Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

How Many Teeth in this Small Chainring?

Notices
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.

How Many Teeth in this Small Chainring?

Old 09-27-13, 11:18 AM
  #1  
Senior Member
Thread Starter
 
TromboneAl's Avatar
 
Join Date: Jun 2008
Location: Far, Far Northern California
Posts: 2,873

Bikes: 1997 Specialized M2Pro

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
How Many Teeth in this Small Chainring?

Last April I replaced the small chainring shown in this photo. The new chainring has 38 teeth. I neglected to note down how many the old one had, though I recall it is greater than 38. The old one was so worn that I threw it away.

From this picture, taken before the replacement, how many teeth do you think there are?



I figure 39 (7.8 teeth between the bolts, times 5 = 39). This is a 1995 Specialized M2 Pro.
TromboneAl is offline  
Old 09-27-13, 11:52 AM
  #2  
working on my sandal tan
 
ThermionicScott's Avatar
 
Join Date: Aug 2011
Location: CID
Posts: 22,638

Bikes: 1991 Bianchi Eros, 1964 Armstrong, 1988 Diamondback Ascent, 1988 Bianchi Premio, 1987 Bianchi Sport SX, 1980s Raleigh mixte (hers), All-City Space Horse (hers)

Mentioned: 98 Post(s)
Tagged: 0 Thread(s)
Quoted: 3873 Post(s)
Liked 2,574 Times in 1,581 Posts
My money is on 39T as well -- it doesn't stand proud enough of the chainring bolts to look like a 42T.
__________________
Originally Posted by chandltp
There's no such thing as too far.. just lack of time
Originally Posted by noglider
People in this forum are not typical.
RUSA #7498
ThermionicScott is offline  
Old 09-27-13, 12:01 PM
  #3  
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,459
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 130 Post(s)
Liked 12 Times in 10 Posts
1) wow, that is quite the stretched chain! and resulting shark-finned teeth on the small chainring. I take it the large chainring was less-worn and works fine with the new chain?
2) I can't confidently tell if the chainring pictured is a 38t or 39t, but am confident it's not 42t (the other common small chainring on a road bike). It's most likely 39 because that's much more common than 38. Plus you recall it was more than 38t.
3) It appears that your large chainring doesn't have pins/ramps/gates to aid shifting, and so it's less important to match it perfectly to a certain designation of small chainring. You'll be fine with the 38.
__________________
"c" is not a unit that measures tire width
TallRider is offline  
Old 09-27-13, 12:37 PM
  #4  
The Drive Side is Within
 
Standalone's Avatar
 
Join Date: Dec 2007
Location: New Haven, CT, USA
Posts: 3,334

Bikes: Road, Cargo, Tandem, Etc.

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 120 Post(s)
Liked 44 Times in 28 Posts
https://www.bikepedia.com/quickbike/B...el=M2+Road+Pro

says 42 for a 95. But I also think it looks like a 39.
__________________
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
Standalone is offline  
Old 09-27-13, 02:31 PM
  #5  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,926

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5898 Post(s)
Liked 2,761 Times in 1,543 Posts
You can "count" teeth my measuring how far above the rim of the bolt the tooth shoulder is. On a 130BCD ring, the shoulder just touches the bolt. Add 1 tooth for every 2mm or so of added clearance.

BTW- it's easier if you look from the back. but based on it not showing in the cutout, I'll join the 39t crowd
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.

Last edited by FBinNY; 09-27-13 at 02:51 PM.
FBinNY is offline  
Old 09-27-13, 02:41 PM
  #6  
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,357 Times in 863 Posts
given 130 accepts a 38 or 39, and common sets in roadie world is 53 -39. and its probably
the original stuff , I'll vote 39..


Campag opted for their 135 BCD the 39 is their minimum.
fietsbob is offline  
Old 09-27-13, 02:51 PM
  #7  
Senior Member
Thread Starter
 
TromboneAl's Avatar
 
Join Date: Jun 2008
Location: Far, Far Northern California
Posts: 2,873

Bikes: 1997 Specialized M2Pro

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Thanks for the confirmation.
TromboneAl is offline  
Old 09-27-13, 03:05 PM
  #8  
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,357 Times in 863 Posts
Obviously you didn't want to get your hands dirty and just count them .
fietsbob is offline  
Old 09-27-13, 03:20 PM
  #9  
Let your bike be the tool
 
cranky old road's Avatar
 
Join Date: Jun 2006
Location: NC/SC border
Posts: 943

Bikes: '66 Raleigh Carlton, '70 Ron Cooper, '95 Bianchi CD'I, Zonal Frame with Xenon gruppo, Carbon Frame with Record Gruppo, Columbia Twosome, Terry Classic, Bianchi SX, Gravity SS/FG

