smsexton

Hello,

At the Moment I have a 46t Chaining and a 16t cog I feel like its a bit to hard for me.
So my question is should I go up to 17t or 18t?
I have to go up a lot of hills on my way home from town. But once i'm in town everything is flat.
Would moving up to 18 be to easy. Ive heard i could skid a lot better with it.
But would a 17 be better because its more of a medium.

Thank you.

i2oss

My bike came stock with a 46-15 and it was a bit hard for me to get started, i got a dura ace 17 and noticed an instant ease in my stroke. i kinda muscle up hills so i cant accurately recall the change, skidding went from impossible to easy even though i still suck.

46x16=67.4 gear inches
46x18=71.4 gear inches

Someone will correct me if i'm wrong but the consensus is right around 70 is nominal?

as far as skid patches:

https://sheldonbrown.com/fixed.html#skid

Again someone right me if I'm wrong, this is my first try at being a contributing member.

CharneK

Yeah 70 GI is pretty normal. If you're not in a hurry, 67-68 is nice

Squirrelli

The numbers are incorrect...how did you get these numbers?

46/16 should be 75.6 GI with 23c tires
46/17 should be 71.1 GI with 23c tires
46/18 should be 67.2 GI with 23c tires


Tire width will slightly affect your gear inches.

Gear ratio is totally up to the rider and the route, if you are struggling to push a gear, you might want to go down a tooth on your cog. Try 46/17 first, it is a pretty moderate ratio for hills and you should be fine on flat.

This handy calculator can calculate gear inches, gear ratio, gain ratio, speed, skid patches etc etc.

You can also find out your gear inches with a simple calculator but have to remember number for the tire width you have.
Chainring number divided by cog number then times tire width in inches = Gear inches (round of to nearest tenth)

Common tire widths in inches:
26.275 (700x23c)
26.375 (700x25c)
26.775 (700x28c)
26.995 (700x32c)

hairnet

play around with different gears and find what works. I found I really like low gearing and currently use 46x19

i2oss

Vixtor, I did 46x17 at 700x25c same with 46x18. Perhaps I should have been more specific.

Squirrelli

How can a lower gearing, such as a 46/18 be higher than 46/16?
Also...46/16 with 25c tires should be: 75.8 and 46/18 with 25c: 67.4. I'm just bashing on you too hard...my apologies.

i2oss

How about you assist me and the OP in using the Sheldon Brown Gear Inches calculator, instead of treating me like a student in your high school math class. I just punched in the chainring number in the chainring spot, the cog in the custom sprocket space and set the wheel size to 700 X 25 (25-622). Then hit calculate. Now what did I do wrong? No, I dont fully understand the way the GI are calculated, so it doesn't jump out at me that the math for a lower gearing didn't add up. I appreciate you setting the OP straight and not letting me share bad info, but your tact leaves a bit to be desired. Thanks again.

hairnet

gear inches are calculated by (chainring/cog)x(wheel diameter inches)

higher gear ratio - more gear inches - harder gear
So, your numbers are wonky

six30nine

You didn't do anything wrong. Your procedure for using the gear calculator was spot on, but you flip-flopped (pun intended) the numbers when you typed your post.

While I understand gear inches, and find them helpful when comparing different bikes and/or tire sizes, but if all I want to know is whether a different chainring or cog will be easier/harder to push I use gear ratio instead. Divide the number of teeth on the chainring by the number of teeth on the cog. Bigger number = harder to push, smaller number = easier to push.

Squirrelli

My apologies, I shouldn't crush you like that...but you didn't do anything wrong with the calculator, as six30nine said, you just flipped the number. Sorry again.

i2oss

Bahhh is it even worse that I made a conscious effort to NOT do that. Oh well, thanks for letting me know. No worries Vixtor, I appreciate you giving us little guys a shot every now and then.

tFUnK

46/16 is a pretty good street gear that allows you to keep up on medium-fast group rides and weave up hills without totally spinning out on the way down. it might be a bit much if you are using the bike as a commuter in a hilly area. i think high 60's-low 70's is a good commuting gear.