different chain rings on Shimano road double and triple cranks

[Byron Sheppard]

Two questions:

1) Does anyone know why Shimano puts different rings on road triples than on road doubles? Doubles
seem to come with 53/39 combos, while triples come with 52/42/30. This seems odd to me; why not
just add a third ring and leave the other two the same? Is it a silly marketing thing, or is
there a good technical reason for this?

So of course, I'd like to change the rings on a recently acquired Ultegra triple to 53/39/30 (or
perhaps even a 28 small ring). My LBS tells me that the rings are actually different and that such a
change would be "difficult." So...

2) Is this true, or can I easily change my triple rings to double rings?

And question 3 of my two questions: if I have the long cage Ultegra derailleur, can I use an old
(unused) 28 Shimano MTB ring I have kicking around, or is the small ring road specific?

thanks, byron

 

[daveornee]

Originally posted by Byron Sheppard
Two questions:

1) Does anyone know why Shimano puts different rings on road triples than on road doubles? Doubles
seem to come with 53/39 combos, while triples come with 52/42/30. This seems odd to me; why not
just add a third ring and leave the other two the same? Is it a silly marketing thing, or is
there a good technical reason for this?

Take a note pad and write down your cassette cog teeth numbers.
Visit the gear calculator at Sheld Brown's web site URL:
http://sheldonbrown.com/gears/
I think that Shimano is trying to give you more discrete and useable gearing combinations.

So of course, I'd like to change the rings on a recently acquired Ultegra triple to 53/39/30 (or
perhaps even a 28 small ring). My LBS tells me that the rings are actually different and that such a
change would be "difficult." So...

2) Is this true, or can I easily change my triple rings to double rings?

You can easily change the larger two if you still want to after seeing what gear combinations you will gain and loose.

And question 3 of my two questions: if I have the long cage Ultegra derailleur, can I use an old
(unused) 28 Shimano MTB ring I have kicking around, or is the small ring road specific?

Each chain ring has a specific BCD mounting circle. If the mounting BCD mounting circle is the same, you can mount it.
However, your Front Derailer may not have the range to give you good shifting + the ramping and pinning on the chain rings won't likely line up as well as the Shimano original set.
If the BCD is the same and you still want to go through with this, you will likely have to pull the crank from the Bottom Bracket to get the old ring off and the new ring on.

thanks, byron

 

[Qui Si Parla Ca]

byron-<< 1) Does anyone know why Shimano puts different rings on road triples than on road doubles?
Doubles seem to come with 53/39 combos, while triples come with 52/42/30. This seems odd to me; why
not just add a third ring and leave the other two the same? >><BR><BR>

With a well set up triple, where you can use the middle with the entire cogset range, a 42 is more
useable than a 39, IMO, YMMV.

byron<< So of course, I'd like to change the rings on a recently acquired Ultegra triple to 53/39/30
(or perhaps even a 28 small ring). My LBS tells me that the rings are actually different and that
such a change would be "difficult." >><BR><BR>

If you use a 39t with pickup pins and ramps it will work fine, use a TA. If you just put a road 39t
on there, it may not shift well as shimano triples really rely on the pins and ramps.

bryon- << if I have the long cage Ultegra derailleur, can I use an old (unused) 28 Shimano MTB ring
I have kicking around, or is the small ring road specific? >><BR><BR>

if it is 74mm BCD, it'll work.

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

 

[Mike Jacoubowsk]

> 1) Does anyone know why Shimano puts different rings on road triples than
on
> road doubles? Doubles seem to come with 53/39 combos, while triples come with 52/42/30. This seems
> odd to me; why not just add a third ring and
leave
> the other two the same? Is it a silly marketing thing, or is there a good technical reason
> for this?

The most difficult front shift of all is moving from the middle chainring (on a triple) down to the
smallest. The problem is mostly due to the height of the front derailleur over the chainring; the
further it is from the "action", the less-efficient it is at moving the chain. Thus is it *much*
easier for a derailleur to shift off of a 52/42/XX option than from a
53/39/XX. The 53/39 requires that the front derailleur to high enough to clear an additional 4
teeth (53-39=14t differences, vs 52-42=10t).

That's the reason why, despite all the fancy stuff they've done to the inside plate of the DuraAce
triple front derailleur, the Ultegra triple absolutely, positively makes the shift from middle to
smallest better.

Please note that you can change the smallest chainring with no ill effects, since the difficult
shifts are the ones going to a smaller chainring (going "down") and the inside chainring is already
as "down" as you can get.

