Tuning derailleur

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Sclass
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Tuning derailleur

Post by Sclass » Thu Aug 11, 2016 9:33 pm

Hi bike gurus. I just had a very frustrating afternoon trying to get a shimano grip shift system to go through all the gears.

Bought a Diamondback Hybrid bike for $40 on Craigslist. I was trying to replicate a hit I got on a nice mountain bike I bought on CL for $75. There are deals out there but today I got stung a bit.

The bike was a bit rusty but it cleaned up ok. When I got it cleaned I tried riding it and the derailleur out back didn't shift up or shift down. The grip shifter had too much friction.

So I cleaned up the cable and found the rear derailleur was jammed. I dejammed it with penetrating oil and it "seemed" to work. I could swing it back and forth. Felt stiff and gritty. Barely shifted into low and wouldn't shift into high when I released the tension in the cable. As if he return spring was too weak to overcome friction.

So I was at a loss. I gave up on one of these derailleurs before and never got it working perfectly before dumping the bike. This was really frustrating. I was almost ready to post up to you bike gurus here. I just don't know what is important here. Are these things that sensitive? It had the right freedom of movement but just a tad too much friction from grit or junky coagulated lubricant.

I think so. I dunked the entire derailleur, chain and freewheel cassette into the parts wash. It came out grit free and grease free. It not only worked manually in my fingers but it also shifted well as I rode the bike up and down the street.

So I guess what I'm asking is do you guys have to keep these parts super clean for them to function perfectly? They seem very unforgiving. The return spring tension is pretty marginal as is the tension in the cable. It seems to function in a very narrow margin of functionality.

Is this what expensive bike tuneups are all about? (I never got one).

And what do you suggest lubing with? I used Teflon based chain lubr on my old bike. Pedro's chain lube. Gummed everything up after awhile. This bike was full of gummy lube and fine grit.

Thanks.

tommytebco
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Re: Tuning derailleur

Post by tommytebco » Fri Aug 12, 2016 7:35 am

I'm following this. So far, on my own:

1.I have learned that brake cables (compression) don't work well with derailleurs. And, that derailleur cables have their own installation tricks.

2. I would say "yes" that the apparatus is finicky and bike shops charge a lot, but, I don't believe they fiddle with them. They replace them and charge for the parts (much like auto mechanics do.). the easy part is setting the total range of motion. The finicky is fine tuning the shifting to get the "snick snick" type performance of a new bike.

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Gilberto de Piento
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Re: Tuning derailleur

Post by Gilberto de Piento » Fri Aug 12, 2016 8:02 am

When I have derailleur problems I usually replace the cable first and housing second.

Make sure the housing is routed properly - avoid sharp turns. Just because it arrived with the cable routed a certain way doesn't mean it's right.

The derailleur spring isn't designed to overcome any resistance.

Make sure the derailleur hanger is straight. If it isn't you won't ever be able to get it to work right. Make sure there aren't any other problems like a loose cassette or wheel bearing.

Modern drivetrains seem to work well (9/10/11 speed) but some of the old stuff didn't work perfectly in the first place. Don't expect too much. Availability has dried up now but I really liked SRAM 9 speed for price/durability/low maintenance/performance.

Youtube has lots of bike tuning videos.

If you are riding only in dry conditions try a dry chain lube. I like rock and roll absolute dry or gold: http://www.rocklube.com/products.html

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Re: Tuning derailleur

Post by jacob » Fri Aug 12, 2016 8:09 am

http://www.sheldonbrown.com/cables.html

When you had the cable off, the derailer should snap right out to the smallest ring. Like snap! If it's stiff/hesitant, it's still gunked up and the spring is too weak to drive it. The spring supplies 100% of the force. In particular, it might have problems once you put some chain tension on it. Shifting to bigger rings happen with the cable pull. You supply 100% of the cable pull.

They shouldn't really need to be super clean or even marginally clean. However, they shouldn't be completely rusty or full of dirt either. The other thing to consider is that some of the cheap ones just aren't inherently that well-constructed. Also, does it look like it took a hit or got bent or something?

