Deep dive into SRAM’s new DUB system

Making sense of the contentious bottom bracket landscape

Company Spotlight Components
About the Ride

At the end of the day, the goal is not calling to the components but the ride itself.

Few areas of mountain biking are as confusing and contentious as the bottom bracket landscape. Many standards have been invented. Problems and mass confusion ensued. So it is worth digging deeper into the details of SRAM’s new effort called DUB. Here’s everything you need to know.

What does “DUB” stand for?
Durable Unifying Bottom Bracket

What are the main differences between DUB and GXP?
DUB uses an oversized aluminum spindle, while GXP uses a 24mm steel spindle. DUB cranks fit into all major existing frame BB shell standards while GXP only fits into the 24mm specific versions. DUB BBs are also more durable than GXP BBs.

Crank and BBs

The bottom bracket and crank is often called the heart of the bicycle system since it is central to its efficient (and hopefully) silent operation.

Is the DUB spindle the same as your 30mm cranks?
No. The DUB spindle is still an oversized aluminum spindle but is slightly smaller than our current 30mm spindle cranks.

What is the weight difference between your XX1 GXP and XX1 DUB system?
We have dropped about 80g from our current XX1 GXP crankset and now are easily the lightest carbon crankset on the market. 498g = SRAM XX1 DUB, 175mm, 32T with BB 576g = SRAM XX1 GXP, 175mm, 32T with BB. For reference the Race Face Next SL G4, 175mm, 32T with BB is 518g. Weights do not include crank boots.

Do all levels of DUB cranks lose as much weight as the XX1 version?
No. Each level of the crank has a different change in weight from our current offering. Please refer to SRAM.com for exact weight information for each model of the crank.

Are all the DUB spindles the same?
No. The DUB spindles will vary based on the level of DUB crank they are used on. XX1 – DUB SL bonded spindle. X01 – DUB bonded spindle. Desc C/Stylo C – DUB 7000 series press-in spindle
GX – DUB 7000 series press-in spindle. Desc 6k/Stylo 6k – DUB 6000 series press-in spindle.

Bottom Bracket Specs

Bottom bracket specifications.

Are DUB spindles removable?
No. DUB spindles are either bonded into the cranks (XX and X0) or they use a press in interface (all other models). No matter which model, the left arm will come with a non-removable spindle. The good part about this is that the same spindle will work for all major standard BB configurations.

How do the new DUB cranks align with the current SRAM product offering?
SRAM will have an equivalent DUB Eagle crank offering at all of the levels of SRAM/TRUVATIV Eagle crank offerings today.

What is the price of DUB cranks compared to current SRAM cranks?
The prices of each equivalent model level of DUB cranks will vary in the range between where the 24mm version and 30mm version was priced at last year. Please refer to SRAM.com for exact price comparisons.

What is the difference in Eagle rings between the levels?
The rings used throughout the DUB Eagle crank line differ in construction method and material, but all will have the same proven chain retention and wear characteristics that you have come to know from our current Eagle offering.

XX1 – Aluminum CNC Eagle SL ring
X01 – Aluminum CNC Eagle ring
Desc C/Stylo C – Aluminum cold forged Eagle ring
GX – Aluminum cold forged Eagle ring
Desc 6k/Stylo 6k – Steel stamped Eagle ring

Do DUB cranksets come in Super BOOST Plus chainline configuration?
No. Currently the DUB platform does not offer a Super BOOST Plus compatible crankset.

Holding System

Many engineering and testing hours were spent in SRAM’s San Luis Obispo facility.

What ring sizes are offered for each level of DUB crank?
DUB cranks are fully compatible with all of SRAM’s existing 3-bolt direct mount interface rings.

SRAM XX1 – 30/32/34/36/38T
SRAM X01 – 30/32/34/36T
All other models – 30/32/34T
Please refer to SRAM.com for specific details of sizes of each ring type.

Do DUB cranksets come in BOOST 148 chainline configurations?
Yes. All of our DUB Eagle cranks come in both BOOST (52mm) and Non-BOOST (49mm) chainlines. These specific chainlines are critical for proper Eagle system functionality/performance.

Do you have Fatbike versions of DUB cranks?
Yes, we have various price points of both 4” (170mm OLD) and 5” (190mm OLD) fatbike configurations. Please refer to SRAM.com for specific details.

Do you have DH versions of DUB cranks?
No. At this time we do not have our DH cranks converted over to the DUB platform. But it is in our plans in the future. For this model year, please continue to purchase our 24mm GXP systems for DH applications.

What BBs do you offer for with DUB?
We have BBs that will fit into all major existing frame BB shell standards.

DUB BSA 68 DUB BSA 73 DUB BSA 100 DUB PF89.5

DUB PF92 DUB PF121 DUB BB30 73 DUB PF30 73

Are DUB cranks compatible with my current bikes? Can I use my current BB with a new DUB crankset?
No. DUB cranksets are only compatible with DUB BBs. DUB is a system platform that includes both Crank and BB.

Are my old chainrings compatible with DUB cranks?
Yes. DUB cranksets use the same chainring offsets and interface that are used in production today. 3mm offset for BOOST and 6mm offset for Non-BOOST. 3-bolt interface.

Crank Specs

Crank specifications.

Are DUB BBs compatible with E-type chain guards?
Yes, the “DUB BSA 73E” version of our BB has the correct spacers to compensate for a 2.5mm E-type chain guard configuration.

Is DUB compatible with Cannondale BB30Ai frame shell standards?
No, not at this time. For that Cannondale specific frame shell standard, you should continue to use SRAM BB30Ai specific cranks.

