Tech Talks: Derailleur Limits and Cable Tension, Presented by Park Tool - Video

Jan 26, 2017
by Pinkbike Staff  
Tech Talks Presented by Park Tool


Tech Talks Presented by Park Tool is a monthly video series hosted by Park Tool's own wrench whisperer, Calvin Jones. The series will cover the A to Zs of some of the most prevalent repair jobs, with the seventh episode demystifying derailleur limits and cable tension.

Contrary to what it sometimes seems like, your derailleur is not controlled by a mix of witchcraft and luck, but rather by cable tension and limit screw settings. Those two things are independent of one another, but they also both need to be adjusted correctly in order for your shifting to work properly. Below, Calvin Jones explains how limit screws and cable tension affect your shifting, as well as how and when to adjust them.


Tech Talks - Derailleur Limits and Cable Tension


Views: 12,023    Faves: 74    Comments: 1



Need more Calvin in your life?
Episode #1 - Tubeless tire installation and conversion
Episode #2 - Saving that bent disc rotor
Episode #3 - Derailleur hanger alignment
Episode #4 - Shimano and Crankbrothers pedal service
Episode #5 - Trailside wheel repair
Episode #6 - Trailside chain repair

Stay tuned for more mechanical how-to videos with Calvin returning on the last Thursday of every month to show you the easiest way to get the job done. Want to know more? Park Tool's how-to section has you and your bike covered.

www.parktool.com / @ParkToolCompany


60 Comments

  • + 95
 Quit teaching people how to steal my 14 dollar an hour job from me geez!
  • + 1
 That's the 14$ an hour dream job that I can't even when I applied everywhere.
  • + 32
 Very informative video for beginners or people that are generally interested. Calvin always does a great job explaining everything. It's also worth it to mention that there are other factors that contribute to a poor shift as well. These are just the basics.

Corrosion on cables or deteriorated housing can cause poor shifting and are common issues. Especially for bikes that don't have a full run of housing from shifter to derailleur. Even if the exposed cable doesn't have rust/corrosion, inside the housing could be different.

Also check for proper routing, kinks, breaks or if the housing is too short.
  • + 2
 +1 on the cables. I may convert the fiance's bike to full housing at the next change out.
  • + 6
 For real! People always mess with the tension and high/low screws and don't realize that a tiny kink in the cable or a little bit of oxidation on the cable inside the housing plays a HUGE role in shifting performance.

A little lube down the cable housing when replacing a cable goes a long way for smooth shifting.
  • + 3
 @Kenfire24: Depending on the cable quality and type I shy away from dumping dirt/dust-collecting lube in the housing. I know Shimano cable housing comes pre-lubed, but in my brain it's the ingress of junk that causes the problem, not the cable inner itself. Hence why I may go full housing on the fiance's bike...keep that junk out in the first place and you'll have fewer problems.
  • + 3
 @iammarkstewart: Same here. I always think that lubing the cable is just going to attract more crap in there. If its clean the cable should slide just fine in the housing without it.
  • + 6
 Unless someone has messed with them or they were never set properly when the bike was built they shouldn't need to be changed, unless a wheel is swapped. most common is the derailleur hanger is out of alignment. 90 percent of the time the hanger is out and then people try to adjust the cable and limits to compensate. Nothing will run properly til the hanger is aligned, once aligned cable tension and limits are going to be wrong if you messed with them and you have created more work. Gee my bike was running good then it fell over or i crashed, then my gears didn't shift properly let me mess with the limit screws that should fix it, telling people the basics without the previous basics is a disservice in my mind. painful to watch for anyone who knows what they are doing. most bikes from the factory have a bent hanger to some degree. A low end bike with a straight hanger shifts better than a high end one with a misaligned one.
  • + 6
 To lube or not to lube cables? This may depend on how straight your gear line is. If if suffers from any tight bends due to your suspension design you are better off with lube to stop it wearing into the cable outer. If you are running full length outer cables you shouldn't worry about getting dirt in there.
  • + 1
 @Kenfire24: Also I run full housing
  • + 1
 @RideWonderlandSquamish: cables stretch putting gear shifting out slightly
  • + 1
 @Ghp-Bmx: sorry meant limit screws
  • + 2
 @iammarkstewart: on my bikes I use dry lubes. Most of the bikes that I deal with at the shop are not high-end bikes that see off-road use. Typically they're people who ride on rail trails and around town. I won't disagree though, lube is not always the answer.
  • + 1
 @Kenfire24: Gotcha. I'm a noob-level tech with mostly box-store experience. I dealt with the same demographic of bike but it was all or nothing...either completely abused/neglected (read: unsaveable) or diy'ers who used too much of whatever lube was in the garage on everything.

