bubber

Got a Specialized Allez Elite Triple for Christmas. Of the 27 gears available to me, how many should be useful? In other words, how many should not grind excessively because of the extreme angle of the chain?

DogBoy

setup properly, none of them will grind due to chain angle. This is the case with my road triple, but I still avoid big-big and little-little combos

sydney

Because of the increased chain angle of the triple you should avoid more than just the big/big.

Rex

26 of them

khuon

I could give a flippant answer by saying that all of them can be useful given the proper circumstances. That said, on a 27-speed road setup, I would probably as a rule of thumb, avoid the last two cogs if not last three while in the big ring and the first two if not three while in the small ring so that's purposefully putting 6 combos in contention. However, if you really have to enter those combinations then do so but try not to stay in them any longer than you have to. Now different cogs and chainrings sizes will of course give you different combos and thus different usable gears as well as overlaps but just as an example, here's what the gear plot of my 27-speed MTB setup looks like. Note that the lighter the colour of the gearpoints, the more contentious they are.

christian

I usually use the seven smaller cogs with the larger ring, the seven middle cogs with the middle ring and the seven larger cogs with the smaller ring.

Anyway, some cog/ring combinations are redundant. Just use an Excel table to determine all your 27 ratios and you will find out.

Christian

sydney

Bull

F1_Fan

What application is that?

Avalanche325

The idea of three chain rings up front is to give you three different speed RANGES. It is not intended to give you 27 seperate sequential gears. Lots of people on this forum calculate all of the gear - inch ratios and shift a million times trying to shift up and down through all of the gears. That is not how it was designed to work. You generally select a range (Hi, med or low) with the front chain rings. Then you have the gears on the rear to move up and down in within that range.

Looking at the chart above and trying to shift sequentially you would go, 32/23, 44/30, 22/14, 32/20, 44/26, 32/18, 44/23, and 32/16. This is nonsense. You would simply stay on the middle chainring and use the rear cogs and go 32/23, 32/20, 32/18, 32/16. A nice speed RANGE which your legs can handle. (Khuon, I know YOU weren't saying to do this. But some people here think that is the way to do it. I am just trying to show that if you think "3 speed ranges" instead of "27 gears", the gears are not very complicated. And, you don't need to shift a million times.)

Shimano states, and I have found this to be true with my triple when adjusted properly, that you can use all combinations except big-big and small-small. Some people go more conservative and stay off the extremes by two.

This gives you, eight gears in low range, nine gears in the middle range, and eight gears in the high range.

PS. Bubber, I am originally from Myrtle Beach. I miss SC.

53-11 alltheway

I think the word you are looking at is "non-overlapping". I think most triples have about 15 gears that are non-over lapping.

khuon

It's actually a Tcl script that uses the now defunct and forgotten Tcl-plugin. It was written by Brent Welch (an engineer working for Sun Microsystems and author of Practical Programming in Tcl and Tk) as an example/demo of how to utilise Tcl. I've been able to massage the plugin to work in Mozilla with some effort. He had a webpage set up which demo'ed this. I run a copy of it with some small personal modifications. You can find it here. Of course, in order to make it work, you will need to download and install the Tcl-plugin. I'm sure somewhere out there is a Java applet or JavaScript piece of code that does the same thing.

khuon

I agree. The idea behind overlapping and redundant gear combos is to give the rider the ability to switch between these ranges without radically shifting and imposing undue wear and load on the drivetrain. Also, as most of us know, shifting the front chainring is at best a bit fussier than shifting the rear cog so you don't necessarily want to be constantly flipping your front derailleur about with abandon lest you desire an increased probability of throwing the chain. The other reason for overlapping gears is to help you out with chainline management so that trimming just a tad to smooth out your spin doesn't result in an extreme amount of shifting.

bubber

From what everyone has said, the gears in blue in the attached jpeg should be consider within the range of that "speed" (ring). So, if there is an excessive amoung of mechanical noise from the 42/14 combination, I should head back to the LBS for some tweaking. Does this sound right?

my58vw

I think that approximetly 20 gears on a 9 speed bike are actually avalable for use. I have experienced the overlapping gear issue as most have and it is true that the triple is different speed range. For example I can go almost 23 MPH in the second ring and when I shift to the big ring up front I have to use the 6th or 7th ring to avoid losing speed at the same cadence. Same with downshifting, but less on the granny gear. When I go down lets say at 10 MPH on a hard hill and I go to the granny gear I can only really use the largest 4 or so cogs on the back and have an easier gear. Translated that is about 16 gears or so. Of course your usage will vary.

HunterBee

Chainstay length has some to do with how many gears you can use. If you have 41cm chainstays you should have 23 to 25 useful gears. With 45cm chainstays you can use all 27 gears, although the chain angle will not be very forgiving of poorly adjusted derailleurs.