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 340 Post(s)
Liked 316 Times in 196 Posts
Are you guys are messing with my head? I count 8+ teeth between the bolts. Putting a right angle centered on the spindle center just outside the picture's frame I count around 11 teeth making the old chain ring at least a 42?
__________________
Never try to teach a pig to sing...
cranky old road is offline  
Old 09-27-13, 04:23 PM
  #10  
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Posts: 9,868
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 814 Post(s)
Liked 745 Times in 393 Posts
Originally Posted by TromboneAl
From this picture, taken before the replacement, how many teeth do you think there are?

However many teeth it had, it was long overdue for replacement. If you had ridden it much longer, it wouldn't have any teeth left.

It's a '90's Shimano Ultegra "tri-color" crank. My money's on the standard 39-53 combination.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline  
Old 09-27-13, 04:38 PM
  #11  
Senior Member
 
TallRider's Avatar
 
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,459
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 130 Post(s)
Liked 12 Times in 10 Posts
his small chainring is pretty bad, but it can get worse...


I remain curious about how the large chainring has fared with the new chain. I assume the cassette (rear gears) has been replaced, right?
Attached Images
File Type: jpg
IMG_1534.jpg (99.3 KB, 19 views)
__________________
"c" is not a unit that measures tire width
TallRider is offline  
Old 09-27-13, 06:42 PM
  #12  
The Drive Side is Within
 
Standalone's Avatar
 
Join Date: Dec 2007
Location: New Haven, CT, USA
Posts: 3,334

Bikes: Road, Cargo, Tandem, Etc.

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 120 Post(s)
Liked 44 Times in 28 Posts
guys, the bikepedia is saying 42.... and if we're seeing 8+ teeth, which looking again, I do.... 42 should be it.

It is the meaning of the universe, too, you know.



Don't panic.
__________________
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
Standalone is offline  
Old 09-27-13, 07:09 PM
  #13  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,926

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5898 Post(s)
Liked 2,761 Times in 1,543 Posts
Originally Posted by Standalone
guys, the bikepedia is saying 42.... and if we're seeing 8+ teeth, which looking again, I do.... 42 should be it. .
I don't know about the meaning of the universe, but I do understand geometry. Every tooth adds 1/2" to the circumference. Therefore each tooth adds roughly 1/3" or 4mm to the diameter, or 2mm to the radius.

Now take a look at the photo, and note that the inner diameter of the chainring rim passes close to the line of the bolt circle, but certainly to within the rim of the bolts. eNow take a look at the inner rim of the ring, and compare it to one pitch. So since a 38t is possible, that means that if this is a 42t you'd have to take 8mm out of that rim. I don't see 8mm there to rob, so I'll bet a case of beer that this was not a 42t.
__________________
FB
Chain-L site

An ounce of diagnosis is worth a pound of cure.

Just because I'm tired of arguing, doesn't mean you're right.

“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FBinNY is offline  
Old 09-27-13, 07:31 PM
  #14  
The Drive Side is Within
 
Standalone's Avatar
 
Join Date: Dec 2007
Location: New Haven, CT, USA
Posts: 3,334

Bikes: Road, Cargo, Tandem, Etc.

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 120 Post(s)
Liked 44 Times in 28 Posts
hmm, fbinny. what you say makes sense, and here's a 42....



which does look bigger. But I think the grease plays tricks on the eye. Stock is clearly 42.... but i think you're right.
__________________
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
Standalone is offline  
Old 09-28-13, 09:20 AM
  #15  
Senior Member
Thread Starter
 
TromboneAl's Avatar
 
Join Date: Jun 2008
Location: Far, Far Northern California
Posts: 2,873

Bikes: 1997 Specialized M2Pro

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
This is how I see it:

TromboneAl is offline  
Old 09-28-13, 09:25 AM
  #16  
Senior Member
Thread Starter
 
TromboneAl's Avatar
 
Join Date: Jun 2008
Location: Far, Far Northern California
Posts: 2,873

Bikes: 1997 Specialized M2Pro

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
And here it is today with a known 39 tooth chainring:



7.8 teeth from one bolt to the next.

