Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

What's with this crankset? Derailleur problem.

Notices
Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

What's with this crankset? Derailleur problem.

Old 02-27-12, 01:14 PM
  #1  
Gear41
Member
Thread Starter
 
Gear41's Avatar
 
Join Date: Feb 2012
Location: Denver, CO
Posts: 37

Bikes: 1989 Schwinn Voyageur | 1987 Trek 400 (sold) | 1984 Trek 520 | 1996 Trek 750 Multitrack

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
What's with this crankset? Derailleur problem.

I recently purchased a 1988 Trek 400T. The gearing on the crankset is a little strange to me (it's not the original crankset). It is a triple with 52t, 48t, and 26t chainrings.

Anyway, I changed the shift cables today and I'm having trouble adjusting the front derailleur to accommodate the innermost chainring. Could it have something to do with the large range between the largest and smallest chainring, or am I just doing something wrong?

Either way, I really want to replace either the 26t chainring. Now, I've just got to find a replacement.

Gear41 is offline  
Old 02-27-12, 01:18 PM
  #2  
JReade
Senior Member
 
JReade's Avatar
 
Join Date: Sep 2010
Location: Oregon City, OR
Posts: 1,618
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 95 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
Half step with granny!
JReade is offline  
Old 02-27-12, 01:36 PM
  #3  
w98seeng
Full Member
 
w98seeng's Avatar
 
Join Date: May 2008
Location: Incognito
Posts: 395
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked 0 Times in 0 Posts
Derailleurs have a max tooth range they will accommodate. The difference on your bike is 28, probably too big a difference for your front derailleur (probably a double derailleur). If the derailleur changed properly before the cable change, it might be a double derailleur adjusted right at the outside limit of the derailleur and was able to change gears.

What model is your derailleur?

Here is an explanation from bikepro.com...
Front derailleurs have a rating known as "capacity". Capacity is a rating for the difference in the number of teeth between the chainring sizes. If the "capacity" of the front derailleur was 14 teeth, the difference between the largest and smallest chainring sizes must be 14 teeth or less. For example, if you had a road racing double crankset that was 52-40 (52 teeth for the large outer one and 40 teeth for the small inner), we would find that 52 minus 40 is equal to 12, we have a 12 tooth difference between the two chainrings. Because 12 is less than the 14 tooth "capacity" of the front derailleur, it would work with no difficulty. If, however, it were a 54-36 crankset the result would be (54 minus 36=18) 18 and this would exceed the front derailleur's "capacity". The front changer couldn't lift the chain comfortably to the large chainring. In the case of a triple crankset, the same principle applies, however you would use the difference between the outermost and the innermost chainring.
w98seeng is offline  
Old 02-27-12, 02:03 PM
  #4  
Gear41
Member
Thread Starter
 
Gear41's Avatar
 
Join Date: Feb 2012
Location: Denver, CO
Posts: 37

Bikes: 1989 Schwinn Voyageur | 1987 Trek 400 (sold) | 1984 Trek 520 | 1996 Trek 750 Multitrack

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Okay, that explanation from bikepro.com made a lot of sense. I remember hearing something about capacity in the past, and had a feeling the jump from 48t to 26t was quite large.

I am pretty sure the front derailleur is a triple (although there is a chance it could have been replaced). I've spent a lof of time on vintagetrek.com , and all the specs match up with the 400T (except the replaced crankset). The derailleur was changing properly between the three chainrings before I replaced the cables, however there was a lot of rub when on the outer rings.

Since I really do not like the current gearing (half-step with granny – thanks JReade), I may not play with it much more. Maybe I can work out a crankset trade at the co-op or find some replacement rings.
Gear41 is offline  
Old 02-27-12, 03:09 PM
  #5  
illwafer
)) <> ((
 
illwafer's Avatar
 
Join Date: Mar 2008
Location: San Diego, CA
Posts: 2,411
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked 3 Times in 3 Posts
lower your derailleur. it looks like you can squeak by...
illwafer is offline  
Old 02-27-12, 03:21 PM
  #6  
T-Mar
Senior Member
 
