Gear Ratios- can someone explain?
1796
Member
1542 days
PrinceofClydes posted 2 years ago.
56 teeth on the front, 11 teeth on the rear.
Therefore the wheel rotates 5 and 1/11th times per pedal rotation, 56/11, or 5.09 times.
A 700c wheel goes 2.199 metres per rotation, so 5.09 times 2.199 = 11.19 metres.
This varies a little depending on your tire profile: 700x18c to 700x25c
So your bike would move 11.19 metres down the road per pedal rev.
Now, with this gear ratio and a cadence of 90 rpm, your bike travels 1007 metres per minute or 60.44 KPH!
This is a gear ratio for windless flats and fast descents, but very few humans could pedal it for very long at 90rpm, maybe some track cyclists.
You may have heard Bobke talk about a "dinner plate" up front. This is the chainring he's talking about.
I think Honchar rode one in a time trial once when he was feeling good. He bombed though.
And here's a tech article on gears FYI.
PoC
"Pain doesn't last, chicks dig scars, glory is forever!"
- Shane Falco.
417
Member
1231 days
BrianMc posted 2 years ago.
56-11? Wow, I couldn't push that for very long.
Just for info, most people probably ride with a 53-39 up front ( thats the number of teeth on the big and small chainrings), and maybe something like a 25-12 on the back (again biggest and smallest rings on your cassette)
695
Member
1155 days
deepbluex posted 2 years ago.
wow that is a huge ring up front. Another factor to consider in the amount of force required to push those pedals is the length of the crank arms. The longer the arms, the more leverage you have and the less effort you need to exert compared to the same setup with shorter crank arms. However, longer crank arms make fast cadence more difficult.
Right now my biggest ring up front is a 53 with 175mm arms and my smallest cog in the rear is a 11 I believe (it might be a 12...) and I ride with 700c wheels.
Smaller wheels like a 650 also affect the gearing as their small radius make them act like though you are on an easier gear than a 700, everything else being equal.
4953
Member
1728 days
beads1985 posted 2 years ago.
PrinceofClydes wrote:
56 teeth on the front, 11 teeth on the rear.Therefore the wheel rotates 5 and 1/11th times per pedal rotation, 56/11, or 5.09 times.
A 700c wheel goes 2.199 metres per rotation, so 5.09 times 2.199 = 11.19 metres.
This varies a little depending on your tire profile: 700x18c to 700x25c
So your bike would move 11.19 metres down the road per pedal rev.Now, with this gear ratio and a cadence of 90 rpm, your bike travels 1007 metres per minute or 60.44 KPH!
This is a gear ratio for windless flats and fast descents, but very few humans could pedal it for very long at 90rpm, maybe some track cyclists.
You may have heard Bobke talk about a "dinner plate" up front. This is the chainring he's talking about.
I think Honchar rode one in a time trial once when he was feeling good. He bombed though.And here's a tech article on gears FYI.
PoC
This has always been a little confusing.
I like your explanation. Concise and clear. Thanks,
Nothing to it, but to do it
4508
Member
1646 days
kylie posted 2 years ago.
Awesome PoC... Thanks! Everyone I've ever heard explain it made it complicated... :)
7
Member
1053 days
kstuff posted 2 years ago.
PrinceofClydes wrote:
56 teeth on the front, 11 teeth on the rear.Therefore the wheel rotates 5 and 1/11th times per pedal rotation, 56/11, or 5.09 times.
A 700c wheel goes 2.199 metres per rotation, so 5.09 times 2.199 = 11.19 metres.
This varies a little depending on your tire profile: 700x18c to 700x25c
So your bike would move 11.19 metres down the road per pedal rev.Now, with this gear ratio and a cadence of 90 rpm, your bike travels 1007 metres per minute or 60.44 KPH!
This is a gear ratio for windless flats and fast descents, but very few humans could pedal it for very long at 90rpm, maybe some track cyclists.
You may have heard Bobke talk about a "dinner plate" up front. This is the chainring he's talking about.
I think Honchar rode one in a time trial once when he was feeling good. He bombed though.And here's a tech article on gears FYI.
PoC
This is why I've always thought roadies are crazy :eek: . I mean don't get me wrong it makes sense and the more knowledge the better, but can't I just ride or do I have to take advanced calculus before I can become a good rider. ;)
1796
Member
1542 days
PrinceofClydes posted 2 years ago.
kstuff wrote:
This is why I've always thought roadies are crazy :eek: . I mean don't get me wrong it makes sense and the more knowledge the better, but can't I just ride or do I have to take advanced calculus before I can become a good rider. ;)
You Drama Queen!
It's simple multiplication.
5.09 x .7 x 3.14 x 90 x 60 = 60.44kph
PoC
"Pain doesn't last, chicks dig scars, glory is forever!"
- Shane Falco.
4953
Member
1728 days
beads1985 posted 2 years ago.
kyillee wrote:
PoC, you forgot your units! ;)
Hey fresh girl!! Talking about units!!
OH!! Units of measurement.... :D
Nothing to it, but to do it
1796
Member
1542 days
PrinceofClydes posted 2 years ago.
Just trying to keep it simple for kidstuff.
They all come out in the wash.
(5.09m x .700m x 3.142) x 90rpm x 60mins = 60.44kph
11.19m / rev @ 90rpm = 1.007km/min, x 60mins = 60.4kph
better?
or did you want that in light-seconds?
Reduce it all to electron volts and it doesn't matter.
Time, distance, they all disappear.
PoC
fussy, fussy.
"Pain doesn't last, chicks dig scars, glory is forever!"
- Shane Falco.
4508
Member
1646 days
kylie posted 2 years ago.
Yes, thanks :)
Part of me just wanted to be picky... part of me wanted to make sure I was picturing it all right. You know, I've never really thought about how there is an easy way to figure out speeds/etc based on the gearing. I mean, I knew there had to be, but this made me picture how the gears actually work. I think grasping how the 56/11 part gives you rotations per pedal was the neat part to me. =)
1796
Member
1542 days
PrinceofClydes posted 2 years ago.
Well I have a Bianchi road bike with a triple chain ring up front: 52-42-34
and I have a freewheel gear set on a 27" rear wheel that is 34-15 range.
This means that I can have a 34-34 gear ratio or 1:1 in my lowest possible configuration (small chain ring, big rear cog).
Each pedal rev means one turn of the 27" wheel or 85 inches on the road
With that, I can climb just about anything!
on the other end of the speed spectrum:
On my IM race bike with the Campy wheels and groupo I have a double chainring of 50-42 and a freewheel of 23-11
My big gear is 50-11, a 1:4.55 ratio
(4.55 x 2.199)m x 90x60 = 53.91kph @ 90rpm
On this, I'm really spinning going downhills and coming out of the Richter or Yellow lakes I can only coast - so I max at 74kph in the aero bars.
But with a 56-11 I could top 85kph easy.
Trouble is I can't climb UP the Yellow Lake hill on a 42-23!
So you must choose your gear ranges for each race according to your mass and ability.
Geoff
and thanks. I'm glad you found my explanation satisfying. :)
"Pain doesn't last, chicks dig scars, glory is forever!"
- Shane Falco.
62
Member
1443 days
AZBuckeye posted 2 years ago.
Thanks everyone for the input. Pretty cool stuff.
Can anybody explain gear ratios, and the corresponding numbers? I was watching the Tour of California and Bob Roll mentioned the gear of choice would be "56 11". What does that mean?
Thanks