Single speed sprocket size?

[jimbog]

I have a 39 tooth chain ring and need to understand what size rear sprocket would be best to run with this? I was thinking between 18t and 20?

I mostly ride tow paths and flat single track. Not many hills around here thankfully.

Need a good all round set up.

 

[foz]

18 or 20 is probably about right to start with, see how you go - you can always change later if you're under or over geared

 

[feetabix]

Start at 2:1 for off road and 3:1 on road......dilute as per taste and size of thighs/level of punishment felt acceptable!......

 

[feetabix]

The truth is you will be in the right gear for 1% of a ride!......I find single speeds charming though, great for smoothing your technique out and fitness.....easy to maintain and clean too!.....enjoy!....

 

[kingoffootball]

If you have access to a geared bike, practise just staying in one gear and see which one works best. Then just figure out the ratio (bearing in mind any differences in crank length or wheel size).

Mine's geared 44-14 for the road.

That's the approach I took and it worked really well. Single speeds work best where it's flat!

 

[jimbog]

Thanks peeps. Raced to the local bike shop tonight to get the bits. Got a nice Onza conversion kit for £14 but unfortunately the owner, who knows a lot about retro bikes and single speed was on his day off. The newbie behind the counter could not find the 18/20t sprockets that I wanted (he only had surly ones at over £25!).
I have fitted the 15t that came with the kit but I can already imagine that this may be a bit hard work. No worries either way as I can test it out and can always change it at a later date.
Hoping to finish the build tonight as I have enough parts to do so, although on payday I will get the saddle etc that I really want.

 

[jimbog]

Btw if anybody is interested, my build is the 1991 dyna tech single speed build in white/blue. I'm hoping to get her built and photos up in the next few days.

 

[SiRvInO]

38:16 is good for trails, 38:19 off road with hills

I ride 42:16 on the road, it cruises at 20-25 MPH

 

[suburbanreuben]

39t chainring? Use a 20T cog. Psychologically, it's easier than 38;19 , 32;16 et al ratios, but only just.
I run 33;17 on the North Downs. I'd imagine the Hills are much the same round your way.

 

[bm0p700f]

It's a 1:2 ratio not 2:1!