How Many Teeth in this Small Chainring?
09-27-13, 11:18 AM
#1
Senior Member
Thread Starter
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.
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.
09-27-13, 11:52 AM
#2
working on my sandal tan
Join Date: Aug 2011
Location: CID
Posts: 22,629
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: 3871 Post(s)
Liked 2,568 Times
in
1,579 Posts
09-27-13, 12:01 PM
#3
Senior Member
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,454
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 128 Post(s)
Likes: 0
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.
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
"c" is not a unit that measures tire width
09-27-13, 12:37 PM
#4
The Drive Side is Within
https://www.bikepedia.com/quickbike/B...el=M2+Road+Pro
says 42 for a 95. But I also think it looks like a 39.
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
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
09-27-13, 02:31 PM
#5
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,725
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: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5791 Post(s)
Liked 2,581 Times
in
1,431 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
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.
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.
09-27-13, 02:41 PM
#6
Banned
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.
the original stuff , I'll vote 39..
Campag opted for their 135 BCD the 39 is their minimum.
09-27-13, 03:20 PM
#9
Let your bike be the tool
Join Date: Jun 2006
Location: NC/SC border
Posts: 939
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: 338 Post(s)
Liked 314 Times
in
194 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...
Never try to teach a pig to sing...
09-27-13, 04:23 PM
#10
Insane Bicycle Mechanic
Join Date: Mar 2008
Location: other Vancouver
Posts: 9,843
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 809 Post(s)
Liked 712 Times
in
380 Posts
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
Comcast nuked my web page. It will return soon..
09-27-13, 04:38 PM
#11
Senior Member
Join Date: Oct 2005
Location: Fresno, CA
Posts: 4,454
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 128 Post(s)
Likes: 0
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?
I remain curious about how the large chainring has fared with the new chain. I assume the cassette (rear gears) has been replaced, right?
__________________
"c" is not a unit that measures tire width
"c" is not a unit that measures tire width
09-27-13, 06:42 PM
#12
The Drive Side is Within
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.
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
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
09-27-13, 07:09 PM
#13
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,725
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: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5791 Post(s)
Liked 2,581 Times
in
1,431 Posts
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.
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.
09-27-13, 07:31 PM
#14
The Drive Side is Within
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.
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
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
09-28-13, 09:25 AM
#16
Senior Member
Thread Starter
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...
7.8 teeth from one bolt to the next.
And if those two pictures don't convert you to paraffin lubing...
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
09-28-13, 10:43 AM
#18
Senior Member
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.
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.
09-29-13, 11:07 AM
#19
Senior Member
Thread Starter
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
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.
09-29-13, 11:28 AM
#20
Banned
Surly Stainless steel chainrings are long wearing .. I have a 38t on my R'off bike..
skeptical, but I cannot supervise and consult from a keyboard.
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.
09-29-13, 01:26 PM
#21
The Drive Side is Within
09-30-13, 07:34 AM
#23
The Drive Side is Within
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.
I know, I know--- probably all three.
__________________
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
The bicycle, the bicycle surely, should always be the vehicle of novelists and poets. Christopher Morley
