christerljung said:
Seriously, do you happen to know the difference between a 8-speed system, like HG-40 and a 9-speed system with HG-90 chain? Is the HG-40 much stronger? Is it wider?
btw, i still haven't snapped a HG-40 chain with my +3kw GNG. But i does jump coggs in the lowest gears(11,13) when accellerating hard above 50kp/h.
An 8-speed chain is slightly wider, but with the same internal clearance for sprocket teeth. The 9-speed chain has more heavily riveted pins to withstand the same forces projected on smaller areas. Neither 8- nor 9-speed chains can be unpinned without damaging them, so using a snap link or special flared rivet pin to reassemble them is mandatory.
The skipping you describe is the result of pitch elongation of your chain, combined with resultant tooth wear of your smallest sprockets. There are various tools for measuring pitch elongation, and any bicycle service shop will have one available to check your chain. If the chain is worn to an indicated 1% elongation, you may assume that it has worn out your sprocket teeth in turn. Often (but not always), such tooth wear is visible as small ridges of upset metal on the back edges of the teeth. The sprocket below labeled as "slightly worn" is characteristic of cassettes that skip under load.
11 tooth sprockets wear to destruction quickly even in pedal-only applications, which is mitigated by the fact that muscle-powered cyclists don't use the 11t sprocket very much if they use the correct ring for conditions. For wear life and mechanical robustness, using bigger rings and sprockets to achieve the same overall ratios is always better than using smaller cassette sprockets.
As an example, a 14-32 cassette has the same overall range as an 11-25 cassette. If you use a common MTB crank with a 42t large ring in combination with an 11-25 cassette, then you could switch to a common road bike crank with a 53t large ring and a 14-32 cassette, and have equal gearing with much better durability of your chain and sprockets. If you are already using a 52t or 53t ring with an 11t cassette, then you can get a 60t ring and a 13t cassette for an equivalent high gear. You'll have more teeth to distribute loads and wear, the chain will articulate through smaller angles, and it will be under less tension at the same crank RPM and power.
7-speed sprockets are a little bit thicker than 8-speed, which are a little bit thicker than 9-speed. Likewise, the wear surfaces inside the chain become a little smaller as you increase the number of gears. So for high power applications, using fewer gears yields significantly better durability. This effect is smaller than the effect of using larger sprockets, though.
