mscycler

I mean, I am not a COMPLETE idiot, but sometimes I remeber that I am not as smart as I always tell my wife I am.

What my real question here is what are the physics behind the gears. I have a triple on the front, and 8 on the back cassette. I generally ride in the middle ring up front and the third or fourth "up" on the back. I was told by my lbs that the best gear (for my bike at least) climbing was small up front and big in the back. When I tried this today, it seemed like I couldnt get anywhere, the wheels were almost "free spinning".

Thanks in advance,
mscycler

neil0502

Here's a start....

https://sheldonbrown.com/gears.html

martin_j001

Like the link probably says, you need to find the cadence that you are comfortable peddling at on the given terrain. After you know the cadence you are comfortable at, then you switch to whatever gear is required to maintain that cadence--there's no magic gear for everyone, and its pretty ridiculous for someone who works at a bike shop to tell you that you should be in a specific gear, unless they are riding right next to you and making suggestions then.

mscycler

Kinda what I figured. What I try to do when I ride is switch gears that allow me to maintain the speed that I want. Dont know if this is right. When I feel "slack" in my chain, I switch gears to get rid of the slack. Does this make sense?

mscycler

crosscut

I think one of the hardest things for newbies or anyone that is starting out is learning gearing and how is applies to their riding style. There is not clear cut answer other than keeping your cadence between 80-100. Now I don't like spinning at 95-100 so I keep my cadence around 80-85 during my rides. Also I don't spin in the larger ring (up front) when I can spin (keeping my cadence at the level I want) in the middle ring with the correct rear gear ring.

In time you will learn what works best for you and your rides, and learning when to shift will come more naturally.

jitteringjr

How can adults possibly not understand what gears are easier to turn on a bike? Any 10 year old on a Schwinn 10 speed can figure this out within 5 minutes of riding.

53-11_alltheway

It's simple.


If your gearing is 1:1 (30T chainring with a 30T cog) you will turn the tire one revolution per turn of the crank.

If the ratio is 4:1 (48T chainring and a 12T cog) you will turn the tire four times for every turn of the crank.

ivan_yulaev

All you have to understand is that the gears are there to help you keep the RPMs of the pedals right. You want to keep it at about 70-100 rpms (in time, you'll learn what your 'preferred' RPM is). If you feel that your RPMs are too slow, you down shift. If you feel they are too fast, upshift. Also, try to keep the chainline straight, that is, if you are in the smallest ring up front, try to be in the bigger half of the rear sprockets. If you're in the biggest ring up front, try to be in the smaller half of the sprockets. The middle ring, try to avoid the smallest and biggest sprocket.

53-11_alltheway

Maybe they drive automatics?

MrCjolsen

If you have an 8 speed cassette, the cogs are probably 12-13-15-17-19-21-23-25.

In front you have 52-42-30.

Once you confirm or deny these number (they're what's found on most entry level road bikes), go to the Sheldon Brown website and figure out the order that your gears are in terms of ratios. On my bike (8 speed triple) if I start at 42-17, the next higher gear is 52-19, then 42-15 and then 52-17. So you should be going up and down between the middle and big chainring as conditions (wind, hills, etc) change.

For most of us mere mortals, the best cadence is between 90 and 100. That is where you are the most efficient in terms of energy. Use the sheldon brown site to figure out the speed and gear combos that you do at 90 rpm. Or you can use this chart based on my numbers:

Gears Speed at 90 and 105 rpm
52-12 31 36
52-13 29 33
42-12 25 29
52-15 25 29
42-13 23 27
52-17 22 25
42-15 20 23
52-19 20 23
42-17 18 21
42-19 16 18
42-21 14 17
42-23 13 15
42-25 12 13
30-19 11 13
30-21 10 12
30-23 9 11
30-25 8 10

Now affix the bold numbers to your bike somewhere if you don't have a computer that gives cadence. Basically, you want your cadence to be as constant as possible with gear changes being dictated by the speed you want to go. After a while you'll know what gear you need to be in to to which speed.

jitteringjr

Yeah but that doesn't tell them which is easier to turn. They would need a BRAIN to figuire that one out.

neil0502

If all you have are insults, feel free to end your participation in this thread.

Really.

Retro Grouch 

You're doing it right. I suspect that you're making it harder than it needs to be but, from scanning some of the other answers, that's a common affliction.

Keep your chain in the middle front chainring most of the time. If you find yourself gasping for breath, shift into a harder gear in back. If your legs start acheing, shift into an easier gear in back.

