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

How do I know if the front derailleur limit screws are doing anything?

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 do I know if the front derailleur limit screws are doing anything?

Old 12-07-23, 02:02 PM
  #1  
Newbie
Thread Starter
 
Join Date: Feb 2021
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked 2 Times in 2 Posts
How do I know if the front derailleur limit screws are doing anything?

When I adjust the front lower and upper limit derailleur screws, I don't see the bracket move. I know that my fidgeting with the screws does something, but I don't visually see the bracket moving. What am I doing wrong here? And how do I tell apart the lower limit screw from the upper limit screw?I am working on a low-end Shimano derailleur...Thanks!
nvossoug is offline  
Old 12-07-23, 02:13 PM
  #2  
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Posts: 9,796
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 780 Post(s)
Liked 674 Times in 358 Posts
The limit screws donít move the derailleur cage, they limit how far the cage is moved by the cable. The best way to see this in action is by putting the bike on a repair stand and shifting the chain with the shift levers. If the chain doesnít shift to the chosen chainring or if it shifts too far, then you need to adjust the limit screws.
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline  
Likes For Jeff Wills:
Old 12-07-23, 02:14 PM
  #3  
Insane Bicycle Mechanic
 
Jeff Wills's Avatar
 
Join Date: Mar 2008
Location: other Vancouver
Posts: 9,796
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 780 Post(s)
Liked 674 Times in 358 Posts
This should help you sort out what you need to do:

https://www.parktool.com/en-us/blog/...eur-adjustment
__________________
Jeff Wills

Comcast nuked my web page. It will return soon..
Jeff Wills is offline  
Likes For Jeff Wills:
Old 12-07-23, 04:28 PM
  #4  
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,384

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: 138 Post(s)
Tagged: 1 Thread(s)
Quoted: 5620 Post(s)
Liked 2,241 Times in 1,256 Posts
They're called "limit" screws because that's exactly what they do ----- Establish the limits for travel. If the RD (or FD) were an elevator, the limits would be set so it can't crash into the roof or basement. However, for both elevators and derailleurs, the actual position depends on the cable they are hanging from.

On your bike, the easiest way to check the limits is to shift to RD high (or FD to low) then ignore the lever, and tug the bare cable away from the frame. If the limits are right the cage will move between the freewheel sprockets or chainrings but not overshoot at either end.

Last edited by FBinNY; 12-07-23 at 05:40 PM.
FBinNY is offline  
Likes For FBinNY:
Old 12-07-23, 07:39 PM
  #5  
Senior Member
 
Join Date: Dec 2020
Location: Wake Forest, NC
Posts: 5,369

Bikes: 1989 Cinelli Supercorsa

Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 3255 Post(s)
Liked 2,675 Times in 1,622 Posts
You would be able to see the cage move if it was in contact with either limit screw, either high or low, and you tightened that particular screw.
smd4 is offline  
Likes For smd4:
Old 12-08-23, 08:06 AM
  #6  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,603
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4138 Post(s)
Liked 1,323 Times in 863 Posts
General comment:

If you don't know how the derailleur works or is adjusted, the chances of you correctly fixing it are very low. Read the instruction manual for that model derailleur (available online by model number), get some help from a more experienced buddy or take it to a shop. Basic front derailleurs have 5 parameters necessary to function correctly, and newer Shimano derailleurs have more like 9.
Kontact is offline  
Likes For Kontact:
Old 12-08-23, 08:18 AM
  #7  
Newbie
Thread Starter
 
Join Date: Feb 2021
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked 2 Times in 2 Posts
My thing is that I enjoy the challenge of repairing the bike myself. Plus, I have three kids and can't afford to pay for repairing 5 bikes every couple of months. Or even paying for one.