> So of course, I'd like to change the rings on a recently acquired Ultegra triple to 53/39/30 (or
> perhaps even a 28 small ring). My LBS tells me that the rings are actually different and that such
> a change would be "difficult." So...
>
> 2) Is this true, or can I easily change my triple rings to double rings?

If you simply switch your 42t triple middle to a 39 that's designed for a double, you're going to
have a pretty nasty-shifting setup, for two reasons. First, for the reason I gave above (that the
bigger difference between middle & large chainring puts the derailleur in a less-optimal position),
and second, because you'd be using a "middle" chainring with no shifting pins/ramps on the inside
surface, which are designed to make it easier to shift from smallest to middle.

As Peter noted in this thread, TA does make a 39t 130mm bolt pattern chainring that's designed to be
used as the middle chainring in a triple environment.

> And question 3 of my two questions: if I have the long cage Ultegra derailleur, can I use an old
> (unused) 28 Shimano MTB ring I have kicking around, or is the small ring road specific?

If it's a 74mm bolt pattern, no issue.

Please note, regarding the change from 42 to 39t middle, that we have customers who do this all the
time, insisting that it should work just fine and we're just trying to spoil their fun. I'd say at
least 75% of those people come back to us, telling us that we were right, it doesn't shift as well
as they'd like (and can we please fix it somehow?). Another 15% say it doesn't work quite as well,
but they can deal with it. And 10% think there's no difference.

It's truly amazing, though, how many people change their middle chainring and insist that any
problem with shifting is a result of something else (bad chain is a popular one, frame alignment
another). But switch back to the stock chainring and those "defects" go away. Hmmm...

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

 

[meb]

Originally posted by Mike Jacoubowsk
> 1) Does anyone know why Shimano puts different rings on road triples than
on
> road doubles? Doubles seem to come with 53/39 combos, while triples come with 52/42/30. This seems
> odd to me; why not just add a third ring and
leave
> the other two the same? Is it a silly marketing thing, or is there a good technical reason
> for this?

The most difficult front shift of all is moving from the middle chainring (on a triple) down to the
smallest. The problem is mostly due to the height of the front derailleur over the chainring; the
further it is from the "action", the less-efficient it is at moving the chain. Thus is it *much*
easier for a derailleur to shift off of a 52/42/XX option than from a
53/39/XX. The 53/39 requires that the front derailleur to high enough to clear an additional 4
teeth (53-39=14t differences, vs 52-42=10t).

That's the reason why, despite all the fancy stuff they've done to the inside plate of the DuraAce
triple front derailleur, the Ultegra triple absolutely, positively makes the shift from middle to
smallest better.

Please note that you can change the smallest chainring with no ill effects, since the difficult
shifts are the ones going to a smaller chainring (going "down") and the inside chainring is already
as "down" as you can get.



--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

That explains why standard road triples went to a 10T difference.
Why 52/42 instead of say 53/43 or 54/44?

 

[Arthur Harris]

"meb" wrote:
> That explains why standard road triples went to a 10T difference. Why
> 52/42 instead of say 53/43 or 54/44?

Or 50/40/30 which has a nice round numerology. But we shouldn't question these things. Shimano knows
what's best for us, right?

Art Harris

 

[Mike Jacoubowsk]

> Or 50/40/30 which has a nice round numerology. But we shouldn't question these things. Shimano
> knows what's best for us, right?

Precisely. Just like Campy knows that, if we need a 29t rear cog, then we shouldn't be riding
anything smaller than a 13t at the small end.

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

 

[Rick Onanian]

On Fri, 26 Dec 2003 17:24:12 GMT, "Mike Jacoubowsky"
<[email protected]> wrote:
>> Or 50/40/30 which has a nice round numerology. But we shouldn't question these things. Shimano
>> knows what's best for us, right?
>
>Precisely. Just like Campy knows that, if we need a 29t rear cog, then we shouldn't be riding
>anything smaller than a 13t at the small end.

Well, don't forget, we're not allowed to have a wide range of available gears -- who would need
that, anyway? I mean, maybe if there was such a thing as a "hill", but have you ever heard of one on
THIS planet?

Really, the triple's largest is a 52 while the double's is a 53...it makes no sense whatsoever. The
42 triple middle vs. the 39 double small I can understand...

