Workshop Stories: The Drive Train Sequel

[slowtwitch]

SO we've discussed at length the correct method of measuring chain wear to ensure more happy miles than what a commercial chain measuring tool allow us. <?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

The next step is to ensure cassettes and chainrings are still in good nick so as not to chow up our chains.

 

Besides using the blue Park tool  chain measuring tool's rounded end, what is the other way of checking wear of cassettes and blades?

[splat]

A well trained eye?

Common sense?

Experience?

 

What if you are limited in all of the above? (like me)

 

[Gasping]

A well trained eye?

Common sense?

Experience?

 

What if you are limited in all of the above? (like me)

 

 

Like a lot of us Splat.

 

You are  not alone.

[Matchstix]

as hy gly is hy in sy tjops in

[Gasping]

as hy gly is hy in sy tjops in

 

All this technical jargon makes my head spin.

[Johan Bornman]

SO we've discussed at length the correct method of measuring chain wear to ensure more happy miles than what a commercial chain measuring tool allow us. <?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

 

The next step is to ensure cassettes and chainrings are still in good nick so as not to chow up our chains.

 

Besides using the blue Park tool  chain measuring tool's rounded end' date=' what is the other way of checking wear of cassettes and blades?[/quote']

 

The beauty of it all is that chains wear cassettes and chainrings, not the other way around.

 

Therefore, you NEVER have to worry about cassette wear until your new chain skips on an old cassette.

 

In the front, you can pretty much ride it until it needs a set of false teeth - unless on your MTB you get chainsuck, then you replace the ring that sucks, not the others.

 

 

[slowtwitch]

Kom nou Johan, met al jou 1/100ste van mm akuraatheid is daar sekerlik 'n meer tegniese andwoord as daai een?

[Johan Bornman]

OK, you ask so nicely:

 

 

Everything you need to know about Bicycle Chains<?: prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Bicycle Chain Glossary

Pin. Short rod that holds the links together and supports the roller.
Sideplate (inner and outer)  Flat, camphered pairs of metal plates with holes for accommodating the pins and in the case of the inner plates, with a collar for supporting the roller.
Roller. The floating cylindrical inner part of a chain shaped to mesh with cogs.
Pitch. The distance from tooth to tooth or link to link.
Driving sprocket (chainring). The sprocket attached to the crank.
Driven sprocket. Rear sprocket, receiving force via the chain, from the driving sprocket.
Idler pulley. A pulley tensioned by a spring, designed to take up slack in a chain. On bicycles, also known as jockey wheels.
Sprocket. A flat gear with many cogs.
Chainring. A specific bike sprocket ? the front sprocket.
Cross-chain. The act of engaging front and back sprockets diagonally far away from each other i.e. large and large or small and small.
Chain suck. A front chain wheel that doesn?t release the chain at the beginning of its return cycle.
Collar ? the flange on the inside sideplate that supports the roller.
Cog: - Single tooth on a sprocket.

The bicycle chain needs no introduction. On second thoughts, listening to the many misconceptions about bike chains bandied about on the average Sunday muffin-run, it does need introduction. Most of us can vaguely define its function: to make the back wheel turn when we turn the cranks. We also know that it is the filthiest part on a bicycle and consequently the only exposed part we avoid contact with. I?ve seen bike owners caress stems, frames and saddles, but never a chain, not even a new chain. No-one brags about their bike?s new chain or even point it out to their mates. It?s a bit like a saddle-sore, no-one cares about it.

You should care. Riding with a chain past the prime of its life is expensive. Worn chains eat sprockets which cost between R240 and R900 per meal. Changing your chain at just the right time, saves you money. Change it too often, and you waste money. Abusing your chain is hard on sprockets and the chain itself. Minor riding style adjustments can money and improve your chain?s reliability.

Therefore, let?s start with a formal introduction of the common bicycle chain. What does it do? It transfers torque generated by the legs, to the rear wheel. Without a chain, you?ll end up with a direct drive system like that of a high-wheeler, which was abandoned because of its serious safety flaws and inability to change gears. Gears? there?s another function of the chain. It?s laterally-flexible design allows you to, by means of the derailleur, move the chain to adjacent sprockets, a process known as changing gears. Single-speed bikes, track bikes and motorbikes have rigid chains designed not to flex sideways, improving their ability to stay on the sprocket.