The other posts have proven very valuable.
nvossoug is offline  
Likes For nvossoug:
Old 12-08-23, 08:28 AM
  #8  
Senior Member
 
Join Date: Oct 2008
Location: Northern NY...Brownville
Posts: 2,525

Bikes: Specialized Aethos, Specialized Diverge Comp E5

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 222 Post(s)
Liked 422 Times in 242 Posts
Keep 'fidgeting', I'm sure you're doing it correctly...
Kai Winters is offline  
Likes For Kai Winters:
Old 12-08-23, 08:28 AM
  #9  
Senior Member
 
Trakhak's Avatar
 
Join Date: Jan 2005
Location: Baltimore, MD
Posts: 5,181
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 2333 Post(s)
Liked 2,755 Times in 1,574 Posts
Originally Posted by nvossoug
My thing is that I enjoy the challenge of repairing the bike myself. Plus, I have three kids and can't afford to pay for repairing 5 bikes every couple of months. Or even paying for one.

The other posts have proven very valuable.
Three kids, at least one of them on a bike with a front derailleur---learning to do the adjustments is a very good idea. Especially if any of them are at an age where fooling around with bike adjustments (when you're not looking) seems like fun.
Trakhak is offline  
Old 12-08-23, 08:36 AM
  #10  
Senior Member
 
Join Date: Jan 2009
Location: San Diego, CA
Posts: 3,613
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 829 Post(s)
Liked 1,028 Times in 724 Posts
Originally Posted by nvossoug
My thing is that I enjoy the challenge of repairing the bike myself. Plus, I have three kids and can't afford to pay for repairing 5 bikes every couple of months. Or even paying for one.
There are tons of YouTube vids on how to do just about anything on your bike so they can be very helpful. "Park Tools" do some very good how-to vids as well as some that show you how a component works. "RJ the Bike Guy" is another good source for vids and usually works on used parts with a little dirt on them just like us home mechanics will do and offers ways of making some of your own tools if you don't want to spend a bunch of money on special bike tools. Plenty of other vids from other sources but these two I can vouch for.
Crankycrank is offline  
Likes For Crankycrank:
Old 12-08-23, 08:42 AM
  #11  
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 17,908

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4127 Post(s)
Liked 3,700 Times in 2,219 Posts
When advising newbies in learning how to maintain/understand their bikes, besides suggesting what others above here have mentioned, I often suggest that one finds a "curb lawn" bike to do the initial efforts on. If one screws things up it won't mater. The basic principles of der function are the same across the price range for the most part. So to for brakes, spokes wheels and more. The learner bike won't care if one takes weeks to do a job on it. It won't care if all one does is to look at it for 5 minutes while the dinner pasta water is heating up. When the time comes to work on bikes that are in use the repairs will go faster and often be less frustrating.

Many ft ders (and rears) are constructed so one can view the parallelogram link tabs that contact the limit screw ends. If the cable is exposed one doesn't even have to pull a lever to move the cage in and out. If the ends of the limit screws are hidden (and some are) one can hold the cage at it's outer most travel point and at the same time turn one of the limit screws to feel if that's the one controlling the outward travel. By keeping that cable taut one can often feel the change in cable tension or pull with the screw moving the tab. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Likes For Andrew R Stewart:
Old 12-08-23, 09:09 AM
  #12  
Newbie
Thread Starter
 
Join Date: Feb 2021
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked 2 Times in 2 Posts
Thank you all for your very helpful suggestions! What I find most amazing about the bicycle is how much of an art the repair process is.

Robots won't be replacing bicycle maintenance anytime soon.
nvossoug is offline  
Likes For nvossoug:
Old 12-08-23, 09:20 AM
  #13  
Senior Member
 
Trakhak's Avatar
 
Join Date: Jan 2005
Location: Baltimore, MD
Posts: 5,181
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 2333 Post(s)
Liked 2,755 Times in 1,574 Posts
Originally Posted by nvossoug
Thank you all for your very helpful suggestions! What I find most amazing about the bicycle is how much of an art the repair process is.

