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14

In order of least expensive to most expensive, you either have a misadjusted derailleur, a very worn out cassette, or a crack in your frame. If you're not noticing any problems shifting under normal circumstances, I'd odds are good that your cassette is worn out and your chain no longer meshes with the cogs correctly.


13

Since it only happens when you stand I would say it is definitely a combination of a worn chain and worn chainring, and nothing to do with shifters or derailleurs. As a chain wears, it 'stretches', meaning the distance between the pins in the chain grows. This is a result of the side plates wearing into the pin. Once the chain starts to 'stretch', it starts ...


10

Learning some better shifting technique may solve this. It also could be that, despite your best efforts, the derailers are out of alignment. Two questions: Is the chain falling off on the front chainring or on the rear cogs? If so, is it happening on the inside or outside? (If it's happening in the rear and the chain is hitting the spokes, this can be ...


10

Yes, there is a difference between front chainrings for derailleur equipped bikes compared to bikes without a derailleur. A derailleur suitable chainring is designed to assist the chain climbing onto the chainring, via ramps and pins that the chain engages into. Non-derailleur chainrings are much simpler and are just the straight teeth. To solve your ...


8

I expect that after 10,000 km your chainring also needs to be replaced (frankly, I find it astonishing that you made it that far without replacing anything else. That's amazing.). Am I correct in guessing that you spend most of your time in your middle chainring? If so, it will be significantly more worn than your large or small rings, which would explain ...


7

It is absolutely possible to skid the back wheel, but you really need to be deliberate about it to do it. In this case, however, it sounds like you were applying back pressure to slow down and noticed something surprising, so it was not likely to be the tire skidding. It was probably the cog slightly loosening. If you're going to apply any back-pressure at ...


7

I'd go with the following hypotheses, beyond that already proposed: Your derailer is a bit misadjusted, so the gear is already almost shifting down. When you pedal hard, your frame flexes, thus releasing some cable, and the gear shifts "automatically". This is specially true if you have a brazeon on front part of downtube, then the cable runs outside of the ...


7

Cogs and chains "wear together" (regardless of whether they are front rings or rear sprockets). The old chain does not slip on the ring, because the old chain's rollers are worn down. They have an overall smaller diameter than the rollers of a new chain, and also a different shape: new rollers are cylinders, but worn ones look like small pulleys, they have ...


7

If everything is shifting smoothly and the hanger is aligned, it's very likely the freehub body slipping intermittently, which feels much like the chain slipping. Usually it takes a visual to be sure it's the freehub and not the chain. Different freehub designs call for different procedures to fix and investigate this. The root cause could either be overly ...


6

I would have started by noting which gear (front or rear) is slipping and adjusting the tension on the corresponding shifter/derailleur to bring it closer to correct adjustment. A rule of thumb is, make the adjustment and if it gets worse then you are going the wrong way :-) If the shop changed your chain did they also change the cassette (rear gears). The ...


6

That sounds like the rear cogs are worn, the likely fix is a new chain and set of cogs for the rear (you have to replace them both at the same time otherwise the problem will persist, perversely even worse). I suspect the bike shop fixed/replaced the stuff that was obviously visibly knackered and hoped for the best. In truth I suspect they needed to do ...


5

There are some pitfalls beyond the correctly pointed worn teeth, mentioned by Colin Newell: Derailer hanger might be misaligned, which causes some gears to not properly engage; The "bent" derailer, which was straightened by the shop, might not be totally straight yet, even if it looks so (there is a parellellogram that needs to be perfectly aligned to work ...


5

Assuming it's not been used it probably needs a touch of lube and some adjustment. If your friend only rode it for a month he probably didn't even get the bedding in service done on it. New cables on a bike normally bed in after a little while (time depends on use) and so things go out of line fairly quickly initially which is why bike shops normally do ...


5

Only 500 km from new? Sounds like cable stretch where the inner cable increases in length from new as it beds in. Did you use up your free service? Most new bikes from shops come with a 2-8 week "tweakup" to fix minor things like this. If you bought the bike off the web, then its up you to fix it. Firstly check out your brake line - there should be some ...


4

I would bet for the chain having rusted, leaving some links "locked" and not turning free between each other. Also, if rust built over the sprocket's teeth surface, it can cause the chain to skip under pedal load, bacause the chain doesn't engage properly. I am telling you this because my damn lovely(#@%) cat pissed the cog cluster of one of my bikes, and ...


