Importance of Derailleur Compatibility on New Drivetrains

 One of the best features of many new component groups is the ability to run a wide range of chainring and cassette setups.  1x, 2x, and even triple crank setups are possible within the same component group, and cassettes range from 28t to as big as 52t.  

All this availability has made it more important to ensure you're using compatible parts, but sometimes it's difficult to know the correct derailleur to use with the cassette you're using.  I hope this article helps understand why.

Shimano relies on the upper derailleur pulley tracking as close as possible to the cogs.  This is why their rear derailleurs have a low tolerance for cassette sizes.  Let's take Deore XT M8100 series 12 speed rear derailleurs for instance.  There are three versions, each with a specific purpose:

GS- Short cage, designed for a single chainring

SGS - Medium Cage, designed for a single chainring

M8120 SGS - Long cage, designed for a double chainring

All of these derailleurs look very similar and can easily be mistaken for each other.   Looking at the specs at bike.shimano.com, we see that there's very specific cassette compatibility:

GS- 10-45 12 speed cassette

SGS: 10-51 12 speed cassette

M8120 SGS: 10-45 cassette with a maximum chainring difference of 10 teeth

Of course, there's some cross compatibility that will work, but there's some that won't work at all.  For instance, the M8120 SGS derailleur can easily be used on a single chainring setup and 10-45 cassette with no problems.  If you attempt to use it on a 10-51 cassette it MIGHT shift if you turn the 'b adjust' screw all the way in.  However, shifting will suffer in the smaller cogs because the upper pulley will track too far away from the cogs.  Likewise, an M8100 SGS derailleur will shift on a 10-45 cassette but the gap between the pulley and the cogs will not stay constant, and shifting won't be as quick and smooth as it should.  You should never use the short cage GS derailleur with a double crank - the capacity (the difference in cog sizes plus the difference in chainring sizes) is too small.  When you size the chain according to Shimano's instructions, the chain will be too long when using the small chainring and smaller cogs because the derailleur cage isn't long enough to take up the slack.

All this is true because each rear derailleur is designed with a specific geometry that tracks the cogs at a precise angle.  This keeps the pulley-cog distance constant, ensuring smooth and accurate shifting.  If you mix up the compatible parts,  shifting will begin to suffer.  Sometimes it's an acceptable amount, sometimes it could slip and mis-shift.  This is why Shimano 'requires' a specific derailleur for each setup.

SRAM approaches the issue a little differently.  The position of the upper pulley on the cage allows the pulley to track different range cassettes.  However, they rely on proper chain length to do this.  Even though an Eagle rear derailleur will work on both a 10-50 and 10-52 cassette, it's best to size the chain to the specific cassette.  If you use a chain that's sized to a 10-52 cassette with a 10-50 setup, the upper pulley could track too closely to the cog when the 'b-adjust' screw is adjusted properly.  You could possibly have some grinding in the larger cogs.  If you were to adjust the 'b-adjust' screw in to compensate, then the upper pulley won't track the rest of the cogs properly and you could end up with unreliable shifting.  Likewise, if you use a chain sized for a 10-50 cassette on a 10-52, it might shift to all the gears, but the upper pulley will track farther away from the smaller cogs and shift accuracy will suffer.  Beware though - running a chain that's too short could break the derailleur, especially if you have a full suspension bike.

In many of these cases, the drivetrain may shift acceptably.  From a mechanic's point of view, it's our job to make it shift as smoothly and precisely as possible so we recommend using the correct setup to achieve that.

SRAM's AXS standard road derailleurs are compatible with 10-28, 10-33, and 10-36 cassettes with either single or double chainrings; the Xplr road derailleur is compatible with 10-44 or 10-36 cassettes and a single chainring.  Like before though, proper chain length is critical for precise shifting.

I hope this helps clear up some confusion about compatibility issues that aren't straightforward.  Thanks for reading!

My Top 5 Tips to Make Your Bike Ride Smoother

  I've worked as a mechanic in the bike industry for over 35 years.  I get asked for bike care tips a lot so I thought I'd pass along my top five.

