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Road Bikes, Gears, how They Work, and a Lesson: The Flaw in the Ten Speed 11-28 Cassette

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All of the pros are riding the 11-28 cassette nowadays, especially when things get vertical.  Flat stages, I’d imagine they stick with a corncob, but I don’t have my own mechanic and a supply of anything I want as gearing goes, so it’s a little bit of trial and error… by fire for me when I put a cassette on the bike(s).  I know for a fact, I don’t need a corncob, though.

So I decided to put a ten speed 11-28 on my bikes, both the Venge and the Trek.  The following post is my experience, so that you might save some headache, consternation, and money.  And don’t think the 11 speed will bail you out (as the extra gear usually helps – not in this case).

I’ve ridden, for as long as I can remember, an 11-26 cassette on the Venge and an 11-25 on the Trek (keeping in mind the Trek was a triple about four weeks ago).  I’ve always enjoyed the 11-26 because the gears seemed tight enough that I could pick a decent cadence and pace to match the group I was riding with.  The jump in teeth between gears, worked.  The thinking went, if 11-26 is good, that extra oomph of the 28 will really help in the hills when I take the Venge climbing.  Not only that, on the Trek, with it’s compact crank, well I’ll be able to climb anything with a 34/28 front to back combo.

It was sound thinking.  Or at least the thinking made sense at the time.

Then came my first ride on the Venge with the 52/36 pro compact on the front and the 11-28 cassette on the back…  I immediately knew I had a problem.

Here’s the gearing for the 11-26, then the 11-28:

The 11/26 includes: 11,12,13,14,15,17,19,21,23,26
The 11/28 includes: 11,12,13,14,15,17,19,22,25,28

The 11 sp 11-28 is as follows:  11,12,13,14,15,16,17,19,22,25,28  Same top end gap.

If you haven’t seen the flaw yet, look at it this way; each tooth increase in the cassette, from one gear to the next, represents 5 rpm on a 52 tooth crank.  So the 52/14 will spin 5 rpm slower than the 52/15 at the same speed.  The 1 tooth increase in cassette cogs allows the rider to perfectly tailor their cadence to the speed they’re going.  On the other hand, you won’t get any good climbing gears pushing an 11-23 cassette.  So we have a balance to strike.  To do that, we jump two, and even three teeth at a time as the gears get bigger.  On the 11-26 cassette, only the last gear jumps three teeth.  On the 11-28, the last four cogs jump three teeth.  So if a one tooth jump is five RPM, two is ten RPM, three would be a difference of fifteen RPM between gears.  Getting right to the punch, fifteen RPM between the top gears is no bueno.

See, I like to cruise right around 19-21 mph when I’m by myself.  With the 11-28 cassette I’ve got an 18-1/2 mph gear and a 22 mph gear.  One is too easy and the other is too hard.  Simply, there’s a big hole between my normal favorite cruising gears.

Where I get into trouble is the difference between the two cassettes for just three gears.  Observe:
19,21,23 vs. 19,22,25

All is not lost!  There is hope for the 52/36 pro compact!

So this is where Mrs. Bgddy isn’t going to be a happy camper…  My normal 20 mph cruising gear is the 21.  22 is too easy and 19 is just a touch harder than I’m used to.  What will happen is I’ll spend a lot more time in the 19 until I become used to cruising in that gear.  This will mean two things:  I’ll be stronger and faster.  My wife likes me right where I’m at.

This is where the Trek comes in with the 50/34 compact crank, though.  Dropping two teeth on the front chainring will mean that instead of messing around with the 19 and 22 teeth cogs, I’ll drop a couple of gears – the normal cruising gears will be the 17t and 19t cogs.  That two tooth jump is a little easier to manage.

So that’s how gear selection works on the road.  Just something to consider.

Now, I can make this interesting, if a little geeky.  I’ll try to keep the exercise and math short.  I’m taking the Trek on DALMAC this year and we’ve got one whopping hard hill to climb 90 miles into the third day.  We’ll climb 2-3% for three miles before we hit the 18+% monster.  I took my Trek up that way earlier this year, when it was still a triple, and managed the climb easily with a gear left in the bank.

When I hit that hill again, it’ll be a compact double with a bigger cassette.  If I choose too easy a gear, climbing the hill will blow my lungs up (definitely not literally).  On the other hand, too hard a gear on an 18% pitch and you’re pooched.

Well, I have my answer before it ever became a problem.  I go to Sheldon Brown’s gear calculator webpage and enter in the old gearing, crank length, tire size/width and hit calculate.  Then I do the same for the new gearing:

So I thought, up until about two minutes ago, that I was riding an 11-25 cassette on the Trek when it was a 9sp.  It may have been a 26.  Anyway, that’s inconsequential.  I climbed “The Wall” as they call it, in the 30/23 gear and made it up just fine.  The last gear was a little too easy.  If I look at the 34 tooth chainring on the right, all I have to do is match up the closest speed to the 30/23 combo and I know which gear I’ll need:  34/25.  The second to the last gear should do it.  9.2-mph vs. 9.6.

There’s a problem, though, that I have to account for, but there will be a mitigating factor as well.  First, the problem:  I’ll be on tired legs.  Third century in three days, 90 miles into the third day, that hill SUCKS.  That would lead me to believe the last gear might be necessary for the climb.  On the other hand, I’m in much better shape today than I was when I last did the climb more towards the beginning of the season in  early to mid-May.  In other words, meh.  34/25 oughta do just fine.

The point is, and where my experience can benefit the more fearful in all things cycling; I can research most of the fear out of the equation if I just know what I’m doing.  I’ll know exactly which gear to push come DALMAC, no fear necessary.

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7 Comments

  1. heavyman927 says:

    I think what makes your task hard is that there is only one 18%er on the ride. Do you choose gearing to suffer on the one climb or on the rest of the ride? Oh wait, it’s cycling, you’re going to suffer every day. 🙂

    • bgddyjim says:

      Well, there’s only on 18%’er but there are plenty 10+%… the wall is just the hardest hill on the ride and it’s 90 miles into the third century in three days. Because it’s so hard, it deserves extra consideration. In the end, it’s more important to know I’ve got a gear I can make it up the hill in… and it’ll be a bonus that I’ll have an extra on the cassette if I need it.

  2. You could always get a 12-28T cassette? Gets rid of the gap but you do lose the 11 tooth cog. That’d be fine for me as I hardly touch the 11T, but it may cost you the town sign sprint if you use that one on your Tuesday night thrash.

    12-13-14-15-17-19-21-23-25-28

    My “climbing” bike has a 50/30 bottom gear. Some mornings on the way up the mountain it’s nice to know I have an extra bail-out ratio.

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