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:[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
 
Neaudl wrote:
> 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