XTR cranks on road bike--help!



N

Neaudl

Guest
I had ridden an Ultegra triple with a 12-34 9 speed cassette
extensively without trouble on both Trek 5200 and Calfee
Luna road bikes, and recently rode a mountain century with
an 11-34 cassette without trouble. But I wanted a still
lower gear, and put XTR 952 cranks on the road bike (Calfee
Luna). These have 26-36-48 chainrings. I did not change the
Ultegra triple front derailleur (It was moved downward on
the seattube.) but the chain was shortened. Chain and
cassette had only 100 miles on them before cranks were
changed, so everything is brand new. However, I find I can't
use all the cogs on the cassette with the middle chainring.
The three largest cogs, 26 and larger, with the 36 tooth
middle chainring result in pulling the chain off the middle
chainring onto the granny whenever a real load is applied
(i. e. pushing hard up a hill or standing). As far as I can
tell, both cranks have a 47.5 mm front chainline. (I have
the shorter of the two available 952 bottom brackets.) Of
course, the spacing in the rear is road spacing (130mm)
rather than mountain bike spacing (135). On a mountain bike,
the cassette would be farther out by
2.5 mm, but it looks like it would need to move more than
that not to have a problem, and obviously there's no
problem with an 11-34 cassette on all modern mountain
bikes. Is this problem the result of both the small size
of the 36 and the lack of mountain bike rear wheel
spacing? Do others using smaller than 42 tooth middle
chainrings on road bikes have similar problems with larger
cassettes? If I went back to the Ultegra and changed to
26-38-48 chainrings, would I be likely to have the same
problem? Any help would be much appreciated, especially
before the Markleeville Death Ride in July.

L. D. Lide
 
Road bikes also have shorter chainstays, resulting in a
greater angle in your problem gear. If you are using the
112mm BB, would the 2mm inboard shift of the 109 cause the
26 to rub? If not,use it. Tom

--
Bruni Bicycles
"Where art meets science"
brunibicycles.com
410.426.3420
NeauDL <[email protected]> wrote in message
news:[email protected]...
> I had ridden an Ultegra triple with a 12-34 9 speed cassette extensively
> without trouble on both Trek 5200 and Calfee Luna road bikes, and recently
rode
> a mountain century with an 11-34 cassette without trouble. But I wanted a
> still lower gear, and put XTR 952 cranks on the road bike (Calfee Luna).
These
> have 26-36-48 chainrings. I did not change the Ultegra triple front
derailleur
> (It was moved downward on the seattube.) but the chain was shortened.
Chain
> and cassette had only 100 miles on them before cranks were changed, so
> everything is brand new. However, I find I can't use all the cogs on the
> cassette with the middle chainring. The three largest cogs, 26 and
larger,
> with the 36 tooth middle chainring result in pulling the chain off the
middle
> chainring onto the granny whenever a real load is applied (i. e. pushing
hard
> up a hill or standing). As far as I can tell, both cranks have a 47.5 mm
front
> chainline. (I have the shorter of the two available 952 bottom brackets.)
Of
> course, the spacing in the rear is road spacing (130mm) rather than
mountain
> bike spacing (135). On a mountain bike, the cassette would be farther
out by
> 2.5 mm, but it looks like it would need to move more than that not to have
a
> problem, and obviously there's no problem with an 11-34 cassette on all
modern
> mountain bikes. Is this problem the result of both the small size of
the 36
> and the lack of mountain bike rear wheel spacing? Do others using smaller
than
> 42 tooth middle chainrings on road bikes have similar problems with larger
> cassettes? If I went back to the Ultegra and changed to 26-38-48
chainrings,
> would I be likely to have the same problem? Any help would be much
> appreciated, especially before the Markleeville Death Ride in July.
>
> L. D. Lide
 
When I had a roadbike, I ran a 1st generation XTR crank on
it with 48,36,24 rings. I worked very well. The smallest BB
length listed for the XTR crank was 107mm. I had to use a DA
103mm bb to get the correct chainline. I do not know if you
have the option of a shorter BB with the newer XTR cranks.

