chain ring swap

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kgmcpheeters

kgmcpheeters

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Hey everyone! So I have some potentially dumb questions, but I've only recently forayed into single speed stuff, so please forgive me. First of all, is the front gear on a single speed one piece crank still called a chainring like on my MTB's or is it a chain wheel? If not, what's the difference?
Ok, that was not the main question, but came up while I was thinking about it. Need some advice about what ratio to choose. I have inherited a Sun Atlas cargo bike (like the one pictured) from a friend of mine. I haven't weighed it, but its a pretty heavy pig. It does ok unloaded on flat ground, but I think I want a smaller chain ring to be able to carry actual cargo and/or be able to go up rolling hills. I took it about a mile to the climbing gym the other day with my pack on the back rack, weighs about 50 pounds. For the ride home my girlfriend had just finished work and was walking home so she jumped on top of the pack and off we went! Obviously not the kind of load I'll carry on a regular basis, but the current ratio had me working hard!! :p It also should be noted we only attempted this type of shenanigans because we were on a pedestrian only section of our commute. It currently has 44t front with 20t rear, on 26x2.125" tires. Calculator shows that at something like 57 gear inches. What would be a more reasonable size front gear for my application? Not super concerned with "spinning out" at higher speeds, this will be a slow speed bike, probably not needing to go more than 10 mph, but was worried if I grabbed something like a 32t it would be too small/low of a gear. Appreciate any advice/knowledge on the subject!

sun-bicycles-atlas-x-type-78637-1.jpg
 
I wouldn't go smaller than 40t myself. Try riding an mtb with a load around on your various terrain in only one gear for a while and check the ratio that seems to work for you.
 
Oh, this is going to be one of those semantics discussions, and likely there will be a whole lot of different opinions. In my view:

-ANY round thing with teeth that interacts with the drive chain to propel the bike is a sprocket, front or rear. It's the generalized term, and is pretty much always correct, but never specific.
-Rear sprockets are almost always referred to as cogs, but this is technically incorrect, as a cog meshes with other cogs, and not with a chain.
-A chainring is a front sprocket that bolts onto a spider (or, in some cases, a powerdisc). It can take 3, 4, 5, or 6 chainring bolts to attach, and when unattached, it looks like a RING b/c the center part of the circle is open, to make way for a spider. The spider itself can be integrated with the crankarms, as in many road- and mtb-style 3 piece cranks, or the spider can bolt-on when used with a bmx-style 3 piece crank, or it can be tightened down with the drive-side crank cone and work with a drive-pin on a 1 piece crank (exactly like a chainwheel does on a 1 piece...)
-So, yeah, the sprockets on most 1 piece cranks and bmx-style cranks are chainwheels. These do not take chainring bolts, but rather take a single sprocket bolt (3 piece) or else they are tightened down by the drive-side cone of the BB and ride on a drive-pin on a 1 piece crank. Chainwheels cannot be used with a spider, whereas chainrings must be used with a spider. (Some 3piece cranks, such as single-sprocket cottered cranks and White Industries ENO cranks also take chainwheels, although White sells his as "chainrings" anyway; they attach on the crankarm's splines and are held in place with a lockring...)
-Whether or not the sprocket is inch-pitch or 1/2"-pitch is irrelevant to the nomenclature. For what it's worth, the vast majority of inch-pitch (aka "skiptooth") sprockets I've seen are chainwheels.

After that big ol' diatribe, which plenty of folks will likely disagree with, all I gotta say is, you might want to just swap the rear sprocket for a 22, 23, or 24t instead of the 20t. It'd be less work to change it, in most cases it'd be cheaper, and it'll look cooler (especially b/c your bike has a chainguard...) Downside is, you might need a longer chain, depending on where hyour wheel currently sits in the dropouts. If you do decide to change the front instead, may I suggest using a OPC-compatible spider? Once installed, that will make it easier to swap front rings without removing the crank--in case you want to go back to the stock gearing, or you select another intermediate gear.
redline-spider-12-26-2014...1_blowup.jpg

http://www.niagaracycle.com/categories/redline-spider-for-one-piece-cranks-110-x-5mm-black

HTH!
Rob
 
Oh, and a final note: many bike retailers will interchange the terms "chainwheel", "chainring", and "sprocket" indiscriminately, so keep that in mind when you're searching for parts online or asking at the LBS. And, if you're looking for the rear sprocket, you may as well type in "cog" n/c right or wrong, that's how they're being described online 99 times out of 100.
 
I really don't mind swapping out the front sprocket to lower the gear ratio and gear inches.
Schwinn%20Cruiser%20Four%20001_zpshnofw8xs.jpg

Cheap or free kids bikes are everywhere and these 32t to 40t sprockets are easy to swap.
 
Thank you guys for the feedback and education!! I had just assumed that swapping the chainwheel ( ;) ) would be the easiest/most available swap, didnt realize there were bigger rear sprockets so readily available to yield similar results, and good point about the chain guard. Horsefarmer's smaller chainwheel doesnt look out of place, but no chain guard. Not super worried about looks on this one, but would be nice to keep the front chain wheel and have the guard look as it should. Some food for thought for sure! Thanks so much everyone!

Kyle
 
Yeah, I once ran a 40t on a Worksman with the chainguard, and the lines were just off... too much gap between the guard and the ring, y'know? So I put a 44 on there and sorted it out from the rear. I'm at the point now where I have a bunch of different sized rears in the box, so I can usually find the ratio I want without changing the front. Thankfully, most all coaster and/or gear-hubs from the 70s on take the same 3tab sprockets, and many of the older ones do, too.
 
Yeah, I expect you're right, though hopefully I can try it out and order the part if need be, then have some down time for it to ship and for my buddy to bring me back my chain break :p
 
kgmcpheeters said:
Thank you guys for the feedback and education!! I had just assumed that swapping the chainwheel ( ;) ) would be the easiest/most available swap, didnt realize there were bigger rear sprockets so readily available to yield similar results, and good point about the chain guard. Horsefarmer's smaller chainwheel doesnt look out of place, but no chain guard. Not super worried about looks on this one, but would be nice to keep the front chain wheel and have the guard look as it should. Some food for thought for sure! Thanks so much everyone!

Kyle
Click to expand...
I was able to grab a cool chrome chainguard at Ann Arbor swap for a buck that I think looks pretty good with the small sprocket.
2016%20RRB%20Cal%20Bagley%20014_zps8tsedm5c.jpg
 
kgmcpheeters said:
Yeah, I expect you're right, though hopefully I can try it out and order the part if need be, then have some down time for it to ship and for my buddy to bring me back my chain break :p
Click to expand...
A measurement is so much more helpful than any guesswork. You're going up 2 teeth, but b/c a sprocket is circular, only 1 of the 2 add'l teeth will be engaging the chain at any given time. So, that's equal to one half-link, which is 1/2" long. So, measure your dropouts; if there is >1/2" of real estate forward of the axle, you won't need to add any links. :thumbsup:
 

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