Join Date: Nov 2004
Posts: 23,230
Mentioned: 629 Post(s)
Tagged: 1 Thread(s)
Quoted: 4702 Post(s)
Likes: 0
Liked 2,968 Times in 1,841 Posts
Originally Posted by illwafer View Post
lower your derailleur. it looks like you can squeak by...
+1. The subject derailleur appears to be a mid-1980s Shimano FD-Z204-GS (designation stamped on back of cage). This derailleur has an advertised capacity of 27T, so you're pushing the limits, but it should work, probably grudgingly.
T-Mar is offline  
Old 02-27-12, 03:27 PM
  #7  
ColonelJLloyd 
Senior Member
 
ColonelJLloyd's Avatar
 
Join Date: Dec 2009
Location: Louisville
Posts: 8,382
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 110 Post(s)
Liked 10 Times in 9 Posts
https://www.parktool.com/blog/repair-...ur-adjustments
__________________
Bikes on Flickr
I prefer email to private messages. You can contact me at justinhughes@me.com
ColonelJLloyd is offline  
Old 02-27-12, 03:39 PM
  #8  
Puget Pounder
Wookie Jesus inspires me.
 
Puget Pounder's Avatar
 
Join Date: Mar 2011
Location: Seattle, WA
Posts: 2,225
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Likes: 0
Liked 1 Time in 1 Post
How accurate are front derailleur capacity ratings? I've run 26 grannies and 53 max before with no problems. I've also consitently exceeded the capacities on doubles as well.
Puget Pounder is offline  
Old 02-27-12, 03:45 PM
  #9  
ColonelJLloyd 
Senior Member
 
ColonelJLloyd's Avatar
 
Join Date: Dec 2009
Location: Louisville
Posts: 8,382
Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 110 Post(s)
Liked 10 Times in 9 Posts
Originally Posted by Puget Pounder View Post
How accurate are front derailleur capacity ratings?
Well, you can't blame manufacturers for placing a conservative rating on them.
__________________
Bikes on Flickr
I prefer email to private messages. You can contact me at justinhughes@me.com
ColonelJLloyd is offline  
Old 02-27-12, 03:53 PM
  #10  
Puget Pounder
Wookie Jesus inspires me.
 
Puget Pounder's Avatar
 
Join Date: Mar 2011
Location: Seattle, WA
Posts: 2,225
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by ColonelJLloyd View Post
Well, you can't blame manufacturers for placing a conservative rating on them.
True. I've just never run into problems exceeding a triple FD's capacity. I have with a double, but never a triple.
Puget Pounder is offline  
Old 02-27-12, 05:07 PM
  #11  
Gear41
Member
Thread Starter
 
Gear41's Avatar
 
Join Date: Feb 2012
Location: Denver, CO
Posts: 37

Bikes: 1989 Schwinn Voyageur | 1987 Trek 400 (sold) | 1984 Trek 520 | 1996 Trek 750 Multitrack

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by T-Mar View Post
+1. The subject derailleur appears to be a mid-1980s Shimano FD-Z204-GS (designation stamped on back of cage). This derailleur has an advertised capacity of 27T, so you're pushing the limits, but it should work, probably grudgingly.
Thanks for the advice on lowering the derailleur. Will do. Also, thanks for finding the info on the capacity.
Gear41 is offline  
Old 02-27-12, 07:10 PM
  #12  
Captain Blight
Senior Member
 
Captain Blight's Avatar
 
Join Date: Oct 2009
Location: Minneapolis
Posts: 2,473

Bikes: -1973 Motobecane Mirage -197? Velosolex L'Etoile -'71 Raleigh Super Course

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Also? Back the limit screws out like all the way after you lower your derailleur and before you clamp the cable down tight. I don't know what it is about that particular mech, but I've always found them to be a PITA to adjust.
Captain Blight is offline  
Old 02-27-12, 07:35 PM
  #13  
BluesDaddy
I got 99 projects
 
