Flandry

Good afternoon; newb warning.

I'd like to decrease the number of teeth on my chainring. The current ring is a Sugino Messenger 42t and says 130 pcd on it. In looking around, it seems the smallest ring for 130 pcd is 38t, but i know nothing about chainrings, especially single speed chainrings.

My understanding from reading here is that any 130 pcd ring that is non ramped and has 5 holes will work with my crank. (Example: https://www.amazon.com/Rocket-Alloy-N.../dp/B000BMT2I8)

So my questions:
1) is my understanding correct?
2) Is changing the ring simply a matter of removing the 5 bolts, swapping the ring, and replacing the bolts?

The reason i'm looking for smaller rings is that i put an Alfine hub in the back wheel and want access to substantially lower gears than the current 42/19 allows.

Thanks in advance for your help!

Grand Bois

You can buy an 18 tooth Alfine cog for less than $10 on Amazon. That's about the same as switching to a 39 tooth ring, but cheaper.

JanMM

Correct that 38 is the smallest 130 ring

HillRider

That will make the gearing higher, not lower. The OP's current cog is a 19T. It would take a 21T cog to make the same change as going from a 42T to a 38T chainring. Will the Alfine accept a 21T or larger cog? If so, this is indeed the cheapest change.

Yes, switching chainrings is really as simple as removing the 5 bolts, replacing the ring and reinstalling the bolts. BTW, it's bcd (bolt circle diameter) and, as you noted, a 38T ring is the smallest that will fit on a 130 mm bcd.

If you want to go smaller, you will have to replace your crank with one with a smaller bcd and the next common size down is 110 mm which will take down to a 33T chainring.

Flandry

Thanks for info. It says 130mm PCD on the chainring. Maybe that's a Sugino peculiarity?

Alfine cogs are available up to 23t, and i may go that route, as well. My current low gear is something like 30.5 inches and i'd like to get in the low 20s, which will require both chainring and cog changes.

Regarding a suitable chainring, is that one i linked ok? Is there a difference in the width of the chainring for 6-10 speeds vs singlespeeds that would pose a problem, or is it really just down to the whether it's ramped or not?

tatfiend 

Nexus/Alfine cogs are available to 23 teeth and are available from a number of on line sources.

https://aebike.com/parts-accessories-...exus+cog&Brand=

or

https://sheldonbrown.com/harris/shima...html#sprockets

Changing rear sprockets is much cheaper than changing chainrings.

HillRider

Maybe it is. Hozan, another Japanese company, once made a bottom bracket and headset Lock Ring spanner tool with the name "Rock Ring Wrench" cast into the handle.

Some single speed and track chainrings and cogs are made for 1/8" width chain but your Alfine uses a 3/32" width derailleur width chain. So, be sure the chainring you buy is intended for a 3/32" chain. All 6 through 10-speed chainrings are made for derailleur width (3/32") chains.

dbassi

PCD is Pitch Circle Diameter a term widely used in car wheel sizing, It's the same as BCD.

tcs

But in this case he'd want a bigger rear sprocket so he might need a longer chain which might mean he's going to have to buy a new chain. +$

With a smaller chainring, he could just remove links on the existing chain.

tcs

Grand Bois

Of course you're right. I don't know what I was thinking, especially after building three IGH bikes from bare frames.

Maybe it was the wine.

fietsbob

I , for single speed use really like QBP/Surly stainless steel chain-rings, For taller teeth
and the lack of the shifting details of new Hyper Index derailleur mechs ,
in addition to the longer wearing characteristics of Steel.
they are for fixies too as opposed to real track bikes so use a 3/32 chain ..

Older design full bushing chains will wear longer than newer Bushing-less types,
for single chainline set-ups.
The bushing-less design came into existence to increase lateral flexibility ,
to have the chain bend sideways for derailleurs to work better.
but wear is concentrated on the edges of a surface then instead of the wider
bushing surrounding the chain pin.

Flandry

Thanks for the PCD clarification.

Actually, i'm still using the original 1/8" chain. I haven't had any trouble yet.

Is there an actual problem with doing this, or is it simply that the opposite doesn't work (i.e. a 3/32" chain isn't going to fit on a 1/8" chainring or cog)?

HillRider

There shouldn't be any problem using 1/8" chain on 3/32" cogs and/or chainrings but, as you surmise, the opposite isn't going to work. I presumed you had a 3/32" chain already and wanted to be sure you didn't get a 1/8" chainring.

Bianchigirll 

UH UM isn't a Alfine a 7spd IGH? I have a Nexus 8 and I think I used the 18 and a 42/48 in front. that 42x18 in the lowest gear is pretty low for here in SoCen Pa or So Jersey where I ride.

Dan Burkhart 

Negatory. The Alfine is 8 speed, all the same ratios as your Nexus 8.

Bianchigirll 

OK so it is an 8spd. still when I set mine and started with a 38/48 the 38 was just way to small.

Flandry

It sounds like i have all the information i need now. Thanks again to everyone. It looks like the 38t rocket chainring will be a good option.

With 42/19, the low gear is 31.5" (https://www.sheldonbrown.com/gears/internal.html). It's low enough for cruising but too high for fully loaded touring, hence my search for lower gearing options. I think going to 38/23 will shift the gearing range too far down to be comfortable for normal terrain. I've yet to evaluate whether changing the Alfine cog or chainring is easier. Whichever ends up being so, i'll probably reserve for just before long days of climbing if the track fork gives enough room to fit the necessary chain.