Double vs. Compact

Russell Seaton said:

Get a triple if you are in the mountains.

That alone doesn't say "triple." Not all mountain roads have grades implicating
a triple.

Quoted message said:

Get a 135 or 130 mm bcd
double for other parts of the country. Use a 110 mm bcd double if
its given to you free or you have it laying around or just want to
monkey with it to get in on the current fad.

Fad? I think the 110 came *before* the 130 or the even later 135, or at least
nearly so.

Quoted message said:

Going from a 39 to a 34 gets you one lower gear roughly.

It is close about 14%. That's more like a 1.5 gears, or even 2 for corn cob
fans.

Quoted message said:

About 4-5
gear inches.

Think percentage for difference, not inches. Percentage is completely
generalized.

Quoted message said:

You can get much
lower gears with a triple crankset.

Sure, but there may be no need for these lower gears, even in some mountains.

Quoted message said:

The 110 mm bcd double with the usual configuration of 50/34 chainrings
gives terrible gaps between gears.

I don't think so. The gaps (steps) are not typically dependent upon the front
rings. They are dependent upon the back cluster these days. Back in the days
of the half-step, this was true, but not anymore. For example, I sometimes use
a 53-33 rings with a 13-25 cassette. There are no big gaps. I ride in the 53
most of the day.

Quoted message said:

Unless you change to a cassette
such as 11-21. If you use a 13-26 cassette for instance, the 34 ring
produces too low of gears to use unless you are riding about 12 mph.

I don't think so. Anyway, your point is that lows are needed, so I don't get
why you're saying the lows enabled by the 34t are "too low." Lots of folks
climb at less than 12 mph. Really, if you can climb faster, you don't need a
triple. I usually just ride along in the big ring until I run out of gears,
then shift to the little chainring. I don't use full chain cross gears usually.

Also, you said the extra low is "one lower gear roughly." If that is true, then
it sure does weaken your argument in this part of your post. Is it "only one"
or not? On one side of your argument it is small and on the other side it seems
to be big.

Quoted message said:

And the large ring has too big of gaps between gears when riding
around 20 mph. In my everyday riding I use a 42 inner ring with a
13-26 cassette. The 42 with 13 to 17 straight block gives nice 5 gear
inch changes that are just right for riding between 15 to 29 mph. And
then the 19 and 21 cogs are OK changes in gear inches too.

Many people tolerate the 17-19 gap okay. Again, percentage is a far more
general format than gear inches. 5 inches at 100 is small. 5 inches at 30
inches is big. I'm more likely to pedal a 53x14 at 29 mph than a 42x13. For
one thing, chain wear and tension is less.

Quoted message said:

With the compact 110 mm bcd double crank, the outer ring of 50 or 48
gives too large 8 to 10 gear inch changes between cogs.

Again, this is not really true unless you say 17-19 is way too big of a step. I
think most folks think it is okay, especially recreational riders. I say it is
a tad on the high side for a racer, but certainly tolerable. That is a nearly
always existing gap in my gearing for both racing and not racing.

Quoted message said:

And the 34
inner ring just doesn't give high enough gears for the mph range I
ride in. Unless you go to something like a 11-21 cassette. In which
case the 50 outer ring is then useless for anything except going down
mountains.

I don't know about that. I used to use almost nothing but a 12-21 8sp with a
53-39. It seemed okay at the time, and I only got out of the 53 on climbs, and
I lived in Santa Cruz, with big mountains. Granted, I didn't climb Alba Road
with that setup.

I like a triple too. I actually have one on a bike. I cruise around on it. I
understand your favor for it, but I also use 110 doubles to, and they work
fine. I like the binary shifting and the lower q-factor. I think both work
well. If grades are less than 10% for most all of the riding, I would not even
consider a triple. I ride long and steeper stuff around Sonoma County with a
double. It works. And so does a triple.

Drew Eckhardt said:

Quoted message said:

Is a compact a good solution or would a triple be better.

It depends on how high you want, how low you want, how many cogs you have,
and what sort of gear spacing you like.

Play with the numbers.

Exactly. Also, don't neglect to think about the amount of overlap. A
typical 53/39 with a 12-23 9-speed has three ratios that are repeated:
The 53/19 is the same gear (72"😉 as the 39/14, the 53/21 is essentially
the same as the 39/15, and the 53/23 is the same as the 39/17. Now, I
would not use the 53/23 because it is an extreme crossover, but there is
no reason for this much overlap except that the 53/39 is essentially the
only choice for road cranks. With a compact crank you have a lower low
with no loss of the close shifts you would want in between.

Quoted message said:

YMMV. 53-39 really only makes sense when have a

6 speed corncob and

Quoted message said:

want tight gears with minimal overlap. With 9 or 10 cogs it's a bit
silly.

Exactly.

--

David L. Johnson

__o | What is objectionable, and what is dangerous about extremists is
_`\(,_ | not that they are extreme, but that they are intolerant. --Robert
(_)/ (_) | F. Kennedy

Russell Seaton said:

Going from a 39 to a 34 gets you one lower gear roughly. About 4-5
gear inches. A 39x26 is identical to a 34x23. Both right at 39 gear
inches. A 34x26 is 35 gear inches. One lower gear roughly. I've
ridden in the mountains and I wanted more than just one lower gear.
The triple provides many lower gears. A 30x26 is 31 gear inches.