1. Find a mechanic you trust and have them check your bike regularly

I know - exactly what you'd expect a mechanic to say (I also follow this advice with my car.)  Once you find a good mechanic, your loyalty should be rewarded with a smooth-running, problem-free ride.  If you log thousands of miles, ride in poor conditions, or are generally hard on equipment you may need more service than normal and it's good to have someone who knows your unique needs.  If you return to the same mechanic time after time, they'll have a personal interest in your experience when you ride.  That'll show every time you get on your bike.

I'd also recommend calling ahead to make an appointment.  Sometimes it's just the polite thing to do, but many shops are overwhelmed in the summer.  Making an appointment means you'll likely spend less time without your bike.

2. Oil your chain with a good quality chain-specific lube

Lubricants that are made specifically for chains are designed for the high load and contamination-rife drivetrains on bikes.  There are also many lubes available that won't make a greasy mess.  Silca Super Secret truly can't be beat.  It's a liquid wax that doesn't make a mess and runs super smooth, but it's pricey (well worth the money).  Rock n Roll Gold is a good, more affordable alternative.  Try to avoid using thin lubes like Tri-flow on your chain - they wear out quickly and attract a lot of dirt.  And WD-40?  It's not really a lube, it's made to displace water to prevent rust.  I like it to clean chains, but it will only last a few miles if you attempt to use it as a lube.

For more scientific research on chain lubes, see zerofriction.com

3. Pay attention to air pressure

This means that you may need to do some trial and error to find the correct pressure.  There's a lot of information going around the industry about what 'correct pressure' really is.  I've been running 90psi in 700x25c tires for over 25 years, even when everyone recommended 120psi.  To me, the ride quality on the rough roads was more important than 1.5 watts saved at higher pressure.  I also found that if I ran less pressure, I would pinch flat my tubes.  Tubeless road tires might allow for even lower pressure, as would a bit wider tire (if it fits your frame).

Also, better quality tires offer much better ride quality.  Period.  Everything you read about Vittoria Corsa and Continental GP5000 tires is true - they're both great tires.  The downside is that they're nearly $100 each now, but consider it an investment in your riding experience.

Want more scientific information about tire pressure vs rolling resistance?  Check out bicyclerollingresistance.com.  He offers a lot of information about how tire pressure affects rolling resistance.  

4. Preventative maintenance is better than waiting until you have a problem

Bikes don't break down when they hang in the garage.  They break down at the worst possible moment, usually climbing a big hill.  Routine preventative maintenance will catch problems before they lead to a ruined afternoon ride.  Preventative maintenance will make sure your derailleur hanger is aligned properly for better shifting, check your chain for wear or damage, and check your cable condition.  When was the last time you replaced the batteries in your wireless shifters?  Are your stem bolts tight?  Spokes tensioned properly?  Don't wait to find out during the grand fondo you've trained for all year.

5. Replace your cables.

Cables and housing wear.  Although they do last a long time, nothing shifts better than new cables.  Cables wear grooves inside the housings, increasing friction.  I replace my cables about every 2000 miles, my housings every 4000 miles.  Don't ride that much?  At least have your cables lubricated.  It makes a big difference in shifting quality.

You shouldn't be surprised to hear me say this: better quality cables shift better.  My choice for all of my bikes is Jagwire Pro slick polished cables.  This is the best working cable I've ever used.

There you go, my top five tips.  There's more where these came from, but these are the tips I tell everyone first when they ask.  I hope they help you have a great ride!

Why don't my Inner Tubes hold air very long?

 For many years, I've heard older people say that inner tubes don't hold air as well as they used to.  It's usually the same thing - 'I never had to air up my tires when I was a kid.'   Others seem to think that tubes puncture easier now than they did even 15 or 20 years ago.  All of this got me wondering if there really is a difference between the quality of tubes and if it's changed through the years.

First, a (very) short history:

 Originally tires and tubes were made from natural latex from rubber trees (Hevea brasiliensis) that are grown almost exclusively in Indonesia and Malaya.  During World War II, Japan had invaded these countries and cut off the world’s supply of natural rubber.  This led to a shortage and the need for an alternative.   At the time, German engineers had already been working on a synthetic rubber, but it wasn't until 1942 that U.S. engineers were able to develop it into a useable rubber compound called Butyl.   Butyl synthetic rubber is the most common material used to make inner tubes today.  