Robots won't be replacing bicycle maintenance anytime soon.
Post of the day. Never thought of that!
Trakhak is offline  
Old 12-08-23, 10:09 AM
  #14  
Newbie
Thread Starter
 
Join Date: Feb 2021
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked 2 Times in 2 Posts
Yeah, it is striking to me how non standardized the bicycle is. The range of spoke sizes alone is astonishing. And the process of tensioning the spokes can't be routinized the way you can lug nuts on a car wheel.

​​​​​​I got the front derailleur mostly right by realigning the front derailleur cage and then playing around with the limit screws. Thanks again!
nvossoug is offline  
Old 12-08-23, 08:28 PM
  #15  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,603
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4138 Post(s)
Liked 1,323 Times in 863 Posts
Originally Posted by nvossoug
My thing is that I enjoy the challenge of repairing the bike myself. Plus, I have three kids and can't afford to pay for repairing 5 bikes every couple of months. Or even paying for one.

The other posts have proven very valuable.
How is advising you to read a manual instead of blundering around in the dark have no value?
Kontact is offline  
Likes For Kontact:
Old 12-08-23, 08:36 PM
  #16  
Senior Member
 
Join Date: Dec 2020
Location: Wake Forest, NC
Posts: 5,369

Bikes: 1989 Cinelli Supercorsa

Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 3255 Post(s)
Liked 2,675 Times in 1,622 Posts
Originally Posted by Kontact
How is advising you to read a manual instead of blundering around in the dark have no value?
Probably the way the message was delivered had some negative effect.
smd4 is offline  
Likes For smd4:
Old 12-08-23, 08:49 PM
  #17  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,603
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4138 Post(s)
Liked 1,323 Times in 863 Posts
Originally Posted by smd4
Probably the way the message was delivered had some negative effect.
I suppose politely encouraging people to screw up their bikes by continuing to guess is always the most comforting thing to hear.

People don't start screwing with limit screws for no reason. The OP has a derailleur that isn't shifting correctly, and explaining only a single part of derailleurs work is a disservice.
Kontact is offline  
Likes For Kontact:
Old 12-08-23, 10:19 PM
  #18  
Really Old Senior Member
 
Bill Kapaun's Avatar
 
Join Date: Feb 2007
Location: Mid Willamette Valley, Orygun
Posts: 13,767

Bikes: 87 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.

Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 1749 Post(s)
Liked 1,189 Times in 827 Posts
Originally Posted by nvossoug
When I adjust the front lower and upper limit derailleur screws, I don't see the bracket move.........
DON'T "make" the bracket move by turning screws. The metal in the DER body is very soft vs the STEEL screw threads.
"Pull" the DER off the stop to relieve tension/force and then turn the screw.
The screw heads are a JIS Phillips. Not our "usual" Phillips. That's why the screw heads are getting screwed.
Bill Kapaun is offline  
Likes For Bill Kapaun:
Old 12-08-23, 10:34 PM
  #19  
Senior Member
 
soyabean's Avatar
 
Join Date: Feb 2022
Location: GMT-5
Posts: 794
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 457 Post(s)
Liked 367 Times in 243 Posts
Although it's relatively safe to adjust the FD-L screw while the shifter+chain is on the smallest ring, since the cable is slacked, attempts to adjust the FD-H screw while the shifter+chain on the largest ring, as the cable is taut, can strip out the threads of that screw, as well as bend the FD.
soyabean is offline  
Likes For soyabean:
Old 12-09-23, 03:36 AM
  #20  
Newbie
Thread Starter
 
Join Date: Feb 2021
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked 2 Times in 2 Posts
Originally Posted by Kontact
How is advising you to read a manual instead of blundering around in the dark have no value?

