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


Go Back   > >

Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

User Tag List

Reply
 
Thread Tools Search this Thread
Old 08-10-05, 12:28 PM   #1
DanO220
SoCal Commuter
Thread Starter
 
DanO220's Avatar
 
Join Date: May 2004
Location: Agua Dulce, CA
Bikes: Surly Crosscheck single/9 speed convertible, Novara Buzz beater
Posts: 592
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Big rings vs compact

I've got a 42/16 that's about 70 inches, and a 48/18 that's about 71. Given they produce nearly the same gear inches, is there any advantage to running one vs the other? I'm running single speed, not fixed. I'd like to pick up some freewheel cogs with one and two less teeth to get in the neighborhood of 75 and 80 inches respectively, but don't know which chain ring I should stick with. Thanks.

DanO
DanO220 is offline   Reply With Quote
Old 08-10-05, 01:06 PM   #2
monkey
.
 
monkey's Avatar
 
Join Date: Sep 2004
Location: Chicago
Bikes: Gios track,Miyata roadie, GT mtb
Posts: 759
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Sounds like you're good to go at 48/16.
monkey is offline   Reply With Quote
Old 08-10-05, 01:08 PM   #3
jrowe
Senior Member
 
Join Date: Nov 2004
Location: DC
Bikes: De Rosa Corum, custom Kalavinka, Bianchi RC Pista, Cannondale MT Track, Workcycles Gr8
Posts: 795
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you skip or skid, refer to the skid patch table before you switch to 48x16. It's in many threads. Edit--Ignore me. I missed the SS part.
jrowe is offline   Reply With Quote
Old 08-10-05, 01:09 PM   #4
Judah
Slower than you
 
Judah's Avatar
 
Join Date: Nov 2004
Location: SF, CA
Bikes: IRO Mark V & Don Walker Custom
Posts: 1,800
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The 48 will give you more of a range for changing your gearing up in the future since the smallest track cog available is a 12t from suntour. As for freewheels, I'm not sure what the smallest is, but I'm guessing it's probably pretty hard to make anything smaller than a 14t...
Judah is offline   Reply With Quote
Old 08-10-05, 01:21 PM   #5
beatifik
say, by the way...
 
Join Date: Mar 2005
Location: brooklyn, fo'rilla
Bikes: 2 wheels...
Posts: 306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
the smallest freewheel is 13t but it only threads onto the small side of a bmx flip-flop hub. the smallest conventially threaded one is 14t.

i know that when running really compact gears, like 25-9 on a bmx the chain is under a great deal of stress and will break more often.

go for the bigger chainring.
beatifik is offline   Reply With Quote
Old 08-10-05, 01:28 PM   #6
DanO220
SoCal Commuter
Thread Starter
 
DanO220's Avatar
 
Join Date: May 2004
Location: Agua Dulce, CA
Bikes: Surly Crosscheck single/9 speed convertible, Novara Buzz beater
Posts: 592
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by monkey
Sounds like you're good to go at 48/16.
Yea, that's the classic gear, isn't it? Problem is I have a few grades I climb on a regular basis that I can't quite lug the 48/16 up - at least not yet. The 42/16 gets me up and over alright, but then I spin it out pretty quickly. For a while I was running 48 and 38 rings up front with the 16 in back and a tensioner in between. But the bike looks much cooler without all that going on.

DanO
DanO220 is offline   Reply With Quote
Old 08-10-05, 01:51 PM   #7
Ken Cox
King of the Hipsters
 
Join Date: Jan 2005
Location: Bend, Oregon
Bikes: Realm Cycles Custom
Posts: 2,129
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I presently ride 52X17 for 81".

Some time back, after an injury, I went to 47X18, which, if I recall correctly, gave me 70".

I like the big ring and cogs for intuitive reasons; meaning, I can't prove what I suspect intuitively.

It seems to me big rings and cogs, with their larger radius and all-around largeness in general, work more efficiently and with lower stresses than do tiny rings and cogs.
A few extra teeth and an extra inch or two of chain adds a little weight to the bike.
I can only say that the same inch ratio with big rings and cogs seems more efficient to me than the same inch ratio with small rings and cogs, and I have a sense of less wear and tear.
The difference could exist only in my mind.

Anyway, I can go up any hill with 81" that I could go up with 70".
The big difference happens on the downhill side.
With 70" I have much, much more control than I do with 81".
With 81" I can go faster with less monkey-motion, and in some ways I feel safer at speed with 81", except for the braking thing.
I actually thought about going back to about 72" for the all around control and acceleration, but now having lived at 81" for awhile I have picked up some downhill braking skills I didn't have before and I might just stay here.

Anyway, I worked up from 70" to 81" in small steps by using a 47t, 48t and 52t ring in different combinations with 16t, 17t and 18t cogs.
I had a lot of fun experimenting and I might still go back to 72".
Ken Cox is offline   Reply With Quote
Old 08-10-05, 02:04 PM   #8
Aeroplane
jack of one or two trades
 
Aeroplane's Avatar
 
Join Date: Jun 2005
Location: Suburbia, CT
Bikes: Old-ass gearie hardtail MTB, fix-converted Centurion LeMans commuter, SS hardtail monster MTB
Posts: 5,637
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The guys who are doing the Furnace Creek 508 (see this thread ) basically said the same thing as Ken. More engagement, happier roll.

