesting one.

Polar Norway 2010, short cyclo-hiking or carry-cycling

In August 2010, I made a fast 4-day cycling and bike-carrying trip over northeast Norway. Varanger peninsula, one of real “ends of the world”, is almost encircled by roads, the gap is “just” some 20 km. Here is the map, with the blue track following the roads where I was riding on my bike, and the red track showing the part where the bike was riding on me:

Route map

Report with photos here. I’m wondering how is it possible that I’ve been to that region already three times and I’m ready to select it for my vacation trip once again.

Me on a plateau

Bicycle in Finnish Pendolino train

In Finland, most trains allow transportation of bicycles, but the fastest “Pendolino” trains do not.

Recently I traveled with my MTB, and Pendolino was the only feasible option (it was the first morning train, the next one arrived already too late). The only way was to partially disassemble and pack the bike so that it becomes normal luggage.

Packed bike in the room


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Winter fun plus a survival training

27012010305 We have a beautiful, real winter here in Finland. The weather I just desire: stable negative temperature never creeping to zero, enough snow for any winter fun – about which I may blog more some time later. One of the cool things to do this time of the year is to ski, skate, walk or cycle over the frozen water. For example, last cold (or, better say, just normal) winter of year 2003 we cycled from the Åland archipelago to the continental Finland. When not going this far, I regularly ski around the Suvisaaristo islands next to which I live (recorded route here). Moving over ice is great!

But what if the ice breaks and you fall in the zero degrees cold water?

There is a simple answer: try this before it hits. Your chances to get out alive become higher. Read on for the boring theory and a short report of how I did this recently in a mild -17°C afterwork evening. Continue reading

Shimano Nexus-7: how it works, how many teeth the gears have

Previously, I have tried to find “theoretically” the tooth counts of the Nexus-7 internal gear hub. Some nice numbers were obtained, but there were some suspects (you may think yourself what can be wrong with the numbers given in the link). Soon after, I disassembled the real hub and counted the teeth of all rings. Here are the real numbers. Continue reading

Heavy-duty self-made mudflap

DIY heavy-duty bicycle mudflap
Bicycle mudguards are frequently made shorter than they should have been. I was not able to find a front mudguard which would protect front chainrings from water jets pouring from the front wheel. So I made my own from a 2mm thick rubber sheet. It is heavy and non-aerodynamic. It is heavy-duty! It makes difference when riding in the rain. It is tested. Highly recommended for bike commuters.

Trip report from Indian Himalayas – 2008

Lahaul valley
I’ve started writing about my last year bike trip in the Indian Himalayas. Before I had not forced myself to more than one blog post and an unsorted pile of photos. Now I’ve started with a short illustrated text about practical issues, answering questions which I had at the planning stage:

Cycling in Himachal Pradesh: practical issues

My next plan is to publish the daybook with facts and impressions. Stay tuned.

Cycling in Himachal Pradesh, India

It has been a month since I have returned from solo cycling trip in Indian Himalayas.

Impressions clearly overloaded my brain. This was first time I’ve been to Real Mountains – the highest pass, Kunzum, was at 4500m. And this was my first time I’ve been to a non-Western country (not counting my home Russia, which I’d put “on the border”).

The route was easy: start at Shimla, and follow the National Highway 22 (with some variations in the beginning) until Manali. Oh the highway… Never have seen anything like this before.

Numbers, mostly of interest to cyclists only:

  • 9 ride days
  • 750km covered
  • Total altitude gain is still not counted, although three biggest gains were 1600, 1300 and 1000 meters

What else:

  • Was caught in a snowfall in Lossar, 4000m:
  • In the plains (Chandigarh), the temperature was in +30 range
  • On the National Highway 22, passed landslides three times. Two of them, the bike could just ride through, like this one:

    once had to wait until it’s cleaned (I waited just half an hour, but others were there from the morning to the evening):

  • Stayed in the tent two times, in hotels and various “rooms” 11 times.

In fact the impressions of India as a country overweigh the “mountain-cycling” impressions. It deserves much more than one blog post – even much more than one book. All my perception of the surrounding world is now a little bit different than it was before. Probably such thing is called “cultural shock”. I’m so happy that this happened; now I see how terribly narrow view I previously had.

Of the real India, I have seen only Chandigarh, which is described in all guides as most comfortable city in the country. Still it is, of course, Indian city (just like my home Saint Petersburg is the most European of the Russian cities, but still fully Russian).

I’m feeling own deficiency of not being a good writer to describe my thoughts about these two weeks. So far I have produced a technical report, with details for cyclists such as what tires to put on your bike and how much food to carry.

All pictures (unprocessed) piled here.

Strange failure of a studded tyre

Cycling from work yesterday, I noticed something… well, uneven, on my rear wheel. At the cellar door, the exploration has revealed three places where the sidewall cord of the tyre was torn, two of them longer than 3 cm! Inner tube was buldging out. What a luck that it still got me home and did not explode, say, on half way to work – clear failure of the Murphy’s law!

torntyre1.jpg

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Disassembling Truvativ GXP crankset

Road cycling season has started in Helsinki! I did my first roadbike ride after snow-ice-mountain biking winter, and discovered clicking sounds in the bottom bracket area.

The crankset is Truvativ Elita Cross with GXP axle. Manuals at ParkTool say that only 8mm Allen key is required to remove the left side crankarm. The fixing bolt unscrews counter-clockwise:

truvativgxpremoval11.jpg

After the bolt is removed, the crank is still press-fit, so it is not possible to just pull it off:

truvativgxpremoval2.jpg

I was kind of stuck at that point, not knowing what to do next. The solution which did the work was to insert the bottom bracket cup removal tool under the crank. Fortunately I had a half-circle wrench, the “full circle” would not have fit over the crank! The unscrewing cup worked as a crank puller, effectively removing the left arm from the splined axle.

truvativgxpremoval31.jpg

When the left arm is removed, the work is done.

truvativgxpremoval4.jpg

I’d say that the claim about “no special tools required for GXP crank removal” is overstated, because the cups still need a wrench with a long lever. But it is still better then other designs such as Shimano Hollowtech and later Sram/Truvativ models, which, in addition to the cup tool, need a specific left arm extractor or tightener.

Backpacking trip to Polar Ural!

I’m leaving to St. Petersburg today with the intention to take the train to Polar Ural in three days.

I have been there in 2001, six years ago, and longing to get there again.

Polar Ural, 2001

This region is a known touring place. Nowadays there are not so many places on the Earth where you can wonder for several weeks and meet not a single human being. Backpacking there is nothing like “hiking trip from a hotel to a restaurant” along marked route. There is no services – you just go wherever you can. No cellular network (and we don’t take a satellite phone, as it weighs over kilo). All food has to be carried – we plan to fit in 700g/day, which makes 15kg of “consumable” start weight.

More facts:

  • The region is extremely wet. Expect your feet to be wet all the time. There is positively no reason to dry down the boots, as they fill up with the water during first 15 minutes of walk-time.
  • The temperature can be anything between 0°C and 25°C. At 0, the rain with heavy wind makes for a rich experience. Snow is possible starting from beginning of August.
  • If the weather is warm, there can be really much mosquitos and gnats. Normal situation is when you must wear mosquito mesh and gloves to protect. It is impossible to eat with the mesh; so eating becomes challenging and people eat either inside the tent or walking/running around.
  • Mosquitos in the sunset

We’ll have 3 weeks of full autonomy. My heart is already in the mountains.