But then the difference between the 50/34 double and the 50/40/30 triple
is, again, one gear. On the other hand, the triple tends to shift less
reliably than the double.

Quoted message said:

The 110 mm bcd double with the usual configuration of 50/34 chainrings
gives terrible gaps between gears.

No, it doesn't. With a 12/23 9-speed there is no jump more than 8
gear-inches.

Quoted message said:

Unless you change to a cassette such
as 11-21. If you use a 13-26 cassette for instance, the 34 ring
produces too low of gears to use unless you are riding about 12 mph.

Depending on the hill, 12mph might be pretty fast.

And

Quoted message said:

the large ring has too big of gaps between gears when riding around 20
mph.

Um, no.

In my everyday riding I use a 42 inner ring with a 13-26 cassette.

Quoted message said:

The 42 with 13 to 17 straight block gives nice 5 gear inch changes that
are just right for riding between 15 to 29 mph.

Well, the 42/39 gives a poor chainline, and will likely rub the chain on
the large ring. You can get the same gears with the large ring on a 50/34
with better chainlines and better durability.

Quoted message said:

With the compact 110 mm bcd double crank, the outer ring of 50 or 48
gives too large 8 to 10 gear inch changes between cogs.

The only range in which you get 8-inch changes is in the larger gears
(50/12 to 50/13 is an 8.4" change). The 53 gives the same gaps.

--

David L. Johnson

__o | Arguing with an engineer is like mud wrestling with a pig... You
_`\(,_ | soon find out the pig likes it!
(_)/ (_) |

Drew Eckhardt said:

53-39 really only makes sense when have a 6 speed corncob
and want tight gears with minimal overlap. With 9 or 10 cogs it's a
bit silly.

Using 39/53 (or 52) as a "dual range" setup, I find the overlap between ranges
is really useful. I'm not put off by duplicate gears between chainrings; to the
contrary, with a 39/53 crank the only useful gear* on a 9-sp 12-23 that might
be worth a double shift is the 81- inch 39/13. That lies in the gap between the
53/19 (75.3"😉 and 53/17 (84.2"😉. What a nice place for an 18t cog (79.5"😉...
yes, more cogs are *good*.

The only problem I have with 39/53 is that I rode a 42t inner for so long that
I don't get on the 52-3 soon enough sometimes (when group speed goes up or for
known or obvious terrain changes), and I have to double shift at inconvenient
times. Even with brifters, and otherwise modern chain moving mechanisms, I'm
not much on double shifts. To each his own. No, really. Some people like double
shifting, and thinking about their gears, etc. I don't.

* Well there is the 53/23, giving a 62-in. gear that splits the 39/17 - 39/16
gap (58.5 in.- 65.8-in.). My chain is long enough, I've grabbed the gear and
used it briefly, but it seems noisy and unhappy. And that would be a double
shift anyhow. --TP

Quoted message said:

(do not spam) said:

In article <[email hidden]>,

Donald Gillies said:

When your cadence dips below about 70 rpm, your muscles are using pre-
stored glycogen (fast-burning body sugars.) There is only a 10-minute
supply that is stored in the muscles of the body.

Quoted message said:

Do you have a reference for this? Doesn't intensity level factor into
that somewhere?

Effective Cycling, 6th edition, MIT press.

- Don Gillies
San Diego, CA

Quoted message said:

Dear Donald,

Quoted message said:

A smaller front chain ring may encourage a higher cadence,
but dropping from 39 to 34 teeth won't raise many all-day
climbing cadences from less than 70 to 90-110 rpm.

I agree completely. Probably the most widely sold campy gear setup is
a 39/53 and 12/25 setup. This gives a low gear of 39:25 which is 42
inches.

If you instead change to a 36/50 and 13/29, then your low gear would be
36:29 which is 33.5 inches.

If you cadence is 70 rpm at 42 inches, your cadence would be about ~88
rpm - which is close enough for government work.

- Don Gillies
San Diego, CA

Wasatch-<< Double tooth count- 53/39
Compact tooth count- 50/34

How big of a difference with the 3 or 4 tooth difference make? I live in
the rockies and tend to climb a lot of canyons. >><BR><BR>

Look at a gear chart. With an appropriate rear cluster, a 50/34 will have a
higher 'high' gear, and a lower 'low' gear. Like with a 11-23..Plus if ya have
a 12-25 or so, putting that on will give you a really low low.
I think they are a great idea. The only negative is if you have a 50-13, it may
be a little tall, but that's what I have for the flats here in the rockies w/o
any problem.

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

Donald Gillies said:

Quoted message said:

(do not spam) said:

In article <[email hidden]>,
Donald Gillies <[email hidden]> wrote:
>When your cadence dips below about 70 rpm, your muscles are using pre-
>stored glycogen (fast-burning body sugars.) There is only a 10-minute
>supply that is stored in the muscles of the body.

Quoted message said:

Do you have a reference for this? Doesn't intensity level factor into
that somewhere?

Effective Cycling, 6th edition, MIT press.

Muscles can store 400-500 gm of glycogen, or about 1200 kcal. That
should be enough for at least an hour of cycling. Ten minutes seems
too short a time to deplete muscle glycogen stores.
--
terry morse Palo Alto, CA http://bike.terrymorse.com/