To your point, in the hands of the competent individual with the experience to dictate actions, lube can be the answer. For a lot of stuff...
  • + 2
 @iammarkstewart: It's good practice to put dry lube on cables that have any friction. Usually it's best to recommend switching cables and housing to the customer but if they're trying to keep costs low, dry lube doesn't hurt, when used properly, in those scenarios

On bikes that have exposed cable with too much friction, I always take the housing out of the housing stops and drop a few drops down the housing and slide it up and down the cable. It cleans out any dust from corrosion. If there's a lot, use WD-40 carefully to clean out the housing and then lube it after. You can take some sand paper and lightly sand down any rust off of the cables as well.

Keep in mind there are some cables that you shouldn't put lube on. Shimano has a few cables that have PTFE coatings that act as lubrication. They recommend as soon as the coating wheres off or enough of it has strung out and bunched up, to replace it. (if you haven't seen these cables, it looks stringy when the coating starts coming off. It can bunch up when it enters the housing)
  • + 1
 @scotty1212: Totally reasonable approach. I usually don't have too many problems with my cables but I'm putting this dry lube process on my trouble-shooting/fix list if I end up with cables giving me grief.

Side note: I get customer needing to keep costs low, but when I see any rust on the cable I usually suggest it's mandatory or else I can't guarantee how long the "fixed" cable will last. Of all the things on the bike, the small dollars spent on a new cable/housing can get you the best return on performance, especially when there's rust involved.
  • + 14
 While Calvin mentions it, I think the sequence is misleading. From where I sit, there's absolutely no value in adjusting limit screws or even cable length, until you're absolutely sure that the hanger is square both vertically and horizontally. It's the first item to check before touching anything else. Otherwise you're liable to make a number of adjustments only to find that it still doesn't shift properly, and then you're going to have to make those same adjustments all over again after addressing the hanger issue.
  • + 3
 You beat me to it by a few minutes but good to see who is thinking the same thing,
  • + 3
 @RideWonderlandSquamish: Yeah when shifting goes to shits, first thing to do is check for bent whatever. Usually you can just eye it from behind, or go buy the expensive dish tool. Next inspect the cable and housing. Index housing always fray at the end, so pull out the cable and cut clean ends, add new ferrules. Then using just your thumb push the mech to set your stops/walls. Put the cable back on snug, with barrel a few turns out. Tweak, go ride! Also don't ever use the black teflon coated cable, it sheds and ruins everything.
  • + 3
 Correct crank spacing on a 1x setup would be another recommendation when setting up a new bike. Wasted 20 min on derailleur adjustment only to realize the chainline was all screwed up due to putting in the recommended spacer on the drive side.
  • + 10
 just found out on watching PB vids, if you push the letters J or K on the keyboard. you can watch it by frames. that's really cool so you can watch every move a rider makes and stuff
  • + 6
 Best way to set up your rear derailluer, disconnect the shift cable and set your limit screws first by manually moving the derailluer. Then reattach the cable and adjust the cable tension for clean shifting. This way you will never shift your derailluer into the spokes while adjusting. If your release shifting is slow then you most likely need a new cable and housing.
  • + 6
 these videos are the "Bible" of bike wisdom
  • + 3
 What? Nobody has mentioned gearboxes yet?! Well well well, what are drivetrains on PB coming to...

Mech hangers can go to hell, but yes, they're the first thing to check when your gears are dodgy.
  • + 2
 While Calvin mentions it, I think the sequence is misleading. From where I sit, there's absolutely no merit in making either limit screw or cable length adjustments until you're 100% sure that the derailleur hanger is square (both vertically and horizontally). Otherwise you'll find yourself making a number of adjustments to the derailleur only to find that it still doesn't shift properly, and then you'll have to make those same adjustments all over again after addressing the hanger issue. Hanger FIRST, then worry about the derailleur.
  • + 2
 I too believe that derailleur adjustment is witch craft and luck because everytime I felt the need to adjust, the witch craft fooled me and I had no luck. Case in point. I went riding a week ago and in the middle of my ride, the adjustment went way out of wack. Came home to adjust the derailleur and nothing seemed to keep it tuned. I worked on it for hours. Going back and watching videos, thinking I'm missing something. Well, low and behond, I started to refocus and decided to at least get my chain lubed. This is when I noticed my master chain link was bent badly, probably from sliding down a rock face or something on that ride. The link kept pushing the cable up and down between 2 gears. I went out and bought a new one, did some minor adjustments and bam, I got er fixed. So kids, lesson learned. Check your chain if your adjustments aren't panning out the way you think they should.
  • + 1
 I switched to a 42T (10 speed) and 1x. I have a Shimano derailleur. The B screw (I think it's called) is maxed out, but it shifts well and everything still works good. My question is - is there danger in over B screwing? Or am I ok with it maxed and it won't hurt the derailleur?
  • + 1
 No danger as long as the upper pulley doesn't hit the big cassette ring when you shift from 2 (2nd biggest gear) to 1 (biggest gear). I've seen several bikes where the upper pulley doesn't rub the big gear when its in gear, but it bounces off of it on the shift. Kinda confusing to explain with words.
  • + 2
 Depending on what derailleur you have, it can have some issues. If you have a derailleur that was designed before the era of larger range cassettes, you may have some issues.

