Advice please on chainset ratios

[Peachy!]

Morning,
I popped out for a pootle on my 1954 Claud Butler Jubilee Special, first time since loosing a lot of weight (5st!)
Positives; The Brooks Swallow is less painful , and my lower arms don’t ach as much (less upper body weight?)
Negatives; I find myself running out of gears.
It’s got a 4 speed wide ratio Sturmey hub with 18t x 44t and on this run I pretty much only used 4th & found myself often freewheeling (the Fiamme rims do roll so well)
I’d rather like to keep the 44t Chater Lea although I do have a nice 46t Williams I could swap it out with, but I’m thinking I might change the cog to 16t instead.
Can anyone advise what might be the better option, 18x46 or 16x44? (combined with a 4 speed close ratio Sturmey hub gear)

 

[averagebiker]

First off, great work on the weight loss! I am carrying a couple of extra stone so can use you for inspiration
Secondly what a lovely classic bike to use fir a trip out on the sunshine.
Thirdly/lastly I cannot help with the ratios advice but I will watch with interest as I think I would like to build up a bike with a hub gear as an alternative to a single speed or 1 x 5/6
Rich.

 

[pigman]

46/18 is a ratio of 2.56
44/16 is a ratio of 2.75

so if you feel you need higher gears its 44/16, if you need something lower for hills its 46/18

the other question is youve not mentioned 44/18 or 46/16? i assume those are too extreme

 

[Jonny69]

44 to 46 on the chainring won't make a noticeable difference, in my opinion. The close ratio SA is 1:1 in the middle and +/- 25% isn't it? Yes, your answer is probably to fit a 16T to the back. Crunching the numbers, it might be a bit on the tall side with a 16; 17 might be better.

Alternatively, if you keep the 18T at the back, 48 tooth chainrings are pretty common. That will solve all your problems!

Lovely bike, by the way.

 

[Peachy!]

Cheers guys
@averagebiker I’d got in such a state last Christmas (nearly 20st) I could barely ride, something had to give and it was nearly my heart, down to nearly 15st now with maybe a stone to go hopefully.
@pigman it’s currently 44x18 and I’m climbing in 3rd! Just out of interest what are the ratios for 44-18 & 46-16?
@Jonny69 I’ve just edited my original post, it’s a wide 4 speed not a close
Options I have are;
44t
46t
52t
X
14t
16t
18t
As I said it’s currently set up as 18x44 and it’s too low, it was originally set up as 14x52 but that was way too high for me. (Apart from downhill when it went like a rocket!) I then tried 18x52 but that was still to hard.
I think I’ll start with swapping the 18 for a 16 and keeping the pretty 44t Chater Lea up front.

 

[hookooekoo]

Can anyone advise what might be the better option, 18x46 or 16x44? (combined with a 4 speed close ratio Sturmey hub gear)

Do you know the ratios that the hub produces? I would always recommend calculating the gear inches of what you're using now, and what you are thinking of using. With a few more calculations you can work out the speed in each gear for a given rpm.

I always try to choose rear sprockets with a number of teeth equal to a prime number. Thirteen, seventeen, and nineteen are good choices. If you can do the same for the chainring then all the better. Conversely, 48 x 16 would be an example of a poor choice.

 

[hookooekoo]

If you wanted to you could measure the gear inches of the current setup, by getting someone to help measure how far you travel forwards for each complete crank revolution. Knowing the current chainring/sprocket setup and the tyre circumference, you can then work backwards to get the gear ratios for the hub.

There are 63360 inches in each mile, so from that you can easily calculate mph for a given rpm. Next time you are out on another bike, take note of what rpm you feel comfortable at when on the flat and climbing, then you will know roughly what to choose for this bike.

By the way, I ride a lot on single speed and fixed, and I always think in terms of gear inches, and how fast I will go at a given rpm.

 

[Peachy!]

Just had a muck around with this calculator; https://www.bikecalc.com/gear_ratios
Got some interesting data on there.
So I know that (previous set up) 52/18=2.89 is too high for me and that 46/16=2.88 so pretty much just as bad.
At the other end of the scale (current set up) 44/18=2.44 I'm finding too low so 46/18=2.56 will only be a small improvement.
Looks like 44/16=2.75 might be just the job, may as well give it a go.

Thanks for the replies chaps.

 

[keithglos]

A 1954 bike deserves to have the gear ratios calculated in inches. Chainwheel divide by cog multiply by wheel diameter in inches.
This dates from the old ordinary, a measure of the equivalent front wheel diameter.

I spent too much time in the 50s sorting out SA hubs that were full of rusty water to ever learn to love them.
The ratios are all available on line, and some catalogues have gear tables in inches. I firmly believe having all gears in direct drive to be preferable.

My own choice of gears in 1950 was 2 chainrings 47 and 50, and 13 to 22 5 speed. This gave a range of 10 gear evenly spaced about 8% between gears.

SA FW gear ratio in inches: 46 x 18 26" would be 84 66 52 44.

By the early 50s I had experienced most of the available gear systems. I always regret never trying the famous Vittoria Margherita as used by Bartali in the 30s, although I may be the last person alive to have used the Campagnolo Paris Roubaix gear in a genuine road race (not historic) in 1956.

Keith

 

[pigman]

Do you know the ratios that the hub produces? I would always recommend calculating the gear inches of what you're using now, and what you are thinking of using. With a few more calculations you can work out the speed in each gear for a given rpm.

I always try to choose rear sprockets with a number of teeth equal to a prime number. Thirteen, seventeen, and nineteen are good choices. If you can do the same for the chainring then all the better. Conversely, 48 x 16 would be an example of a poor choice.

Genuine questions, not trying to pull your post apart.
Why the prime number idea? What advantages does that give? Why is the 48x16 a poor choice (I guess its something to do with it simply being 3x, but why is that a poor choice?)