SRAM Simplifies the Crank with DUB 8

SRAM comes up with a clever new way of addressing the multitude of BB frame standards, by creating a new crank and BB system that is compatible with them all.

iceman2058

1/15/2018 1:29pm

GXP, 3 versions of pressfit, "Boost", fat bikes, different spindle lengths - the list goes on and on, just the like headache you get when trying to figure out which BB and crank go with your frame. Well, SRAM had another headache of its own, caused by trying to figure out how to make a better crank, as it was the one drivetrain component that hadn't really received much love as part of the whole Eagle development. Could these two headaches be cured at the same time? The answer is yes, and "DUB" is what SRAM calls this particular flavor of aspirin.

We're not trying to create another standard.

We can already hear a battle cry of rage rising from the depths of the internet at the mere thought of yet another standard, so let us put that fire out before it even starts: DUB is actually a way to make it easier to deal with all the existing BB frame standards out there, but it is NOT another standard of some kind. As far as SRAM is concerned, they have no business telling frame makers how they should design their BB shells. What DUB does is simplify the whole equation by optimizing the BB system around a single crank spindle diameter, which then allowed SRAM to create a set of light, strong, and durable BB options for any BB shell configuration. Because the spindle diameter chosen is new, you can only run DUB cranks with a DUB BB, but it would still be a stretch to call it a new standard of any kind. Think of it as a unit.

So what is the problem with the existing standards, and why not just decide to use the best one and call it good? Because, out of the two major spindle diameter "standards", each offers advantages that SRAM wanted to capitalize on: the 24mm spindle coupled with a GXP BB provides more room between the BB shell and the spindle, which means that there is more room to implement a good seal to protect the bearing (a bearing that makes room inside for bigger balls is also inherently more durable, all other things being equal). However, the 24mm spindle has to be made heavier to reach optimal stiffness. Conversely, the 30mm spindle can be made both lighter and stiffer than its 24mm counterpart, but it eats into the real estate available for the bearing, unless the frame maker makes more room in the BB shell of the frame (PF46, for example). So what did SRAM do? They started from a 30mm spindle, and worked their way down until they found a size that allowed them to come up with a solution for sealing off the bearing and protecting it from the elements regardless of the outer diameter of the BB shell. This is particularly interesting if you look at a PF41 BB, one of the worst offenders when it comes to bearing life, where the outer shield typically consists of a little plastic spacer that barely covers the bearing underneath it. We can already hear you asking, "OK so what's the new spindle size then?" Well, it turns out it's not vastly different to a 30mm spindle...it's actually 28.99mm, to be precise. However, SRAM is quick to point out that this is not a number that means anything in and of itself, as the important piece of news here is that as far as the frame is concerned, there is no change. Pick the DUB crank you want, with the DUB BB option your frame requires, and off you go. All SRAM DUB cranks are compatible with all DUB BBs. And there should be a DUB BB for any frame. Problem solved via "total system integration", in SRAM's words. We'll put these claims to the test as soon as we can get a little trail time in with the new goods.

SRAM DUB Cranks

When it came to the last drivetrain component in line for a complete overall, SRAM felt that while Eagle in general already benefits from a great reputation and much commercial success, they often noticed other brand cranks being specced on mid- to high-end builds. Looking into the issue a bit more, it became clear that weight was often a driving factor here. With the introduction of DUB, SRAM has been able to regain the upper hand in the "weight wars", with its XX1 Eagle DUB SL crankset now weighing in at a mere 422 grams with a 32T chainring, a 30-gram advantage over its nearest rival and hitherto class leader. In fact, looking through the 7 new cranks being launched here today, even the heaviest alloy crank on offer still only tips the scales at 717 grams with the chainring - not exactly portly by any measure. Such weight savings were not only made possible by shaving a millimeter off the spindle diameter, but also thanks to other improvements like carbon layup optimization and a new bonding process between the spindle and the crank arms. The range available today features Boost and fat-bike specific spindles - note that you can simply swap the Eagle chainring if you have a non-Boost frame (no word on the eventual future availability of an 83mm "DH" spindle option as of yet).

SRAM DUB Crank Line-Up Overview

XX1 Eagle DUB SL Crankset

DUB™ technology delivers the lightest, stiffest, strongest crankset available
All-new SRAM CARBON TUNED™ crank technology provides extreme stiffness and light weight
The X-SYNC™2 chainring provides significantly quieter performance, with better mud clearing and extraordinary durability
MSRP: $515 - $525 | €570 - €585 | £510 - £520

X01 Eagle DUB Crankset

DUB™ technology delivers the strongest, stiffest, lightest crankset available
SRAM CARBON TUNED™ crank technology provides extreme stiffness and light weight
MSRP: $485 - $495 | €540 - €550 | £480 - £490

GX Eagle DUB Crankset

Optimized 7000 series forged aluminum arms
DUB™ technology features a uniform approach to bottom bracket fitment, better sealing against contamination and is forward and backward compatible
MSRP: $135 - $185 | €150 - €205 | £135 - £185

Descendant Carbon DUB Crankset

Carbon construction for lightweight durability
DUB™ technology features a uniform approach to bottom bracket fitment, better sealing against contamination and is forward and backward compatible
Fully compatible with any 1x drivetrain
MSRP: $260 | €290 | £255

Descendant 6K DUB Crankset

Optimized 6000 series forged aluminum arms
DUB™ technology features a uniform approach to bottom bracket fitment, better sealing against contamination and is forward and backward compatible
MSRP: $105 | €115 | £105

Stylo Carbon DUB Crankset

Proprietary carbon layup technology
Fully compatible with any 1x drivetrain
DUB™ technology features a uniform approach to bottom bracket fitment, better sealing against contamination and is forward and backward compatible
MSRP: $260 - $310 | €290 - €345 | £255 - £305

Stylo 6K DUB Crankset

6000 series forged aluminum arms
DUB™ technology features a uniform approach to bottom bracket fitment, better sealing against contamination and is forward and backward compatible
MSRP: $105 | €115 | £105

SRAM DUB Bottom Brackets

As we previously alluded to, the main novelty of the new DUB system is the ability to cater to any frame with the just a single crank spindle spec. To adapt any DUB crank to a specific frame, you pick out the appropriate DUB BB. A lot of work was put into sealing the bearings from the elements, as SRAM feels that exposure to moisture and dirt is the main reason for premature BB bearing wear. On the topic of the bearings, they are not "proprietary" per se, but they are of a specific type chosen for the application at hand. The design of the DUB BBs allowed SRAM to shave a little weight in this area as well, citing up to 40 grams of weight savings in certain cases.