>--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com
--
Rick Onanian

 

[Tom Sherman]

Rick Onanian wrote:
>
> Well, don't forget, we're not allowed to have a wide range of available gears -- who would need
> that, anyway? I mean, maybe if there was such a thing as a "hill", but have you ever heard of one
> on THIS planet?

If you can not climb any paved road with a 39/27, you are apparently not enough of a real cyclist to
deserve consideration. [1]

It does not make sense that most recreational road cyclists are riding with the same gearing as the
UCI professionals.

[1] My low gear is 47% of the gear inches provided by a 39/27 with a 23-622 drivewheel.

Tom Sherman - Close to 41½ N, 90½ W

 

[Dianne_1234]

On Thu, 25 Dec 2003 18:37:50 GMT, "Mike Jacoubowsky"
<[email protected]> wrote:

>> 1) Does anyone know why Shimano puts different rings on road triples than
>on
>> road doubles? Doubles seem to come with 53/39 combos, while triples come with 52/42/30. This
>> seems odd to me; why not just add a third ring and
>leave
>> the other two the same? Is it a silly marketing thing, or is there a good technical reason
>> for this?
>
>The most difficult front shift of all is moving from the middle chainring (on a triple) down to the
>smallest.

And the second-most difficult shift is from the smallest back up to the middle.

Think of the chain angle accross the rings during this shift. The front derailleur pushes it into an
angle from the small chainring towards the larger rings. The smaller the middle chainring, the more
likely it is the chain will touch the big ring first and miss the middle entirely.

 

[Carl Fogel]

"Mike Jacoubowsky" <[email protected]> wrote in message news:<[email protected]>...
> > Or 50/40/30 which has a nice round numerology. But we shouldn't question these things. Shimano
> > knows what's best for us, right?
>
> Precisely. Just like Campy knows that, if we need a 29t rear cog, then we shouldn't be riding
> anything smaller than a 13t at the small end.
>
> --Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

Dear Arthur and Mike,

Come, come, fellows, let's not squabble about a few teeth during the holidays!

As a friend often remarked at the Honda shop, it's easy enough to grind off a gear tooth or two--
surely that will fix things, won't it?

Carl Fogel

 

[Werehatrack]

On Fri, 26 Dec 2003 17:02:57 -0600, Tom Sherman
<[email protected]> may have said:

>If you can not climb any paved road with a 39/27, you are apparently not enough of a real cyclist
>to deserve consideration. [1]

Or at least some of the Powers That Be seem to believe so. I think they all must live in someplace
like Miami, where the only way to find a 300-foot elevation climb would be by riding up the fire
escape stairwell of an office building that had one with a handicapped ramp. (As if you'll find
one!) (100 feet can be had in a few parking garages, if you don't get arrested for trespassing.)

(Of course, I shouldn't say too much; I'm in Houston, and just 75 feet above sea level...)

>It does not make sense that most recreational road cyclists are riding with the same gearing as the
>UCI professionals.

But...but...if they had lesser gears than their idols, how would they ever be able to think they
could achieve the same feats?

(The dodge, of course, is to buy a touring bike; selected carefully, it has all the looks of a road
bike, but with a 75% greater gear range...or more.)

>[1] My low gear is 47% of the gear inches provided by a 39/27 with a 23-622 drivewheel.

Would that be a 24/34 bailout combo on an mtb?

I ended up with that combo on a bike last week for a couple of days; I was swapping wheels around to
optimize a couple of things on other units, and a 14-34 cassette ended up on the bike with the
24/34/44 triple. I think I could probably have pulled a loaded tandem up a grade with it. Not very
*fast*, but the effect of the mechanical advantage was immediately evident.

--
My email address is antispammed; pull WEEDS if replying via e-mail.
Yes, I have a killfile. If I don't respond to something,
it's also possible that I'm busy.
Words processed in a facility that contains nuts.

 

[Tom Sherman]

Werehatrack wrote:
>
> >[1] My low gear is 47% of the gear inches provided by a 39/27 with a 23-622 drivewheel.
>
> Would that be a 24/34 bailout combo on an mtb?
>
> I ended up with that combo on a bike last week for a couple of days; I was swapping wheels around
> to optimize a couple of things on other units, and a 14-34 cassette ended up on the bike with the
> 24/34/44 triple. I think I could probably have pulled a loaded tandem up a grade with it. Not very
> *fast*, but the effect of the mechanical advantage was immediately evident.