LordOpie

to everyone else... see 53-11's post, that's what yours should've been. Please take note and follow his example.

HunterBee

I liked the following post by Avalanche. You have no idea how many times I have tried to explain this concept to incurable gearheads.

Think of it like this: BigRing = downhill and jamming on flats / MiddleRing = general riding (most of your riding will be here) / SmallRing = for climbing only (and the stronger you get the less you will need it).

Rowan

Yes all very nice in theory, but practice is often different. The gaps between gears in the same *range* can be wider than preferred with off-the-shelf clusters, and sometimes a double shift (front and rear) will be needed to get the right one (and maintain a comfortable cadence).

HunterBee

You have a good point. But, I have found that the stronger I get the more I stay in the middle ring. I can tolerate bigger gaps and don't need to shift as much. I just spin 10% faster or grunt 10% harder, whichever is needed. This makes a good workout too. It makes you both stronger and more flexible.

Rowan

I'm not dismissing what has been said. In fact, I spend most of my riding in the middle ring. The small ring is handy on really steep hills (a few of those around here) and when I am really tired on long-distance randonnees.

I often wonder if we are overgeared because that is what is sold to us. I am currently commuting on a fixed gear (not trying to start a FG debate), and I am seriously considering fitting up another old tipshop frame (lugged, of course) with a single chainring on the front and a five, six or seven-speed rear to become my daily commuter. Simple, and with a gear range that theoretically should get me around the city and over all the hills if I want to go visit friends after work or attend meetings. The fixie tends to be a bit of a handful on hills steeper than 8% even with 60gi (yes, you might think I am a wuss, but at my age...).

I reckon if you took a close look or recorded the gears you actually do use on a 27speed bike, they would amount to around 13. Realistically you are not going to go through to the smallest rear cog in the middle chainring, then change three or four steps on the rear as you also change to the large chainring to get the next usable gear. And vice versa. That's where Avalanche's post sort of falls over. Maybe you can see by the wear on the cogs in the last couple of clusters you've replaced. Some inevitably are worn more than others. That will change if/when: you get stronger or you change the tooth number on the chainrings.

It's also why I say theory is often different from practice.

HunterBee

I am working on something like that. I have an old Dawes road frame that I am setting up with a single 48t chainring in front with a 12-32 in back. It will be interesting to compare notes when we are done.

boyze

After a few hundred miles you'll "feel" when the angle becomes excessive and where your general sweet spot is for flat, windless riding. Ideally the sweet spot is in the middle ring in a middle cog. A 1,2 or 3 cog shift in the rear can be virtually instantaneous - up or down. Then as the terrain significantly heads up or down you instinctively know when to change the range in the front, which is a bit less instantaneous and a bit more effort.

I've always believed the real benefit of the added cogs in the rear was to provide more incremental shifting rather than added range. I've never had range problems and I've ridden some pretty hilly country over the years and I've always used 2 front rings. More cogs enables more of a constant cadence going over the ups and downs. The more miles on the saddle the more the body likes to be at the sweet spot cadence, at least for me.

Rowan

And this is where the unknowns that theory is supposed to cover start to creep in. How do you qualify your "pretty hilly country" against mine? Are you a power rider or a spinner? Are you a competitive cyclist or a touring one? Do we actually need 27 gears if we ride a fixed/ss with flip-flop rear hub and can still cope with your hills and mine?

FWIW, I can be in middle CR and 32T on the rear, and need to change down to the granny on a steep hill. To change without a double shift would have me spinning wildly while the bike speed drops from, say, 11km/h to 7km/h. To maintain cadence with a slight drop in speed to 10km/h, I need to make a double shift to the 28 or even the 25 at the same time as I drop down to the 22T chainring.

By the same token, I could have planned well ahead of the hill and changed to the granny and say, the 17T and worked my back to the larger rear cogs. But to do that requires trimming to avoid rub on the front der.

Again, practice defeats theory. And boyze is right... the answer lies in practice and what feels best to *you*. Keep away from cross-chaining, though. It's noisy, wears your stuff out, and can lock up your chain going big-big.

HiYoSilver

That is good.

Coming back to biking it took me forever and a year to figure out gears. I also bought into the marketing hype about how many gears were available and thought that was important. I had to get back myunderstanding of gear inches before I understood gears. At first I thought the goal was to go from the slowest speed to the highest speed by shifting through all 27 gears, starting with #1, the lowest, finding the next and then going up to the highest.

The problems with this 27 gear ideal are:
1. a couple chain layouts put extra strain on the components and so are not recommented.
2. no one can remember the correct order of shifting. A few gearhead die hards ride with a chart in front of them to tell them what gear to shift to next.
3. some of the "gears" are so close together in speed that riders cannot tell the difference between going speed X with gear X and speed X+.03 mph in gear Y.
4. the bike manufacturers did not design gears to be used that way.