4

I have experience with DNP freewheels (7 speed, 11-28) and KMC 6-7 speed chains. I had exactly the same chain slip problem (literally word for word) with chain slipping and managed to fix it with great deal of attention to the derailleur setup. You might think that your rear derailleur setup is good because of the evidence provided by good shifting. That ...


4

sounds like your chainrings are worn. Look at the rings and see if they are "shark fin" shaped rather than symmetrical - a google image search for "worn out chainring" will show examples including some really, really worn out rings. The old worn out chain likely wore out the rings as well. I've had exactly what you're describing on a couple bikes and it ...


4

I presume all the new drivetrain parts were replaced close enough together that they were all new or new-ish at the same time. If on the other hand just the chain was replaced, the cassette or rings were highly worn, you rode anyway for some time (say a few hundred miles), and then replaced those too, it's possible you could have put enough wear on the chain ...


4

The freehub was the issue. As it turns out, the bicycle manufacturer (Pinnacle) have issued a recall on the rear wheels of a small number of units of both my bike model (Arkose 4, 2016) as well as another model sharing the same rear wheel (Arkose 4, 2017). It seems there were manufacturing defects in a batch of rear hubs/freehubs, causing the pawls to fail ...


3

There could be several possible reasons for this behaviour - Derailleur could be out of adjustment - can be fixed by barrel adjuster/adjusting the tautness of the shifter cable. You can shift into a cog in the middle of range and visually inspect if derailleur is in line vertically under the cog that chain rests on. When derailleur is properly adjusted, ...


3

I think it could be a few things. Loose / damaged bottom bracket. The play in the crank would cause some ghost shifting. Frame flex or damage. As you stand steel bikes flex, and can cause alignment issues (but should be within reason, unless there is damage loose rear derailleur Check for flex or looseness in the cranks and bottom bracket. Does it wobble?...


3

Yes a new chain can skip in either an old chain ring or old cassette. The length between chain lengths needs to match. So the old chain matched up to the old ring. The new chain does not match up with the old chain ring. I suspect the middle chain ring looks worn. If so for sure time to replace it. What do I need to know to buy new chainrings for ...


3

Assuming that the cabling is clean, that the derailleur is nicely indexed and well alligned, the derailleur hanger not bent, and the chain correctly moves lateraly +/- 4mm for each gear up or down, then I would have a look at the distance between the upper jockey pulley and the sprockets. The distance should be on all sprockets less than 25 mm and more than ...


3

The chain will typically slip under the following conditions: 1. the chain is worn out (this can be measured with a cheap tool, or by your LBS). 2. the cassette is worn out 3. one or more of the chainrings (the cogs on the crankset) is worn out 4. the chain and/or cassette/cogs/pulley wheel are dirty and full of oil/road-grit/gunk. These can occur ...


3

It's possible that during cleaning a grain of sand, for example, has become stuck in the chain causing a stiff link which does not travel cleanly over the cogs. Cleaning chains and cogs often involves a significant amount of moving dirt around before extracting it. A simple test for this is to move the chain through both hands bending every link. You'll ...


3

According to Park Tools: A worn chain shifts poorly and wears sprockets at an accelerated rate. The CC-3.2 is a go/no-go gauge designed to accurately indicate when a chain reaches .5% and .75%, the points at which most chain manufacturers suggest replacement. For 9 and 10-speed chains, replace chain just as the gauge fits the 0.75% side fits flat ...


3

Regarding your second question about exactly how worn a chain has to be before it skips on sprockets that are also worn, I don't believe that a nice clean engineering analysis is possible, because you would need a specific wear model for both the sprocket and the chain. There are far too many variables: alloy composition, heat treatment, and surface finish ...


3

Your lock ring is loose. Normally the cog is quite tight from pedaling and you can do some braking with it. When you brake harder it breaks loose and unscrews until it hits the lock ring. This is what you feel as sliding. The lock ring has left hand thread to keep the cog from unscrewing completely. Now that the cog has tightened against lock ring, the ...


3

Downtube shifters are usually called "friction shifters" and friction is key when fixing the issue you describe. I own and periodically use an old Cannondale with such system. Every now and then I find myself with the same problem as yours. How to fix it? Easy, just tighten the lever of the shifter. Mine came with an integrated metal triangle handle (...


3

What is likely happening (which David and Daniel describe the fix to) is that your rear derailleur has become maladjusted and is moving the chain further outboard--and off the sprocket cluster--than is necessary for your particular cassette or freewheel. In a sense it does "think" there is one more gear since the current adjustment is allowing the derailleur ...


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