(CCN) What do we say to customers that question why their bicycle makes chain noise in first gear? “Just don’t go there.” That does sound rather ‘off-handed’, however, the fact remains, most bicycles are not meant to be shifted so that the condition of “cross-chaining” occurs.
What is “Cross-Chaining?”
Cross chaining is the condition where the bicycle chain is running across the drivetrain centerline. An example of this is revealed when the largest front chain ring is driving the largest rear cassette cogs. The inverse is also true when the smallest front chain ring is driving the smallest rear cassette cogs. This condition stresses the chain-links, and can be viewed clearly when looking from above the chain. From this vantage point we can see its is like running to extremes across the drivetrain centerline.
The industry’s position has been that riders should not cross chain because of the wear caused on the drivetrain. Which includes the chain, chainring, cassette or freewheel and derailleur pulleys. This is especially true when dealing with triple chainrings in 21 speed bicycles and above.
However, that position has softened over the years with the advent of the 2×10 mountain bike drivetrains. On these bicycles you have a double chainring working with a ten speed cassette in the rear. Although the extreme cross chaining is reduced, it still does not negate the mechanical issues it causes, and as a certified bicycle mechanic, I don’t recommend it.
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Why we don’t recommend Cross-chaining?
Many riders will tell us that their bikes shift into first gear on the largest chain ring, and that is just fine. It is really a matter of preference.
But there are issues that can crop up:
- Cross Chaining causes stress that translates into additional wear on the drive system
- This wear translates into friction which in turn reduces the power that drives you forward. Short hauls ok, but ironman type riding is another thing.
- Your chain must be longer to accommodate those gears, which in higher gears can cause slack, which translates into slap on the chain stays. This condition can cause the chain to jump cogs, which in turn becomes a safety concern.
- In many cases rear derailleurs will not properly accommodate the large to large gear position. Take a look at your bicycle and you may see the rear derailleur upper pulley riding your largest cog on your cassette.
If you are building your own bicycle then there are group sets that can take into consideration the cross chaining issue which have been engineered to reduce these issues. However, the condition will always exist, and it is still not recommended.
However, consider building around a 2×10 configuration. You can achieve a reduction in wear around a 2×10 system rather than a 3×8 or even 3×7 configuration.
Other considerations are gear ratios by keeping the tooth count to a moderate level. But in these cases you may experience reduced gear selection as many shifts will produce duplicate gear ratios.
In the end, just avoid cross chaining all together. When your mechanic looks at you and says to you, “Just don’t go there.” You may begin to understand where they are coming from.