Function-wise, that?s about it.

The chain is invariably coated with black, sticky oil that readily traps grit. This black substance that appears in the oil from apparently nowhere is a tiny amount of steel worn off the chain. A small amount dies a lot of oil quickly makes chain oil black. This is a good sign and means that the oil is mobile i.e. flows back in after being squeezed out of the pin/sideplate interface during a stress cycle. Wax lubricants are not mobile and once forced out of an interface; remains out and hence doesn?t transport worn steel particles. The upside, which is what manufacturers punt, is that the chain stays clean. What they don?t tell you is that a clean chain is a chain without lubrication.

 In many ways the chain is the most vulnerable component on the bike ? out in the open, smeared with sticky oil and ready to receive and process destructive grit. Equally so, we also have to pay some tribute to its durability and strength. It is the one wear part on a bike that takes the most punishment, yet seldom fails on a ride.

From time to time we shift carelessly and the chain protests by derailing itself and jumping off the chainring, but that?s easily rectified by even the most novice of cyclist ? grab it from below the chainring, pull it forward by taking up spring slack from the rear jockey and replace it on the chainring closest to the current front derailleur setting. You?ll end up with greasy black fingers, but that?s why you should never, ever wear shorts in a colour other than black. Wipe your fingers on your or your riding buddy?s shorts and get on with your ride.

In spite of their durability, chains have a limited life. Contrary to bike shop lore, its lifespan is not determined by the distance ridden since new or with the emptiness of the shop till, but by hygiene. The cleaner you keep your chain, the longer it lasts. In fact, should anyone come up with a method of keeping a bicycle chain immersed in a bath of clean oil, bike shops will go out of business because chains will last forever. Here?s proof. Motorcycles have two chains. The drive chain is the one you know, it is the exposed chain running from the gearbox to the rear wheel. Its lifespan is limited to perhaps ten thousand kilometres, a bit better than a bicycle?s due to its larger size and robust seals that largely keep dirt off the wear areas. However, a motorcycle also has a timing chain which most people don?t even know about. This short chain connects the crankshaft to the camshaft in the head and is completely encased in the engine where no grit can get to it. I addition to its protection from grit, it runs in a bath of oil and consequently lasts the lifetime of the bike. They last forever in spite of the fact that it actually receives more abuse than its longer counterpart, it is shorter and goes through more bending cycles at each of the two small sprockets than the longer but exposed chain.

 

The astonishing lifespan has to do with hygiene ? internal chains are kept clean and perfectly lubricated whereas your bicycle?s chain is exposed to road grit, poor cleaning methods, poor lubricants and infrequent lubrication.

Unfortunately, the dirt that does the most damage is also the dirt that is the most difficult to clean out ? that deep inside the chain?s joint between the two sideplates and on the pin. Wiping your chain with a rag or even cleaning it with a brush and some degreaser does almost nothing. Unless you really pay attention, use lots of solvent and flush out all the gritty solvent afterwards, chances are that all your chain cleaning is purely cosmetic. To clean a chain well, it really needs a good soaking and agitation in solvent, preferably off the bike. Quick links are really useful for this, making it easy to remove the chain each time you clean it.  I also like those gadgets that clip onto the chain and roll it through a couple of brushes and through a batch of degreases. But, they?re expensive and don?t last all that long.

The best method is to remove the chain and immerse it in a bottle of solvent. Two liter cool drink bottles and 500ml of paraffin works well. Close the bottle and agitate it. If you think the chain is clean, fish it out with a piece of wire and give it a second cleaning with some water-based degreaser. Now flush it with water until the run-off runs clear. Refit it and oil it by dripping a drop of oil on every second link, smack bang onto the roller. Don?t bother trying to oil the sideplates, they?ll get coated with oil soon enough. Decant and re-use the paraffin, discarding only the bit at the bottom together with the grit that collected there.

Mountain bike chains need special and frequent attention. To optimise the lifespan of your MTB chain, you may have to clean it after every ride or at the very least, avoid re-oiling it between washes. Fresh oil on a dirty chain does a great job of transporting grit to the inside the chain where it can set to work as grinding paste, damaging the pins and their holes in the sideplates.
 