If the cable is stretched/bent/rusted ... especially the cable liner, it can be hard to pull the cable through the liner. Too much friction. The inner cable should move smoothly. You can pour oil down there (like triflow) but you shouldn't need to. Lubing cables is more of a rescue operation. Otherwise the cable is best replaced. Don't use grease. Don't use chain oil. They attract dirt. Since the rest of the bike was rusty, I bet that was the case for the cable housing too?

Expensive (like $85) bike tune-ups if done right is generally a complete reassembly of the bike. They take everything about down to the wheel hub bearings. Disassemble the headset. Clean each part separately, lube or pack with grease where applicable, and then put it back together. Not sure they'd go as far as to disassemble the shifters or the pedals.

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FBeyer
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Re: Tuning derailleur

Post by FBeyer » Fri Aug 12, 2016 8:13 am

My bike mechanic told me that pulling the cables out of the liner at the end of winter, and blowing through with a compressor for a second blows a lot of gunk and salt out of the liner. Doing that every year extends the lifetime of cable and liner significantly.

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Re: Tuning derailleur

Post by enigmaT120 » Fri Aug 12, 2016 1:39 pm

I had to clean mine up this summer, for poor/slow shifting. I use dry lube in the dry summers (except last Monday) but in the winter I use pretty sticky stuff to prevent rust. I suspect it can attract dust when I ride my bike on dry gravel roads.

I also had to replace those little pulleys. My lower one had sharp points. It looked fine to me until I saw the new one.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Fri Aug 12, 2016 10:33 pm

jacob wrote:
If the cable is stretched/bent/rusted ... especially the cable liner, it can be hard to pull the cable through the liner. Too much friction. The inner cable should move smoothly. You can pour oil down there (like triflow) but you shouldn't need to. Lubing cables is more of a rescue operation. Otherwise the cable is best replaced. Don't use grease. Don't use chain oil. They attract dirt. Since the rest of the bike was rusty, I bet that was the case for the cable housing too?
Not sure. I cannot really look in there. I slide the cable back and forth (has one of those crimp ferrules on the end). No rust on the cable.

Not bent. But I washed tons of white lithium grease off the mechanism. There were streaks of grease on the back tire too. Somebody tried hard to lube this thing back to life.

So far so good. Thank you all for the tips. I think I should pull the cable out but I'm afraid to cut off the ferrule tip. I guess eBay sells things like this. Good tip on snap back to the smallest gear. It didn't do that after my excessive cleaning. Dropped to the second highest gear but, it turned out to be the little limit screw setting had been mucked with by the PO.

Good stuff. That spring seems to have the function of dropping the chain to the smallest gear when the tension is released in the cable. I wanted the tension to be higher and the spring restoring force to be higher which is why I wondered about the narrow range of operation. Obviously you cannot have both...or at least I learned that while fiddling.

Oddly that thing dangles down near the ground and picks up fine dirt. I want that perfect shifting of a new bike. Dreaming though, I notice the little wavy cutouts on the side of the cassette rings are worn and won't lift the chain as well anymore.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Fri Aug 12, 2016 10:40 pm

Gilberto de Piento wrote:
The derailleur spring isn't designed to overcome any resistance.
Oh yeah I understand you. What you mean is the spring is only strong enough to move the derailleur when the cable tension is released. It is not designed to overcome excess cable friction caused by rust, dirt or kinks.

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Gilberto de Piento
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Re: Tuning derailleur

Post by Gilberto de Piento » Mon Aug 15, 2016 7:41 am

I guess eBay sells things like this.
If you are going to work on at least a couple of bikes Amazon is a good place to buy things like cables, housing, ferrules in bulk. I used to be really into Pricepoint but they recently closed.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Mon Aug 15, 2016 11:57 pm

Everything is running smoothly now. I was happy to get the old derailleur working again rather than buying a new one. Fun stuff, I actually learned how these things work.

The cable survived too. I thought I got a bad deal on the bike but it looks like I was able to pull it out of the fire. Now I'm not so scared to buy a bad shifting bike off
Craigslist.

wheatstate
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Re: Tuning derailleur

Post by wheatstate » Tue Aug 16, 2016 1:24 am

Just to confirm when you are lubing and checking the cable and housing, have you removed the housing from the frame bosses?
The frame bosses have a thin slot to enable release without tools. With chain on large rear gear, shift to small without pedaling and remove housing from frame (leave housing on cable).

