Single Speed Bike Gear Ratio

[Mr Weirdo]

Hello...

My usual dim witted question which has already been answered somewhere before but I can't find it or I'm just to dim to understand it, etc, etc, etc.

Q. I have a 50t chain ring crank set. As I understand the best ratio to start with is 2:1? Therefore 50:25. Are there single speed freewheels out there of that size?

I can't change the chain ring size because I'm too tight and I have this TA one already with appropriate BB.

On a website called twowheelsbetter.net it suggests for road/hybrid 2.5:1 - 2.7:1

Any suggestions?

I will be riding mainly surban/occasional inclines.

Any help as well as cognitive therapy welcomed.

Thank you.

 

[hamster]

2:1 is a good place to start for an MTB offroading. However you will spin out at around 15-17mph on the road.
Are you running a freewheel or singlespeed cog?

24T freewheels are available, not seen any cogs above around 22T. However a 50/22 setup with a 700C wheel will only be a 60" gear, lower than the usual road fixie gear of about 70". So I think 22T is worth a try.

 

[jim haseltine]

50x25 would be very low - it's 54" in old Imperial-speak. I'd go for something like a 19 or a 20 sprocket, which would give you 71" or 67.5" respectively.

 

[Mr Weirdo]

Thank you Jim.

Is there a formula to calculate that or does that come from your experience?

 

[Mr Weirdo]

2:1 is a good place to start for an MTB offroading. However you will spin out at around 15-17mph on the road.
Are you running a freewheel or singlespeed cog?

24T freewheels are available, not seen any cogs above around 22T. However a 50/22 setup with a 700C wheel will only be a 60" gear, lower than the usual road fixie gear of about 70". So I think 22T is worth a try.

Thanks Hammie

I am going to use a single speed freewheel cog.

 

[danc]

That seems a very low ratio to start out with unless you're doing serious off road.

I use 54/16 on my commute but I like a big gear and don't really have hills on the way.

If you're set on sticking to 50t at the front I'd stick an 18t at the back and see how you get on.

Good luck. Single speed is a great choice in most situations I reckon

 

[danc]

Are you using a chain tensioner? If so you can run a slightly longer chain until you're sure you don't want to change that front or back. That's what I've done in the past. It's more of an issue if you need to get the chain length right from the off.

 

[Mr Weirdo]

Are you using a chain tensioner? If so you can run a slightly longer chain until you're sure you don't want to change that front or back. That's what I've done in the past. It's more of an issue if you need to get the chain length right from the off.

That's a good idea...I wondered what there use was for. Ta

 

[pigman]

2:1 is a good place to start for an MTB offroading. However you will spin out at around 15-17mph on the road.
Are you running a freewheel or singlespeed cog?

24T freewheels are available, not seen any cogs above around 22T. However a 50/22 setup with a 700C wheel will only be a 60" gear, lower than the usual road fixie gear of about 70". So I think 22T is worth a try.

Fixie? You now a hipster?

 

[pigman]

That's a good idea...I wondered what there use was for. Ta

The chain tensioner wasn't designed for trial and error chain lengths. Older frames had horizontal dropouts so you could slide the wheel fore and aft. All track frames are designed like this because they are intended to be single speed. Modern frames now have vertical dropouts, so there is no length adjustment to get the chain tension correct. The chain tensioner solves this problem