A chain that looks dry does not necessarily need oil. Oil on the outside does very little for a chain and it?s the oil on the inside that matters. A trained ear will quickly distinguish between a chain that looks dry and one that actually is dry. Sometimes a chain will look like it needs more oil, yet it?ll run quietly ? this means there is still enough oil inside to lubricate the moving parts and flow back into the interface each time the tension is released at the chain?s return cycle. A dry chain is noisy and a very dry chain will squeak. Don?t ride a noisy chain; rather oil it, even if it is dirty.

A word on lubricants:

The science of lubrication, friction and wear is called tribology and is a branch of physics. Tribology is a very well-understood science and tribologists are employed by lubricant companies, bearing manufacturers, vehicle brake manufacturers and just about anywhere you can expect to solve a problem of friction and wear. Tribologists know that the best lubricant for bicycle chains is a long-chain hydrocarbon, commonly known as oil. Not wax, not graphite, not liquid Teflon (which doesn?t exist) and not virgin olive oil, just plain old mineral oil. Often, you?ll see a new chain lubricant on the market that promises to not suffer the same side effects as oil. Stay away!  If the manufacturer uses words like ?dry?, ?wax?, and/or ?clean?, it is probably rubbish. It doesn?t matter that the product?s marketers claim that it was developed by a tri-athlete who won the Australian open three times in a row back in the 1970s when men were still men and bikes made of pig iron. The ?designer?s? day-job is most likely that of third oboe player in the local orchestra or speculating with pork-belly futures. He knows nothing about tribology.

Those popular dry wax lubricants are a combination of a volatile solvent or carrier fluid and a waxy substance. Once squirted onto the chain, the solvent evaporates, leaving a waxy coating. At first, the chain is quiet and lubricated and like the bottle says, there is no black mess. However, this is no free lunch and very quickly ? even after just two or three hours of riding ? the waxy substance is worked out of the joints and being a solid, it cannot flow back into the interface. The result is a dry, noisy chain. Perhaps that?s why they call it ?dry lubrication?.

 Liquid oil on the other hand, gets pushed out with each cycle but also flows back as soon as pressure is taken off the chain i.e. it flows back into the pin/sideplate interface during the link?s journey from where it exits the chainring and enters a rear sprocket.

Testing the difference between wax and oil is easy: squirt some of the ?dry liquid wax? on the market onto a smooth surface and wait until it is dry. Rub it with your fingers and note its texture, slightly rubbery and certainly not slick. Notice that when you scratch a line through the blob, it does not flow back to fill the void. Now put a drop of oil on the surface and do the same. Play around with the two substances and you?ll notice that oil flows, wax doesn?t. You?ll notice that oil can be washed off with soapy water and just about any petroleum solvent. Wax has to be scraped off.

Now imagine the ?wax? on your chain. It coats well, but doesn?t lubricate once it has seen enough work to push it out of the important chain wear interfaces. Washing it off is another matter. After one or two applications you?ll have so much build-up on the jockey wheels and all parts of the chain - where ironically lubrication is not needed - that you?ll be searching for something to dissolve the mess.

I?m sure you?ve often heard someone say that oil ?attracts? dirt. This is nonsense. Oil has no magnetic properties. It merely traps whatever lands on it. Yes it is a problem but far less of a problem than a chain that?s effectively dry after just a short ride. The dirt collecting on the outside of the chain doesn?t matter; it?s the oil that?s still on the inside that is doing the work.

Silicone spray lubricants may silence noisy door hinges but they?re useless for bike chains. Again, this is a two-part liquid ? a volatile carrier and light oil. The liquid is sprayed onto the surface and quickly penetrates deep into the chain. The volatile liquid then evaporates and leaves the surface nicely oiled. However, the oil in silicone sprays is simply too thin for use on a chain and offers little more lubrication than water, and is about as long-lasting as the latter. A chain lubricated with silicone spray makes a sound typical of a dry chain. Try it once and memorise the sound the chain makes after twenty or thirty kilometres. Memorise it and save your chain from wear whenever you hear it again.

Something that looks similar but isn?t, is motorcycle chain lubricant. This is also a spray and therefore appears similar to silicone sprays. It also has a two-part composition ? solvent and lubricant. The latter comprises thick oil in a volatile carrier and does a good job of penetrating the chain and keeping it oiled in prolonged riding.

The drawback of spray lubricants is the mess. If you don?t develop a technique of catching the overspray with a cloth, you?ll end up with grease marks on your garage floor. Overspray also has the habit of getting onto the rear rim, where it at first makes it impossible to brake but later starts to dissolve the brake pad rubber and creating a gooey mess on the rim that makes the brakes grabby and noisy.

