I’ve gotten a lot of e-mails lately that ask me about using smaller front sprockets, so I am going to begin this tech-tip by describing the optimum gear-ratio for a 20-inch bike.The standard gear ratio is 44-16. This ratio is the middle ground and best for all types of riding. Saying 44-16 means that the bike has a 44-tooth front sprocket and a 16-tooth rear freewheel. A lot of Pros have switched to running a smaller front sprocket to save weight and to avoid knocking their sprocket and breaking chains. Many Pros are running cassette hubs that allow a 13-tooth cog on the rear wheel, and to have the equivalent of a 44-16 gear ratio, they are running a 36-tooth front sprocket. This set-up works well, saves the most weight, and has the lowest profile to keep the chain and sprocket out of the way. Unfortunately, the cassette hubs that allow you to run this set-up are in the $200+ range, which is not optimum for the average rider’s wallet. Some companies have recognized this and are beginning to manufacture flip-flop 48-hole hubs that allow you to run a smaller (14-tooth) freewheel. Race hubs have been offered this way for years, but only recently did the freestyle market release such a hub. Note: You cannot run a 14-tooth freewheel on a normal hub, it must be a flip-flop hub. There are several companies that make a 48-hole flip-flop hub; XS, Primo Pro, Odyssey, and GT are the ones that we are aware of. A flip-flop hub has threads for a normal-sized freewheel on one side and threads for a smaller freewheel on the other. To have the same gear ratio as a 44-16 you will need to run a 39-tooth front sprocket with the 14-tooth freewheel. Note: We recommend using an ACS Claws 14-tooth freewheel. This is the set-up that we will be working with today.
First we’ll start off by describing the tools that you will need to complete this procedure. If you do not have the necessary tools we recommend that you take your bike to a shop, because you won’t be able to change your gearing without these tools.
Chain Breaker: We will need to shorten the length of the chain after we put on a smaller gear.
Freewheel Remover: We will need to take the old freewheel off of the wheel before installing the new one on the other side. If you are starting from scratch on a brand new wheel, then you will not need this.
Table Mounted Vise-Clamp: The freewheel remover will work best with this.
Large Adjustable Wrench: If you don’t have a Vise-Clamp, grab the biggest adjustable wrench you can find. The larger the wrench, the more leverage you’ll have.
Socket Wrench: You’ll use this to remove your rear wheel.
Allen Wrench: To remove your front sprocket from your crank-arm. The size needed will depend on your crankset, but I needed a 6mm.
Whatever tools you need to remove your crank-arm. I use XS cranks so I needed a 6mm and an 8mm allen wrench. Other cranks will need different tools.
The parts that are used in this tech-tip are:
ACS Claws 14-tooth freewheel
Haro 39-tooth “Street-Nuke” sprocket
XS “Down Drive” 4×4 hub
XS OS cranks
So now that we have the parts and tools together, let’s get to work.
Step 1: First we need to remove the rear-wheel. Start by loosening both axle bolts, slide the wheel forward, remove the chain from the freewheel and sprocket, then pull the wheel off your bike.
Step 2: Freewheel removal is the tricky part. As I mentioned earlier, this is much easier if you have a table-mounted Vise-clamp. Simply put the freewheel remover in the clamp and tighten. Next, grab your wheel and place your freewheel onto the notches in the freewheel remover. Turn your wheel to the right and the freewheel should start threading off your hub. This could require a fair amount of strength.
If you do not have a a table-mounted Vise-clamp, get the largest adjustable wrench you can find. Notte: If you can’t find a large one, grab a pipe that will fit over your wrench handle. This will give you more leverage. Place your wheel straight up on the ground with your freewheel on the right side, attach the freewheel remover to your freewheel, making sure the notches grab each other. Next place the wrench on the freewheel remover and push down and towards you. This may be more difficult than it sounds. Sometimes the freewheel is really tight, just keep at it and it will eventually come off. Note: To keep the freewheel remover attached to your freewheel, tighten your axle bolt down on to the remover just enough to keep it from sliding off.
Step 3: Grease the hub’s threads and then hand tighten the freewheel on to the hub. Note: When you first pedal your bike after it is put back together, you will notice it tightening onto your hub. This is normal, but don’t take off too fast at first, pedal around slowly until the freewheel is seated on the hub.
Step 4: Now it’s time to remove your front sprocket. First you’ll need to remove your crank arm. Everyone’s cranks are different, so this may not apply directly to you. Loosen the pinch bolts that attach the crank arm to the spindle until there is a good amount of slack. Note: Profile, Solid, and some other cranks do not use a pinch bolt. XS, Primo, and Redline Flight cranks do. Next, remove the spindle bolt and pull the arm off of the spindle.
To take the sprocket off, use an Allen wrench to remove the bolt that attaches the sprocket to your crank arm. Now you can give your old sprocket to a friend.
Step 5: To attach your new front sprocket, line the center hole of the sprocket with the spindle hole on your crank arm. Note: Make sure these two holes are lined up or it will be difficult to place the crank arm onto the spindle. Tighten the bolt that holds the sprocket onto the crank arm as much as possible, but be careful not to strip it. Position the crank arm so it is lined up directly vertical from the opposite side’s arm and slide it onto the spindle. Tighten the spindle bolt so that the cranks are tight but not binding your bottom bracket. Tighten the pinch bolt as much as possible without stripping it.
Step 6: Now place your rear wheel inside the dropouts where you will want them to stay when you’re done. Then, grab your chain and loop it around your new freewheel first, then your front sprocket, and eyeball the amount of links that you will want to remove. Now place the chain tensioner on your chain and remove the necessary links. Use the master link to re-attach your chain then place it around your sprocket and freewheel.
Step 7: Tighten your rear wheel’s axle bolts and you’re ready to go!
I hope that this helps answer any questions you may have. I did want to address one thing before I’m done. Some of you may not have three-piece cranks yet and are still using one-piece cranks with an unsealed bottom bracket. I recommend that you take your bike to a good shop, because they will be able to perform the work quicker and better than you will. Trust me it’s worth the price.