This is the best way to clean and lube the housing and cable. Keeping the cables dry is best. A light lube can revive older parts, but might attract dirt in the long term.

1:20 on the video.
https://www.youtube.com/watch?v=iYiCm-W-nO0

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vexed87
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Re: Tuning derailleur

Post by vexed87 » Tue Aug 16, 2016 9:32 am

For anyone that is curious, the park tools site is fantastic. http://www.parktool.com/blog/repair-help
Pick your part and its in-depth step by step guides help you get things running nicely.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Wed Aug 17, 2016 4:31 pm

wheatstate wrote:Just to confirm when you are lubing and checking the cable and housing, have you removed the housing from the frame bosses?

https://www.youtube.com/watch?v=iYiCm-W-nO0
I slipped the cable out of the braze on things on the frame. But I didn't remove the actual cable from the black casing tube around it. There is a crimped on ferrule that prevents this. The right way looks like somehow removing the ferrule, soaking and blowing out the shield with compressed air and lubricating the bare cable with some light oil.

I might just do this. Sometimes the derailleur fails to drop down to the smallest gear. At that point I do a little bunny hop and the chain clicks down to the smallest gear. There must be just a tad of residual friction in the cable. The cable slides freely in the shield but not quite like a new one.

I was reluctant to cut the ferrule off because I had some trouble on a prior bike with the cable getting all frayed and not wanting to go back in the hole. I kind of remember the pain of getting poked in the fingertip.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Wed Aug 17, 2016 4:36 pm

Ok thanks for that tip. I get it, I don't have to take the cable out. I'll try it like in the video. My bike isn't like his in that there isn't so much exposed cable that I can pull the shield back that much. Let me give it a try though. I was thinking i need to pull the actual cable completely out so I can flush the tube free of grit.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Thu Aug 18, 2016 12:13 am

Well, I tried sliding the cable around and cleaning it without pulling it from the housing like in the video. The bike will downshift but on up shifting where it relies on the spring tension to pull the cable back down the housing it will shift down to the second to smallest gear and no further. A bunny hop gets it to shift to the smallest gear at that point.

I even took the grip shifter apart and cleaned out the part where the cable makes a tight turn.

There is still some residual tension in the cable between 6 and 7 gear. I can tug the open part of the cable on the chain stay and it will pop down to 7. Then I see slack in the cable.

Next step, cut little ferrule of the cable and pull the housing off and clean thoroughly. It is hanging up somewhere around the top tube I think. This is based on the sound I hear as I free it. Tomorrow I'll try the full cable disassembly.

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vexed87
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Re: Tuning derailleur

Post by vexed87 » Thu Aug 18, 2016 6:43 am

Sclass, I sympathise, when I first picked up cycling I had nightmares with a front derailleur. It's probably not worth the hassle of cleaning cables and outers, just replace them, they are dirt cheap. I ride in all weather, wet, dry, salty roads and so its necessary to change these every 12-18 months, expect to do so unless the bike has been ridden and stored in perfect conditions.

If you absolutely must disassemble and re-use cables, you can remove the ferrule with a little force by releasing the pressure from the crimp, but you will have issues re-threading the inner and outer cable if the inner is frayed or bent. Getting the right tension will be tricky if the cable doesn't have plenty of surplus length, particularly if cutting it down to reuse. I always have spare cables in case of these headaches. Just make sure to use a proper cable cutter, and not pliers, I learnt the hard way that's a good way to fray a perfectly good cable.

Are you sure your derailleur spring is not past it's best, or the pivot points simply need lubing? How old is it? Is it rusted? It's odd that this is happening only between 6-7 which would imply its not an issue with cable friction, unless there's a particularly dirty spot! You can give it a thorough clean and try if you have nothing to lose but time and sanity ;)

Also, some older derailleur /shifters just don't shift as smoothly as modern counterparts, the indexing could just be poor on that model. I would douse the derailleur pivots in WD40 too to see if that frees up a stiff pivot. If it's springing back rapidly without the cable attached, that's a good sign that there's nothing wrong with the spring. Another thing to consider is the derailleur hanger alignment, if its out of alignment, you can get weird shifting in particular gears. This tool is pricey, but worth having lying about. My hanger gets knocked in bike racks all the time, it's paid for itself in LBS fees many times over. However, I think this should be a last resort in this case.

