Compact road crankset on a MTB frame...Bonus external bearing content

I have a MTB frame that I want to put a compact road crankset on.
Actually it is a Cannondale Bad boy (stupid name, I know) that is a
kinda sorta hybrid. I found that external bearing cranksets have a
limitation that I didn't know about: it doesn't appear that you can do
any tricks with the chainline. If you buy a road crankset, you will get
the chainline, usually 43.5mm, that is inherent to the design. A MTB
outboard bearing crankset has spacers, but they are only there to
compensate for a the differences between 68mm and 73mm shells. Due to
the design of the assembly, it doesn't look like there is a way to play
with the chainline at all. I would love to hear that I am wrong on that
subject.

So, like many other MTB frames, the 43.5mm chainline on this bike comes
too close to the chainstays for comfort. I haven't actually tried it
yet, but I really don't want to learn the hard way. Cannondale tech
said they didn't think it would work and my measurements haven't been
encouraging. The other option which looks like it may work is to use an
Octalink or Isis crankset and instead of using the 108-109mm BB for
doubles to get the 43.5mm chainline, use a 118mm BB designed for triples
to get the chainline back to about 48mm. Opinions?

Barnard Frederick wrote:
I have a MTB frame that I want to put a compact road crankset on.
Actually it is a Cannondale Bad boy (stupid name, I know) that is a
kinda sorta hybrid. I found that external bearing cranksets have a
limitation that I didn't know about: it doesn't appear that you can do
any tricks with the chainline. If you buy a road crankset, you will get
the chainline, usually 43.5mm, that is inherent to the design. A MTB
outboard bearing crankset has spacers, but they are only there to
compensate for a the differences between 68mm and 73mm shells. Due to
the design of the assembly, it doesn't look like there is a way to play
with the chainline at all. I would love to hear that I am wrong on that
subject.

Nope, you are right.


So, like many other MTB frames, the 43.5mm chainline on this bike comes
too close to the chainstays for comfort. I haven't actually tried it
yet, but I really don't want to learn the hard way. Cannondale tech
said they didn't think it would work and my measurements haven't been
encouraging. The other option which looks like it may work is to use an
Octalink or Isis crankset and instead of using the 108-109mm BB for
doubles to get the 43.5mm chainline, use a 118mm BB designed for triples
to get the chainline back to about 48mm. Opinions?

On cross frames also-using an outboard bearing, road crank...makes for
chainring interference with the chainstay. How about a square taper
crank/BB, the spindle which comes in lots of lengths, to make the
clearance and chainline as good as possible.

Qui si parla Campagnolo says...

On cross frames also-using an outboard bearing, road crank...makes for
chainring interference with the chainstay. How about a square taper
crank/BB, the spindle which comes in lots of lengths, to make the
clearance and chainline as good as possible.

I thought about square taper, but there aren't very many options for
compact. Campy makes a few very expensive ones, Centaur and Chorus
carbon, but that is more than I wanted to spend. Other ones I've seen I
had never heard much about them. Any recommendations?

On Thu, 18 May 2006 17:56:14 -0400, Barnard Frederick wrote:

Qui si parla Campagnolo says...

On cross frames also-using an outboard bearing, road crank...makes for
chainring interference with the chainstay. How about a square taper
crank/BB, the spindle which comes in lots of lengths, to make the
clearance and chainline as good as possible.

I thought about square taper, but there aren't very many options for
compact. Campy makes a few very expensive ones, Centaur and Chorus
carbon, but that is more than I wanted to spend. Other ones I've seen I
had never heard much about them. Any recommendations?

Sugino makes excellent, inexpensive cranks for square taper BBs. They're
widely available too.

There's nothing wrong with using an older crank either.

Matt O.

Barnard Frederick wrote:
Qui si parla Campagnolo says...

On cross frames also-using an outboard bearing, road crank...makes for
chainring interference with the chainstay. How about a square taper
crank/BB, the spindle which comes in lots of lengths, to make the
clearance and chainline as good as possible.

I thought about square taper, but there aren't very many options for
compact. Campy makes a few very expensive ones, Centaur and Chorus
carbon, but that is more than I wanted to spend. Other ones I've seen I
had never heard much about them. Any recommendations?

How about something like a Sugino XD? It comes as a 110/74 triple, but
you can fit the rings of your choice and just leave the inner
("granny") ring off. Nice stuff, available for under $50 with steel
rings (which you won't be using). Sugino also makes a "compact double"
version (i.e., no 74mmBCD inner ring mount for more money.

Barnard Frederick wrote:
Qui si parla Campagnolo says...

On cross frames also-using an outboard bearing, road crank...makes for
chainring interference with the chainstay. How about a square taper
crank/BB, the spindle which comes in lots of lengths, to make the
clearance and chainline as good as possible.

I thought about square taper, but there aren't very many options for
compact. Campy makes a few very expensive ones, Centaur and Chorus
carbon, but that is more than I wanted to spend. Other ones I've seen I
had never heard much about them. Any recommendations?

One of the reasons I muck with this NG-Campag makes aluminum compacts
starting with Mirage at about $115, Veloce at $130 and Centaur at
$170...110mm BCD, very nice and with a $30 BB, very economical.

Mirage is Veloce but bl;ack, Veloce is Centaur with less expensive
rings, Centaur is Chorus quality rings but aluminum.

Qui si parla Campagnolo says...

One of the reasons I muck with this NG-Campag makes aluminum compacts
starting with Mirage at about $115, Veloce at $130 and Centaur at
$170...110mm BCD, very nice and with a $30 BB, very economical.

Mirage is Veloce but bl;ack, Veloce is Centaur with less expensive
rings, Centaur is Chorus quality rings but aluminum.

Thank you, that is great information. I haven't recently seen anything
other than carbon compacts from Campy, but an aluminum Centaur crankset
would be very cool. I could special order one if need be. The next
question is: what is the spindle width for the typical 43.5mm
chainline? 'Cuz what I need to do is get one that is 8-10mm wider to
get an MTB style chainline. Am I correct in assuming that most square
taper BB's will work? If Campy has one in the length I need, that would
be great, but I could be persuaded to spend a few extra bux on a Phil
Wood.

Matt O'Toole says...

Sugino makes excellent, inexpensive cranks for square taper BBs. They're
widely available too.

There's nothing wrong with using an older crank either.

Matt O.

Thanks Matt & Oz. I'll check out Sugino. I believe I have owned
several in the days of yore.

Barnard Frederick wrote:
Qui si parla Campagnolo says...

One of the reasons I muck with this NG-Campag makes aluminum compacts
starting with Mirage at about $115, Veloce at $130 and Centaur at
$170...110mm BCD, very nice and with a $30 BB, very economical.

Mirage is Veloce but bl;ack, Veloce is Centaur with less expensive
rings, Centaur is Chorus quality rings but aluminum.

Thank you, that is great information. I haven't recently seen anything
other than carbon compacts from Campy, but an aluminum Centaur crankset
would be very cool. I could special order one if need be. The next
question is: what is the spindle width for the typical 43.5mm
chainline?

111mm ISO taper

'Cuz what I need to do is get one that is 8-10mm wider to
get an MTB style chainline. Am I correct in assuming that most square
taper BB's will work? If Campy has one in the length I need, that would
be great, but I could be persuaded to spend a few extra bux on a Phil
Wood.

To get 5mm more length of the BB-see Phil Wood. 'Most' BBs will work
but not ideal.