Yesterday, we took acrank and bottom bracket system.And then shit blew up.In the comments section, that is. So I summarized what I thought were some of the most common comment threads and punted a handful of questions back to SRAM. While I was at it, I also reached out to a couple bike company product managers—these are the people whose job it is to spec the bikes you ride. What's their take on DUB?Let's start with Roberts Graudins, the product manager at SRAM who was in charge of developing DUB.

Okay…28.99. You guys had to know that you were going to get a rash of shit for not simply saying “29”. Why, then, 28.99?

Photo by Mike Kazimer

Here is the straightforward answer. We wanted to be as transparent as possible. When I started at SRAM over 12 years ago, I was a design engineer for cranks who was a bit OCD on accuracy and details. So now as a product manager, when I was asked what the diameter was I told you the honest answer. 28.99mm is literally what the nominal dimension on our design drawing says and so that is what we shared with everyone. We could just round up and say 29mm to dumb it down, but when asked what the spindle diameter is, we wanted to be honest. There is no marketing twist to it, just actual values we have machined our DUB spindle to. We also saw a few comments about “Do they really machine to those tolerances?” The answer is yes. We expect the DUB BB/Spindle combination to perform at a really high level and part of that comes from having to hold really tight tolerances on our parts.

In practical terms, how much more durability (in terms of riding hours or, I suppose, hours on the testing machines), did you gain by going to 28.99 millimeters (rather than 30)?

Photo by Mike Kazimer

When we looked to develop the DUB platform, our goal wasn’t to specifically make the system more durable than 30mm systems. It was to make the whole sub-system equal or better than our most durable system today (24mm, GXP threaded), but at the same time reducing the weight like you get from 30mm systems. To do that we benchmarked everything we had with our current platforms (24mm and 30mm systems). And just like all other BBs in the market, each combination of spindle and BB has its particular benefits. Typically you see 24mm platforms being more durable, but heavier than 30mm systems. While on the flip side 30mm systems typically being lighter, but not as durable in certain frame BB shell configurations as 24mm systems.There are compromises in almost all of those systems today because the majority of them were designed with a lot of constraints about making sure things weren’t too far out of the norm. But like we found with Eagle technology drivetrains, sometimes the best solutions out there are the ones that don’t necessarily follow the norm. So we looked at it from a clean slate and asked ourselves how we would design a new platform of cranks/BBs to have the benefits of both 24mm and 30mm systems today, but still be compatible with all the major frame shell standards in the market.Durability was a key part of that, but is also one of the most tricky elements to put numbers to that accurately translate to every rider. Putting durability is terms of riding hours is almost impossible as there are no two riders who ride exactly the same, in the same conditions, with the same cadence or intensity and maintain their bike the same. What would be considered two hours of riding for one rider could actually be equal to what another rider would equal in 10 hours of riding. Which is why having a number to define that doesn’t really help translate to what riders actually see in the field because everyone is different.But as to not skirt the question, we can say that a large number of folks in the industry either know someone or have personal experience with the durability level of SRAM’s 24mm, GXP threaded crank/BB system. And what we can say is that every single DUB BB configuration now outperforms in the lab and in the field where we were from a contamination durability standpoint than our current GXP BB systems. The percentage of what that translates to you as a rider again varies depending on how you ride and where you ride, but it is clear that it will be better. So while I can’t give a number or percent of how much better it will be that translates exactly to every rider individually, I can say it will be better than what is out there today for every rider.

Going to a 28.99-millimeter diameter spindle allows you to run larger ball bearings than is the case with a 30-millimeter spindle (at least, that's certainly true within the confines of a BB92 bottom bracket shell). What is the precise difference in bearing size between 28.99 and the 30-mm compatible models already in your line up?

How/Why exactly did dropping 1 millimeter in spindle diameter result in better sealing? Did it, for instance, allow you to change the size and shape of the seals? If so, by how much? What does that matter?

One of the most common MTB BB shell standards that frame manufacturers use is the PF92 standard. On top of that, the popularity in the market of shoving 30-millimeter spindle cranks in all frame BB shell standards has grown. The problem with this combination is that putting a 30-millimeter spindle in that small of a shell diameter (PF92) makes it so tight you can’t really add any proper seals to prevent premature wear on the BB due to corrosion. Some of the BBs in the market today for that combination (30mm spindle/PF92 shell) have little to no actual sealing of the bearings. And that is something our engineers just weren’t happy with from a performance level.



The most common failure for BBs is not that the balls wear out or are overloaded by impact loads, it is because they start to corrode due to contamination. And so for us, going down in spindle size allowed us to add more sealing both from external contamination and internal contamination. Externally, we were able to have a double layer of sealing to protect from external contamination.

