Beginner's gear question

I do not understand the differences between different cassettes and the relation with the chain ring.

My rear cassette is an 11-34, and the head wrench at my LBS says that certain gears would be easier to shift into if my chain ring had a wider range.

I know about ratios, so I have at least an intellectual understanding of gears in that way. Is there an analogy that I can use that would make this more clear to me? I am just trying to find a way of understanding this that makes more sense to me :o

Back in the old days, people talked about gears in terms of gearing "inches," which relates to how many inches the bike travels with one revolution of the crank.

To calculate, divide rear cog teeth# into front chainring teeth# and multiply by wheel diameter.

So, for a 13-tooth cog in the rear, 52 in the front, with a 27" wheel, you would get 108 gear inches (52/13 * 27). For a 26 tooth cog in the rear, with the other variables identical, you would get 54" (52/26 * 27).

When you analyze gear inches, you quickly discover that reducing or increasing the size of your chainring has a larger effect on the size of the gear than reducing or increasing the size of your rear cog by the same amount.

Does this help?

I don't know what your wrench means that certain gears would "be easier to shift into." In general, drivetrains run a bit "smoother" and there is less likelihood of dropping a chain when there is less discrepancy in size between the large chainring and the small chainring. In the rear, it doesn't make any difference.

How did this come up in conversation? Where you telling him you had some issues or difficulties shifting, or have a hard time climbing or going fast?

That answered, what do you have up front?

How did this come up in conversation? Where you telling him you had some issues or difficulties shifting, or have a hard time climbing or going fast?

That answered, what do you have up front?

This came up in the context of my wrench adjusting my shifter cables and derailleurs. I have had a lot of problems with things getting out of adjustment because of my lack of understanding of "trimming" when the chain rubs the FD. THere has also been some problems with the chain falling off in the front (rarely, but typically when going up a steep hill).

As far as climbing in general, to me that is more of a fitness issue than anything.

The crankset is 48-36-26t. The wrench showed me that in certain gears the chain has a problem hitting the right part of the chain-ring and will tend to rub the actual chain-ring rather than hitting the teeth. Is this the right way to put it? This seems to happen mainly in gears that I shouldn't be using, or duplicate gears. I just have to come up with some way of internalizing all of this so I can start to remember which gear combinations work, and which ones causes these chain-rub problems, and which gear combinations are duplicates and which ones are better to use. Note that I am not referring to the chain rubbing the RD, but the ring itself.

I do understand cross-chaining and why it is a bad idea. I do not do this - so I have at least learned that much. Things have improved since learning how/what/when to trim and also making sure my back gears are somewhere in the middle before shifting the front.

IndySteel has pointed out that I've a wide range of gears and that sometimes it would be better to shift the front to avoid a big leap from one gear to another. I hope that I accuratly reported what she said - it makes sense to me. It is just that looking at numbers on a chart isn't helping me much...

Am I over-thinking all of this?

That's close, but not quite what I was saying. Because you have a triple, you have a fair amount of overlap between your chainrings. Finding the next easiest or hardest gear among all the gears available to you may require a shift between chainrings, not just between cogs. If you look at a gear ratio chart using your bike's specifications, it's really use to see this. You need not memorize the chart; just be generally aware of it. As for what Scott at Nebo said, I'm not sure I understand what he was getting out. Beyond cross chaining, I would suggest trying not to overthink it. Hopefully with his recent adjustments, you won't lose your chain anymore.

Yes, I'm also at a loss for what he means other than cross chaining. If everything's adjusted right, you should be able to go through all the gears other than the cross chained ones.....

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Originally Posted by Catrin

My rear cassette is an 11-34, and the head wrench at my LBS says that certain gears would be easier to shift into if my chain ring had a wider range.

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My first thought when I read this was that he was referring to the fact that derailleurs have a harder time lifting the chain when the tooth difference from one cog to the next is more than 1 or 2. When its try to lift from a smaller cog to a much larger one the shifting might not be as smooth.

For example if you have an 8 speed 11-34 you might have the following:

11-13-15-17-20-23-26-34

But if you have a 10 speed 11-34 you would have:

11-13-15-17-19-21-23-25-28-34

You see with the 8 speed you have bigger gaps and there are more instances when your derailleur is changing to a cog with 3 more teeth rather than 1 or 2.

That's just what occurred to me when I read your question and that he meant the cassette rather than the chain ring. I could be wrong.

It doesn't really matter where your duplications are, because you don't shift sequentially through all your gears anyway. Use the FD for large jumps, the RD to fine tune.