So how do you choose a good lubricant? Go to your bike shop and find a product that openly professes to be oil. Anything with the word ?dry? or ?wax? should be ignored. Find an oil that?s viscous enough (not too thin) to not fly off the chain when you start spinning fast but that?s also not too gooey to develop long toffee-trails where the chain exits from the sprockets. Brand names are not important here because I?m talking good old mineral oil pumped from the guts of the earth and sold by the barrel on the open commodity markets.

Bicycle oil is expensive by petroleum product standards and those little bottles are ridiculously overpriced. If you don?t want to pay the equivalent of one million dollars a barrel, use plain old engine oil. It works well, but I don?t like the fact that engine oil is just a teensy bit too thin and throws tiny little drops of black onto my shiny silver rims. If you don?t want to start your own oil refinery in the garage, I recommend one of the more tenacious bicycle oils typically sold as MTB oil. I have experimented with using chainsaw oil, sometimes called bar oil, on my chain. This oil is very thick and designed not to fly off fast-moving chainsaw chains. However, it is a bit too sticky and soils your back wheel by throwing off spider web-thin trails as the wheel turns. I have experimented with a mix of engine oil and bar oil and came up with the perfect viscosity that neither throws off drops nor pulls trails. This mix, which ended up as a 2-litre batch, will now last me for the rest of my life. I dispense it sparingly onto my chain by using a commercial bike oil dropper bottle.

When touring, I never take oil with me. The bottle always leaks and causes a mess in my saddle bag. Instead, I make use of the free lubrication service offered at every garage in the country. Pull in at a convenience garage, head for the black plastic rubbish bin and scratch around until you find an ?empty? oil can. Inside you?ll find at least 25 ml of oil, enough to lubricate the entire Tour de Farce squad?s bikes. Now courtesy of your average smoker, find a used match. Tilt and maneuver the can until you get some oil on top, dip the match and dispense the oil, one drop on every second link, and ride into the sunset.

Prolonged wet riding effectively cleans all oil from bike chains. This isn?t a problem as long as it keeps on raining. Water is also a lubricant and a wet, oil-free chain is still a happy chain. However, when it starts to dry out, the chain will start squeaking. Pull up at your first friendly Caltex and make use of the free bike lube service.

 

The effects of a worn chain.

Another popular bicycle myth is that a worn chain somehow affects gear shifting. This is not true. Bicycle chains, unlike other drive chains that run on a single pair of sprockets and remain in perfect alignment when operating, are designed to flex sideways. This is to accommodate gear shifting. The jockey, after all, bends the chain onto the next gear. A rigid chain will not shift and a worn chain does not overshift as lore will have it. If the chain is very badly worn and the B-screw setting on the derailleur has the top pulley far removed from the sprocket, then you will experience sluggish shifting. This is an extreme and unlikely case and poor shifting is not a good indicator of a worn chain.

The only effect of a worn chain is invisible ? it quickly wears sprocket teeth and destroys expensive cassettes. A worn chain works perfectly well on a worn cassette. However, a new chain doesn?t mesh with a worn sprocket.  The trick is to change your chain often enough to prolong the sprocket?s life, but not so often as to outweigh the cost of new sprockets. Besides, sprockets don?t last indefinitely. Just like a human?s tooth, a cog (a single tooth in a sprocket) also has a hard protective layer that equates to a tooth?s enamel, encasing a softer material ? dentine in the case of your teeth. On sprockets the protective layer is case-hardened steel, which protects the softer steel inside. Once the thin case-hardened layer is worn away, the cogs quickly deteriorate.

The word cog is so misused that most people now assume it means sprocket. A cog refers to just one tooth on a sprocket. A sprocket can have many cogs ? your front chainring has 53 cogs. Chainring is just another name for a very specific sprocket ? a bike?s front sprocket. It has two or three chainrings, all with many cogs. A cassette is a set of sprockets sold and fitted as a unit to the wheel?s freehub. A cluster is a set of sprockets with a freewheel mechanism built in and screws onto old-fashioned hubs.

How a chain, new or worn, works isn?t all that obvious, but important for the understanding of how damage occurs and why chain elongation is something to care about.

