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
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