Largest inner ring to outer ring jump?
08-18-08, 11:06 PM
#1
?
Thread Starter
Join Date: Oct 2006
Posts: 2,775
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Largest inner ring to outer ring jump?
I got a 28-34-46 Sugino crankset. I'm looking to just skip the 34 and leave it 28-46. That's a 18 teeth jump. Is that doable?
08-19-08, 06:06 AM
#2
Senior Member
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656
Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,095 Times
in
741 Posts
Assuming the crank has 110/74 mm bolt circles, you can't mount the 28T ring as the inner ring of a double since a 34T (ok, 33T) ring is the smallest that will fit on a 110 mm bcd. If you just remove the 34, you will have a huge gap between the 46 and the 28 unless you remount the 46 on the inside of the spider. You will also need single rings chainring bolts.
The 18T jump is doable with a MTB front derailleur but probably won't be real smooth.
The 18T jump is doable with a MTB front derailleur but probably won't be real smooth.
08-19-08, 06:53 AM
#3
Guest
Join Date: Jul 2008
Location: Grid Reference, SK
Posts: 3,768
Bikes: I never learned to ride a bike. It is my deepest shame.
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 6 Times
in
6 Posts
It used to be very common to use "half step" gearing on touring bikes - have a decently small small chainring, then a relatively large middle and a relatively small large... If I recall correctly, something like 28-42-46 might work for you. This gives you lots of room to fine-tune your cadence with your two 'large' rings, and you still have the granny when you need it. Also makes shifting between the middle and the large very smooth.
08-19-08, 10:45 AM
#4
?
Thread Starter
Join Date: Oct 2006
Posts: 2,775
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Assuming the crank has 110/74 mm bolt circles, you can't mount the 28T ring as the inner ring of a double since a 34T (ok, 33T) ring is the smallest that will fit on a 110 mm bcd. If you just remove the 34, you will have a huge gap between the 46 and the 28 unless you remount the 46 on the inside of the spider. You will also need single rings chainring bolts.
I can live with that. Once I get a crank remover, I'll try this out.
08-19-08, 01:21 PM
#5
Really Old Senior Member
As mentioned, it should work, but shift quality will be less than ideal. You may tend to drop the chain more frequently too.
08-19-08, 03:20 PM
#6
Senior Member
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 33,656
Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!
Mentioned: 39 Post(s)
Tagged: 0 Thread(s)
Quoted: 2026 Post(s)
Likes: 0
Liked 1,095 Times
in
741 Posts
It used to be very common to use "half step" gearing on touring bikes - have a decently small small chainring, then a relatively large middle and a relatively small large... If I recall correctly, something like 28-42-46 might work for you. This gives you lots of room to fine-tune your cadence with your two 'large' rings, and you still have the granny when you need it. Also makes shifting between the middle and the large very smooth.
What has made half step gearing obsolete these days is two factors:
1. In the days of 5 or 6-speeds wide range freewheels had huge gaps between gears. The half-step chainrings split these gaps and gave many more gear choices. Now with 8, 9 or 10 cogs the gaps are quite narrow so the need for half steps is minimized.
2. Older front derailleurs had rather shallow inner plates and would clear a middle ring almost the same size as the outer ring. Modern indexing front derailleurs have much deeper inner cage plates and would have to be set excessively high to clear the inner ring if it had less than a 10 tooth difference.
