Hi,

I am a total newbie at this bike stuff so please bear with me. I have a question regarding chain lengths. Here's my situation:

I have single speed bike and want to swap out the freewheel for a smaller one. Currently there is an 18T in there and I want to put on a 16T. Why? Because when I am pedaling on flats I am not getting the acceleration I'd prefer. Instead it feels like I'm spinning away on a stationary exercise bike, at the gym.

Anyhow, I'm digressing. So after I swap out the freewheels my chain will then be too long. I couldn't locate the master link on the current chain, and since the chain is OEM and pretty old I'll probably just put on a new one. My question is: How do I know how long/short to make the new chain?

Thanks in advance.

You won't get faster acceleration with a smaller freewheel. How many teeth are on the chainring?

Faster cadence is good imo but but it should not be too high. Faster cadence builds up your quads!
If you want to, go ahead. You'll likely need to take just one full link out to compensate.

Josh

Thanks!

I'm not sure about the chainring. I'll have to check that out. Are you suggesting, in order to get greater acceleration, it would be better to replace the chainring as opposed to the freewheel?

A freewheel with fewer teeth will give you a "harder" feeling gear but you'll be able to go faster.
A freewheel with more teeth will be easier to pedal from a stop but you'll "spin out" sooner.

Going from 18 to 16 teeth you may not have to shorten your chain at all. It depends on how much horizontal adjustment you have in your bike frame. If you can't tension your chain you'll have to remove 2 links. A special tool is necessary to shorten your chain.

While the OP describes wanting faster acceleration, I suspect he simply wants a lower cadence at his cruising speed, which a smaller rear sprocket will give him.

Few of us with multi speed bikes ride low gears at flat ground cruising speeds so the OP's request and proposed solution aren't unreasonable. (I'm assuming a chainring in the 46-52t range). Rear sprockets or single freewheels are usually less costly than chainrings, so that's the way I'd go.

As to chain length, the OP may not need to shorten or replace if he has horizontal dropouts.

Since the the chain wraps only half way around a sprocket, removing 2 teeth would call for a chain shorter by 1/2" (one link, or one half link depending on how you count).

That 1/2" would be split between the upper and lower loops, so the rear wheel would move back 1/4" to compensate. Therefore if the OP has horizontal dropouts with 1/4" to spare behind the wheel's current position, he's good to go with the same length chain.

Otherwise he has options, cut the new chain 1" (one pair of links) shorter, and move the wheel forward 1/4", or buy a chain with a 1/2" link allowing the chain to be cut to an odd number of links so the wheel can stay in roughly the same place.

Add 1 tooth in back and take away 1 tooth in front and you change the Ratio, lower

but the chain stays almost the same length. almost because there is a radius change

as there is a circumference change..

or do the reverse 1 less in back 1 more in front,for a higher ratio ..

Bob... That has nothing to do with his question, man.

Why the **** should anybody buy both a chainring and rear sprocket to change the ratio when changing either will do.

The OP is on the right track with his original question, and may or may not even need to replace the chain.

Chains were Yanked . obviously ..

Thanks everyone!

Well, I have the new freewheel (16T) and a new chain. You've all given me some good tips, and I can't wait to start experimenting.

I suspect the OP wants what they stated:

"Because when I am pedaling on flats I am not getting the acceleration I'd prefer. Instead it feels like I'm spinning away on a stationary exercise bike, at the gym."

Hard acceleration typically uses lower cadence than cruising, e.g. standing while sprinting.