And if those two pictures don't convert you to paraffin lubing...
TromboneAl is offline  
Old 09-28-13, 10:02 AM
  #17  
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 1,096 Times in 742 Posts
Originally Posted by fietsbob
Obviously you didn't want to get your hands dirty and just count them .
He probably would have except for this quote from the OP; "The old one was so worn that I threw it away."
HillRider is offline  
Old 09-28-13, 10:43 AM
  #18  
Senior Member
 
Join Date: Sep 2012
Posts: 1,739
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 25 Post(s)
Liked 2 Times in 2 Posts
Originally Posted by TromboneAl
Last April I replaced the small chainring shown in this photo. The new chainring has 38 teeth. I neglected to note down how many the old one had, though I recall it is greater than 38. The old one was so worn that I threw it away.

From this picture, taken before the replacement, how many teeth do you think there are?

I figure 39 (7.8 teeth between the bolts, times 5 = 39). This is a 1995 Specialized M2 Pro.
OP; Why and to what purpose... are you suffering from separation anxiety or something?
ksisler is offline  
Old 09-29-13, 11:07 AM
  #19  
Senior Member
Thread Starter
 
TromboneAl's Avatar
 
Join Date: Jun 2008
Location: Far, Far Northern California
Posts: 2,873

Bikes: 1997 Specialized M2Pro

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by ksisler
OP; Why and to what purpose... are you suffering from separation anxiety or something?
If you mean "Why do you want to know how many teeth were on the old chainring?" The answer is in this thread:

https://www.bikeforums.net/showthread...Skip-Woes-Help!

In summary: I had some problems with chain skip that, it turns out, were related to switching to a 38 tooth wheel. I wanted to go back to what I had.
TromboneAl is offline  
Old 09-29-13, 11:28 AM
  #20  
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,357 Times in 863 Posts
Surly Stainless steel chainrings are long wearing .. I have a 38t on my R'off bike..


I had some problems with chain skip that, it turns out, were related to switching to a 38 tooth wheel. I wanted to go back to what I had.
skeptical, but I cannot supervise and consult from a keyboard.
fietsbob is offline  
Old 09-29-13, 01:26 PM
  #21  
The Drive Side is Within
 
Standalone's Avatar
 
Join Date: Dec 2007
Location: New Haven, CT, USA
Posts: 3,334

Bikes: Road, Cargo, Tandem, Etc.

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 120 Post(s)
Liked 44 Times in 28 Posts
Originally Posted by TromboneAl
This is how I see it:

This is why BF is engrossing. I was hoping that someone would do this.

I think I was counting spaces.
__________________
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
Standalone is offline  
Old 09-29-13, 07:37 PM
  #22  
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 4,424

Bikes: '80 Masi Gran Criterium, '12 Trek Madone, early '60s Frejus track

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 521 Post(s)
Liked 455 Times in 342 Posts
Originally Posted by Standalone
This is why BF is engrossing. I was hoping that someone would do this.

I think I was counting spaces.
Simply amazing.
oldbobcat is offline  
Old 09-30-13, 07:34 AM
  #23  
The Drive Side is Within
 
Standalone's Avatar
 
Join Date: Dec 2007
Location: New Haven, CT, USA
Posts: 3,334

Bikes: Road, Cargo, Tandem, Etc.

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 120 Post(s)
Liked 44 Times in 28 Posts
Originally Posted by oldbobcat
Simply amazing.
Wait, amazing b/c I can't count teeth, b/c someone actually made this diagram, or b/c bikeforums is so awesome that I naturally expected someone to come up with it?

I know, I know--- probably all three.
__________________
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
Standalone is offline  
Old 09-30-13, 10:02 AM
  #24  
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 4,424

Bikes: '80 Masi Gran Criterium, '12 Trek Madone, early '60s Frejus track

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 521 Post(s)
Liked 455 Times in 342 Posts
Originally Posted by Standalone
I know, I know--- probably all three.
You got it, friend.
oldbobcat is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
CycleryNorth81
Classic & Vintage
13
05-16-19 09:01 PM
bfloyd6969
Singlespeed & Fixed Gear
12
04-05-12 10:47 PM
Cyclist75354986865
Road Cycling
0
07-18-11 06:10 PM
yummygooey
Singlespeed & Fixed Gear
9
07-06-11 06:35 PM
amirinisrael
Classic & Vintage
1
03-22-11 11:03 AM

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.