Butyl retains air better and costs much less than natural rubber, making it ideal for inner tubes.  It’s biggest disadvantage is that it doesn’t stretch much - as much as 5 times less than natural rubber. For this reason, Butyl is normally blended with natural rubber to give a tube the ability to stretch more.

The majority of the global supply of Butyl is produced by two companies: Exxon in the USA and Polymer Corporation in Canada.   Exxon offers 5 different Butyl synthetic rubber blends.  Each uses a different mix of additives to allow it to withstand heat better, increase it’s durability, or just lower the cost.  These additives decrease Butyl’s ability to hold air so they must balance these additives for the best compromise.   There are only a few companies that still make tubes in the U.S., but there are easily a dozen or more tube manufacturers in China alone.  These companies blend the different butyl compounds with 10 -20 percent natural rubber in order to give preferred results vs cost.  More natural rubber means the tube will stretch more (which also makes it more puncture resistant)  but it won’t hold air as well.  It also increases the cost.  Again, this is a balancing act to achieve the best compromise.

Other factors that influence how well a tube holds air are the wall thickness of the tube and how closely the tube matches the size of the tire.  A thicker tube wall will slow air leaking; a tube that has to stretch to fit the tire causes the wall of the tube to become thinner, allowing air to leak at a quicker rate.  Thus, thorn resistant tubes with thicker rubber will hold air longer than a superlight tube that uses very thin rubber.   Riders looking to save weight are willing give up a tube's ability to hold air for long periods in order to save a few grams.  This is usually acceptable because these are the cyclists who will air their tires up before every ride.

The chart below shows how different brands of tubes use different thicknesses

Brand/Thckness	Ultralight	Superlight	standard	Thorn reist*
Bontrager	.45mm	.6mm	.9mm	4.1mm/1.2mm
Kenda		.75mm	.9mm	3.5mm/1mm
QBP/Dimension		.73mm	.9mm
Michelin		.7mm	.9mm

*thorn resistant tubes are thicker on the tire side, thinner on the rim side

Back to the original point that brought this up.  Is it possible that tubes held air better 50 years ago?  The answer is yes - the tubes had less natural rubber in them because of the shortage of rubber during and after WWII.  As well, since the tube wouldn’t stretch as much (because it lacked natural rubber), they were made to fit the inside of the tire very close.  This maintained the thickness of the tube, helping them retain air.

Finally, here's a neat YouTube video from the TV show 'How It's Made' showing how tubes are manufactured.

So what can we take away from all this?

There are slight differences in the exact formulas used for inner tubes, and that can affect it’s cost and its ability to hold air.  However, with most U.S. tube suppliers,  it's more likely that the reason one tube holds air longer than another is a result of the thickness of the tube after it stretches to fit a tire.  Pick a tube that fits the tire better (so it stretches less) and/or a thicker, heavier tube to ensure that a tube holds air pressure longer. 

note: this is a (slightly) updated post from my other blog: thebikehive.blogspot.com

What is Kashima Coating?

Kashima coating is a feature currently only found on Fox forks and shocks*.  It's easy to spot because of its distinctive goldish-brown color.  But what is it and why do they use it? 

First, a quick definition:
Anodizing is a process by which a metal part (normally aluminum) is electrically charged and submerged in a chemical bath.  This creates an oxide layer that penetrates the metal and changes the microscopic texture and the crystal structure of the metal near the surface.  After a part is treated, it can be dyed to give it color before it is sealed to increase durability. Hard anodizing is a similar procedure that penetrates further into the metal. This increases the surface hardness of the material making the surface even more durable and corrosion resistant.  It does not make the metal part stronger, it affects the durability of the surface of the metal.

Kashima coating is a type of hard anodizing that involves a lubricating treatment as well.  This not only substantially decreases friction, it also increases the hardness of the surface of the part, making it as much as three times more durable than chrome plating.  The process also increases the corrosion resistance 4-5x over normal anodizing.   Kashima coating is a process that is only done by one company in the world, Miyaki in Japan.  Fox ships all component parts to Japan where Miyaki treats them with the Kashima coating.  The parts are then sent back to Fox to be assembled.  

Currently Fox is the only bicycle company using Kashima coating.  It's a feature found on their Factory Series forks and rear shocks.  It increases the durability of the upper legs of a suspension fork and the shaft of rear shocks.  This makes them more scratch resistant than hard anodized finishes found on other shocks, including Fox's Performance Series.   It also gives them a lubricating property that decreases friction between upper legs/shaft and the seals.  The result is a very smooth feel to the suspension and exceptional durability.   

