Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

Gearing Question

Notices
Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Gearing Question

Old 03-11-13, 06:31 PM
  #1  
osiris419
Senior Member
Thread Starter
 
osiris419's Avatar
 
Join Date: Nov 2009
Location: Pepperell MA
Posts: 331

Bikes: 2014 Specialized Allez, Trek Superfly, Trek Farley, Trek Crockett, Trek Rig SS, Bontrager Diesel race BMX, Deluxe Team dirt jump BMX, SE Draft

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked 10 Times in 5 Posts
Gearing Question

I'm building up an old road bike and I have a 6 speed 13-21t freewheel that I'm going to use. I was just wondering what you folks would think a good chainring set-up would be up front? I have a couple of cranksets that I could use a 130 BCD and a 110 BCD both doubles. Any input would help I'm kind of a noob with multi-speeds.
Thanks
osiris419 is offline  
Old 03-11-13, 06:39 PM
  #2  
hamster
Senior Member
 
Join Date: Apr 2006
Location: Escondido, CA
Posts: 2,240
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
What's the intended use of the bike? 13-21t is very narrow and, no matter what, you will end up with a bike that is seriously deficient at one or the other end of gear range. In fact, with 21t low, it will be a very poor hill climber regardless of your choice of front. If you designate it as a flatland bike, 130 BCD 39-53 in front should work for you. If you want to climb hills, you may need to rethink your cassette choice. (A low of at least 34/25, lower than that if possible, is highly recommended for hills.)
hamster is offline  
Old 03-11-13, 06:52 PM
  #3  
osiris419
Senior Member
Thread Starter
 
osiris419's Avatar
 
Join Date: Nov 2009
Location: Pepperell MA
Posts: 331

Bikes: 2014 Specialized Allez, Trek Superfly, Trek Farley, Trek Crockett, Trek Rig SS, Bontrager Diesel race BMX, Deluxe Team dirt jump BMX, SE Draft

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked 10 Times in 5 Posts
Thanks. It's going to be a commuter, beater, something to ride when I don't want to take out my Allez, mainly flats I don't have huge climbs around me. I know its a pretty narrow freewheel but its what I had on the wheel I got. I could put a wider freewheel on I have a few kicking around but they are all 5 speed.
osiris419 is offline  
Old 03-11-13, 07:03 PM
  #4  
hamster
Senior Member
 
Join Date: Apr 2006
Location: Escondido, CA
Posts: 2,240
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
For a commuter, I'd say lower is better. Get a 110 BCD 34-50, it will be a little easier to spin out but more accommodating at the low end.
hamster is offline  
Old 03-11-13, 08:45 PM
  #5  
LesterOfPuppets
cowboy, steel horse, etc
 
LesterOfPuppets's Avatar
 
Join Date: Sep 2008
Location: Valley of the Sun.
Posts: 39,699

Bikes: everywhere

Mentioned: 70 Post(s)
Tagged: 1 Thread(s)
Quoted: 9206 Post(s)
Liked 4,035 Times in 2,173 Posts
I rolled 42/52 x 13-21 when I was young and dumb. Would do again only if I lived in Florida.
LesterOfPuppets is online now  
Old 03-11-13, 11:32 PM
  #6  
Drew Eckhardt 
Senior Member
 
Drew Eckhardt's Avatar
 
Join Date: Apr 2010
Location: Mountain View, CA USA and Golden, CO USA
Posts: 6,341

Bikes: 97 Litespeed, 50-39-30x13-26 10 cogs, Campagnolo Ultrashift, retroreflective rims on SON28/PowerTap hubs

Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 549 Post(s)
Liked 319 Times in 222 Posts
Originally Posted by osiris419 View Post
I'm building up an old road bike and I have a 6 speed 13-21t freewheel that I'm going to use. I was just wondering what you folks would think a good chainring set-up would be up front? I have a couple of cranksets that I could use a 130 BCD and a 110 BCD both doubles. Any input would help I'm kind of a noob with multi-speeds.
Thanks
For flat ground 53/52/50-39 will be fine. 50-34 x 13-21 won't have any overlap between rings, the ends are in a comfortable cruising range, and you're not going to be happy. I rarely want anything bigger than 39x14 or smaller than 39x21 commuting.

For hills you want 53/52/50-42/40/39-30 unless you need lower gears in which case a 28 or 26 would be better; although 30x21 is a bit smaller than the 42x28 we all use to ride in the hills and like a contemporary 39x27 or 34x24 which are ample for fit riders on most paved roads like those in the Rocky Mountains (apart from Magnolia Road and the other Mike Horgan route where they work but you'd do better with lower gears).