One of the most common MTB BB shell standards that frame manufacturers use is the PF92 standard. On top of that, the popularity in the market of shoving 30-millimeter spindle cranks in all frame BB shell standards has grown. The problem with this combination is that putting a 30-millimeter spindle in that small of a shell diameter (PF92) makes it so tight you can’t really add any proper seals to prevent premature wear on the BB due to corrosion. Some of the BBs in the market today for that combination (30mm spindle/PF92 shell) have little to no actual sealing of the bearings. And that is something our engineers just weren’t happy with from a performance level.The most common failure for BBs is not that the balls wear out or are overloaded by impact loads, it is because they start to corrode due to contamination. And so for us, going down in spindle size allowed us to add more sealing both from external contamination and internal contamination. Externally, we were able to have a double layer of sealing to protect from external contamination.

The reason for us going to 28.99mm wasn’t to have a larger ball size for the traditional 30mm frame BB shell configurations. The diameter actually came from us listening to the market about them wanting less configurations on cranks, but at the same time not wanting to give up any of the benefits of their current 24mm configuration or their 30mm configuration. We would hear things like, “I love the light weight and stiffness of the 30mm crank setup, but I wish it had the durability of the 24mm crank setups.” And so our target was to find a single solution that would be the best of both worlds.Our goal for DUB was to achieve three key factors to address that desire from the market. Simplicity, durability and compatibility.Simplicity in that we wanted to find a solution that would allow us to provide a single crank design that would fit onto any MTB bike regardless of the frame BB shell standard that was chosen by the OE to use in their design. Durability in that we wanted to ensure the BBs of this single crank solution would be just as durable in any frame BB shell standard configuration that the OEs chose to design to. And finally to make sure that simple and durable solution is compatible with those frame BB shell standards that are out there today.So in order for us to achieve a single solution that gave us good sealing and durability in all of the common frame BB shell standards that exist today, we ended up with a 28.99mm DUB spindle. This was the diameter our engineers landed on that provided us the balance of having a simple, durable and compatible solution to all major frame BB shells standards in the market. The ball size was just one small item we looked at in the landscape of all the things that add up to our DUB BB solution (ball size, bearing race thickness, internal/external seal design, part tolerances, grease fill, grease type, spindle/interface, spindle/crank attachment features, frame BB shell standards, frame BB shell tolerances, etc.)Internally, it allowed us to have a better sealed bearing and fully-sealed center tube to protect from internal contamination caused by water getting into the BB shell of the frame. Both of these reinforcements to sealing we felt were needed to make sure our BBs did not wear out prematurely.So, yes, while itsound small, 1 millimeter is enough to add these types of seals to add that corrosion protection. Other frame BB shell standards that OEs use in their designs don’t have the same constraints for space as the 30mm/PF92 combination, so aren’t as big of a concern on space. But as we don’t control what frame BB shell standards OEs use on their designs, we have to make sure our designs have the best possible performance in any configuration. And DUB does exactly that for the main MTB frame BB shell standards that are being used by manufacturers today.

Some people might see the release of DUB as a move made specifically to close your component ecosystem from companies such as Shimano, FSA and, specifically, RaceFace, the latter of which you are currently in a lawsuit with. How do you respond to that?

Our intention isn’t to close anyone out from anything. Our intention is to make the best possible drivetrain systems and components that fit on bikes that are in the market. Sometimes that means not just following the norm. If we did that, we’d all still be riding 26” hardtails with 80-millimeter travel forks and 3x8 gearing. Sticking with the norm often comes with a bunch of compromises on the design and with Eagle technology (DUB included) drivetrains that isn’t what we were after. With Eagle technology, our goal was to make the best possible drivetrain system in the market. The only way for us to be able to deliver what we did with Eagle was to go away from the norm. And so far, based on the number of riders we see in the market on Eagle drivetrains, we feel we did a pretty good job in achieving that. DUB technology on our crank products is just one more step to furthering the Eagle technology package.

I think that part of the anger from readers in our comments section stems from the fact that your video states that DUB is "backwards compatible." In some ways that’s true—in others it’s not. To wit, DUB will fit on any existing frame AND you can now swap a DUB crank from one bike to the next with no compatibility problems.



DUB cranks and bottom brackets, however, are not backwards compatible with existing cranks or bottom brackets. How do you respond to some of the reader statements that suggest that your video is being a bit disingenuous with its "backwards compatibility" claim?

Photo by Mike Kazimer

...AND NOW FOR THE BIKE COMPANIES....