Are the spindle spacers the same between your 30mm cranks and DUB cranks?
No. The spindle spacers for our 30mm cranks are not compatible with our DUB system. The DUB platform has its own spacers that are designed with the smaller diameter of the DUB spindle. They are all clearly marked with the “DUB” logo to help make sure you have the correct ones for the DUB system.

Yes. DUB is fully compatible with all major existing frame BB shell standards. So you will not need to re-design anything on your existing frames. DUB BBs will fit into the following frame BB shell standards.

BSA 68 BSA 73 BSA 100 PF89.5
PF92 PF121 BB30 73 PF30 73

Do I need a custom tool for installation or removal?
No. DUB BBs can be installed using existing tools in the market today. For press-in DUB BBs, a standard bearing press tool will work. There will be some tool suppliers that will be making custom DUB specific drifts to aid for ease of installation. For threaded DUB BBs, a 12-tooth 46mm OD cup tool can be used. (ie: Park BBT-79).

Laid Out on Table

Laying out the key components.

What is the diameter of a DUB oversized spindle?
The diameter was reduced from our 30mm version just enough in order to allow for proper sealing with all standard BB configurations. We shrunk the diameter just enough to get the seals we wanted into each of our DUB platform bottom brackets. The spindle diameter ended up at 28.99mm.

How is the same DUB crank able to fit into every BB shell standard without making any major sacrifices?
The first part of it was that we had to make sure the bearing location is the same on all of our DUB BBs independent of which BB shell they are put into. This means we have external bearings in some cases where they were previously internal (BB30/PF30 shell standards).

The second part was optimizing the oversized spindle diameter to ensure it would still give the benefits of the weight to stiffness we wanted, but not sacrifice durability and sealing on the worst case BB (PF92 standard).

How did you lose so much weight on the new XX1 DUB crankset?
Taking our systems engineering approach and translating that to this subcomponent, we looked at all areas to reduce weight.

Reduced weight in our BB designs while increasing durability at the same time.
Reduced spindle weight by going from a steel 24mm press-in spindle to an aluminum oversized bonded-in spindle.
Reduced ring weight by creating a new “SL” version of our CNC Eagle rings.

I have heard that oversized spindles are stiffer than 24mm spindles. So are all of your DUB cranks stiffer than GXP cranks?
Having a larger diameter spindle can provide benefits of stiffness, but it is ultimately a balance between weight and stiffness. With our new DUB platform we have worked to refine that balance between the weight loss and stiffness of the new system. In many cases our cranks stayed the same stiffness (which is already industry leading) and reduced significantly in weight. In other cases (X01 for example) we lost weight and added stiffness at the same time.

Are all of the DUB spindle spacers the same thickness?
No. Each configuration of BB has a designated spindle spacer that should be added to the assembly. Some BB types share the same thickness of spacer, but it is not consistent for every BB configuration.

Please refer to the DUB Crank and BB user manual for clarity on which spacer thickness should go with which BB type.

How has the durability of the DUB BB increased from GXP?
DUB BBs are based of the architecture of our most durable BB today, GXP BSA. We took that basic architecture and improved upon it in the following ways and then implemented that across the entire family of DUB BBs.

Worked directly with bearing supplier to create a custom bearing profile and seal design.

Tightened up tolerances for better fit and sealing.
Added additional o-ring sealing between spindle and BB shields.
Improved component handling and assembly process of BBs.

SLO

Testing in the scenic hills of San Luis Obispo, CA.

How has the adjuster changed from your current 30mm cranks?
We have made two improvements to the adjuster system on DUB compared to our current 30mm systems.

1) We have improved upon the ergonomics of the adjuster so that it can be reached and adjusted easier.

2) We have increased the thread pitch in order to provide a much more noticeable feeling when the adjuster has bottomed out on the bearing shield. This helps with not overtightening the system which can lead to over pre-loading the bearings and reducing bearing durability.

Has the crank bolt removal torque improved from SRAM’s current BB30 cranks?
Yes, we have made changes to our design to reduce the removal torque needed when removing the crankarms compared to our BB30 systems. DUB will be much more similar to the removal torque seen in a GXP system.

What makes the bearings more durable if they are smaller bearings vs. the bearing system they are replacing?
In all of our development, lab testing and field evaluation of the DUB BB we found that the durability of the bearings on a bicycle bottom bracket are much more influenced by the sealing and contamination of the system vs. the size of the balls. We found that smaller ball sizes can far surpass the durability of larger ball sizes if the smaller balls are sealed better from contamination. It is the contamination that almost always is the cause of poor durability in a bicycle bottom bracket. And that is exactly why we did not follow some of our competitors and just use a 30mm system that limits sealing in certain configurations. We needed the extra room for proper sealing to ensure our BB durability.

Photo Thumbnails (click to enlarge)

About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a dirt jumper, singlespeed, trail bike, lugged commuter or ultralight carbon road steed. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. Francis also believes that IPA will save America.


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NOTE: There are two ways to comment on our articles: Facebook or Wordpress. Facebook uses your real name and can be posted on your wall while Wordpress uses our login system. Feel free to use either one.

Facebook Comments:



Wordpress Comments:

  • dan says:

    So it’s like the Praxis crank/bb system?

  • I'mRight says:

    Can we solve bigger issues now like: rusty stem cap bolts?

  • adaycj says:

    Ah, so it fits with every BB so they can sell them to whomever, but 24mm wasn’t stiff enough, 30mm was too big. The market here is already an epic cluster, so what is another 370 part numbers?

    SRAMhas done a pretty good job of holding a large portion of the market for new 1X stuff. This “it fits almost any” BB without making a warranty mess just solidifies it. Not that anyone else will care, its not like its upgrade worthy.

  • Chris says:

    No 165mm? No sale.

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