Gear definition
Gears were designed as ranges: slow, regular, fast. On a "triple", the front set of 3 chainrings, the smallest ring is for slow, middle is for regular, and largest is for fast.

Comparison #1 - bikes to autos
I have found that with automatic transmissions in vehicles, few understand "low gear", "high gear", much less overdrive. Comparing bikes to autos/trucks, if you understand gearing, then the best explanation is:
low range == regular transmission but with the OverDrive turned so the engine has more power to climb those steep hills
middle range == regular transmission, for day to day driving
high range == regular transmission but with UnderDrive turned on so the engine turns at 2,500 rpm instead of 3,800 rpm when you are cruising at 90 mph. Thus saving gas.


Comparison #2 - bikes to shoes
Again this is Greek to those who don't understand gearing, so better analogy is:
low range is like walking with a pair of big heavy hiking boots on. Your steps are smaller and closer together, but now you can walk up the steep climb at the top of the mountain.
middle range is like walking with regular shoes on. Steps are average but you can keep on walking forever and ever.
high range is like running with tennis/track shoes on. Your steps are very long and you cover large distances fast, but you need more energy to keep going and going and going.

The 9 gears in, say the middle range, would be like changing shoes while walking. The slowest would be an old pair of shoes that are worn out, the fastest would be a new pair of walking shoes that give spring to your step.


Ideal gearing system

Evidently there is not enough demand for my ideal gearing system. I think one gear system should provide:
1. a smooth transition for each change in gear from Low1 to Low9, from Mid1 to Mid9, from High1 to High9.
A smooth transition is 10% or less change between gears.
2. Rather than having a ton of bikes, a rider should be able to have one system that would handle the steepest uphill with a fully loaded bike, or a downhill with an unloaded bike.
3. No need for double shifting. Maybe only when switching from low range to middle range, or from middle range to high range.

Current Gear Market environment
The frustration is that the above ideal is almost available now. All that is preventing it is the derailer mechanisms that shift the chain along the 3 chainrings in front. The current shifters can only handle a 26 tooth spread between the number of the teeth in the smallest ring and the number of teeth in the largest ring.

So you have to choose one of these compromises:
A. Solution A - the turtle
This is the solution used by mountain bikes and touring bikes. Hills are the biggest problem and top speeds are not usually possible, so adjust the gears to make going up hills the best.

B. Solution B - the rabbit
This is the solution used by road/performance bikes. Slow speed is the biggest problem. Assumption is that rider will be an athlete and in great physical shape. Weight is kept low and gears are set up for ease of going fast on level ground.

C. Solution C - the treadmill
This is the solution used by most bike makers. You are offered a high range of gears but in the mix of gears there are usually about 6..8 gear traps, where it takes an additional 1/3 extra effort to shift from gear X to gear Y. [ percentage change usually is about 13..14%, a 33% increase from the 10.0% change, but can jump as high as 16% ]

Hope this helps.

alanbikehouston

Gearing on bikes has two different goals:

-helping the rider perform better

-helping the marketing boys sell bikes

These goals are rather different. From around 1950 to 1985, pro riders were racing through the mountains of Europe on bikes equipped with just ten speeds, of which eight provided good chain alignment. Eight speeds were more than enough, when the proper gears were selected for each day's route, and for the strength of the rider.

Likewise, tourists, going up those same mountains carrying sixty pounds of gear did well with just eight speeds - again matching the gears to the strength of the rider and to the needs of that particular ride.

The "marketing boys" figured out that a 12 speed bike would outsell a 10 speed bike. Today, they figure that a 20 speed "racing" bike will outsell an 18 speed "racing bike. And, that a 30 speed touring bike will outsell a 27 speed touring bike.

And, those 30 speeds are usually so poorly chosen that two or three of the ten rear cogs are likely to be as "new" looking in ten years as when they left the factory.

Here in the swamps of Houston, almost all of my riding is done with gears between 50 inches and 85 inches. I would be happy to have eight well-spaced gears, running at around 50, 55, 60, 65, 70, 75, 80, 85. In theory, that goal could be met with a single chain ring in front, and eight selected cogs in back.

But, modern marketing dictates that I must hunt among 27 or 30 possibilities for the eight speeds I actually use, with the remaining 22 speeds being dead weight, and useless clutter.

MY favorite eight speeds are not YOUR favorite eight speeds. But, most riders would be better off with a gearing system that allowed them to select and use their own "favorite" seven or eight useful speeds, rather than have a 110 inch gear that is never used, or a 30 inch gear that is never used.