I am not going to complain and ask why the bicycle industry does not embrace unified standards for commonly purchased parts. I understand the perceived need for 1.5" headsets. I know that different suspension designs are easier to package with different length shocks. I am not confused as to why manufacturers offer something newer, different, and possibly better than their competitors. However, as a consumer, I think there has been too little action taken by the bicycle purchasing public to reduce the disintegration of parts standards.
To keep things simple, I will focus on two components that are frequently built to different specifications on different bicycle frames: seat tubes and rear axles.
Different sizes of aluminum, steel, and carbon have been used for seat tubes on different frames throughout the history of the sport as we know it. However, not enough has been done to consolidate what is now a vast array of standards. This proliferation costs the consumer in more ways than you might initially think.
First, the obvious. If you buy a new frame, you will likely need to buy a new seatpost. If not that, you will need to buy a shim to properly insert your current seatpost in your new frame. Using a shim adds weight, can weaken the overall interface and costs you. You will probably have to order this item, and that means more time off the bike. My guess is that the majority of bikes sold in America, and the world are ridden with their original seatpost (possibly in its original position) until they are lost, stolen, or discarded. It is only in the high-end market that seatposts are swapped, sold, changed and broken. If the post breaks on your $79 bike, it is unlikely that you will replace it with an aftermarket model of the same dollar value.
Besides the obvious financial cost to the consumer, there is the cost in that you are not getting the best product. Why? Because no small-time component manufacturer is going to invest the research and development spending in a product of which they only produce a small number. For a given brand and model, each post size demands different engineering and specific testing. Ex. a 27.2mm OD Thomson Elite has different stiffness to weight than another Thomson Elite in 31.6mm. Theoretically, the manufacturer would have to optimize and test every size shaft, as well as their overall material analysis and their head clamp design. This seems like an unecessary headache to me, especially as there is no clear differentiation for posts. It's not as though road bikes all use thinner or thicker posts than MTB, or that DH bikes use fatter posts than XC bikes.
You'd think that material and frame design would dictate post size, with steel frames (that generally use thinner tubes) using the smaller posts. However, steel tubes of a smaller OD also have thinner walls, and therefore use a similar sized post. There isn't even necessarily continuity within the same brand!
For a given application (or range of applications) there is usually one or a small number of very similar designs that provide the most efficient structural benefit. Many bicycle-part sizes are arbitrary legacy items from past generations and different materials. Who knows? Maybe 40mm is a better size for a seatpost.
What are the specific concerns and demands placed on a seatpost (ignoring proprietary clamping designs and methods of fastening the head to the shaft)?
Rigidity--a seatpost needs to be stiff enough not to flex when you sit or fall on it
Strength--torsional, compressive, tensile...etc. A post shouldn't break under normal use, and should not be dented by the collar
Durability--a post needs to have some abrasion resistance to preventi t from wearing out if it is telescoped out of the seat tube often, but this is wear and not as critical as ultimate strength.
Seatpost size is somewhat subject to materials available to frame builders. Component manufacturers will have a hard time selling posts with an OD bigger than the ID of any tubes available to frame builders. That said, 27.2 and smaller sizes do not have any place in the world anymore, IMO. I do not have empirical data to back this up, but I think that larger sizes provide additional stiffness at the same weight, or possibly equal stiffness at the same weight.
Cleaning up the number of seatpost sizes and ending this ridiculous and lengthy proliferation would allow component makers to focus on optimizing just a few seatpost designs. Of course a few builders would make proprietary sizes again and the cycle would repeat, but setting a precedent of parts-standard reform could benefit both parties on both sides of the equation.
Thus far, frame builders have enjoyed relative freedom in regard to rear axle specifications. Options range from 9x135mm to 20x165mm and anywhere in between. 10x135 and 12x150 have emerged as popular choices, but they are not alone. Some frames use 14mm axles, some 20, some 16 with step up or step downs at the dropouts...etc.
Incorporating the rear axle as a structural member of the rear triangle is great. If it's light weight you're after, you can use thinner walled tubes for the rest of the triangle and spread some of the load to the axle. If maximum stiffness is what you want, clamping the rear wheel solidly in place helps triangulate the entire structure and reduce unwanted wobbles. Quick release skewers may work on road bikes, but they are remnants of a different era. New alloys, when used in appropriately larger sizes, can work just as well or better as solid steel skewers did 25 years ago.
On the other end of the spectrum, some manufacturers go overboard with their materials without spending more time on design. Giant builds its FR and DH bikes with rear axles more appropriate for your uncle's lifted 4x4 than anything powered by humans. Despite using all this extra metal, the axle just snugs down like a regular threaded axle. Most of the benefit of the extra heft isn't utilized. Rock Shox is on to something with the Maxle, and I hope that we--as consumers--are able to steer more manufacturers towards similar standards.
