Digger Goreman

Glad to help! People, here, are phenomenal in expertise. But I didn't understand my gears (well) until someone explained the math in "feet per pedal revolution". Now I know that in the granny I won't be out-running a kid on a big wheel, at 4-5 feet per revolution

A lot is down to feel, as some have mentioned. I stand to wear out (if ever) my 15 tooth, 7th (out of nine) cassette first, simply because that's the gear that is easiest to maintain good, efficient speed in the second and third front rings for me... at this time AND in my particular riding location. Then, you never know: last week a miscue took me down a perfect road where I exceeded my maximum gear's ability for the first time! Have to admit, my initial thought was, "I need more gears!"

By the gods that aren't, and the wrath of my wife, I will not go down that path....

southpier

it's your legs that are doing the handling. they will tell you when it's getting too hard or easy enough to want more. good onya for asking questions some people just ignore as they pedal down life's highway completely oblivious!

southpier

yes; don't do it. you're in control. get a chain and hold each end. move it up & down and feel how smooth it articulates. now extend sideways pressure as you move it and feel how the links start to bind. time to go wash your hands and head out for a ride all the much wiser.

southpier

whatever you do, don't get "them" started on 'gear inches'!

kaiserschmarrn

I understand what cross chaining is, as indicated above. My question was, is that only one sprocket from the big or small end on the rear sprockets, or two, three? I am getting some derailleur/chain rub in those conditions, up to maybe three sprockets either way.

Danny

cyccommute 

It can depend on the derailer you are using. Shimano’s more expensive derailers have a narrower space between the inner and outer plate than Shimano’s less expensive derailers. Cable tension and the limit screws play a role as well. If the cable is too tight and if the limit is set too far outboard, the derailer will be pushed out too far. For the low end, the cable may be too tight and the limit set to far outboard.

Notso_fastLane

In addition to what was said above, there really is no 'should' here. Do what it comfortable for you. I get your trepidation, and as the exception to the rule, the only 'shoulds' are that you would avoid the big-big and small-small combinations. Other than that, do what works comfortably for you.

My velomobile is a completely different beast, and I have it set up rather different than a standard bike's gearing. My setup is 3 x 9. (30-44-56 and 11-36)

For starting on level ground, I'm in 1 x 3. I only have two 'granny gears lower than that for hill climbing, but that's because my velo weighs ~70 lbs and I don't like mashing. My setup is such that my smallest front ring works well on the whole range of the rear cassette (so I can readily use the small-small combination, though I tend to avoid it). The flip side is my large ring binds pretty bad on anything lower than the 3rd gear on the back. My middle ring works with the whole range as well.

My typical shifting pattern is: Start in 1 x 3, shift to 1 x 5 (or maybe even 1 x6 if I'm going to be stopping again soon anyway), when I get to about 17-19 mph, I shift to the middle ring, and often drop one on the back, then it's 2 x 4-7. At about 24 mph I will shift to the big ring and with that, I can cruise up to about 34 mph, and if I have a little more of a downhill, I spin out around 48 mph.

Shifting up happens when I start 'spinning out', for me, that's around 105 rpms. Shifting down happens when I start mashing the pedals (or a little before, really) and that's typically around 80, but on flat ground with out much effort, I might relax down to about 70 rpms.

rydabent

This is my approach too. I notice you said you rode mainly in the center ring, and that is what I do. Since it is fairly level here in Lincoln, I pretty much stay in the center ring and just shift across the rear cluster as needed.

And again Granny for up hills. Center for most riding conditions. And the big ring for down hill and or with the wind. Some may suggest complicated shifting of the front, but it is kind of a waste of time. Just stick with what Retro and I suggest and you will get along just fine and enjoy your ride.

rydabent

One more thing. Cross chaining. If I am in the center ring I use all 8 or 9 sprockets in the rear depending on if I am riding the bike or trike.
Some would try to convince you that I am cross chaining doing that. But think about this, some bikes only come with a single chain ring in front and may have as many as 12 gears in the rear cluster. Yet no one calls it cross chaining on those bikes. So-------it would seem that we can use the whole cluster in the rear with the center ring.

Digger Goreman

To piggyback a little on rydabent : When (if safe) looking down at my front derailleur cage (an old 7 spd, supporting a 9 cassette) I, too, can shift my 2nd ring through 2-7 and not rub or have problems. Only rub on 1, 8, and 9. Third ring I' ve done 9-5 no problems.
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kaiserschmarrn

My derailleur is a Shimano 105 R7000. I adjusted it slightly, but when I took it back to my dealer (it is brand new) to get shifting onto the small back sprocket adjusted, they thought I was talking about shifting onto the small front chainring, so they adjusted the derailleur. I then told them that it was the REAR, so they adjusted the rear derailleur and got that squared away. Right now, the front derailleur is adjusted so that there is a bit of chain contact on the big three rear sprockets and the little three sprockets, but it is actually not split evenly between big and small. There is probably more rub on more big sprockets, but it is not by much. Can all of it on both large and small rear sprockets be totally eliminated?

Danny

cyccommute 

The 105 is in the range of fiddly Shimano fronts. Get the installation sheet for your front and follow the instructions precisely. Make sure that the plate on the derailer is absolutely parallel with the chainring.

If all else fails, get a Tiagra front. Front derailers are cheap.

kaiserschmarrn

Thanks for the help. I was eyeing the alignment of the derailleur body. It is ever so slightly kicked inward at the rear. When I found that the derailleur is what they call a "braze on", I was not sure how this could be corrected. I briefly watched a Youtube video for this derailleur. I see that there is a set screw in the body of the derailleur that sets alignment to the chainring. I will soon get the manual. Right now, when Corona dies down, I am due a fitting with my shop. I will bring that up with them. I don't want to fiddle with it while they are responsible for the adjustments. I don't want them thinking that I am causing them extra work. If they don't get it solved, I will.

Danny

cyccommute 

That can cause your problem.

Phil_gretz

Here's the calculator:

https://www.sheldonbrown.com/gear-calc.html

And here is the numerical table that results in "gear inches" for a 3 x 7 system like the OP describes. Gear inches mean the relative difficulty of pedaling, or the distance that your bike travels for one rotation of the cranks:




Note that in the center column, you'll find the relative difficulty of pedaling when solely in the middle chainring. Also notice how the numbers in the columns overlap one another in a pattern. That's the pattern that your gearing represents over the entire range of your front chainrings and rear cogs. Now to relative speed:




The numbers above are miles per hour assuming that you pedal at a constant 80 rpms. As one poster said above, you should find the rpm rate that you find challenging but sustainable. Bike riding doesn't require you to be straining all of the time, but should be (normally) at a sustainable pace that balances the load on your heart/lungs with the strain on your muscles. 80 rpms would be a good starting cadence. 90 would be better, and you might reach that comfortably in a year or two. This is meant for average folks who ride, not for the very muscled or for the very wiry. Simply average.
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