I also was using a 12x27 cassete, so I do not know if your
larger cassette is the issue. your're not using an Ultegra
rear deraileur with the 11x34 cassette are you??? Do you
really need an 11x34 cassette with a 26 small ring on a road
bike? I find the smaller gaps of a 12x27 or 12x25 to aid me
in climbing long hills on the road.

Another thought: What chain are you using? The SRAM chains
work better for me on mix-and-match drivetrains.

Even another thought: Are the shifting ramps on the 36T XTR
ring derailling the chain? I have experience this a little
when using a 9spd chain on an 8 spd XTR ring.

For road ridding, I have my MTB set up with 1.25" slicks and
a 12x25 cassette. I am using a 46,34,19 chainring combo on
my XTR crank. I can climb just about anything, even pulling
my son on his tag-along-tandem that attaches to my seatpost.

A nice setup for you might be: a 12x27 cassette, a SRAM
9spd chain, an older style compact 5 bolt crank with
48,34,20 chainrings. (I happened to have such a crank I
could let go cheap).

Hope this helps...

"Bruni" <[email protected]> wrote in message
news:<[email protected]>...
> Road bikes also have shorter chainstays, resulting in a
> greater angle in your problem gear. If you are using the
> 112mm BB, would the 2mm inboard shift of the 109 cause the
> 26 to rub? If not,use it. Tom
>
> --
> Bruni Bicycles "Where art meets science" brunibicycles.com
> 410.426.3420 NeauDL <[email protected]> wrote in message news:20040606231418.07406.00000660@mb-
> m03.aol.com...
> > I had ridden an Ultegra triple with a 12-34 9 speed
> > cassette extensively without trouble on both Trek 5200
> > and Calfee Luna road bikes, and recently
> rode
> > a mountain century with an 11-34 cassette without
> > trouble. But I wanted a still lower gear, and put XTR
> > 952 cranks on the road bike (Calfee Luna).
> These
> > have 26-36-48 chainrings. I did not change the Ultegra
> > triple front
> derailleur
> > (It was moved downward on the seattube.) but the chain
> > was shortened.
> Chain
> > and cassette had only 100 miles on them before cranks
> > were changed, so everything is brand new. However, I
> > find I can't use all the cogs on the cassette with the
> > middle chainring. The three largest cogs, 26 and
> larger,
> > with the 36 tooth middle chainring result in pulling the
> > chain off the
> middle
> > chainring onto the granny whenever a real load is
> > applied (i. e. pushing
> hard
> > up a hill or standing). As far as I can tell, both
> > cranks have a 47.5 mm
> front
> > chainline. (I have the shorter of the two available 952
> > bottom brackets.)
> Of
> > course, the spacing in the rear is road spacing (130mm)
> > rather than
> mountain
> > bike spacing (135). On a mountain bike, the cassette
> > would be farther
> out by
> > 2.5 mm, but it looks like it would need to move more
> > than that not to have
> a
> > problem, and obviously there's no problem with an 11-34
> > cassette on all
> modern
> > mountain bikes. Is this problem the result of both the
> > small size of
> the 36
> > and the lack of mountain bike rear wheel spacing? Do
> > others using smaller
> than
> > 42 tooth middle chainrings on road bikes have similar
> > problems with larger cassettes? If I went back to the
> > Ultegra and changed to 26-38-48
> chainrings,
> > would I be likely to have the same problem? Any help
> > would be much appreciated, especially before the
> > Markleeville Death Ride in July.
> >
> > L. D. Lide
 