Add in the freewheel factor, and you are pretty much forced to stay with the 48t. 17t freewheels are available too, so you can step up in increments, if you must.
Aeroplane is offline   Reply With Quote
Old 08-10-05, 02:09 PM   #9
Lucky-Charms
eibwen
 
Join Date: Dec 2004
Bikes:
Posts: 231
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Of course all of this is pretty minute to begin with, but wouldn't a smaller ring/cog combo, while yeilding less engagement, be more efficient because of the smaller amount of friction from that smaller engagement? If you're only pulling on two teeth instead of four, you'd have half the surface friction.
Lucky-Charms is offline   Reply With Quote
Old 08-10-05, 02:16 PM   #10
darkmother
Get the stick.
 
darkmother's Avatar
 
Join Date: Nov 2004
Location: Toronto, ON
Bikes: 12 Y.O. Litespeed MTB, IRO Jamie Roy fixie, Custom Habanero Ti 'Cross, No name SS MTB, Old school lugged steel track bike (soon)
Posts: 1,543
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Bigger is better. Less backlash, lower chain tension for a given pedal force, longer chain and sproket life. Plus it makes you look like an animal with that big a$$ed front ring.
darkmother is offline   Reply With Quote
Old 08-10-05, 08:32 PM   #11
The LT
spin
 
The LT's Avatar
 
Join Date: Jan 2005
Location: Champaign, IL
Bikes: raleigh m-60, azonic steelhead, schwinn world sport fixed gear
Posts: 1,170
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Lucky-Charms
Of course all of this is pretty minute to begin with, but wouldn't a smaller ring/cog combo, while yeilding less engagement, be more efficient because of the smaller amount of friction from that smaller engagement? If you're only pulling on two teeth instead of four, you'd have half the surface friction.
I think that the friction difference will be essentially a neglible factor assuming that your chain is properly lubed. I think the main reason to run bigger is to try and reduce the stress that the chain has to deal with.
The LT is offline   Reply With Quote
Old 08-10-05, 08:42 PM   #12
jim-bob
hateful little monkey
 
jim-bob's Avatar
 
Join Date: May 2003
Location: oakland, ca
Bikes:
Posts: 5,274
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The ladies swoon for the big chainrings.

I run a 38.
jim-bob is offline   Reply With Quote
Old 08-10-05, 08:50 PM   #13
baxtefer
Cornucopia of Awesomeness
 
baxtefer's Avatar
 
Join Date: Oct 2004
Location: not where i used to be
Bikes:
Posts: 4,847
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by beatifik
the smallest freewheel is 13t but it only threads onto the small side of a bmx flip-flop hub. the smallest conventially threaded one is 14t.

i know that when running really compact gears, like 25-9 on a bmx the chain is under a great deal of stress and will break more often.

go for the bigger chainring.
Who makes the 14T? just curious....
the smallest one I know of is a 15T
baxtefer is offline   Reply With Quote
Old 08-10-05, 09:03 PM   #14
eMwolB
Tri Fixed Road
 
eMwolB's Avatar
 
Join Date: Jul 2005
Location: NYC
Bikes: Litespeed, Kestrel, KHS, Pinarello, GT, Mustang, Giant
Posts: 507
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Is there a chart or formula to figure out gear ratios, etc...I feel like I'm in trig...or was it calc??? - where's my abacus?
eMwolB is offline   Reply With Quote
Old 08-10-05, 09:29 PM   #15
beatifik
say, by the way...
 
Join Date: Mar 2005
Location: brooklyn, fo'rilla
Bikes: 2 wheels...
Posts: 306
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by baxtefer
Who makes the 14T? just curious....
the smallest one I know of is a 15T
you're right. sorry.
beatifik is offline   Reply With Quote
Old 08-11-05, 08:10 AM   #16
marcelinyc
R900Campagnolo
 
marcelinyc's Avatar
 
Join Date: Jun 2005
Location: Brooklyn
Bikes: track and road
Posts: 884
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by DanO220
I've got a 42/16 that's about 70 inches, and a 48/18 that's about 71. Given they produce nearly the same gear inches, is there any advantage to running one vs the other? I'm running single speed, not fixed. I'd like to pick up some freewheel cogs with one and two less teeth to get in the neighborhood of 75 and 80 inches respectively, but don't know which chain ring I should stick with. Thanks.

DanO
It will be easier to ride 48/18. But the difference is really very slim. 5 watts?
marcelinyc is offline   Reply With Quote
Old 08-11-05, 12:11 PM   #17
DanO220
SoCal Commuter
Thread Starter
 
DanO220's Avatar
 
Join Date: May 2004
Location: Agua Dulce, CA
Bikes: Surly Crosscheck single/9 speed convertible, Novara Buzz beater
Posts: 592
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by eMwolB
Is there a chart or formula to figure out gear ratios, etc...I feel like I'm in trig...or was it calc??? - where's my abacus?
Do a search for 'Sheldon Brown's Bicycle Gear Calculator'. He's got a page you can enter wheel diameter, tire size, crank length, chain ring and sprocket size and it computes gear inches.

DanO
DanO220 is offline   Reply With Quote
Old 08-11-05, 01:54 PM   #18
Aeroplane
jack of one or two trades
 
Aeroplane's Avatar
 
Join Date: Jun 2005
Location: Suburbia, CT
Bikes: Old-ass gearie hardtail MTB, fix-converted Centurion LeMans commuter, SS hardtail monster MTB
Posts: 5,637
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by eMwolB
Is there a chart or formula to figure out gear ratios, etc...I feel like I'm in trig...or was it calc??? - where's my abacus?
If you're not lazy, here's how it goes:

ratio = ring teeth / cog teeth

gear inches = ratio * wheel diameter = ring teeth * wheel diameter / cog teeth

gain ratio (some statistic that SB made up) = gear inches / crank length = ring teeth * wheel diameter *.5/ cog teeth / crank length

development = gear inches * pi = ring teeth* wheel diameter * pi / cog teeth

There's your formulas... FOREVER!
Aeroplane 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 12:59 PM.