The low on my MTB is 22/32, at which point I am either having the front wheel come up in the air
shortly before I fall over; or my rear wheel is spinning shortly before I lose all forward speed and
fall over. But then I am lousy at riding off-road - but someone has to keep the manufacturers of first-
aid supplies in business.

My low road gear is a 22T granny (Deore LX crank), a 13/20 jackshaft step-up (QBP and Dura Ace track
cogs) [1], and a 34T cog (XT Megarange cassette) on a wheel with a 47-406 tire. Why be simple when
you can have it complicated (or as Mr. Fogel would put it, ride a contraption)? This low gear proves
very useful on the back roads in the "driftless" area of SW Wisconsin, or on the bluffs of the
Mississippi River where many of the grades are considerably steeper than 10%.

[1] <http://www.ihpva.org/incoming/2002/sunset/Sunset005.jpg>

Tom Sherman - Close to 41½ N, 90½ W

 

[Mike Jacoubowsk]

> >The most difficult front shift of all is moving from the middle chainring (on a triple) down to
> >the smallest.
>
> And the second-most difficult shift is from the smallest back up to the middle.
>
> Think of the chain angle accross the rings during this shift. The front derailleur pushes it into
> an angle from the small chainring towards the larger rings. The smaller the middle chainring, the
> more likely it is the chain will touch the big ring first and miss the middle entirely.

True enough, but at least, when it misses the middle on the way up (and goes to the largest), you
can easily shift it from there back down to the middle. If you can't get it to shift from the middle
to small, you're simply out-of-luck (and most likely at a time when you really need it!).

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

"dianne_1234" <[email protected]> wrote in message
news:[email protected]...
> On Thu, 25 Dec 2003 18:37:50 GMT, "Mike Jacoubowsky" <[email protected]> wrote:
>
> >> 1) Does anyone know why Shimano puts different rings on road triples
than
> >on
> >> road doubles? Doubles seem to come with 53/39 combos, while triples
come
> >> with 52/42/30. This seems odd to me; why not just add a third ring and
> >leave
> >> the other two the same? Is it a silly marketing thing, or is there a
good
> >> technical reason for this?
> >
> >The most difficult front shift of all is moving from the middle chainring (on a triple) down to
> >the smallest.
>
> And the second-most difficult shift is from the smallest back up to the middle.
>
> Think of the chain angle accross the rings during this shift. The front derailleur pushes it into
> an angle from the small chainring towards the larger rings. The smaller the middle chainring, the
> more likely it is the chain will touch the big ring first and miss the middle entirely.

 

[Mike Jacoubowsk]

> Dear Arthur and Mike,
>
> Come, come, fellows, let's not squabble about a few teeth during the holidays!
>
> As a friend often remarked at the Honda shop, it's easy enough to grind off a gear tooth or two--
> surely that will fix things, won't it?
>
> Carl Fogel

Carl: I don't know about you, but in my case, you're looking at a 47-year-old that enjoys riding impossibly-
steep roads but... the 27t large cog on a Shimano double just isn't going to cut it too much longer.
A triple is in my future but... if Shimano had a 29... I could put it off for at least another
couple years, maybe more!

I hate to reduce this thread to discussions of practicality, but if we're going to have 10 cogs back
there, why keep the range as narrow as the 9-speed systems? It's d-u-m-b dumb! We're only slightly
better than the 5-cog days, when my racing bike had a 13-24. When we went to 6 cogs I was able to go
wild and have a 26 for the steep stuff, which remained until the 9-speed systems gave me a 27. And
now? Somehow I managed to survive with fewer than 9 cogs in the past... how come they want to keep
cramming more cogs into the same range, instead of extending it out a bit?

Heck, this would even help Division-1 racers on climbs like the Angrilu, where Heras used a triple
to good effect. Had a 29t option been available, that might well have been used instead, saving a
bit of weight.

Sigh. Perhaps one more trip up Sonora Pass on a double, maybe...

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

"Carl Fogel" <[email protected]> wrote in message
news:[email protected]...
> "Mike Jacoubowsky" <[email protected]> wrote in message
news:<[email protected]>...
> > > Or 50/40/30 which has a nice round numerology. But we shouldn't
question
> > > these things. Shimano knows what's best for us, right?
> >
> > Precisely. Just like Campy knows that, if we need a 29t rear cog, then
we
> > shouldn't be riding anything smaller than a 13t at the small end.
> >
> > --Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com
>
> Dear Arthur and Mike,
>
> Come, come, fellows, let's not squabble about a few teeth during the holidays!
>
> As a friend often remarked at the Honda shop, it's easy enough to grind off a gear tooth or two--
> surely that will fix things, won't it?
>
> Carl Fogel

 

[Tom Sherman]

Mike Jacoubowsky wrote:
> ... Carl: I don't know about you, but in my case, you're looking at a 47-year-old that enjoys
> riding impossibly-steep roads but... the 27t large cog on a Shimano double just isn't going to cut
> it too much longer. A triple is in my future but... if Shimano had a 29... I could put it off for
> at least another couple years, maybe more!...