Originally posted by Neaudl
I had ridden an Ultegra triple with a 12-34 9 speed cassette
extensively without trouble on both Trek 5200 and Calfee
Luna road bikes, and recently rode a mountain century with
an 11-34 cassette without trouble. But I wanted a still
lower gear, and put XTR 952 cranks on the road bike (Calfee
Luna). These have 26-36-48 chainrings. I did not change the
Ultegra triple front derailleur (It was moved downward on
the seattube.) but the chain was shortened. Chain and
cassette had only 100 miles on them before cranks were
changed, so everything is brand new. However, I find I can't
use all the cogs on the cassette with the middle chainring.
The three largest cogs, 26 and larger, with the 36 tooth
middle chainring result in pulling the chain off the middle
chainring onto the granny whenever a real load is applied
(i. e. pushing hard up a hill or standing). As far as I can
tell, both cranks have a 47.5 mm front chainline. (I have
the shorter of the two available 952 bottom brackets.) Of
course, the spacing in the rear is road spacing (130mm)
rather than mountain bike spacing (135). On a mountain bike,
the cassette would be farther out by
2.5 mm, but it looks like it would need to move more than
that not to have a problem, and obviously there's no
problem with an 11-34 cassette on all modern mountain
bikes. Is this problem the result of both the small size
of the 36 and the lack of mountain bike rear wheel
spacing? Do others using smaller than 42 tooth middle
chainrings on road bikes have similar problems with larger
cassettes? If I went back to the Ultegra and changed to
26-38-48 chainrings, would I be likely to have the same
problem? Any help would be much appreciated, especially
before the Markleeville Death Ride in July.

L. D. Lide

Can you get a Chain Line Checker to verify where you are starting from?

It sounds like the chain line moved out when you swapped cranks.

I ride the combination you attempting, but on a touring bicycle, with longer chainstays. The chainline is fine on my setup; Litspeed Blue Ridge, but I also use 135 mm OLD in the rear.

I think you need to look at the chainline and then look at the gear ratios offered by the combinations you have. Sheldon Brown's site has a good calculator for gear inches that can help.

<http://sheldonbrown.com/gears/>

You might be able to gain a little on the chainline by a shorter BB spindle and/or spacing the cassette a few (1, 2, or 2.5 mm) off the back of the cassette body. You want to get as much as you can with the BB spindle length. Make sure you still get chain clearance and enegagement of the smallest cog on the cassette body. There are manufacturing tolerances in the widths of cassettes and freehub bodies.
This may all be academic once you learn what gear inches are avaialble from Sheldon's calculator and make sure that you use combinations that get the straightest chain.
 
"NeauDL" <[email protected]> wrote in message
news:[email protected]...
> I had ridden an Ultegra triple with a 12-34 9 speed
> cassette extensively without trouble on both Trek 5200 and
> Calfee Luna road bikes, and recently
rode
> a mountain century with an 11-34 cassette without trouble.
> But I wanted a still lower gear, and put XTR 952 cranks on
> the road bike (Calfee Luna).
These
> have 26-36-48 chainrings. I did not change the Ultegra
> triple front
derailleur
> (It was moved downward on the seattube.) but the chain was
> shortened. Chain and cassette had only 100 miles on them
> before cranks were changed, so everything is brand new.
> However, I find I can't use all the cogs on the cassette
> with the middle chainring. The three largest cogs, 26 and
> larger, with the 36 tooth middle chainring result in
> pulling the chain off the middle chainring onto the granny
> whenever a real load is applied (i. e. pushing hard up a
> hill or standing). As far as I can tell, both cranks have
> a 47.5 mm
front
> chainline. (I have the shorter of the two available 952
> bottom brackets.)
Of
> course, the spacing in the rear is road spacing (130mm)
> rather than mountain bike spacing (135). On a mountain
> bike, the cassette would be farther out by
> 2.5 mm, but it looks like it would need to move more than
> that not to have a problem, and obviously there's no
> problem with an 11-34 cassette on all modern mountain
> bikes. Is this problem the result of both the small size
> of the 36 and the lack of mountain bike rear wheel
> spacing? Do others using smaller
than
> 42 tooth middle chainrings on road bikes have similar
> problems with larger cassettes? If I went back to the
> Ultegra and changed to 26-38-48 chainrings, would I be
> likely to have the same problem? Any help would be much
> appreciated, especially before the Markleeville Death Ride
> in July.
>
> L. D. Lide

Which length BB are you running? I have a Dura Ace BB
(109.5?)/XTR crankarms on my cross bike and don't have
any issues.

M