Go Back  Bike Forums > Bike Forums > Fifty Plus (50+)
Reload this Page >

38 Teeth versus 39 Teeth

Notices
Fifty Plus (50+) Share the victories, challenges, successes and special concerns of bicyclists 50 and older. Especially useful for those entering or reentering bicycling.

38 Teeth versus 39 Teeth

Old 09-30-13, 09:07 AM
  #1  
TromboneAl
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
38 Teeth versus 39 Teeth

I put a new and different (Willful Neglect Corrosion resistant chain) on my bike, and got a chain skipping problem that only occurred when I had a 38 tooth chainring as my small ring on the front. Switched back to a 39-tooth chainring, and the problem disappeared.

I can either stay with this setup, or get a new chain, put the 38T back, and try to resolve the issues.

The climbing seems slightly harder with the 39T, but perhaps that's just a placebo thing. It's only one gear inch different.

Do you think climbing really is harder with the 39T? Should I just HTFU?

Are there advantages to a 39 tooth ring?

Please do not respond with "Do whatever YOU want to do, why do you need us to tell you?"

Front: 39, 53
Rear: Shimano HG51 8-Speed Cassette (11-28T)




TromboneAl is offline  
Old 09-30-13, 09:10 AM
  #2  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,322 Times in 832 Posts
Should I just HTFU?
shall we bring another mattress, princess, is that pea still bothering you?
fietsbob is offline  
Old 09-30-13, 09:14 AM
  #3  
Gerryattrick
Beicwyr Hapus
 
Gerryattrick's Avatar
 
Join Date: Feb 2011
Location: Cambria Australis
Posts: 1,516

Bikes: Genesis Equilibrium, Genesis Datum, Whyte 901 Dawes 701,1973 Harry Hall

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 144 Post(s)
Liked 13 Times in 7 Posts
Phew! I thought it was another bike accident thread.
Gerryattrick is offline  
Old 09-30-13, 09:19 AM
  #4  
Number400
Senior Member
 
Number400's Avatar
 
Join Date: Jul 2010
Location: South Central PA
Posts: 972

Bikes: Cannondale Slate 105 and T2 tandem, 2008 Scott Addict R4, Raleigh SC drop bar tandem

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by Gerryattrick View Post
Phew! I thought it was another bike accident thread.
Ha! Yuck, yuck , yuck!
Number400 is offline  
Old 09-30-13, 10:00 AM
  #5  
NOS88
Senior Member
 
NOS88's Avatar
 
Join Date: Mar 2006
Location: Montgomery County, Pennsylvania
Posts: 6,489
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 3 Times in 1 Post
It seems possible that the smaller circumference of the 38 makes a difference. If a link were just a bit stiffer than the others it might cause it to skip. But, I’m not sure this makes complete sense, because the rear cog has much smaller circumferences than your 38 up front. I’ve got to tell you, this is one that would drive me crazy until I knew why what was happening was happening. The other possibility is that new chain ring is not designed to work with your current setup. Is the new one designed for an eight speed system? In terms of should you just HTFU, you can do that with a 38 or 39 tooth up front if that's your goal. Just push harder. But, your post leads me to believe you want the 38.
__________________
A conclusion is the place where you got tired of thinking. - S. Wright
Favorite rides in the stable: Indy Fab CJ Ti - Colnago MXL - S-Works Roubaix - Habanero Team Issue - Jamis Eclipse carbon/831
NOS88 is offline  
Old 09-30-13, 10:15 AM
  #6  
oldbobcat
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 3,451

Bikes: '79 Gios, '80 Masi, '06 Felt, early '60s Frejus

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked 119 Times in 88 Posts
Or the smaller circumference of the 38 may have caused the chain to hit a chainring bolt that was machined just a little too close to the valley between two teeth. For one tooth, you can guess at my recommendation.
oldbobcat is offline  
Old 09-30-13, 10:23 AM
  #7  
TromboneAl
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 NOS88 View Post
It seems possible that the smaller circumference of the 38 makes a difference. If a link were just a bit stiffer than the others it might cause it to skip. But, I’m not sure this makes complete sense, because the rear cog has much smaller circumferences than your 38 up front. I’ve got to tell you, this is one that would drive me crazy until I knew why what was happening was happening. The other possibility is that new chain ring is not designed to work with your current setup. Is the new one designed for an eight speed system? In terms of should you just HTFU, you can do that with a 38 or 39 tooth up front if that's your goal. Just push harder. But, your post leads me to believe you want the 38.
My current theory is that sometimes the wider chain hadn't shifted all the way over onto the small chainring when I applied pressure. Perhaps the 9-speed I had prior to that shifted faster, so it was never "in between" when I mashed.

