Road (105) cranks on MTB'ish frame?

Carl said:

Ive got a ~97 Cannondale m300se thats been my get'round
bike for many faithful years, now the components are very
much near dead. Commuter bike, road use only.

Most importantly are the cranks/BB, which give
considerable play and have now cheesed the chainrings to
the point of me not ever shifting out of high.

I can get my hands on a set of good cond shimano 105
double road cranks, but am curious if anyones ever tried
to get these to fit on a MTB? i know ill need a new BB
(ill need one anyways) and im aware that the gearing is
higher (kinda looking forward to it). Additionally, im
pretty sure that the front deraileur wont work, but then
again i've gotten pretty used to never shifting up front,
so ill probably just ditch it 'til i'm done with the rear
drive upgrade (must do next).

FWIW, im replacing a set of Shimano altus cranks, with acera-
x derailleurs. Dont Laugh (they _have_ lasted this long!)
Oh, and please dont tell me to get a new bike as im rather
fond of this one.

There is no reason you can't do this, but there are a couple
issues you will probably have to deal with:

Chainline: you will need a shorter BB spindle to keep the
chainrings centered on the rear sprockets. The combination
of the shorter spindle and the larger chainrings can, on
some bikes, result in interference between the chainrings
and the chainstay. You may need to have a less than ideal
chainline to avoid this.

Front derailer: The larger chainrings mean that the usual
MTB derailer will be too sharply curved in comparison to the
rings, resulting in crummy shifting. A road derailer
requires a different cable pull than your shifters give.
There are one or two Shimano models that have the cable pull
and the radius of curvature that you want. The model name
escapes me; Sheldon Brown or Andy Muzi can help you here.

Hope that helps.

--
Ted Bennett Portland OR

A shy person said:

Ive got a ~97 Cannondale m300se thats been my get'round
bike for many faithful years, now the components are very
much near dead. Commuter bike, road use only.

Most importantly are the cranks/BB, which give
considerable play and have now cheesed the chainrings to
the point of me not ever shifting out of high.

I can get my hands on a set of good cond shimano 105
double road cranks, but am curious if anyones ever tried
to get these to fit on a MTB? i know ill need a new BB
(ill need one anyways) and im aware that the gearing is
higher (kinda looking forward to it). Additionally, im
pretty sure that the front deraileur wont work, but then
again i've gotten pretty used to never shifting up front,
so ill probably just ditch it 'til i'm done with the rear
drive upgrade (must do next).

This may be a bit of a chainline problem due to the wide,
fat chainstays on your 'Dale. It almost certainly won't work
with the standard bottom bracket for whichever version of
105 you're using. The chainrings are liable to hit the
chainstays, if not the ends of the cranks as well.

Using a longer bottom bracket can probably get the cranks
far enough out to clear the frame, but this may result in
unacceptable chainline. Basically, you're going to have to
do a bit of experimentation.

If it's an older tapered-square 105 crank, try it on the
existing BB first to get an idea of clearance. This will
give you a starting point to calculate from.

See also sheldonbrown.comchainlineOpen ↗

Sheldon "Strictly Speaking, Possibly" Brown +---------------------------------
+
| Is ambivalence a bad thing? | Well, yes and no. | --
| Garrison Keillor |
+---------------------------------+ Harris Cyclery, West
Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041
harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped
Worldwide captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

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Looks like Sheldon really showed you up in the post below
there Ted, is = this too a matter of semantics? "Ted
Bennett" <[email hidden]> wrote in message = news:tedbennett-
[email hidden]... Carl

Quoted message said:

Ive got a ~97 Cannondale m300se thats been my get'round
bike for =

many

Quoted message said:

faithful years, now the components are very much near
dead. Commuter =

bike,

Quoted message said:

road use only.
=20
Most importantly are the cranks/BB, which give
considerable play and =

have

Quoted message said:

now cheesed the chainrings to the point of me not ever
shifting out =

of

Quoted message said:

high.
=20
I can get my hands on a set of good cond shimano 105
double road =

cranks, but

Quoted message said:

am curious if anyones ever tried to get these to fit on
a MTB? i =

know ill

Quoted message said:

need a new BB (ill need one anyways) and im aware that
the gearing =

is

Quoted message said:

higher (kinda looking forward to it). Additionally, im
pretty sure =

that the

Quoted message said:

front deraileur wont work, but then again i've gotten
pretty used to =

never

Quoted message said:

shifting up front, so ill probably just ditch it 'til
i'm done with =

the

Quoted message said:

rear drive upgrade (must do next).
=20
FWIW, im replacing a set of Shimano altus cranks, with
acera-x =

derailleurs.