The pitch ? distance between links ? on a bicycle chain is exactly 1 inch. No use translating to metric here, this measurement is standard all over the world and  probably a relic of the <?: prefix = st1 ns = "urn:schemas:contacts" />Roman chariot?s standard wheelbase or something equally arcane.
The indent between cogs on a new sprocket exactly matches that of the chain?s roller, but the tops of the teeth flare open slightly so that the chain can exit easily even when worn or when you?re cross-chaining. This arrangement also reduces noise under these last two conditions. The derailleur idler pulleys are tapered toward the ends of the teeth for accepting a chain entering them at an angle.
Although sprockets and pulleys are designed to still work when the chain enters and exits at an angle, one should not cross-chain i.e. use gears which engage the large chainring and largest sprocket and vice versa. This greatly increases wear on the sprockets and chain, which are then loaded on one edge only.
Now let?s picture the chain rolling over the two sets of sprockets by focusing on a few links which for the purpose of this demonstration are painted bright red so you can follow them around their loop. The rider is pedalling and the red links are now right at the bottom of the loop between the chainring and jockey. These links are not under load as all the load is carried at the top and they only experience the light tension from the derailleur spring. These links approach the idler pulleys and zig-zag through them to the rear sprockets where, still under no load, they enter easily, thanks to their perfect lateral alignment set up by the idlers.
Because both chain and sprockets are new, we know each link is loaded by a corresponding cog as the chain enters the rear sprocket. The load is distributed evenly amongst all the links making sprocket contact and the position of the derailleur ensures that there is enough wrap (engaging almost three quarters of the sprocket at once) so that the chain doesn?t jump up and skips.

The red links now move around the sprocket towards their exit at the front from where they will approach the chainwheel. Looking from the side on, you can see how the links articulate to accommodate the sprocket shape. Remember our formula; articulation angle = 360 degrees divided by number of teeth. Whilst on the sprocket, the contact angle (as seen from the top) between chain roller and sprocket is perfectly parallel but the instant the red link exits the rear sprocket, things change, unless of course the rider is now in the only gear that perfectly aligns the front and back sprockets and therefore keeps the chain in a straight line. Assuming the bike is in any other than the perfectly-aligned gear, the links now suddenly bend laterally to accommodate the chain?s diagonal path to the front. This does two things; it loads only the one side of the cogs and forces a similar shift in force inside the chain, to one side of the pin and sideplate as well. The more you are cross-chaining, the more you?re applying to pedalling force to a smaller contact area.

The length of chain between these links is perfectly straight and all the bending is experienced at the two ends. The worse the cross-chaining, the worse these angles are and the more abuse you?re inflicting on your drivechain.
Now our red links are just about to enter the chainring. The way the links enter the chainring is different from the way they entered the sprockets, simply because at the front they entering under tension whereas they entered the sprockets freely. If there is cross-chaining, there is another lateral bending motion in the chain and a skew loading of the first cog, just like that at the link now exiting the back sprocket.  Our red links now move around the chainwheel and again articulate to accommodate the ring?s shape.
The then exit under no tension. Visualise the various stresses on the chain as this cycle is repeated and note the different dynamics up front from at the back. Because both the chain and sprockets are in perfect synch, all engaging teeth and links are loaded equally.
The problem comes when the chain starts to wear. Wear happens as the link pins and their sideplates (outer) wear down, effectively enlarging the hole and reducing the pin?s diameter. This creates play and the chain pitch then lengthens. The chain elongates (but as you can see, doesn?t stretch). Chain pitch is no longer a perfect half inch between links but slightly more whilst the cog pitch, even on worn teeth, is still one half inch. The synchronisation between the two is thus no longer perfect and the chain now applies more load on the last tooth of
a sprocket before disengagement because the chain pitch now doesn?t match the pitch of the sprocket. This uneven loading increases wear.

Look carefully at your loose piece of chain again and visualise what happens when the chain wears. Pivot wear means the link pins can both move outwards under tension, which allows the two inner links attached to one outer link, to move apart. The rollers inside the inner links always retain their half-inch pitch regardless of wear since they float inside their retaining flanges in anyway and have built-in play.
This all means that only every second link elongates and when a worn chain rolls over a sprocket, only every second link no longer meshes perfectly. The only way for the chain to compensate for this imperfect match is to ride higher up the teeth which in turn then load only every second tooth. It is quite easy to see such a worn chain by looking for light shining through under the chain and sprocket. This represents a 50% reduction in engagement surface and a 100% increase in load on the teeth which do engage. It leads to rapid wear of the sprocket teeth.
Wear causes visible pockets on the rear of each tooth. These pockets are clearly visible if you compare a good tooth from a worn one. You?ll also notice that the wear is not at the bottom of the tooth but slightly higher up ? the chain rides up, remember? Tooth pitch remains exactly ? inch even on worn sprockets.