The 38 tooth ring (got it used from LBS box) has this on it: FSa 38T 130 mm BCD 7075/T6

Tell me how an 8-speed chainring would be different from a 9-speed.

Thanks,

Al
TromboneAl is offline  
Old 09-30-13, 10:30 AM
  #8  
NOS88
Senior Member
 
NOS88's Avatar
 
Join Date: Mar 2006
Location: Montgomery County, Pennsylvania
Posts: 6,489
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 3 Times in 1 Post
Originally Posted by TromboneAl View Post
My current theory is that sometimes the wider chain hadn't shifted all the way over onto the small chainring when I applied pressure. Perhaps the 9-speed I had prior to that shifted faster, so it was never "in between" when I mashed.

The 38 tooth ring (got it used from LBS box) has this on it: FSa 38T 130 mm BCD 7075/T6

Tell me how an 8-speed chainring would be different from a 9-speed.

Thanks,

Al
9 and 10 speed chainrings have the teeth ever so slightly farther to the right than a 6, 7 or 8 speed chainring (according to Sheldo Brown that is:https://sheldonbrown.com/speeds.html) . Try flipping the chainring and see that that solves the problem.
__________________
A conclusion is the place where you got tired of thinking. - S. Wright
Favorite rides in the stable: Indy Fab CJ Ti - Colnago MXL - S-Works Roubaix - Habanero Team Issue - Jamis Eclipse carbon/831
NOS88 is offline  
Old 09-30-13, 10:31 AM
  #9  
Dudelsack 
A might bewildered...
 
Dudelsack's Avatar
 
Join Date: Oct 2011
Location: Loovul in summer. Jensen Beach in Winter.
Posts: 6,587

Bikes: Bacchetta Giro ATT 26; Lemond Buenos Aires

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 106 Post(s)
Liked 36 Times in 17 Posts
Either way is a dumptruck full of awesome. It's all good. YMMV.
__________________
Brevity is the soul of wit.



Dudelsack is offline  
Old 09-30-13, 12:29 PM
  #10  
B. Carfree
Senior Member
 
Join Date: Jan 2010
Location: Eugene, Oregon
Posts: 7,048
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 509 Post(s)
Likes: 0
Liked 8 Times in 8 Posts
Are you sure the 38T ring isn't just so worn that it can't properly hold the chain? By the time the teeth get pointy, it's long gone.

As far as which would be the better choice between 38T and 39T, there are two things I consider.

1. Is my low gear low enough for me?
2. Which one creates the greatest "gap fill" gearing relative to the big ring. Graph the gear inches with a log scale and see where the 38T and 39T gears sit relative to your big ring.
B. Carfree is offline  
Old 09-30-13, 01:57 PM
  #11  
TromboneAl
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 NOS88 View Post
9 and 10 speed chainrings have the teeth ever so slightly farther to the right than a 6, 7 or 8 speed chainring (according to Sheldo Brown that is:https://sheldonbrown.com/speeds.html) . Try flipping the chainring and see that that solves the problem.
Oh, that''s a neat idea.

Are you sure the 38T ring isn't just so worn that it can't properly hold the chain? By the time the teeth get pointy, it's long gone.

As far as which would be the better choice between 38T and 39T, there are two things I consider.

1. Is my low gear low enough for me?
2. Which one creates the greatest "gap fill" gearing relative to the big ring. Graph the gear inches with a log scale and see where the 38T and 39T gears sit relative to your big ring.
Yes, the 38t one isn't worn.