See the Kashima Coating website for more information about anodizing in general and technical specs on Kashima coating.  I encourage everyone to visit ridefox.com to see all Fox has to offer, including the updates to their 2021 product.

Please note: the above article is a simplification of a very complex process that (I hope) makes it easier to understand without getting overly technical.


*Kashima Coating is used in other industries, primarily in shocks for off road equipment, some machinery, and on pistons in some high performance automobiles.  Fox is the only company in the bike industry using Kashima coating on their products.

note: this is a re-post of an article that I wrote in 2015 on my other blog: thebikehive.blogspot.com

All about Aluminum

What is 6061 and ‘7000 Series’ Aluminum?

In the mid-90’s we saw aluminum quickly become the popular medium for building bikes due to it’s low weight.  By the end of the 90’s bike companies were plastering stickers on their frames showing the fancy ‘7000 series’, 7075, and 6061 aluminum tubing.  What’s the difference and what do the numbers mean?

Aluminum is an element that is naturally occurring in the earth and is one of the most plentiful metals found in the crust.   It is mined as a material called Bauxite Ore that contains aluminum oxide (sometimes referred to at alumina).   After Bauxite is removed from the ground, it’s crushed and sent to a refinery where the aluminum oxide is separated from other impurities.  After refinery, it is in a powder form that is then sent to the smelter where the aluminum is extracted from the alumina.  This is done by running a large amount of electrical current through molten alumina that’s been dissolved in a 1,750 degree cryolite bath. The molten aluminum can then be made into different alloys by mixing other minerals with it. 
   After the smelting process is complete, it is then cast by mixing it with other minerals to impart different qualities to the metal, creating an aluminum alloy. It’s important to note that pure aluminum is rarely ever used - it is a very soft metal that forms easily but does not have much strength.

The largest alumina mining and refinery company in the world is Alcoa, producing 14 million metric tons per year- nearly one-third of the world’s supply.  It is mined in the US, Jamaica, Brazil, Spain, and Australia   Alcoa’s Australian mining and refinery plant is the largest aluminum producing country in the world and produces 15% of the world's supply of aluminum alone.  Alcoa’s Tennesee  smelting facitlity produces enough aluminum sheet to make 100 billion beverage cans per year.

In North America, aluminum alloy compositions are registered with The Aluminum Association Inc .  There are currently more than 400 aluminum alloys registered with the Aluminum Association.   These alloys are categorized into several groups based on their main alloying element.
 The first digit (Xxxx) indicates the principal alloying element, which has been added to the aluminum alloy and is often used to describe the aluminum alloy series, i.e., 1000 series, 2000 series, 3000 series, up to 8000 series.
The second single digit (xXxx), if different from 0, indicates a modification of the specific alloy, and the third and fourth digits (xxXX) are arbitrary numbers given to identify a specific alloy in the series. Example: In alloy 5183, the number 5 indicates that it is of the magnesium alloy series, the 1 indicates that it is the 1st modification to the original alloy 5083, and the 83 identifies it in the 5xxx series.
The only exception to this alloy numbering system is with the 1xxx series aluminum alloys (pure aluminums) in which case, the last 2 digits provide the minimum aluminum percentage above 99%, i.e.,  1350 aluminum alloy is 99.50% minimum aluminum.

1000 series aluminum alloy are nearly pure aluminum, being 99+% pure.  These are soft, weak alloys that can be welded easily but can not be heat treated.  They have good corrosion resistance and are used where high electrical conductivity is required.
2000 series aluminum alloys are high strength alloys that are considered non-weldable.  The bike industry uses 2024 alloy for components such as handlebars and seat posts because of it’s high strength and resistance to cracking.  It’s main additive is copper.
3000 series aluminum have manganese added to increase strength and response to cold work.  They are moderate strength, have good corrosion resistance, and can easily be welded.  It’s used mainly for non-structural situations such as air conditioning systems.
4000 series aluminum alloys add silicon to reduce the melting point and are used primarily for welding and brazing filler material and in castings.  They are the most sensitive to cracking of all the aluminum alloys.
5000 series alloys have magnesium added to increase strength and ability to work-harden.  They are very corrosion resistant, easily weldable, and are the strongest of the non-heat treatable alloys.  They are normally available as sheets or plates and are the most common structural alloys.  However, they are normally not available in extruded sections (tubing) because of the high cost to extrude.

