Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I have a 2009 Koga Signature high-end touring bicycle (internal hub gear, hub generator, half-open chainguard, ...). I'm cycling around 100 km/week (8½ km one-way commute) plus trips, so I've probably done over 10.000 km (bicycle+odometer is currently at the local workshop, so I can't check the exact number right now). I live in a sub-Arctic climate with 5–6 months per year of temperatures below 0°C, typical mid-winter temperatures of -20°C with extremes down to -40°C, and snow lasting from October to May. I cycle year-round and have so far surrendered to bad weather only once (on my previous bicycle, in 2008). I live in Kiruna, Sápmi, Sweden.

Since yesterday, I have noticed that the crankset moves sideways and the bottom bracket is almost entirely loose. The problem may have existed before, but it should have been significantly less severe or I would have noticed earlier. Although cycling is still possible, I didn't do so out of fear of damaging the bottom bracket shell. This morning, I brought my bicycle to the local service place, and the handyman at the workshop immediately said that it needs replacing, and ordering from The Netherlands (where I indeed bought the bicycle; as a footnote, I am positively surprised that this was the immediate reaction, as responses when I asked advice earlier were along the lines of "I have never seen such a thing before" in response to some part of my bicycle — not many people around here go regularly by bicycle, and I really do hope the people working at the local workshop know what they're doing). Ordering the part will take time, at least a week, probably longer. A long time to be bikeless :(.

Questions:

  • Does the bottom bracket moving sideways indeed mean it needs replacing?
  • Is it normal that this happens already after 2½ years, under the aforementioned conditions, on a Koga (not the cheapest kind of bicycle)? If not, might I still have guarantee? Unfortunately, it is not practical to return to the store where I bought the bicycle, as this is approximately 2665 km away.
  • Is it indeed potentially detrimental to continue riding, or is this fine? If it is fine, I could do so until the new bottom bracket arrives.

Similar but different questions:

share|improve this question
add comment

2 Answers

up vote 1 down vote accepted

Unfortunately, Koga insists nowadays on using Shimano Hollowtech bottom brackets. Their quality is are notoriously bad, in comparison to most classic bottom brackets with a square taper.

You needn't be worried that you damage the bottom bracket, it probably already is beyond repair.

Many of those Hollowtech things are known to have failed within 10000 kilometers. [See for a spectacular example this video, at 6:34 ]

Replacing it with another Hollowtech will not do much about this problem. If I were in your position, I'd get another bottom bracket and thus different set of cranks.

share|improve this answer
    
Thanks. Why do they insist on using those? –  gerrit Jan 22 '12 at 0:21
add comment

Hard to say without knowing a bit more.

The BB could use a cartridge or could use loose bearings. With loose bearings the situation you describe would generally only happen if one of the cups came loose, in which case the balls could slip out of their races, leaving you grinding metal-to-metal.

With a cartridge, if the cups retaining the cartridge get loose the cartridge can slip-slide around a bit, but a real problem would only occur if a cup came loose enough to let the end of the cartridge slip out, at which point the cup would be nearly ready to fall out anyway.

Either of these loose cup scenarios would be immediately obvious to the trained eye of the service tech, without having to take the BB apart, and either could be simply rectified. So more likely there is a cartridge and it has come apart internally (though along the lines of the loose bearing scenario).

Normally a bottom bracket should last a long time. Loose bearings can be repacked every 10-20 thousand km or so, and cartridges may need replacing at maybe 50,000 km. The type of failure you describe (absent the involvement of a clumsy mechanic) is unusual.

If indeed the cartridge has disassembled itself internally then probably no great harm would come from riding on it, other than it could lock up suddenly without warning, or at the very least leave you stranded somewhere. But with a loose cup scenario you should not ride the bike, as this could damage otherwise-repairable parts.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.