I'll look into those other things and ride for a while with this.
TromboneAl is offline  
Old 09-30-13, 02:06 PM
  #12  
skilsaw
Senior Member
 
skilsaw's Avatar
 
Join Date: Jul 2010
Location: Victoria, Canada
Posts: 1,541

Bikes: Cannondale t1, Koga-Miyata World Traveller

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
What solution costs the most money?
Go with that. Isn't that what cycling is all about anyway?
skilsaw is offline  
Old 09-30-13, 08:13 PM
  #13  
oldbobcat
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 3,451

Bikes: '79 Gios, '80 Masi, '06 Felt, early '60s Frejus

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked 119 Times in 88 Posts
Originally Posted by skilsaw View Post
What solution costs the most money?
Go with that. Isn't that what cycling is all about anyway?
This certainly cuts to the chase. Thanks.
oldbobcat is offline  
Old 09-30-13, 09:05 PM
  #14  
B. Carfree
Senior Member
 
Join Date: Jan 2010
Location: Eugene, Oregon
Posts: 7,048
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 509 Post(s)
Likes: 0
Liked 8 Times in 8 Posts
Originally Posted by skilsaw View Post
What solution costs the most money?
Go with that. Isn't that what cycling is all about anyway?
Oh drat. Yet another thing I've been doing wrong all these years.
B. Carfree is offline  
Old 10-01-13, 10:20 PM
  #15  
jyl
Senior Member
 
jyl's Avatar
 
Join Date: Aug 2006
Location: Portland OR
Posts: 7,642

Bikes: 61 Bianchi Specialissima 71 Peugeot G50 7? P'geot PX10 74 Raleigh GranSport 75 P'geot UO8 78? Raleigh Team Pro 82 P'geot PSV 86 P'geot PX 91 Bridgestone MB0 92 B'stone XO1 97 Rans VRex 92 Cannondale R1000 94 B'stone MB5 97 Vitus 997

Mentioned: 140 Post(s)
Tagged: 0 Thread(s)
Quoted: 389 Post(s)
Likes: 0
Liked 43 Times in 28 Posts
HTFU is clearly the answer :-)

It'll make a man out of you!
jyl is offline  
Old 10-02-13, 07:32 AM
  #16  
rydabent
Senior Member
 
rydabent's Avatar
 
Join Date: Apr 2010
Location: Lincoln Ne
Posts: 9,094

Bikes: RANS Stratus TerraTrike Tour II

Mentioned: 29 Post(s)
Tagged: 0 Thread(s)
Quoted: 2454 Post(s)
Liked 732 Times in 433 Posts
b carefree +1

The simple answer is that the 38T chain ring may just be worn out. One tooth smaller is no reason at all that the chain has problems. Just look at it logically. Look at all the 30 tooth grannies and smaller that work fine if not worn.
rydabent is offline  
Old 10-02-13, 08:39 AM
  #17  
TromboneAl
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 rydabent View Post
b carefree +1

The simple answer is that the 38T chain ring may just be worn out. One tooth smaller is no reason at all that the chain has problems. Just look at it logically. Look at all the 30 tooth grannies and smaller that work fine if not worn.
True, that would be a good explanation. But it just doesn't look worn enough to me -- what do you think?



TromboneAl is offline  
Old 10-02-13, 01:59 PM
  #18  
big john
Senior Member
 
big john's Avatar
 
Join Date: Sep 2005
Location: In the foothills of Los Angeles County
Posts: 17,334
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 3299 Post(s)
Liked 2,610 Times in 1,441 Posts
If the chain is worn to the 39 it might skip on a new ring. If you buy a new chain you might need a cassette, too.
big john is offline  
Old 10-02-13, 09:34 PM
  #19  
oldbobcat
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 3,451

Bikes: '79 Gios, '80 Masi, '06 Felt, early '60s Frejus

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked 119 Times in 88 Posts
My money says the skips are happening when rollers of the chain pass through the valleys that are directly over bolt holes, especially the one at 1 o'clock in the top photo. Notice what looks like extra wear between those teeth. Then notice the imprint left by the crank spider where it is attached. The chain is riding so low that plates are hitting the end of the crank spider, causing the chain to jump. It doesn't happen on the 39t ring because the ends of the crank spider are farther from the chain.

