Tech Talk
Welcome to Tech Talk. Short and to the point, our monthly articles aim to keep the average cyclist informed on how to keep their bikes running smoothly, longer.
Carbon Fibre, Aluminium and 10 Speed Chains
What's the connection you ask? Well we serviced a bike the other day that needed a new 10-speed chain and it's head set tightened.
Many years ago in middle earth it was discovered that carbon fibre was very corrosive, particularly to aluminium. The potential problem was that aluminium seat posts in carbon fibre frames may corrode and be stuck forever. If my memory serves me correctly, Trek solved the problem on their carbon fibre frames with a fibreglass insert in the seat tube.
Now this may all seem strange given the number of carbon fibre frames around today but the problem is well known by the marine and aerospace industries. So why can such a major problem be apparently solved by the bike industry? Or has it?
The bike we serviced had a carbon fibre fork with alloy steerer and carbon fibre head set spacers. We could not get the play out of the fork so we had no option but to remove it to see what was going on. Guess what? We could not move the carbon fibre spacers. After many tries we had to chisel them off. What we found was that the aluminium steerer had "swollen" under the spacers. After cleaning it back to size with wet and dry we were left with corrosive pitting.
We think part of the problem may be that the spacer manufacturers do not treat the inside of the spacers. The short-term answer is if you have an alloy steerer with carbon spacers check regularly that these spacers will still move and perhaps put some Vaseline on the steerer. The danger is that with cartridge bearing head sets you may not need to pull the head set apart for many years and thus not know there is a festering problem. The long-term solution is being investigated so stay tuned.
But what about the 10-speed chain you ask? Well the chain on this bike was very well stretched; as has every other 10-speed chain we've checked, (with minimal kilometres on board). Easy answer, Check and change regularly.