BluesDaddy's Avatar
 
Join Date: Nov 2008
Location: Hills of Central NH
Posts: 1,603
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 1 Time in 1 Post
My $.02
Detach cable from mech*.
Lower mech until it just barely clears the big ring as it swings out.
Leaving the cable off, put the bike in a stand or otherwise raise the rear wheel.
To set the limit screws, pedal and cycle the mech across its travel to get the limits right.
Put the shifter and mech in low gear and attach cable with minimal tension.
Test ride.
*"mech" is easier to type/say and I would love if we could switch over, just like we did with Metric.
BluesDaddy is offline  
Old 02-27-12, 08:26 PM
  #14  
IthaDan 
Senior Member
 
IthaDan's Avatar
 
Join Date: Jan 2012
Location: Ithaca, NY
Posts: 4,915

Bikes: Click on the #YOLO

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Likes: 0
Liked 8 Times in 8 Posts
^^ I've become a fan of "FD" and "RD"

Yeah, check out the chainline, no wonder you're having issues. This is a VERY rough approximation of your "granniest" gear. See how it barely clears the bottom of the FD cage?

Lower that FD. Set it so it just barely clears the large chainring.

IthaDan is offline  
Old 02-27-12, 09:05 PM
  #15  
AZORCH
Senior Member
 
AZORCH's Avatar
 
Join Date: Aug 2010
Location: Liberty, Missouri
Posts: 3,128

Bikes: 1966 Paramount | 1971 Raleigh International | ca. 1970 Bernard Carre | 1989 Waterford Paramount | 2012 Boulder Brevet | 2019 Specialized Diverge

Mentioned: 23 Post(s)
Tagged: 0 Thread(s)
Quoted: 127 Post(s)
Liked 63 Times in 32 Posts
Originally Posted by IthaDan View Post
^^ I've become a fan of "FD" and "RD"

Yeah, check out the chainline, no wonder you're having issues. This is a VERY rough approximation of your "granniest" gear. See how it barely clears the bottom of the FD cage?

Lower that FD. Set it so it just barely clears the large chainring.

I'll betcha this will do the job.
AZORCH is offline  
Old 02-27-12, 09:21 PM
  #16  
noglider 
aka Tom Reingold
 
noglider's Avatar
 
Join Date: Jan 2009
Location: New York, NY, USA
Posts: 40,190

Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem

Mentioned: 495 Post(s)
Tagged: 0 Thread(s)
Quoted: 7026 Post(s)
Liked 1,797 Times in 1,114 Posts
Front derailleurs can be trickier than rears!

It doesn't look like a triple FD.
__________________
Tom Reingold, tom@noglider.com
New York City and High Falls, NY
Blogs: The Experienced Cyclist; noglider's ride blog

“When man invented the bicycle he reached the peak of his attainments.” — Elizabeth West, US author

Please email me rather than PM'ing me. Thanks.
noglider is offline  
Old 02-27-12, 09:36 PM
  #17  
jjhabbs 
Senior Member
 
jjhabbs's Avatar
 
Join Date: Feb 2012
Location: Chicagoland
Posts: 1,742

Bikes: to many to list

Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 250 Post(s)
Liked 572 Times in 181 Posts
easy. Change the middle ring to a 44 or so. Then lower your deraileur to about 2mm above the top ring.
jjhabbs is offline  
Old 02-27-12, 09:57 PM
  #18  
IthaDan 
Senior Member
 
IthaDan's Avatar
 
Join Date: Jan 2012
Location: Ithaca, NY
Posts: 4,915

Bikes: Click on the #YOLO

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 26 Post(s)
Likes: 0
Liked 8 Times in 8 Posts
Originally Posted by jjhabbs View Post
easy. Change the middle ring to a 44 or so. Then lower your deraileur to about 2mm above the top ring.
Serious question: Why do you have to change the middle to lower the FD.

EDIT: OH, I get it. Because the inner cage will hit.

Those giant 110BCD chainrings look kinda odd the more I look at them.
IthaDan is offline  
Old 02-28-12, 09:41 AM
  #19  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 23,931

Bikes: Several, mostly not name brands.