The 6XXX series of alloys are the alloys most often encountered in structural work, and the most common alloy used in bicycle frames. They are relatively strong (although not as strong as the 2XXX or 7XXX series) and have good corrosion resistance.  6061 aluminum is cast with magnesium and silicon as its primary additives.  This makes 6061 aluminum alloy much easier to weld than other aluminum alloys. However, care must be taken to use the correct type and amount of filler material when welding, otherwise it can crack easily.  Even so, it is the most common heat treatable structural aluminum alloy.   It is easily extruded and cold worked so it is available in many different tube shapes and sizes.   6061 alloy is used on a vast majority of aluminum bike frames and makes very light, strong, and low-cost frames.

7000 aluminum is cast with zinc as its primary additive, making it a very high strength alloy. It's more costly to use zinc as an aluminum additive, making the 7000 series more expensive.  It also has higher levels of magnesium and copper than 6061, making it as hard as some steel alloys.  This lightness and strength come at the expense of its corrosion resistance - 7000 series alloy will corrode much easier than 6061.  With only a couple exceptions, 7000 series aluminum can not be welded.
The only 7000 series alloy that can be welded is 7005*.  This is the tubing used in many high-end aluminum frames and creates a very strong, very light frame that is more costly than any other aluminum frame.
7075 aluminum alloy is the most commonly used of the 7000 series alloys, however, it is considered non-weldable.  It is most commonly used in the bicycle industry on components.  However, it was used in frame tubing form when bonded (lugged and glued) frames were in style during the mid-90’s.

Although 7000 series aluminum is a harder alloy that makes a frame stronger, it also makes the ride quality much more rough.  6061 aluminum alloy is softer so it dents and bends easier but will give a smoother ride.
*There are other exceptions to the general rule that 2XXX and 7XXX alloys are unweldable but not in the bike industry. They are rare, expensive and not used in the bicycle industry. 

Through the years, there have been ‘boutique’ aluminum tubing used for bikes.  many people remember Easton Elite  tubing in the late 90’s as the best available.  Easton Elite tubing is made from 7005 alloy that Easton made into double and triple butted tubes in order to make extremely light and stiff frames.  No special metallurgy, but custom thickness, diameter and shapes that give the structural qualities Easton wanted.
Aluxx aluminum that Giant uses on their aluminum bikes currently is 6061 alloy that is specially formed by Giant.  Aluxx SL is a 6011 alloy that they specially form and Aluxx SLR is a butted 6011 alloy that’s specially formed.  Giant utilizes fluidforming, pressforming,  and warmforming to get the special shapes of their tubes.  

Heat Treating
The process of welding results in a loss of strength around the weld by approximately  80%. The material can be re-heat-treated to restore -T4 or -T6 temper for the whole piece. Heat treatment is done by raising the alloy temperature to about 980 degrees F and holding it there for about an hour. The purpose of this is to dissolve all the alloying elements in a solid solution in the aluminum. Then we quench the alloy in water. At this point, this is called the T4 temper. For a T6 temper, it is once again heat treated at a temperature between 325 and 400 degrees F, so that the alloying elements begin to form ordered arrays of atoms in the aluminum matrix. These arrays are called GP zones, and they strengthen the aluminum considerably. This heat treatment is called aging, resulting in material with a T6 temp.  The bike industry nearly always heat treats to a T6 rating.

Aluminum corrosion
Many of us have been told that aluminum will never rust.    While that statement may be true, but it is very misleading .  Rust is IRON oxide-steel, not aluminum.   Aluminum has excellent  corrosion resistance because it forms a natural aluminum oxide layer that protects it.  However, it will corrode when exposed to environments with high chloride levels, e.g. sweat or areas bordering the sea or oceans.  Low or high pH values (less than 4 and more than 9) lead to the oxide layer dissolving and, consequently, rapid corrosion of the aluminium.
 This is many times found along with ‘pitting’ of the aluminum - small holes or indentions where the aluminum looks as if it’s been ‘eaten away’.  Because of this, it is important that aluminum frames be finished by painting or anodizing and making sure it’s protected from sweat or humid coastlines.

