Esos

I have folding bike that has single speed for front gear which IDK exactly how many teeth it has but it's quite big and my RD is on 8 speed which I believe the biggest gear is 32T.
I've searched on Google about what should I use when going uphill and most of the answers is mid or small cogs for front gear and biggest cogs for rear gear but I've never found the other way around.
So my question is what should I use when having only single speed front gear which is big gear on the front when going uphill?

Bill Kapaun

You didn't find it the other way around because you would have opposite answers to the same question.
Illogical.

dsbrantjr

Since you only have one front gear there is no choice. Shift your rear to easier/larger cogs when climbing. https://www.sheldonbrown.com/gears.html

gregf83 

Try it both ways and report back.

Andrew R Stewart 

Is the unasked question what front chainring would I install (instead of the OEM one) to make up hills easier?

I have to admit the OP is a bit confusing to read. Andy

shelbyfv

You can count the teeth and not have to guess.

Iride01 

It doesn't matter what the stuff you've looked up says you should use for climbing a hill. They don't know how strong and fit you are or aren't. Nor do they know how steep and long that hill is.

You simply just shift to the gears that are easier to pedal until you find the one that lets you climb that hill.

You shouldn't have to struggle to climb the average hill on your rides. If your bike doesn't have low enough gears to handle the hills you encounter on your typical ride, then something has to change. New bike with lower gearing, change the gearing on your bike or get stronger and fitter.

79pmooney

Someone fundamentally doesn't understand gearing, comes on a forum where people know and you welcome him with "illogical". So I guess he should have gone ti the library to study gearing until he understood it well enough to pose a question that was logical.

I'm glad we have some kinder posters that have tried to share their knowledge.

Retro Grouch 

fify

Bill Kapaun

And EXACTLY what did YOU do to help?
KMA

GAtkins

Small in front, big in back, in a combination that let's you climb the hill comfortably, if there is comfort on a hill.

79pmooney

Esos, you have a small wheeled bicycle. Wheel size makes a large difference in the effect any gear ratio has in effort required. I will attempt an explanation.

Think back to the old highwheelers, those early bikes with an enormous front wheel attached directly to the pedals. Actually just like a child's tricycle. The bike travels one wheel diameter every full pedal revolution. Say that wheel was 6 feet in diameter. The bike travels pi X 6 feet = 18.8 feet. Now a tricycle that has an 18" front wheel; it goes 4.7 feet. The oldtimers didn't have calculators, so dealing with pi was a nuisance. They simply talked about riding 6' or 72" wheels. Their 4 year old rode an 18" wheel. And guess what, 72" wheels were MUCH faster than 18" wheels!

So already, even though they did not yet have gears, the basic tenet of gears was understood. Big wheels went fast, And very quickly they figured out big wheels were much harder to go uphill on. That has stayed true to this day. So has their means of defining how big or "hard" that wheel was, "gear inches" or GI. Simply the gear ratio that gets you the effect of a highwheeler wheel of that diameter. Going to the "safety bicycle", ie the modern bike with chain and sprockets meant that the wheel diameter no longer defined the gear, but it still played into the effective gear ratio, Using the GI system, that effective wheel diameter can be calculated by the following formula:

GI = chainwheel teeth divided by cassette teeth times wheel diameter in inches. (Wheel diameter being the diameter of the tire tread.)

Let's say you have a 60 tooth chainring and a 13-32 cassette, 20" wheel. This gives you a high of 60/13 X 2o = 92" and a low of 60/32 X 20 = 38" Racing bicycles have gears as high as 130", touring bikes as low as 15".

Count your teeth. Calculate your gear inches. Go to Sheldon Brown;s website mentioned above. Now you can make sense out of what you have and what changes you can make to better suit how you ride. (You will also be starting to learn that small wheeled bikes have their challenges in this world of almost entirely large wheeled bikes; that you have fewer choices that are feasible and some equipment issues that are unique. You might want to go to the Folding Bikes forum for advice from others with experience there.)

And last but most important - welcome to Bike Forums (and cycling!)

Ben

dabac

Bicycle front and rear gears work indepently of each other.
So if you can’t follow advice aimed at bikes with 2-3 chainrings on account of your bike only having one, then you simply ignore the part that isn’t applicable.
But you use the part that fits your bike - how to shift the rear.
So when it gets heavy to turn the pedals, shift to a bigger rear sprocket.

79pmooney

Nothing as of your post because because it took me longer to write a useful response.

Iride01 

Calculating gear ratios won't tell you if you can get a bike up a hill if you don't have experience to know what specific gears you need to get up the hill.

