Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 08-18-08, 11:06 PM   #1
mrbubbles
?
Thread Starter
 
Join Date: Oct 2006
Bikes:
Posts: 2,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
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?
mrbubbles is offline   Reply With Quote
Old 08-19-08, 06:06 AM   #2
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
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.
HillRider is offline   Reply With Quote
Old 08-19-08, 06:53 AM   #3
LarDasse74
Guest
 
Join Date: Jul 2008
Location: Grid Reference, SK
Bikes: I never learned to ride a bike. It is my deepest shame.
Posts: 3,769
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by mrbubbles View Post
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?
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.
LarDasse74 is offline   Reply With Quote
Old 08-19-08, 10:45 AM   #4
mrbubbles
?
Thread Starter
 
Join Date: Oct 2006
Bikes:
Posts: 2,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by HillRider View Post
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.
Already done that. 28 on the inner, 46 on the middle.


Quote:
Originally Posted by HillRider View Post
18T jump is doable with a MTB front derailleur but probably won't be real smooth.
I can live with that. Once I get a crank remover, I'll try this out.
mrbubbles is offline   Reply With Quote
Old 08-19-08, 01:21 PM   #5
Bill Kapaun
Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Bikes: 86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
Posts: 9,195
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
As mentioned, it should work, but shift quality will be less than ideal. You may tend to drop the chain more frequently too.
Bill Kapaun is offline   Reply With Quote
Old 08-19-08, 03:20 PM   #6
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Quote:
Originally Posted by LarDasse74 View Post
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.
I had just about that exact half-step w/granny combination on an '85 Bridgestone. My rings were 46/42/26 with a 13x28 6-speed freewheel. There were nearly no duplicate gears in the entire range.

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.
HillRider is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 04:39 AM.