Quoted message said:

Dont Laugh (they _have_ lasted this long!) Oh, and
please dont tell me to get a new bike as im rather
fond of =

this one.

There is no reason you can't do this, but there are a
couple issues = you=20 will probably have to deal with:

Chainline: you will need a shorter BB spindle to keep the
chainrings=20 centered on the rear sprockets. The
combination of the shorter = spindle=20 and the larger
chainrings can, on some bikes, result in interference=20
between the chainrings and the chainstay. You may need to
have a less =

than ideal chainline to avoid this.

Front derailer: The larger chainrings mean that the usual
MTB = derailer=20 will be too sharply curved in comparison
to the rings, resulting in=20 crummy shifting. A road
derailer requires a different cable pull than =

your shifters give. There are one or two Shimano models
that have the =

cable pull and the radius of curvature that you want. The
model name=20 escapes me; Sheldon Brown or Andy Muzi can
help you here.

Hope that helps.

--=20 Ted Bennett Portland OR ------
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0
Transitional//EN"> <HTML><HEAD> <META http-equiv=3DContent-
Type content=3D"text/html; = charset=3Diso-8859-1"> <META
content=3D"MSHTML 6.00.2800.1400" name=3DGENERATOR>
<STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Looks like Sheldon really
showed you up = in the post=20 below there Ted, is this
too a matter of semantics?</FONT></DIV> <BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-
LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-
RIGHT: 0px">
<DV>"Ted Bennett" <<A=20
=
href=3D""][email hidden]">tedbennett@earthli-
nk.net</A>>= wrote=20 in message <A=20
=
href=3D"news:tedbennett-
[email hidden]">n= ews:tedbennett-
[email hidden]</A>...</DIV=

Quoted message said:

Carl=20

<<A href=3D""][email hidden]">[email protected]
com</A>>=20 wrote:<BR><BR>> Ive got a ~97 Cannondale
m300se thats been my = get'round=20 bike for many<BR>>
faithful years, now the components are very much = near=20
dead. Commuter bike,<BR>> road use only.<BR>>
<BR>> Most = importantly=20 are the cranks/BB, which
give considerable play and have<BR>> now = cheesed=20
the chainrings to the point of me not ever shifting out
of<BR>>=20 high.<BR>> <BR>> I can get my hands on
a set of good cond = shimano 105=20 double road cranks,
but<BR>> am curious if anyones ever tried to = get
these=20 to fit on a MTB? i know ill<BR>> need a new BB
(ill need one = anyways) and=20 im aware that the gearing
is<BR>> higher (kinda looking forward to =
it).=20 Additionally, im pretty sure that the<BR>> front
deraileur wont = work, but=20 then again i've gotten
pretty used to never<BR>> shifting up front, = so
ill=20 probably just ditch it 'til i'm done with
the<BR>> rear drive = upgrade (must=20 do
next).<BR>> <BR>> FWIW, im replacing a set of
Shimano altus = cranks,=20 with acera-x
derailleurs.<BR>> Dont Laugh (they _have_ lasted
this=20 long!)<BR>> Oh, and please dont tell me to get
a new bike as im = rather fond=20 of this
one.<BR><BR>There is no reason you can't do this, but
there = are a=20 couple issues you <BR>will probably have
to deal = with:<BR><BR>Chainline: =20 you will need
a shorter BB spindle to keep the chainrings <BR>centered
= on the=20 rear sprockets. The combination of the
shorter spindle <BR>and = the=20 larger chainrings can,
on some bikes, result in interference = <BR>between
the=20 chainrings and the chainstay. You may need
to have a less = <BR>than ideal=20 chainline to avoid
this.<BR><BR>Front derailer: The larger =
chainrings=20 mean that the usual MTB derailer <BR>will
be too sharply curved in = comparison=20 to the rings,
resulting in <BR>crummy shifting. A road derailer =
requires=20 a different cable pull than <BR>your shifters
give. There are = one or two=20 Shimano models that
have the <BR>cable pull and the radius of = curvature
that=20 you want. The model name <BR>escapes me;
Sheldon Brown or Andy = Muzi can=20 help you
here.<BR><BR>Hope that helps.<BR><BR>-- <BR>Ted =
Bennett<BR>Portland=20 OR</BLOCKQUOTE></BODY></HTML>

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