A chain with worn rollers will ride even lower, exacerbating the effect. Get a new 38t ring, preferably one with all the bolt holes beneath teeth instead of valleys. Or, if you insist on using this ring, file a half-millimeter or so of material from the ends of the crank spider so the chain will clear it, if you're not at all worried about compromising the strength of the crank. I'd be worried, though.
oldbobcat is offline  
Old 10-02-13, 09:35 PM
  #20  
NOS88
Senior Member
 
NOS88's Avatar
 
Join Date: Mar 2006
Location: Montgomery County, Pennsylvania
Posts: 6,489
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 3 Times in 1 Post
Originally Posted by oldbobcat View Post
My money says the skips are happening when rollers of the chain pass through the valleys that are directly over bolt holes, especially the one at 1 o'clock in the top photo. Notice what looks like extra wear between those teeth. Then notice the imprint left by the crank spider where it is attached. The chain is riding so low that plates are hitting the end of the crank spider, causing the chain to jump. It doesn't happen on the 39t ring because the ends of the crank spider are farther from the chain.

A chain with worn rollers will ride even lower, exacerbating the effect. Get a new 38t ring, preferably one with all the bolt holes beneath teeth instead of valleys. Or, if you insist on using this ring, file a half-millimeter or so of material from the ends of the crank spider so the chain will clear it, if you're not at all worried about compromising the strength of the crank. I'd be worried, though.
Good eye!
__________________
A conclusion is the place where you got tired of thinking. - S. Wright
Favorite rides in the stable: Indy Fab CJ Ti - Colnago MXL - S-Works Roubaix - Habanero Team Issue - Jamis Eclipse carbon/831
NOS88 is offline  
Old 10-02-13, 09:51 PM
  #21  
oldbobcat
Senior Member
 
oldbobcat's Avatar
 
Join Date: Jul 2005
Location: Boulder County, CO
Posts: 3,451

Bikes: '79 Gios, '80 Masi, '06 Felt, early '60s Frejus

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 162 Post(s)
Liked 119 Times in 88 Posts
There's a reason why most chainring manufacturers stop at 39t on a 130 mm crank. Clearance.

Just because somebody makes a part doesn't mean it will work. Well maybe it will, for some applications, for that short window when everything is brand new.
oldbobcat is offline  
Old 10-03-13, 12:14 AM
  #22  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,322 Times in 832 Posts
with a 53t big ring , 39t is 14 less.
fietsbob is offline  
Old 10-03-13, 09:28 AM
  #23  
TromboneAl
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 oldbobcat View Post
My money says the skips are happening when rollers of the chain pass through the valleys that are directly over bolt holes, especially the one at 1 o'clock in the top photo. Notice what looks like extra wear between those teeth. Then notice the imprint left by the crank spider where it is attached. The chain is riding so low that plates are hitting the end of the crank spider, causing the chain to jump. It doesn't happen on the 39t ring because the ends of the crank spider are farther from the chain.

A chain with worn rollers will ride even lower, exacerbating the effect. Get a new 38t ring, preferably one with all the bolt holes beneath teeth instead of valleys. Or, if you insist on using this ring, file a half-millimeter or so of material from the ends of the crank spider so the chain will clear it, if you're not at all worried about compromising the strength of the crank. I'd be worried, though.
OK, that's a theory worth throwing some money at, and I'm finally understanding what ThermionicScott said in another thread. I might just put the 38T back on to eyeball it and see if that's what's happening.

A chain with worn rollers will ride even lower, exacerbating the effect.
The problem didn't happen until I put a new chain on (8 speed instead of 9), but perhaps that new chain is slightly different.

Last edited by TromboneAl; 10-03-13 at 09:31 AM.
TromboneAl is offline  
Old 10-03-13, 10:57 AM
  #24  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,322 Times in 832 Posts
TA, in 110. sells a 33t chainring , to use it they machine the ends of the crank spider with a clearance notch..

the clearance modification , can be done with a steady hand and a sharp file. .. in this case as well..
fietsbob is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
ronin4740
Fixed Gear Freestyle
4
11-07-19 11:29 PM
alathIN
Bicycle Mechanics
8
05-11-17 12:48 PM
FatBottomedGirl
Bicycle Mechanics
7
10-26-13 01:46 PM
Zan
Mountain Biking
6
07-09-10 12:00 PM
ElJamoquio
Road Cycling
7
03-02-10 07:36 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.