Philphine

at one time i found a nexxus 4 speed hub and was told i needed a small front sprocket because the gear ratios didn't work well with a larger one. would this be true for the 7-8 speed hubs too?

here recently i've been fooling with a alt type bike i can't get a good deraileur chain line worked out for. i put a coaster brake wheel on for now, and i'm thinking of trying an internal 7-8 speed hub instead (if i can ever afford one).

my front sprocket is 52t. i don't want to change that because i need this particular sprocket to make my idea work.

so will it work? i mean i know i can physically do it, but i don't want to shell out that much for the hub and not be satisfied with the gear range. thanks.

HillRider

The overall gearing can be lowered by choosing a larger rear cog if you want to use the 52T chainring but i don't know if single speed individual cogs are available larger than about 20T. I think the recommendation for a smaller chainring was made because the Nexxus hub doesn't offer a wide range of gears itself.

fietsbob

a crankset with the chainring removable, will also take shim washers

to shift the chainline sideways.

I like the Stainless Steel chainrings, under the Surly brand, that QBP sells,
with my IGH. they are made for single speed drivetrains..

DCB0

There is a gear calculator on Sheldonbrown.com and it includes ratios of common internally geared hubs. You can use this to compare your desired gear ratios to what you would get with an IGH and whatever cogs and chainrings you want to use.

mrrabbit 

Important point to remember...

Chainrings see a chain - not cogs...
Cogs see a chain - not chainrings...
Humans see gear ratios...

Go grab the gear ratio chart as suggested...plan from there.

=8-)

Ex Pres 

I'll have to look to be sure, but IIRC my Nexus7 bike is using a 45 or 46 front with the 21 rear and that gives me gear inch range of about 40 into the 80's? They do make a 23 rear cog, but paired with a 52 front is still not going to give you very low gearing. Depends on your terrain I guess.

Edit: running a quick test using sheldon's calc, I think I'm using 46x21 with a range of 37.6 to 92gi.(700x35 tires)
Using a 52x23 wouldn't change it that much, so you'd be OK.

MichaelW

Typically, IHG are run with a chainring in the mid 40s to give an spread of useful gears.
Small-wheeled bikes use larger chainrings to give the same gear inches so a 52 ring would be useful on a 20" wheel bike.
If you run a std bike with IHG and 52 ring, your gears will all be higher and you may lack any useful low gears.

Philphine

i've been trying to work through the calculator and i think maybe it'll be ok. i'm trying to make a comparision on it to another bike i have that has a 52 front and a 13 or 14-34 rear. if the range is close to comparible i'd be satisfied.

hueyhoolihan

if i recall correctly, i had a nexus 7 on a 26" wheel using the original rear cog and a 38T chainring. i estimate 35-80 gearinches. extrapolate...

fietsbob

https://sheldonbrown.com/gears/internal.html

38t CR, 19t cog ?

32.9

38.5

43.8

51.4

59.5

69.4

80.3