I know this suggestion will horrify some people (What a Fred!), but why not put a Shimano MTB
derailleur and cassette on the back and have a 32T cog for the hills? Or is this not STI compatible?
(It works fine with Shimano bar-end shifters.)

Tom Sherman - Close to 41½ N, 90½ W

 

[Arthur Harris]

"Tom Sherman" wrote:
> I know this suggestion will horrify some people (What a Fred!), but why not put a Shimano MTB
> derailleur and cassette on the back and have a 32T cog for the hills? Or is this not STI
> compatible? (It works fine with Shimano bar-end shifters.)

I just upgraded my wife's road bike with an 11-32 (9-sp) cassette and a Deore LX rear der. Works
fine with STI.

Art Harris

 

[Carl Fogel]

"Mike Jacoubowsky" <[email protected]> wrote in message news:<[email protected]>...

[snip Carl]

> Carl: I don't know about you, but in my case, you're looking at a 47-year-old that enjoys riding
> impossibly-steep roads but... the 27t large cog on a Shimano double just isn't going to cut it too
> much longer. A triple is in my future but... if Shimano had a 29... I could put it off for at
> least another couple years, maybe more!
>
> I hate to reduce this thread to discussions of practicality, but if we're going to have 10 cogs
> back there, why keep the range as narrow as the 9-speed systems? It's d-u-m-b dumb! We're only
> slightly better than the 5-cog days, when my racing bike had a 13-24. When we went to 6 cogs I was
> able to go wild and have a 26 for the steep stuff, which remained until the 9-speed systems gave
> me a 27. And now? Somehow I managed to survive with fewer than 9 cogs in the past... how come they
> want to keep cramming more cogs into the same range, instead of extending it out a bit?
>
> Heck, this would even help Division-1 racers on climbs like the Angrilu, where Heras used a triple
> to good effect. Had a 29t option been available, that might well have been used instead, saving a
> bit of weight.
>
> Sigh. Perhaps one more trip up Sonora Pass on a double, maybe...
>
> --Mike-- Chain Reaction Bicycles

[snip]

Dear Mike,

While we both agree that everyone of any importance is currently 47, I'm baffled by your outlandish
claims of bicycles that sport more than 7 rear cogs. I just counted mine and confirmed that there
are only seven. More would be ostentatious.

As for the front, where would you put a third chain ring? I looked again, just to be sure, and
am positive that there is no place to mount such a thing. In any case, Shakespeare warned us
against them:

"Triple-turn'd *****!"

-- Antony & Cleopatra, IV, xiii

Have you considered the more practical solution of mounting smaller wheels to gear down for hills? A
650 rear wheel might help. A 650 would also be needed in the front to prevent the bike from sloping
backward and going uphill even on level ground.

I'm always glad to help bicycle dealers and engineers solve these knotty technical problems.

See you at 48.

Carl Fogel

 

[David L. Johnso]

On Sat, 27 Dec 2003 07:43:06 +0000, Tom Sherman wrote:

> I know this suggestion will horrify some people (What a Fred!), but why not put a Shimano MTB
> derailleur and cassette on the back and have a 32T cog for the hills? Or is this not STI
> compatible? (It works fine with Shimano bar-end shifters.)

It will work fine. The only problem is using a mountain-bike front derailleur with STI.

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems. _`\(,_ | -- Paul Erdos
(_)/ (_) |

 

[Mike Jacoubowsk]

> I know this suggestion will horrify some people (What a Fred!), but why not put a Shimano MTB
> derailleur and cassette on the back and have a 32T cog for the hills? Or is this not STI
> compatible? (It works fine with Shimano bar-end shifters.)

Been there, done that, a couple years ago on Sonora Pass. May do it again, but I would really like
just one gearing setup that I can use for everything, and the 12-32 setups space the gears a bit
further apart than I like. Maybe when mountain bikes get 10-speed systems?

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com