Last edited by Drew Eckhardt; 03-11-13 at 11:46 PM.
Drew Eckhardt is offline  
Old 03-11-13, 11:41 PM
  #7  
Drew Eckhardt 
Senior Member
 
Drew Eckhardt's Avatar
 
Join Date: Apr 2010
Location: Mountain View, CA USA and Golden, CO USA
Posts: 6,341

Bikes: 97 Litespeed, 50-39-30x13-26 10 cogs, Campagnolo Ultrashift, retroreflective rims on SON28/PowerTap hubs

Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 549 Post(s)
Liked 319 Times in 222 Posts
Originally Posted by hamster View Post
For a commuter, I'd say lower is better. Get a 110 BCD 34-50, it will be a little easier to spin out but more accommodating at the low end.
I think that's a horrible idea. Wide rings do not mate well to narrow cogs. I tried 50-34 x 13-23 9 cogs because it provided the same range and spacing as the 50-40-30 x 13-21 8 cogs I rode in that era and 2 rings are better than 3.... front shifts went from infrequent to constant with small bumps or changes in wind.

50x21 is the same as 34x14
34x13 is the same as 50x19

Eschewing the fully cross-chained combinations there's no overlap between rings and even if you don't do that there's still going to be a _lot_ of front shifting.

Last edited by Drew Eckhardt; 03-11-13 at 11:47 PM.
Drew Eckhardt is offline  
Old 03-11-13, 11:57 PM
  #8  
NMBuff
Senior Member
 
Join Date: Jul 2012
Location: Albuquerque, NM
Posts: 116

Bikes: 2012 Cannondale Syanpse 5 105

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
How strong of a rider are you and how much do you weigh? I'd assume Massachusetts is flat, but I could be wrong.
NMBuff is offline  
Old 03-12-13, 12:48 AM
  #9  
hamster
Senior Member
 
Join Date: Apr 2006
Location: Escondido, CA
Posts: 2,240
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Drew Eckhardt View Post
I think that's a horrible idea. Wide rings do not mate well to narrow cogs. I tried 50-34 x 13-23 9 cogs because it provided the same range and spacing as the 50-40-30 x 13-21 8 cogs I rode in that era and 2 rings are better than 3.... front shifts went from infrequent to constant with small bumps or changes in wind.

50x21 is the same as 34x14
34x13 is the same as 50x19

Eschewing the fully cross-chained combinations there's no overlap between rings and even if you don't do that there's still going to be a _lot_ of front shifting.
Not that 53-39 is a huge improvement. 50-34 x 13-21 has an overlap of 1 gear (this being a 6sp, it's probably 13-14-15-17-19-21), and 53-39 x 13-21 has an overlap of 2 gears.

In terms of speed, at 90 rpm and likewise excluding cross-chaining, 50-34 would result in the low ring ending at 17.1 mph and the high ring beginning at 18.6 mph, 53-39 would be 19.7 and 19.7. We are looking at a lot of front shifting in either case. If 53-39 is better at all, it's mainly because it has gears shifted to the point where the commuter has no real need for 53 anyway.

A good compromise could be 46-36, with the small ring ending at 18.1 mph and the big ring starting at 17.1 mph @ 90 rpm (or 14.2 mph @ 75 rpm.) That way flatland riding could be done while staying mostly in the big ring.
hamster is offline  
Old 03-12-13, 01:34 AM
  #10  
hueyhoolihan
Senior Member
 
Join Date: Dec 2010
Location: Above ground, Walnut Creek, Ca
Posts: 6,681

Bikes: 8 ss bikes, 1 5-speed touring bike

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
i don't know what kind of rider you are, so i'll say what i would do.

i'd put a 4o-45t ring on there. BCD doesn't really matter to me. then i'd ditch the front derailleur and center the chain with the better of the inside or outside chainring positions on the crank spyder.
hueyhoolihan is offline  
Old 03-12-13, 08:31 AM
  #11  
JimPz
Senior Member
 
Join Date: Mar 2011
Posts: 50
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
You *could* run into one other problem, you are talking 5 & 6 speed freewheels, at least with the compact crank, I take it your talking 9/110 speed cranks.. You need a wider chain for the rear & a narrower one for the fron\t. You may not get good shifting with this. The suggestion above may be your best bet - a single ring.
JimPz is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
dbikingman
Bicycle Mechanics
20
09-28-13 03:46 PM
merganser22
Road Cycling
13
08-02-12 10:24 PM
hagen2456
Bicycle Mechanics
6
12-15-11 06:04 PM
reducedfatoreo
Folding Bikes
10
09-23-11 07:51 AM
lil'hobo
Classic & Vintage
21
10-19-10 11:14 PM

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.