Fatbike and maintenance.

Less than 500K on the Fatbike, a.k.a. Fat Freddy, and the chain was shot. Shock!

Do fatbike chains wear out this quickly compared to normal bikes?

I had just replaced the single chainring with a triple chainring (because I had a barely used triple chainring sitting around doing nothing). The bike was geared too high, like a road bike. I was able to climb some serious hills on the small chainring that none of my other bikes can handle (even with lower gearing) and it was easy to get up to the same speeds as on my other bikes with the smaller chainring. Awesome!

Usually I get about 1,000km on a chain for a new bike and 1000-1600K for a better quality chain with frequent cleaning and lubing of chains.

The learning experience came from replacing the chain. The more expensive nickel plated replacement chains like those on Fat Freddy come with 122 links. Fat Freddy needs an extra 8 chain links. Good thing I bought 2 packs of chains. Was able to cannibalize the second chain for extra links. It took 3 tries to get the chain installed but was not difficult to do.

Shimano chains come with this cool replacement link pin to connect the ends of the chain together. Having never used them before, the process went very smoothly. When shortening chains for a second bike I never use these pins and just push the original link pin back in place.

The Shimano pins have a narrow end that is inserted through the links that are to be joined. A chain breaker pushes the pin through and a pair of pliers breaks the part of the pin that is sticking out, off. Very satisfying SNAP!

After doing this twice to install the extra links, I realized the chain wasn’t properly fed through the derailleur and had to take it apart and correct the problem. That was the easy part.

I measured the second bike chain to make sure the second chain was long enough for the second bike. It was 2 links short!

Scrounging around uncovered short pieces of new chain leftover from shortening previous chains for the second bike which now uses 110 links. Originally the bike chain was 4 links longer until installing a smaller chainring set which reduced the required chain length by 4 links. Make sense? Too long or short a chain causes derailleur tension problems so getting the length right is important.

The second chain was put away until needed.

A couple of rides on Fat Freddy and the chain started jumping around in one gear. Wasn’t sure if the chain was jumping to another gear (derailleur problem) or jumping on the same gear (worn gear problem).

I’ve been replacing chains on my bikes for many years. What gets me is that sometimes the gear wear is just enough to let the chain skip but isn’t worn enough to be really obvious. So how do you tell?

A better method was needed to determine when gears were worn and by how much. By the time a chain has worn enough to be measured, gear wear has already happened in spades.

I have been told 2 or 3 chain replacements is the norm before gears need changing and this seems to be the case. But why find out gears are too worn after putting a new chain on? A new chain will wear out much faster on worn gears and may cause skipping problems under load like I was having. Usually I’ll check for chain wear close to 1,000kms and frequently thereafter.

I did not expect the fatbike chain to wear out so quickly but then fatbike chains often rub against tires, collecting dirt and dust more quickly.

The way to determine how worn gears are is to take the end of a new chain, stick it into the space between the gear teeth and slide it back and forth. The more worn a gear is, the more room there is for the end of the chain to move around. Simple!

This quickly determined that the gear on which the chain was skipping was indeed more worn than the other gears. It also revealed that the gears I seldom use have no wear.

Larger gears tend to require more wear before the chain skips since there are more teeth for the chain to pull against. Smaller gears tend to wear out more quickly. The gears that wear out the fastest tend to be the gears that are frequently used. This means that on any freewheel or cassette you will have varying degrees of wear on different gears.

After using this quick check method on other bikes it was discovered that 1500km on the road bike had worn the chain barely .5mm but some gears were badly worn. Within a few minutes I was able to identify how much wear the gears had on all the bikes.

Gear wear is as important as chain wear but I have never heard of anyone, bike mechanics included, who knew of an accurate and simple way to determine gear wear.

Perhaps shops have a special tool for measuring gear wear but the average owner finds simple and inexpensive ways to check for wear more useful.

Looks like this will be an expensive month for replacing gears and chains! Good thing gears and chains are relatively cheap parts to buy compared to car parts. A cassette or freewheel may cost around $35 and a chain costs around $25-$35. Buying better quality gears and chains can pay off in the long run. Once gears are worn, a new chain may new create problems. Sometimes it is better just to leave the old chain on until both worn gears and chains can be replaced as a set. Worn gears and chains will often work better because they are both worn. A chain wear tool that shows .75mm of chain wear is a good indication that both gears and chain need replacing as a set.

Replacing freewheel gears and cassettes is the big problem. You need a special socket and chain tool to crack the nut free to replace the gears and you will need a very long bar to get lots of leverage. Once the gears are removed it is very easy to install a new one. Don’t over tighten though! The gears will tighten up under use until they are very difficult to remove anyway. No point making gears impossible to remove.

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One thought on “Fatbike and maintenance.

  1. I only ride road bikes these days so chain and gear wear are few and far between. The one that does the most miles is running on a 30 year old chain at the moment, the bike is the one I use to get to work on. It only cost me £20 on ebay then about £60 to refurb.

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