Wear pockets form slowly at first, but as soon as the case-hardened outer sprocket is worn through, the chain rapidly eats into the softer steel inside. The chain and sprockets now wear each other down and thus stay in pitch. The problem comes when you put on a new chain. This now no longer matches the distorted pitch of the sprocket and the chain starts to skip under load. It does this because the load forces the rollers up along the teeth into the wear pocket. The next incoming roller now cannot engage because it catches on the next tooth and up it rides, over the tooth and you get the familiar skipping action.
On a bike stand, a new chain on a worn sprocket will not be evident. It is only when you ride the bike and apply force to the chain that the skipping starts. Therefore, when you replace a chain, do a short test ride and make sure you apply force in all gears, before accepting the job as successful.

The worse the sprocket wear, the quicker a new chain will skip. A slightly worn sprocket will only produce skip under very high loads. You?ll also notice that chainrings last much longer. They still wear, but because the chain enters them with force, they don?t skip. However, a badly worn chainring refuses to let go of the chain in what is known as chain suck. This happens when the cogs are worn into hooks that cannot allow the roller to freely disengage. They hold onto the chain where it should normally exit and rolls it up the rear of the chainwheel and jams it under the incoming chain. Chain suck brings your pedalling to an abrupt stop. Mountain bikers who experience it a lot, quickly develop and ear and technique that saves the drivechain from self-destructing under powerful pedalling forces whilst the chain is, should we say, sucking? If your experience chainsuck, don?t immediately replace the chainwheel. Very dirty chains, particularly on muddy mountain bikes, suck badly because the dirt jams the chain around the sprocket. Mountain bikes with their long cage rear derailleur which offer lots of give at the slack side of the chain, are more prone to chainsuck than road bikes with much shorter derailleur cages. Water cures chainsuck caused by dirty chains and that?s why you?ll always find mountain bikers bathing their bikes in streams during foul-weather races.

Your chain performs its two functions with great efficiency and keeps energy losses to a minimum. For close to a century, inventors have been attempting to replace the bicycle chain with other devices and yet the humble, if filthy chain remains. More on its filthy habits later. For now, let?s concentrate on its function. Perhaps you should go and find a short piece of bike chain now and keep it with you as you read the following paragraphs. It?ll give you a better insight into this wonderful bike component.

If you examine your piece of bike chain and start playing with some measurements, you?ll notice that it measures exactly 1 inch (25,4mm) over two (or one, depending how you approach the definition) links. We?re talking about a new chain now. Worn chains measure slightly more because internal wear elongates the chain by leaving larger gaps between pins and sideplates.

Speaking of pins and sideplates: the anatomy of a chain is simple. Starting with the smallest, the first to notice are link pins (pins for short) - the short rods you push in and out in order to ?break? the chain. The other two components are sideplates (two types if you want to be pedantic ? inner and outer) and rollers. Looking at your piece of chain, all of this will be self-explanatory. All of these components are made of hard steel designed to withstand wear from articulating under tension. Bending, or more correctly, articulating the short piece of chain in your hand is easy. However, under the tremendous tension you put on it by pedaling, you can imagine what sort of friction exists between the pins and sideplates. Add some fine grit in there and you?ll understand what causes chain wear. Just have a careful look at the pin of a used chain and you?ll notice wear in the form of an indent over less than half of the pin?s circumference, where the sideplate moves over it with every articulation. The pin effectively gets smaller and the hole in the sideplate bigger, resulting in play between the two and ultimately, a longer chain.

The wear comes from the chain?s bending action as it rolls over a sprocket. Rear sprockets cause more wear then front sprockets (chainrings, in bicycle parlance) simply because a chain has to bend more to accommodate the smaller number of teeth. For instance, a chain being driven around a typical 52 tooth chainring undergoes a 7-degree bend at each link (360 divided by 52 = 6.9 degrees). For a 12-tooth sprocket, the bending angle and therefore internal abrasion is much more ? 30 degrees in this case. Although the jockey pulley wheels (called idler wheels) are smaller than the smallest rear sprocket and therefore subjects the chain to more articulation, they have very little effect on the chain?s lifespan because the chain negotiates their chicane bends whilst unloaded.