Kevin Dana, Product Manager, Giant Bicycles

Tara Seplavy, Product Manager, GT Bicycles

Josh Kissner, Product Manager, Santa Cruz Bicycles

Alex Cogger, Product Manager, Rocky Mountain

Ian Schmitt, Product Manager, Kona Bicycles

We view “compatibility” in terms of our systems being compatible with MTB bikes that exist today. Like you have heard in articles before on Eagle drivetrains, our target for Eagle was to create the best possible drivetrain system—not a bunch of random components that are hung on a bike. And now that DUB is the latest technology of the Eagle technology family, we view it the same way. As a system. When that is how you look at it, we have a hard time seeing how it isn’t backwards compatible to the existing frame BB shell standards that are in the market today. Hence, why we were genuine when we said it is “backwards compatible”.This does, however, highlight the difference of how some of the readers might have been looking at it. They potentially see DUB as 2 separate sub-components (BB and Crank), where we see it as one sub-system (crankset) that is ultimately part of one full drivetrain system (Eagle). If we look at viewing it as individual components between BB and crank, then you can make the argument that no BB/cranks in the market are fully “backwards compatible”. Not even the existing ones that folks in the forum were mentioning (24mm systems). They are all based on being used as a sub-system and only those sub-systems can really be called “backwards compatible”. For example, not all 24mm cranks/BBs are created equal. The diameters, bearing placements and even attachment methods aren’t the same between all 24mm crank configurations. So if those sub-systems are considered backwards compatible, how isn’t DUB in that same boat?"I have spent ample time on the new DUB system on both XC and Enduro applications, with the latter having being ridden everywhere from Whistler, to Sedona, to SoCal, dry and dusty to sloppy at times, and back to dry and dusty. I honestly can’t complain about the new system at all, and in Giant's case, the new system actually shaves some weight off of the previous generation SRAM product. Not saying that weight is a defining factor in product decisions, but let’s face it, nothing is really getting much lighter these days, so you take it when and where you can if it makes sense. As far as durability claims, time will tell the truth, but the new system is sealed relatively well, and I’ve experienced a system that has actually settled in quite nicely with no slop, and no creaking. To me, that’s always a win."As for making product decisions simpler? Nah. Not for us, at least. There’s no complications in choosing a BB; it’s either compatible or it’s not. In terms of choosing the overall drivetrain? While some brands are more apt to break up and “Mr. Potato Head” drivetrains, for Giant, it’s traditionally a system approach to drivetrain spec. The various systems offered now generally meet the needs of most (not all) of Giant’s customers. There’s enough aftermarket options out there to meet any individual needs these days, but Giant’s focus is delivering a solid core foundation in which each part works together as intended, and is easy to service and troubleshoot when issues do arise. Let’s face it, not every manufacturer’s frame tolerances are up to snuff, which in turn leads to shifting issues, which then you start chasing individual components. Is it the RD hanger alignment? The frame? Cheap chain? Oval chainrings? (kidding)."Cranks and BB’s haven’t changed too disruptively in a while, and I certainly won’t get caught up in what diameter the spindle is. Do they fit my bike? Are they strong enough? Do they look rad? Spin freely? Sweet, let’s go smash some rocks.""For us it was just a swap over. The old ones will no longer be available for OEM purchase after a certain date. It also does not impact all of the crank models. Because SRAM enforces purchase of the full Eagle group (FC, RD, SL, CS, CN) it kinda locks you in anyway to a crank purchase."As for longevity, we haven't had enough ride time to really comment yet. But, if this makes it easier for brands to spec a single BB part number, or simplifies production for factories, or increases the chance that your local shop will have the BB you need in stock, then all the better!""I've had a set of cranks for a few months now and they've been problem-free. I'm not the best durability tester, as I ride too many different bikes to put a proper thrashing on anything in a short time period. Plus I live in California... I will say that we've never had BB durability issues with SRAM products, I suspect because we've always used threaded/GXP cranks on our bikes. I think the bearing/sealing issues people were having are on bikes with pressfit BBs, especially the smaller diameter ones (BB 86/92, etc)."How will it impact my job? No real change in that regard, but it will make our bikes lighter as we can use the aluminum spindle with our threaded BB's now. Which is sweet. Where we spec Eagle, SRAM forces us to buy complete drivetrains (cranks included), so there's no change to the amount of work/debate (or lack there of) to decide specs. Obviously we're happy when something we're already purchasing gets improved, and that's what's happening with DUB.""Since SRAM delivered samples to us for ride evaluation in the fall (and believe it or not 2019 spec needs to be locked in and final in December), we have only put a little bit of time in on the new DUB cranks, and so far have not encountered any issues. Hard to say what the future holds, but we have to have faith they have done their homework."As far as DUB's impact on our jobs goes... it’s same same but different. SRAM cranks have always used SRAM-specific BB’s (unlike Race Face and Shimano which are interchangeable, for example). So DUB or no DUB, we still buy SRAM BB’s for SRAM cranks. This is not a new standard, simply a change in the design in their components. I recognize that it’s tough for dealers however, who need to stock new BB’s now."SRAM is the dominant drivetrain in performance MTB (for good reason, thanks to leading the charge in 1x and the advent of Eagle), and they have decided all new performance cranks will get DUB’ed (get it?). Furthermore, their drivetrains are a closed systems as they pertain to cranks / rings / bottom brackets, so we are all in with DUB if we want to spec Eagle (which we do).""The durability [with DUB] has been very good. I’ve had the same bottom bracket in my bike since August and have had no issues with it. Normally I have 24mm or GXP cranks on my bikes and I replace my BB when its worn. Usually 4-8 months depending on how much I am riding and the conditions. The bearings in my crank still spin freely and have no grinding or play. I’d say that the claims are valid and that the new BB and spindle interface is an improvement."DUB doesn’t really change my job one way or another. The ordering process is the same whether I’d spec a GXP crank or a DUB crank. No change to the frame-fitment or design and an ostensibly better product make it an easy decision, which doesn’t impact the value of a consumer's current bike."