Nearly 75 percent of all aluminum ever produced is still in use today.

Aluminum is Infinitely recyclable and highly durable- nearly 75 percent of all aluminum ever produced is still in use today. Aluminum is 100 percent recyclable and retains its properties indefinitely. Aluminum is one of the only materials in the consumer disposal stream that more than pays for the cost of its own collection.

references:

http://www.ehow.com/info_8078719_difference-between-6061-7075-aluminum.html

http://www.ehow.com/info_7857163_6061-vs-7005-aluminum-bikes.html

Linclon design - properties of different series aluminum alloys

Wikipedia -7075 series aluminum, 6061 series

Alotec.com

The Aluminum Association

What is Chromoly and what does 4130 mean?

This posting is a shortened version of a technical paper I wrote for work. I hope you enjoy, and learn in the process!

At one time, all bikes were made of steel.  Steel has been popular thanks to its strength to weight ratio and ease of use.  These factors as well as it’s low cost and availability make it ideal for use in bicycles.  The most common type of steel used for bikes is chromoly, and 4130 chromoly is the most widely recognized.  So what does chromoly mean and what do the numbers 4130 refer to?

Steel is an alloy of iron and other metals.  The term ‘alloy’ is commonly used to refer to aluminum but it actually refers to any metal that’s mixed with other elements in order to achieve the desired mechanical properties such as strength, weight, durability, hardness, weldablitly, etc.  'Chromoly' refers to a specific type of steel alloy that combines Iron with Chromium and Molybdenum (chro-moly, get it?) along with small amounts of other metals.  Changing these small amounts of other metals in the alloy creates grades of chromoly with different mechanical properties and costs.  These steel alloys are identified by four digit codes set forth by the American Iron & Steel Institute (AISI) and are defined by their approximate chemical composition. 

In ‘4130 Chromoly’,  the "41" means that it is a low alloy steel containing chromium and molybdenum (about 1% and 0.2% respectively). The "30" indicates a carbon content of 0.30%.* These small percentages don't seem like much, but changing the amounts only slightly will affect mechanical properties of the steel quite a bit. For comparison, in '4340 chromoly', '43' means that it contains 0.8% Chromium and 0.25% molybdenum. The '40' indicates a carbon content of 0.4%. 4340 is a much stronger and harder steel alloy that is more difficult to bend and cut, plus it's a bit heavier than 4130. It costs more as well.

Since most steel bikes constructed in similar fashion when they’re built, 4130 Chromoly happens to have the best mechanical properties for use in bicycle frame building, and the low cost makes it ideal.  There are other chromoly alloys that are stronger, but they are more difficult to cut, bend, shape, and weld than 4130, or they are more costly.

It is widely thought that companies like Reynolds, Columbus, Deda, and Tange (among others) have their own formulas for steel alloys.  Actually, name brand tubing is normally off the shelf 4130 chromoly tubing that they will then make into double or triple butted tubing with butted sections in different lengths.  They are then sold as tubing sets designed for specific ride qualities (and sometimes rider sizes).  Newer name brand steel tubing sets (Reynolds 853 for example) offer technology that relates to how the tubing is annealed or hardened - this offers more resistance to weld and brazing weakness than others.  This allows for lighter, stronger frames.

I hope this offers some useful information about what 4130 chromoly is and why it's used for bikes. Want the full document with more information about different types of steel, including name brand steel (Reynolds, Columbus, etc), cheap department store steel bikes, and a comparison between 4130 and other steel? Send me a message and I'll forward the entire document to you.

I originally posted this on my other blog but I thought it was a good way to start off this blog.

An Introduction

I started this blog several months ago, the same time I started thebikehive blog.  I wasn't sure what I was going to do with both, and I ended up not doing anything with this one.   I knew on my other blog that I wanted to keep it riding-related with no product reviews, mainly about riding and maybe a bit of learning.  I had different ideas for this blog but never made much happen.

I finally decided to make this blog about the technical side of bikes.  So here's where I'll have product reviews, how to articles, and technical related stuff.  Much like thebikehive blog, since I'm not a writer it will be pretty simple.  I hope you enjoy!