If you see yourself coming up to an Oh-my-god steep hill, shift into the little front chainring just as you staart up the hill. Follow the advice above for finding the right rear cog.

Save the big ring in front for fast downhills or for the two times a year when you have a tailwind.

That'll get you started, you can work out the fine points out for yourself.

jitteringjr

I'm sorry, but I can't imagine anyone needing to ask this question. He has to be fishing. He is sitting back and asking a silly question so he can laugh at all the people who do not get the humor. Furthermore, I have been following mscyclers posts and he seems way too sharp to have to ask this question.

My comments are not an insult to him, but a raising of a flag to let him know that I get it. If I am wrong, and don't get it, then I offer my humblest of apologies to you mscycler.

primaryreality

Comments like this--and your other ones above--really discourage new and inexperienced and not-so-technically inclined people from asking questions. Can you possibly remember a time when you didn't know EVERYTHING?

SimpleCycle

Not all of us are the spawn of a one night stand between Lance Armstrong and those guys from Car Talk. We might understand the basics, or even have moderately sophisticated cycling knowledge. Then we hear things that sound more complicated, like gear ratios and chainlines and begin to scratch our heads. Just because we're bright and caught on to most things quickly doesn't make the bike self-explantory. Understanding how to operate the shifters doesn't mean we understand the concepts behind gearing. A guy at the LBS saying your best climbing gear is 30-25 further complicates the matter for a newbie. I say this as a fellow newbie who doesn't understand the exact science of gearing.

I haven't figured out what the true order of my gears is, and use Retro Grouch's excellent method. I have a cadence function on my computer, and pretty much shift according to that. Soemtimes I'll focus on pedaling form instead of shifting if I see my cadence drop, but I try to keep the cadence above 90 and shift accordingly. Right now that means a lot of time on my middle chainring.

AlanS

Jitteringjr-

Arrogant response on your part. The original question was to describe the physics behind gearing -- and I bet only 1% of this audience could really answer the question properly.

The key to understanding gearing is that it establishes a relationship between the torque the rider exerts on the crank and the torque exerted on the rear wheel. By changing gears, the rider is able to select the torque of his/her choice at the crank.

Now the goal is always to optimize the power delivered to the bike -- which is proportional to the torque at the crank times the RPM. The human body cannot effectively pedal at 500 RPM nor can the body exert 1000 ft-lbs at the crank. So gearing allows the rider to choose the torque at the crank to optimize the power delivered to the bike. In engineering this "matching" of power between two systems is called "impedance matching" and comes up in thousands of mechanical and electrical systems.

khuon

Only 1% of this audience passed highschool physics? Okay... I guess that's unfair as many people have forgotten if they haven't used that specific bit of knowledge. I guess what I'm getting at is that while jitteringjr's response was arrogant and insulting, it's equally insulting to state that only 1% of the readers understand gearing.

jitteringjr

If I am arrogant for saying then I am sorry, but so be it. I still still can't believe anyone actually not understanding how gearing works. I have more hope for the human race then that.

And I am not talking about knowing everything here.

mscycler

You seem to be a little on the insulting side. As a matter of fact, I have a BS in Chemistry, a BS in Business Information Systems, and an MBA. So, smarta$$ I have a friggin brain. I am new to road biking, and am not looking for the almighty gear that will make my cycling life easier. I was merely trying to gather information. Since I have gone out and just ridden a few times on my new bike, I have been focused on just riding. But, I know there is more than just going out there and pedaling. I am trying to be more efficient with respect to my riding. Any more comments you would like to make regarding this post would be welcomed in the form of a PM. Please do not feel the need to berate me anymore here.

Thank you,
mscycler

jitteringjr

Then I am sorry; I thought you were messing around. and I say again:

va_cyclist

Perfect explanation. Too bad the thread couldn't have ended right here.

Kenal0

Here is another question about gear changes.
When downshifting from the large ring to the middle ring going uphill, and also making a change with the rear derailleur, do you shift the large ring first and then the rear or visa versa?
You either have a few pedals where you are going way above your cadence or a few pedals that are really hard until you get them both switched. Is there a correct method for making this shift?
Thanks
KL

jitteringjr

Campy or Shimano? With Campy, I can shift the two at the same time and it is very smooth. On Shimano (both Sora and Ultegra for me) I had better luck shifting the front then the rear.

Kenal0

Shimano.
KL