To keep things simple, I will focus on two components that are frequently built to different specifications on different bicycle frames: seat tubes and rear axles.
Different sizes of aluminum, steel, and carbon have been used for seat tubes on different frames throughout the history of the sport as we know it. However, not enough has been done to consolidate what is now a vast array of standards. This proliferation costs the consumer in more ways than you might initially think.
First, the obvious. If you buy a new frame, you will likely need to buy a new seatpost. If not that, you will need to buy a shim to properly insert your current seatpost in your new frame. Using a shim adds weight, can weaken the overall interface and costs you. You will probably have to order this item, and that means more time off the bike. My guess is that the majority of bikes sold in America, and the world are ridden with their original seatpost (possibly in its original position) until they are lost, stolen, or discarded. It is only in the high-end market that seatposts are swapped, sold, changed and broken. If the post breaks on your $79 bike, it is unlikely that you will replace it with an aftermarket model of the same dollar value.
Besides the obvious financial cost to the consumer, there is the cost in that you are not getting the best product. Why? Because no small-time component manufacturer is going to invest the research and development spending in a product of which they only produce a small number. For a given brand and model, each post size demands different engineering and specific testing. Ex. a 27.2mm OD Thomson Elite has different stiffness to weight than another Thomson Elite in 31.6mm. Theoretically, the manufacturer would have to optimize and test every size shaft, as well as their overall material analysis and their head clamp design. This seems like an unecessary headache to me, especially as there is no clear differentiation for posts. It's not as though road bikes all use thinner or thicker posts than MTB, or that DH bikes use fatter posts than XC bikes.
You'd think that material and frame design would dictate post size, with steel frames (that generally use thinner tubes) using the smaller posts. However, steel tubes of a smaller OD also have thinner walls, and therefore use a similar sized post. There isn't even necessarily continuity within the same brand!
For a given application (or range of applications) there is usually one or a small number of very similar designs that provide the most efficient structural benefit. Many bicycle-part sizes are arbitrary legacy items from past generations and different materials. Who knows? Maybe 40mm is a better size for a seatpost.
What are the specific concerns and demands placed on a seatpost (ignoring proprietary clamping designs and methods of fastening the head to the shaft)?
Rigidity--a seatpost needs to be stiff enough not to flex when you sit or fall on it
Strength--torsional, compressive, tensile...etc. A post shouldn't break under normal use, and should not be dented by the collar
Durability--a post needs to have some abrasion resistance to preventi t from wearing out if it is telescoped out of the seat tube often, but this is wear and not as critical as ultimate strength.
Seatpost size is somewhat subject to materials available to frame builders. Component manufacturers will have a hard time selling posts with an OD bigger than the ID of any tubes available to frame builders. That said, 27.2 and smaller sizes do not have any place in the world anymore, IMO. I do not have empirical data to back this up, but I think that larger sizes provide additional stiffness at the same weight, or possibly equal stiffness at the same weight.
Cleaning up the number of seatpost sizes and ending this ridiculous and lengthy proliferation would allow component makers to focus on optimizing just a few seatpost designs. Of course a few builders would make proprietary sizes again and the cycle would repeat, but setting a precedent of parts-standard reform could benefit both parties on both sides of the equation.
Thus far, frame builders have enjoyed relative freedom in regard to rear axle specifications. Options range from 9x135mm to 20x165mm and anywhere in between. 10x135 and 12x150 have emerged as popular choices, but they are not alone. Some frames use 14mm axles, some 20, some 16 with step up or step downs at the dropouts...etc.
Incorporating the rear axle as a structural member of the rear triangle is great. If it's light weight you're after, you can use thinner walled tubes for the rest of the triangle and spread some of the load to the axle. If maximum stiffness is what you want, clamping the rear wheel solidly in place helps triangulate the entire structure and reduce unwanted wobbles. Quick release skewers may work on road bikes, but they are remnants of a different era. New alloys, when used in appropriately larger sizes, can work just as well or better as solid steel skewers did 25 years ago.
On the other end of the spectrum, some manufacturers go overboard with their materials without spending more time on design. Giant builds its FR and DH bikes with rear axles more appropriate for your uncle's lifted 4x4 than anything powered by humans. Despite using all this extra metal, the axle just snugs down like a regular threaded axle. Most of the benefit of the extra heft isn't utilized. Rock Shox is on to something with the Maxle, and I hope that we--as consumers--are able to steer more manufacturers towards similar standards.