Mentioned: 146 Post(s)
Tagged: 0 Thread(s)
Quoted: 3120 Post(s)
Liked 2,358 Times in 1,391 Posts
Originally Posted by JReade View Post
Half step with granny!
Half-step with granny doesn't like the modern front derailleur designed for modern compact crank; the dropped inner plate interferes with the middle chainring. Replace it with a vintage front derailleur without the dropped inner plate, e.g:



Then lower the derailleur so the outer plate clears the large chainring by only a couple millimeters.
JohnDThompson is offline  
Old 02-28-12, 09:53 AM
  #20  
himespau 
Senior Member
 
himespau's Avatar
 
Join Date: Jun 2008
Location: Louisville, KY
Posts: 13,050
Mentioned: 31 Post(s)
Tagged: 0 Thread(s)
Quoted: 3570 Post(s)
Liked 2,350 Times in 1,394 Posts
Probably a stupid question, but what's the value of the halfstep? I mean I guess it can give you tight spacing for cadence but it seems like it'd be rather limiting to your terrain choices and then you'd have a huge drop to the granny, no?
himespau is online now  
Old 02-28-12, 10:22 AM
  #21  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 23,931

Bikes: Several, mostly not name brands.

Mentioned: 146 Post(s)
Tagged: 0 Thread(s)
Quoted: 3120 Post(s)
Liked 2,358 Times in 1,391 Posts
Originally Posted by himespau View Post
Probably a stupid question, but what's the value of the halfstep? I mean I guess it can give you tight spacing for cadence but it seems like it'd be rather limiting to your terrain choices and then you'd have a huge drop to the granny, no?
The half-step with granny set up allowed for a large number of closely and evenly spaced gears for most riding, and bail-out gears when the going gets steep.

Modern freehubs with ten or more cogs and a compact crank provide a similar range of gearing, but that wasn't possible when you were limited to only 5 or 6 cogs in the back.
JohnDThompson is offline  
Old 02-28-12, 12:41 PM
  #22  
jjhabbs 
Senior Member
 
jjhabbs's Avatar
 
Join Date: Feb 2012
Location: Chicagoland
Posts: 1,742

Bikes: to many to list

Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 250 Post(s)
Liked 572 Times in 181 Posts
That campy front deraileur wont work well with that granny. The one on the bicycle is fine. You dont have to replace the middle to a 44t in order to lower the front deraileur.. You just want to lower it to make it more responsive..
jjhabbs is offline  
Old 02-28-12, 12:56 PM
  #23  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 23,931

Bikes: Several, mostly not name brands.

Mentioned: 146 Post(s)
Tagged: 0 Thread(s)
Quoted: 3120 Post(s)
Liked 2,358 Times in 1,391 Posts
Originally Posted by jjhabbs View Post
That campy front deraileur wont work well with that granny.
Don't tell that to my wife's bike:

JohnDThompson is offline  
Old 02-28-12, 01:20 PM
  #24  
Puget Pounder
Wookie Jesus inspires me.
 
Puget Pounder's Avatar
 
Join Date: Mar 2011
Location: Seattle, WA
Posts: 2,225
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by JohnDThompson View Post
Don't tell that to my wife's bike:

Owned.
Puget Pounder is offline  
Old 02-28-12, 04:16 PM
  #25  
Gear41
Member
Thread Starter
 
Gear41's Avatar
 
Join Date: Feb 2012
Location: Denver, CO
Posts: 37

Bikes: 1989 Schwinn Voyageur | 1987 Trek 400 (sold) | 1984 Trek 520 | 1996 Trek 750 Multitrack

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by JohnDThompson View Post
Half-step with granny doesn't like the modern front derailleur designed for modern compact crank; the dropped inner plate interferes with the middle chainring. Replace it with a vintage front derailleur without the dropped inner plate, e.g:



Then lower the derailleur so the outer plate clears the large chainring by only a couple millimeters.
Okay, I see the difference between this derailleur and the one on my bike. When I lowered the FD, I noticed that the inside plate was uncomfortably close to the middle chainring when shifted into the outer ring.

Switching to an appropriate FD is a good suggestion, but I think I will instead replace the 48t middle ring and possibly the 26t ring also. For now, though, I'll just stay out of the granny gear – no big hills or heavy loads in the foreseeable future anyway.
Gear41 is offline  

Thread Tools
Search this Thread

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

Copyright © 2022 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.