Replacing chainwheel on single speed bike
 

I am lowering my gearing on my fixed gear bike and decided to swap out the front chainring from a 42T to a 40T ( I have the bolt-holder tool for in back).

Couple of quetions.

1. Do I need to remove the whole crankarm or can I remove/install the chainwheels with the crank still attached.

2. Do I grease or not grease the chainring bolts? I have seen people argue both.

3. I plan on using medium size hooked allen wrench to tighten bolts. Can I achieve proper torque this way by going as tight as I can get, or do I need to get a torque wrench?

4. Do I need to replace chain and/or rear cog? Rear cog is about 4 years old and chain 2 years old. I am just dropping 2 teeth so I shouldn't have to worry about tension issues--just wondering whether using the old chain will mess with the new chainwheel.

1. You can remove chainring without removing cranks. Just remove the chainring bolts.
2. I always grease my chainring bolts. I have not had any problems doing this.
3. I also use an allen wrench to tighten my chainring bolts. You will need the chainring bolt tool to hold the back of the bolts or a nickel or quarter to be able to fully tighten them down. If not the back bolt will spin and you will not be able to fully tighten.
4. Check the teeth for wear on the rear cog. If it looks ok, then keep using it. If the teeth look like sharkfins, missing or bent, it is probably time for a new one. Measure the stretch on your chain to see if it is in need of replacement as well. I usually change my chain about every 3-4 months or so because of stretch while riding fixed. It helps to reduce the amount of wear on the cog and chainring and is the cheapest thing to replace in the drivetrain.

Your new drivetrain may be a little nosier than the old setup, but that is just because of the new parts being used with the old parts. It should quite back down some as the parts begin to wear together some.

Thanks much. Bikeforums at its best. Fast helpful response. Cheers!

I also support using grease on the threads. Around here any fastener on a bike that isn't greased welds itself in place due to rust after a year.

When you torque down the bolts you don't need or want to do it hard enough that it hurts your hand. Most folks on their bicycle stuff seem to overtorque. Especially the smaller to medium size stuff. And the chainring bolts are at best just barely medium size. You want them tight but there's no need to make them "deathly" tight.