The issue you'll have is since you've adjusted the b-tension so the derailleur won't contact that largest cassette cog, It now puts the derailleur further away from the smaller cogs.

This may not be an issue but depending on the wear and age of your drivetrain, It can make adjusting your gears more finicky. It may also make your drivetrain go out of adjustment more often as well. Another issue you may have, since the screw is dialled most of the way in, the B-tension screw may slide off of the derailleur hanger(or what the screw contacts) that it's supposed to push against.

The new derailleurs that have the appropriate range, climb the cassette at a different angle than previous gen so it can be as close as possible without contacting the largest cogs.
  • + 2
 @scotty1212: it's a 2016 slx, don't think it's large cog specific. I read that shimano derailleurs would need a larger B screw for it to work but mine didn't, shifts very well with stock screw fully turned in. Just didn't want any long term issues which it looks like there won't be any.
  • + 4
 @zombiejack33: On Shimanos website, all the SLX RD-M670/M675-GS and SGS cages have a listed maximum sprocket of 36 teeth. It can be used outside of that range, they just say it isn't optimal. It won't destroy your drivetrain, it just wasn't designed to be used with large range cassettes.

The issue with using a longer B-tension screw is that it still puts the derailleur too far from the smaller cogs. If you're going through rough terrain, you may jump gears. It's not as bad as what i'm explaining though. Many people have modified their cassettes using one-up conversions and I've actually tuned a bike that had an oval chainring with a one-up conversion in his cassette. It worked perfectly fine after I adjusted it. I'm a bike technician and have taken shimanos s-tec courses. I think you'll be fine.
  • + 1
 @scotty1212: thanks for the help! Much appreciated!
  • + 1
 @scotty1212: Didn't even cross my mind, but since you mention it, if its a full suspension bike that 36 tooth count is closer to 34 with the suspension fully compressed.
  • + 1
 @gordon2456: I think you're thinking of capacity. Capacity is mainly a concern if you're running a front derailleur. Since the derailleur cage is a certain length, it only works with a certain capacity difference.

That's why shimano makes GS and SGS cage options. GS is a medium cage capable of doing 1x and most 2x options and SGS is for 3x.

The suspension curve only affects chain length. The jockey wheel placement barely moves in relation to the wheel through suspension travel. The pivot between the axle of the rear wheel and where the derailleur attaches to is too small for a suspension curve to affect it.

Even if it did affect it, it still would have the same space between the cassette and jockey wheel as it would when the travel is neutral because the cassette is a circle and the derailleur would pivot around the wheels rear axle since it's in a fixed position.

Hope that makes sense lol.
  • + 2
 I know all you guys posting here know this, but... Make sure all the hanger attachment screws are tight and that the hinge rivets aren't sloppy before adjusting anything.
  • + 1
 Why has no one mentioned how much Calvin looks like Frank Zappa???? He did mentioned the tension of guitar strings. Maybe Frank's long lost brother? Great step by step instruction
  • + 1
 I see at least 6 spoke tools hanging on their wall. Are there really that many different sized nipples? I always thought it was 3 or 4 different sizes.
  • + 3
 Mavic. Plus torx heads. Must be more than 6
  • + 1
 Double post, see below...
  • + 1
 @gordon2456: I was trying to sum up why there are more than 3-4......
  • + 3
 I wish they would put the barrel adjuster back at the derailleur end.
  • + 2
 There used to be one there...
  • + 0
 Then you couldn't make adjustments on the fly. They're better at the shifter for the rider, and better at the derailleur for the mechanic!
  • + 1
 @thebikings: That is the idea of the barrel adjuster at the shifter end to make minor adjustments on the fly! the adjuster at the derralleiur was easier to use with the left hand.
  • + 2
 These videos are very helpful. Thank you, Calvin and Pinkbike.
  • + 2
 Thanks for posting these videos!
  • + 1
 Can you tell me how to fix my dog shit syntace hanger on my norco range so it's straight, and stays straight?
  • + 2
 I want this guy to work on my bike
  • + 2
 These are really great.......thank you Pinkbike and Park Tools!
  • + 2
 I quite like these Tech Tuesday, keep them coming Smile
  • + 1
 Maintaining drivetrain crispness and precision - my arch nemesis for 10 years and going strong.
  • + 1
 Derailleur Limits. They're even going for the subconscious now?
  • + 1
 Damn, Mike Levy really grew old.
  • + 1
 That is an old school XTR!
  • + 1
 Calvin is getting sassy this week! Love it.
  • + 1
 i want to hear the goldilocks story!!!
  • - 2
 I imagine that since the front derailleur has gone the way of the dodo, we wouldnt need to show people how to adjust those....
  • + 1
 To be fair it is kind of similar...
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