Let's say I've just crested a hill, and I'm in a pretty low gear. (Let's assume a double, for the sake of simplicity.) To maintain a steady cadence as I start to descend, I'll shift the RD one at a time until I'm at about #7 in back, then as I continue to pick up speed, I'll shift to the big ring, then shift to the smaller cogs (taller gears) in back if I need them.

So now I'm at the bottom of the hill and starting to climb the next one. I'll shift the RD one at a time to maintain my cadence until I'm at #4 or #5 in back. Then I'll shift back down to the small ring. Now at that point, depending on how steep the hill is, shifting the FD may have put me in a shorter gear than I want, so I may up-shift the rear by one. Then as I continue to climb, if I want shorter gears, I'll shift the RD one by one.

The point being, I'm not worrying about EXACTLY what gear development I'm getting at any particular time. I'm paying attention to my cadence and how my legs feel. So when I'm going up through the rear cogs, I'm going to be using more of them in the smaller ring, and when I'm going down, I'm going to be using more of them in the big ring.

Does that make sense, at all?

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Originally Posted by OakLeaf

The point being, I'm not worrying about EXACTLY what gear development I'm getting at any particular time. I'm paying attention to my cadence and how my legs feel. So when I'm going up through the rear cogs, I'm going to be using more of them in the smaller ring, and when I'm going down, I'm going to be using more of them in the big ring.

Does that make sense, at all?

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Yes it does, and I think that I've been headed that way. I've a 9-speed rear cassette, so I try to shift the back into a gear that will give me some kind of resistance for the front gear that I am going to shift into. Does that make sense? I don't want to lose speed by suddenly being in too easy a gear when I shift the front - this is a very bad thing to happen when I climbing.

He did show me what he meant by the chain rubbing the chain-ring itself, but am not good at explaining it. I asked him about that today and he said it really only mattered for those gear combinations I shouldn't probably use very often so it didn't much matter in the long run.

There is a good video on the Terry website that explains the concept of gearing and cross chaining, and shows how to calculate gear-inches if you are into that sort of stuff. Perhaps it will help you to understand this better.

Scroll down to the video called "Bicycle Gears."

http://www.terrybicycles.com/videos

I rode with a bike trailer this summer in rolling terrain, and had to be meticulous with my shifting, because the extra load would cause me to slow down very fast if I didn't shift in time. The others were riding with panniers and I'd lose them in no time uphill if I didn't keep all the momentum I could. Ditto I wanted to keep up momentum going downhill.

This was on my mtb with a triple, but might be useful for you. I usually just shift by feel. Now I noticed that when I hit say a flat with uphills approaching after a downhill (highest gear) and started to slow down I'd downshift in the rear first, for several clicks. When I could feel that to maintain my cadence I'd have to downshift more, I'd downshift in front once to the middle and simultaneously upshift in the rear a click or two. This gave me a gear ratio very close to the one I already had, but in a position to downshift gradually. The middle chain ring is very forgiving for finetuning so I used that a lot since I couldn't stand and power through anything with the trailer on.

Give the simultaneous downshift/upshift a try and see if it helps to keep you in a range that's useful.

ETA: I see Oak said the exact same thing, only shorter and sweeter :-) No gears should be "hard" to shift into, in my opinion.

Thanks everyone!

I haven't tried shifting both at the same time, though most of the time when my chain has fallen off the front it has been when I've shifted both very close together.

Getting ready to head out the door for my long ride of the week and will try and remember some of this :) Will watch the video this evening - have been trying to focus on learning by experience and not over-thinking too much. I DO that and it gets me in trouble sometimes...

Just looked at the radar...have to wait a few hours. Sigh...though we DO need rain pretty badly. Am determined to get my ride in today but it is hard to decide which forecast to believe :(

Thanks for the great question Catrin, sorry I posted a duplicate.

How did things go on the ride? Any insights you can share with a newbie?

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Originally Posted by schnitzle

Thanks for the great question Catrin, sorry I posted a duplicate.

How did things go on the ride? Any insights you can share with a newbie?

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The ride was great, had more problems with nutrition than the bike. I did not try to shift both at the same time though...but I do need to try that. Seems to me the last time I tried that the chain fell off, but I may have been trying to shift under too much load.

I am a newbie myself, having been riding only since December. I am, however, learning to not over-think things and to just ride. And ride some more, then ride more. Things seem to work themselves out on the bike with just more riding :D

FWIW, I have never attempted to shift both simultaneously and probably never will.

Since I brought it up, I guess I should add:

I don't actually shift simultaneously, as in hit the shifters at the exact same moment (I'm not co-ordinated enough for that :D ). But I do shift in front, and then immediately afterwards in back, if I'm trying to stay in roughly the same gear, but have more room for downshifting for an approaching hill, for example. I have not done this on my road bike with a double, though, as far as I can recall.