​​​​​​It is very valuable information. thank you for the tip!
nvossoug is offline  
Old 12-09-23, 09:56 AM
  #21  
Senior Member
 
Join Date: Mar 2012
Posts: 937
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 488 Post(s)
Likes: 0
Liked 604 Times in 334 Posts
Originally Posted by nvossoug
​​​​​​It is very valuable information. thank you for the tip!
Here is a critical skill for any bike mechanic to develop: look closely at the part you are working on. In this example, you would be able to see the "working end" of the limit screws and see where they contact the derailleur ONLY at the "limits" of travel. From that, you would be able to understand what their purpose is and how they work and how adjusting them when they are not touching anything would not have any effect. As Yogi Berra so wisely stated: You can observe a lot by watching.
KerryIrons is offline  
Likes For KerryIrons:
Old 12-09-23, 10:26 AM
  #22  
Senior Member
 
Kontact's Avatar
 
Join Date: Apr 2011
Posts: 6,603
Mentioned: 41 Post(s)
Tagged: 0 Thread(s)
Quoted: 4138 Post(s)
Liked 1,323 Times in 863 Posts
Originally Posted by KerryIrons
Here is a critical skill for any bike mechanic to develop: look closely at the part you are working on. In this example, you would be able to see the "working end" of the limit screws and see where they contact the derailleur ONLY at the "limits" of travel. From that, you would be able to understand what their purpose is and how they work and how adjusting them when they are not touching anything would not have any effect. As Yogi Berra so wisely stated: You can observe a lot by watching.
At that point you might also note that the stops have little to do with shifting itself, and are rarely involved in fixing poor shifting performance.
Kontact is offline  
Old 12-09-23, 11:53 AM
  #23  
don't try this at home.
 
rm -rf's Avatar
 
Join Date: Jan 2006
Location: N. KY
Posts: 5,885
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 955 Post(s)
Liked 457 Times in 322 Posts
Originally Posted by nvossoug
My thing is that I enjoy the challenge of repairing the bike myself. Plus, I have three kids and can't afford to pay for repairing 5 bikes every couple of months. Or even paying for one.

The other posts have proven very valuable.
I really like doing my own maintenance. The Park Tool guides are the first thing I look at. They start from the beginning,showing each step, no prior knowledge needed.

When derailleurs are out of adjustment and a slight turn in the correct direction of a barrel adjuster doesn't fix it, I like to start from scratch using the Park Tool guide. This involves checking derailleur cage parallel, the clearances to the cog/chainring, adjusting the limit screws, then finally adjusting the shifting itself.

Limit screws: these screws usually hit a spot to bottom out on the derailleur, which limits movement in that one direction. For some reason, they don't often get marked H and L. Shift to the biggest cog, then look at the screw end, not the tool socket end. One screw will be very near part of the derailleur body, the other will have a big gap, since it's for the other limit.

~~~
Tool guides show the correct steps to make an adjustment.

For example, adjusting a stem is quite simple, once you know the process. But it's just not obvious at first, by a visual inspection. The cap is only for setting the bearing preload, not at all for tightening down a loose headset. Follow the correct steps, and it's simple and accurate.

Last edited by rm -rf; 12-09-23 at 12:00 PM.
rm -rf is online now  
Old 12-09-23, 04:37 PM
  #24  
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 17,908

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4127 Post(s)
Liked 3,700 Times in 2,219 Posts
"For example, adjusting a stem is quite simple, once you know the process. But it's just not obvious at first, by a visual inspection. The cap is only for setting the bearing preload, not at all for tightening down a loose headset. Follow the correct steps, and it's simple and accurate." rm -rf

And this would be especially hard to discern if one had a quill stem Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Likes For Andrew R Stewart:
Old 12-09-23, 08:40 PM
  #25  
Senior Member
 
Join Date: Apr 2007
Posts: 6,697
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 1064 Post(s)
Liked 1,142 Times in 729 Posts
I'm not a professional mechanic and don't claim to be an expert, but based on my own experience as a home mechanic, I usually recommend that until adjusting a front derailleur becomes second nature, always use either a good online guide (Park is almost always good) or the derailleur installation/adjustment instructions.

Start at STEP ONE and proceed step by step. Don't skip anything. Even if STEP ONE requires you to remove the cable and derailleur and re install from the beginning. This will almost always work well for a beginner and won't get you balled up figuring out what's going wrong among the various adjustments that are made (derailleur height, alignment, cable tension, limit screws, etc.)
Camilo is offline  

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.