In the case of my own front derailleur troubles, in the end, the only thing that sorted it out was buying a new FD to the cost of £15, which I considered worthwhile exchange for smooth shifting.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Thu Aug 18, 2016 8:48 am

vexed87 wrote:
Are you sure your derailleur spring is not past it's best, or the pivot points simply need lubing? How old is it? Is it rusted? It's odd that this is happening only between 6-7 which would imply its not an issue with cable friction, unless there's a particularly dirty spot! You can give it a thorough clean and try if you have nothing to lose but time and sanity ;)

.
Maybe. I'm not exactly an expert on these things. The springs get tired? The derailleur was dirty. Not much rust. I've cleaned it well in the parts washer. Very good point about the problem between 6-7.

I hear you, I would be buying new stuff if I needed to have this working today. But, what I really needed was something interesting to play with and potentially fail at (my new definition of fun requires a finite risk of failure). I could go down to performance and get a pretty dandy new bike...I have a little spare cash. But what fun is that?

Ok, time to stop typing and time to clip the crimp barrel off that cable and pull it out. I think I'll try to braze the stranding together before I put it back in. Thank you for the tip on cutting. I will try to cut with a cutter that doesn't crush the stranding and birds nest it.

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vexed87
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Re: Tuning derailleur

Post by vexed87 » Thu Aug 18, 2016 9:43 am

Yes the springs will fatigue over time, but this takes some serious use, ageing and neglect. If there's no visible damage/rust I doubt it is the spring that's at fault. Far more likely to be a stiff pivot. Failing the cable cleaning/pivot lubing I recommend you try get your hands on a hanger alignment tool, maybe you can borrow one from a friend? It's often been the mystery issue for me.

As I said before, if it's older tech, it could just be naff indexing.

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Sclass
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Re: Tuning derailleur

Post by Sclass » Thu Aug 18, 2016 10:20 am

Wooohooo!!

Houston 6-7 gear is now shifting. I extracted the cable. Sprayed out the shield with lube. Cleaned a couple of small rust spots on the cable. Put it all back together and it works.

So I looked at the grip shifter and I saw a little bend forming where the cable goes into the shield at the adjuster. It looks like it was hanging up there and bending the cable instead of going down the end of the cable shield. I inspected the cable shield under the ferrule and it was mushroomed out. It was impossible to get the cable back down the smashed hole. I bet that constriction was the issue. Probably a messy cut.

I recut the shield...OMG what did they make that out of? Now I know why there was a messy cut. Wire on the outside was really tough and so was he helical wrap inside. The plastic core was all swollen at the end. Finally made a nice cut with aircraft sheet shears. Really I need one of those park tools cable cutters with the hooked blades. Dang that cable is amazing. The bike industry has taken this aircraft line to another level. Like, why is there steel stranding running parallel to the axis of the cable? Must be a reason.

And that is why I love doing this. If I just bought another bike I wouldn't learn anything.

Ok, last thing. I couldn't get hard solder to stick to the cable end before extracting it. To keep it from bird caging I used superglue. I figured it only needed to stay together for assembly. I think I have some electrical wire ferrules I can crimp on the end. They're gold and blingy.

Thank you all for the tips. Wow what a feeling to nail something frustrating.

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Gilberto de Piento
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Re: Tuning derailleur

Post by Gilberto de Piento » Fri Aug 19, 2016 12:11 pm

Nice!
Really I need one of those park tools cable cutters with the hooked blades.
They do work better. Also get a safety pin or similar. The layer of the housing that the cable runs against is made of plastic tube. This plastic tube gets crushed when you cut the housing. The pin is used to expand it again so you can get the cable through more easily.
Like, why is there steel stranding running parallel to the axis of the cable?
Without it the cable would expand and cause shifting problems: http://www.sheldonbrown.com/cables.html

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vexed87
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Re: Tuning derailleur

Post by vexed87 » Sat Aug 20, 2016 6:52 am

Glad you got it sorted. I've heard of people using solder/super glue to prevent cable ends fraying after installation, definitely more ghetto, but you can get 100 ferrules on ebay, 1p each. Good to have in if you plan to maintain your own bike(s).

http://www.ebay.co.uk/itm/100-X-Bike-Bi ... SwQPlV-RzK

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