Only riding that hill and shifting gears to find the combo that works efficiently for you at your current fitness level will tell you anything.

Once you know what those gears are, or that in fact you don't have them, then calculating the ratios and comparing the ratios of what you have to what you might can get to give you a better gear combo for hills is when calculating ratios will do you any good.

I suppose if you don't know that the bigger rear cogs make it easier to pedal, then maybe knowing the ratios will tell you which way to shift toward. It's not really easy understand what a ratio means when it gets bigger or smaller if you don't experience it first.

GAtkins

If I understand this correctly, and someone correct me if I'm wrong please,...

As an example, if you had a 34t chain ring up front and a 34t cog in the back, that would be a one-to-one gear ratio, or 1:1.

For every time you turn the crank one full revolution, the tires will also rotate one full revolution. If you had a 28t chain ring with the same 34t cog in the back, the ration would be .82 to 1. The wheels would rotate .82 times for every crank revolution. This combination would be easier (a lower gear) to pedal than would be the 34-34.

Conversely, if you had a 50t chain ring in front and an 11t cog in the back, the gear ratio would be 4.54 to 1. For every one turn of the crank, the tires will rotate 4.54 times. This is a much harder (higher) gear.

As Iride01 says, you have to experience it and find the combination that works for you and adjust accordingly.

Glenn

DiabloScott

Correct with the clarification that the *driven* wheel turns that many times per crank rev..

IME, newbs confuse "gear" with "sprocket" so "larger" and "smaller" get conflated.
Cog is a tooth.
Sprocket is a wheel with teeth/cogs on it.
Gear is a ratio of drive rpm vs driven rpm (crank vs wheel)

adipe

search "magic gear calculator" on the interwebs. keep out of the gray area as that area is for chain being too tight.
you should also see to it that the freehub is most likely adding (fluctuating, +/-) about 0.165mm to the chainstay length because of eccentricity.

you can use a new chain (do not cut it yet) to figure out the chainstay length. you put the chain over the cog and the two pieces of the chain that are not connected but are pressed with one of your hands on the chainring. you roughly measure the slack and apply the a^2+b^2=c^2 and do the math. count the links of the chain - either pairs or not and then you can more precisely know the chainstay length by using that magic gear calculator - subtracting the bit of extra length because of the slack that was greater than the minimum needed for a final singlespeed cog purchase - and possibly chainring too - when you measured it and calculated by the square root of (a^2+b^2).

it's very easy once you understand that the slack you guestimate up+down can very precisely point out the small difference in extra length of the new chain over that chainring and cog. you divide that extra length by 2 to subract to the chainstay length that corresponds to the gear ratio you checked the chain over for the chain links counted.
try different cogs as you still have that 8 cogs on the freehub. once you hit a slack that is really small you have more accurately found the chainstay this way.

on the magic gear calculator site you can look which ratios can apply to have a magic gear without a chain tensioner and with a vertically positioned wheel - dropouts that are not horizontal or semihorizontal.

you don't need to count all the links of the new chain when trying it uncut over a chainring and cog. you can measure with the ruler the chainstay length (you don't need much precision, just an approximation) and use the magic gear calculator to figure out how many links the chain should have in order to have some mm of slack. you should pay attention if there is an odd number of links involved when seeing the chain on the cog and chainring - if there are full pairs of links or if ther is an odd number of links. this would make you avoid that gear ratio, even if the chain has very little slack. OR you can use a half link but those are not found easily but usually you need to order half links as well.

adipe

https://www.eehouse.org/fixin/formfmu.php

Litespud

while we’re defining terms - yes, a cog is, strictly speaking, a tooth, making the spiky wheel a “cogwheel”. A “sprocket” is a cogwheel that meshes with another cogwheel via a chain. A “gear” is a cogwheel that meshes directly with another cogwheel, which would also be a “gear” in this scenario. So, a standard bike drivetrain comprises sprockets. If there are multiple sprockets at the rear, these are referred to collectively as a “cassette” (where the coasting ratchet mechanism is built into the rear hub - known as a “freehub”) or a “freewheel” (where the ratchet is built into the sprocket assembly, and is separate from the hub). The collection of rear sprockets may also be referred to as a “block” or “cluster”. The large sprockets at the front are referred to as “chainrings” in cycling parlance. The size difference between the front chainring and the rear sprocket (number of chainring teeth / number of sprocket teeth) is the “gear ratio”, often shortened to “gear” in cycling parlance.
I love the smell of pedantry in the morning…..😀

Iride01 

Check your dates people. Nothing is served making new arguments or even making the last word about long dead arguments.