Because lighters are not always better

For a long time, weight has been a driving factor for product development in the bicycle industry, and its ultimate goal is obviously to reduce weight as much as possible. Let's face it: other things being equal, lighter bikes are more fun to ride (of course, lifting on the showroom floor is also more impressive). Therefore, light metals such as aluminum and titanium are generally more popular than steel, and if you can make things out of carbon fiber, of course you will.

However, "all other conditions are the same" is the key word here, and weight should not be one of the main considerations when deciding on the material.

When two threaded parts are tightened or loosened under tension, what should happen is that the threads slide smoothly against each other-but many of us know that this is not always the case. Wear is a term used to describe the phenomenon when two threaded fasteners engage with each other. Specifically, it's what happens when one or two of these threaded parts start to shed tiny material. These material fragments will create pits or raised bumps on these surfaces. Eventually, the tiny space between the two will be blocked by the metal sticky substance, thus constraining the entire system and preventing the two parts from moving.

In moderation, the parts can be removed from each other by using torque fairly wisely-either in large quantities, such as something you can create with a breaker lever, or delivered very quickly, such as the shock driver you get. In more extreme cases, the threads are severely damaged and the parts are no longer usable. In the worst case, the parts are basically welded together, and it's time to remove the heavy cutting tools.

It is generally accepted that there are many strategies to prevent wear, the most common of which are the use of appropriate lubricants (ideally an anti-seize compound), designing parts with thicker threads, and avoiding softer materials ( Or at least avoid using two softer materials together), apply torque more slowly, not exceeding the recommended torque value, and use special surface treatments such as anodizing and electroplating.

In most cases, bicycle component brands do a good job in all of these aspects, although there are notable exceptions in the name of reducing weight.

One highlight is the fixing bolts in the high-end SRAM DUB (and the previous PF/BB30) chain ring.

If you look at the common recommendations for preventing wear, this situation violates several of them: the spindle and bolts are made of the same soft aluminum, the recommended torque value is very high (54 Nm!), and the threads are relatively thin. So, not surprisingly, it is not uncommon for these bolts to require excessive torque to remove them (Dave Rome and myself have experienced this many times before). Bicycle mechanic forums and forums are also flooded with accounts, not only detailing stuck crank bolts and damaged tools, but also various creative solutions for removing them, most of which involve broken rods, Some combination of impact wrench, heat, cold, extra hands, and swear. 

"I was lucky enough to put the [non-drive side] crank on a raised surface, and then someone was sitting on the bike," someone suggested. "Use a long breaker rod with a pipe at the end for extra leverage. They usually break free. I use this method more successfully than an impact wrench."

"You can clamp the crank to the workbench, let the bicycle hang next to it to lock it in place, and then use a large circuit breaker lever to handle those who are really stuck," another person read.

"I have an Efficient Velo Tools stand," another mechanic said. "I lowered the bike until the wheel fell on the floor, used a block or sturdy object under the non-driving arm to hold it in the 3 o'clock position, and then used the breaker lever/Allen socket to remove it." 

"The impact gun is your best friend. It's much better than putting a big liar column on it."

Regardless of the preferred extraction method, anyone who has read this article who has experienced this problem firsthand may be very familiar with the "guns" smell that accompanies the sound of victory when the bolts finally loosen.

SRAM stated that it modified the thread geometry in the DUB spindle a few months ago, but there are still countless other threads floating around, apparently still prone to jamming. Even better, I found an ultimate solution to the root cause—not only did it prove to be very effective, it was also quite cheap. 

It turns out that SRAM also uses steel to make these bolts, but only uses them in inventory equipment on the low-end SX Eagle and X1 1000 Eagle mountain bike cranksets. However, after a few months of some stimulation from me, the company decided to provide them with an aftermarket.

"Due to your request, we have specified the steel DUB bolt replacement assembly according to the mountain bike crank specification," said JP McCarthy, SRAM Road Product Manager. "The part is in production but has not been communicated to distributors or even our own service center."

Please note that this is in July, and hope that SRAM dealers and service centers will keep up with it from then on. Now you can also consider getting to know yourself.

These steel DUB bolts are a direct substitute for aluminum bolts, tightening and loosening are more predictable and reliable, and they also retain the self-extraction function. What is the retail price? Less than $20 (SRAM part number 11.6118.066.000, for reference only). As a nice bonus, the self-drawing cap also comes with a more reliable 10 mm hex connector for installation and removal, rather than the more discerning original version using a pin wrench.

Of course, switching to these steel bolts will add some weight-the actual weight of the new assembly is 31 grams, while the actual weight of the original aluminum bolts is only 18 grams-if you don't like the large number of signs and labels, then maybe It is worth mentioning that the laser etch on the replacement extractor cover is much larger (although there is nothing good permanent marking that cannot be repaired).

Although I was happy to discover this fix a few months ago, the fact that the problem exists at all is still disturbing. Similarly, based on basic hardware principles, it can be said that these high-torque aluminum crank bolts should not exist at all. However, SRAM not only uses their inventory on all of its current high-end chainrings with 29mm diameter DUB systems, but the company has also used them on cranks with 30mm aluminum spindles for many years, so who knows these things How many are there. several thousand? a few millions? million?

Before you blame SRAM, remember that although the company has a huge influence in the aftermarket, most of its revenue comes from OEM contracts (just like Shimano), and parts purchased by other brands are used for their complete bicycles. These contracts can be large, so even if what the OEM brand wants is not the best for the end user in the long run, SRAM must listen to the question of money.

According to industry sources I interviewed (who prefers to remain anonymous), in this case, the problem is weight. Specifically, bicycle brands are often motivated by consumers’ appeal to lighter-weight bicycles in this cruel market, so much so that product managers will deliberately choose options that can reduce the final count by a few grams, although it may be sacrificed Long-term maintainability. 

What does that mean? Even if SRAM provides OEMs with DUB and BB/PF30 crank versions with steel fixing bolts — and seeing the bolts exist, this is almost certainly an option available to them — the product manager will most likely not choose them, just Because they are a bit heavy. But I certainly hope they will.

Either way, the benefit of all this is that the situation can be corrected easily and cheaply, and the solution is also easy to install (provided you can take out the original aluminum bolts). 

For some people, spending money to make your bike heavier seems stupid. But in this case, I would say that its weight (and money) is well spent.