Chains do not stretch. Not even a Tour de Farce rider fortified with race juice can stretch the hardened steel on a chain. Chains elongate by the mechanism described above. Relegate ?chain stretch? to your lexicon of forbidden bike terms alongside  ?cable stretch?, ?puncture proof? and ?drug-free Le Tour winner?.

 

When to replace that chain?

You prevent sprocket wear by regularly changing your chain. However, most people allow their bike shops to replace their chains too often, which is also unnecessary and in the end, as expensive as a new sprocket cassette. Replace the chain only when it has elongated by 1%. It is easier to determine than it sounds. Regularly measure your chain with a ruler calibrated in inches. These are hard to come by in metric countries but it is worth the search. I found a cheap carpenter?s square with inch markings at my local hardware shop and it works fine ? the short end of the square even gives me a good handle on things and the fact that the measurements start at the edge of the rule means I can hook it against a pin or sideplate when measuring and only focus on the 12-inch side of the rule.
A one half percent elongation works out as 1/16th of an inch per foot of chain (24 links). You don?t even have to count the links, you simply lay the end of the rule against any point on the chain ? I like to jam my steel rule against a pin, pull the chain straight and look at the 12-inch mark where I can quickly see whether my end point lines up or runs over. Your inch ruler will almost certainly be marked in 1/16ths. Up to just below 12 and 1/16th inch mark, the chain is still good, on and above it, it should be replaced. If it has already elongated by 1/8th, you?ve ruined the sprocket. Replace it.
It is interesting to note that the wear (per link) is in fact twice what you measure, since only every second link (the ones with outer sideplates) wears. It is useful to remember that a worn chain will run on new sprockets without skipping, but not vice versa. Running an old chain on a new set of sprockets is not a good idea. This will accelerate wear in the sprockets since it will now only load the last, and perhaps second-last cog and not distribute the load evenly amongst all the available cogs.
What about commercial chain wear indicators?
Don?t bother, get a yardstick. Most commercial indicators engage on the rollers, which have built-in float and remain at a perfect ? inch pitch on inner links. These therefore measure an unknown and variable entity ? roller clearance is not the same for different brands of chain. The only standard you can rely on is the half-inch pitch from link pin to link pin. Compounding this problem is the size of the measured area. These chain wear indicators only measure across a couple of links, compounding any reading or measurement error.
That, in short is everything you ever need to know about your bike?s chain. If you?re just interested in the highlights of this explanation, here?s the bluffers list of chain bullet points:

Chains don?t stretch, they elongate due to wear in the pins.

New chains will skip when used with worn sprockets.

The extent of chain wear is determined by measurement only, not miles, not seasons and not by psychic bike mechanics.

Chain life is a function of hygiene.
Take control back from your bike shop and measure and manage your own chain replacement.

Chain suck really sucks.

 

[slowtwitch]

GOEIE GENIGTIG!!!!!!

 

Ek hoop die andwoord is erns daar binne

[droo]

You did ask for that...

 

 

 

[Gasping]

Please don't ask a question about one of the disciples - Johan will copy and paste the entire New Testament. Gasping2009-09-03 10:07:10

[Johan Bornman]

Please don't ask a question about one of the disciples - Johan will copy and paste the entire New Testament.

 

Except that I don't do unacknowledged copy and pasting. I would have just referred you to a link to the original.

 

 

 

 

[robmac]

You have the original new testament?

[BrendonMyb]

You have the original new testament?

 

Johan has been around the block a couple of times you know

 

takes hat & runs

[Borriz]

so has anyone tried the proposed car oil + bar oil mixture? What is the ratio?

 

I'm very interested to try this concoction. Also willing to buy the required oil and split into "trail" portions to experiment with

[Gasping]

Please don't ask a question about one of the disciples - Johan will copy and paste the entire New Testament.

 

Except that I don't do unacknowledged copy and pasting. I would have just referred you to a link to the original.

 

 

Dear Johan, I never accused you of anything. It was a joke. Maybe I should just stay off this thread..................