Hollowtech vs. DUB (Comparison & Analysis)

This post compares the advantages and disadvantages of DUB and Hollowtech bottom brackets.


Bottom Bracket – a mechanism of cups and bearings allowing a spindle connected to the cranks to spin smoothly. The bottom bracket is installed in the so-called bottom bracket shell – the point where the seat tube and the downtube meet.

Shimano Hollowtech Bottom Bracket

Hollowtech Bottom Bracket – A Shimano bottom bracket operating with outboard (external) bearings allowing the use of a hollow spindle of a much larger diameter.

DUB bottom bracket

DUB Bottom Bracket – A SRAM bottom bracket operating with external bearings. DUB stands for Durable Unified Bottom Bracket. The goal of DUB bottom brackets is to make the selection process easier by offering a more unified standard.

The Advantages of Hollowtech Bottom Brackets

  • Larger/Thicker Ball Bearings

Hollowtech bottom brackets come with a spindle that’s 24mm in diameter. Conversely, the spindle of DUB bottom brackets is 28.99mm in diameter.

The bearings used by Hollowtech bottom brackets are 25x37x7mm in size (inner diameter/outer diameter/thickness). Those of DUB bottom brackets are 29x40x6.8mm.

The bearings of DUB bottom brackets have bigger overall dimensions due to the larger diameter of the spindle. However, we also have to look at the relation between the inside and outside diameter of the bearings.

The size difference between the inner and outside diameter of HT bottom brackets is 12mm whereas that of DUB bottom brackets is 11mm. This means that Hollowtech bottom brackets have 1mm more space for larger ball bearings. Larger ball bearings = potentially longer bearing life.

Also, Hollowtech bearings are 0.2mm thicker. This is a very small difference but deserves a mention.

  • More Common Spindle Size

24mm spindles that Hollowtech bottom brackets operate with are more common than the 28.99mm DUB spindles. Consequently, the rider can choose from a greater variety of cranksets.

The Advantages of DUB Bottom Brackets

  • Made for oversized spindles

The larger spindles that DUB bottom brackets are made for have two potential benefits – extra stiffness and lower weight.

Most of a tube’s strength comes from its walls/periphery. Consequently, when all parameters are equal (material, wall thickness…etc.) tubes with a larger diameter are stronger and stiffer than tubes with a smaller diameter.

The larger diameter of DUB spindles allows the production of axles that are just as strong as those with a smaller diameter while weighing less.

Weight Comparison

The table below compares the weight of Hollowtech and DUB bottom brackets:

DUB BB386 Road115gShimano SM-BB71-41A72g
DUB PF30120gShimano XTR SM-BB9373g
DUB ITA74gShimano Deore XT BB-MT80082g
SRAM DUB T4786gShimano SM-BBR6077g
BSA-DUB 96gShimano Saint SM-BB8095g
BB92 DUB71gShimano Dura-Ace SM-BB92-41B54g
DUB PF4173gShimano Dura Ace BB-R910065g
DUB Pressfit BB9271gShimano BB-MT500-PA72g
Shimano SM-BB72-41B69g
Shimano SM-BB94-41A58g
Average: 88.25gAverage: 71.7g

Conclusion: DUB bottom brackets tend to be ever so slightly heavier than Hollowtech models. The difference, however, is too small to matter unless one is trying to assemble the lightest possible bicycle.

The Difference Is Not Substantial

Truth be told, the practical (perceivable) difference between a DUB bottom bracket and a Hollowtech one is not substantial. Both are modern bottom brackets with external bearings that come in plenty of models capable of satisfying any frame. Consequently, the choice comes down to:

  • Availability
  • Crankset

Cranks Are More Important Than Bottom Brackets

Bottom brackets are an important bicycle component, but at the end of the day, they are not as important as the crankset in the long run. Therefore, one should first choose a crankset and only then review the bottom bracket opportunities in front of him.

It’s better to have an average bottom bracket and a nice crankset than the opposite. Quality cranksets are expected to last a lot longer if not the life of a bicycle. (Of course, this applies to cranks allowing you to replace the chainrings).

Meanwhile, bottom brackets will go bad sooner or later due to bearing wear and are normally replaced more frequently than the crankset.

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