Krien Dawson's dashboard

Kilted Skier has just mailed in a great question:

"Battery - no ISCG tabs and i understand your reasoning for this. There is a severe lack of BB's that will support 73mm e-type. I can't find anything in ISIS and only a Shimano in Octalink. What are you guys suggesting/using?"

First, I'd like to clarify exactly why there are no ISCG tabs on the Battery, as that in itself is a good question.

But before I even do that, let's just remind ourselves that there are two ISCG standards, there is "classic", aka "03", and then there is the new "05" spacing.

From a technical point of view, the ISCG standard made a whole load of things much easier; we can now be reasonably certain that any given frame / chain set / chain device will work together, although there is still plenty of minor niggles/fine tuning. Its 200% better than it used to be...

The Achilles heel of the ISCG system, are the three small tabs on the Bottom Bracket, which are the mounting point between the frame and the chain device.

The main issue is that many manufacturers have difficulty getting these to align correctly (it's surprisingly difficult, although for us not a problem) but the second, and in our opinion most serious issue, is that the tabs are actually very fragile.

With the strength we are now seeing coming from chain devices (I've got one of the new E13 "race" guards, and its about a dozen times more shock resistant than my old MRP was back in the day) there are more and more issues surrounding what happens when immovable object meets chain device... imagine what happens to a bike, when the CD smashes into a rock... something has to give.

Unfortunately, 9 times out of 10, the first thing to break are the tabs, they were never designed to withstand these kinds of forces. End result: instead of having to buy a new chain device or chain ring, you're effectively left footing the bill for a new frame... ;-(

So; when we were designing the Battery, we will fully aware that these kind of blunt force impacts onto the chain device more well within the boundaries of "reasonable use" for this bike. We have always thought of it like a big BMX, it's stunting bike, and we don't want people to be having to worry about what happens to the bike itself if they do some grinding, or seriously mess up a trick.

We sat down with Dave Wiegle, who is the main man behind the ISCG standard, as well as of course E13, and asked for his advice. His answer was very simple; "Use a BB mounted chain device, or a BB to CD adapter"

The advantage of this, is that not only at the tabs removable (so the frame will never get damaged) it also means that actually the chain device can rotate racket slightly) in the event of a really big impact, which will probably save not just the frame but also the CD.

So, that's the why, here is the how:

You will need what is commonly known as a "E type" compatible bottom bracket, this means that when you open the box there will be, on the right-hand side of the bottom bracket assembly, (at least) one 2.5mm spacer.

When Shimano designed the E type system, their intended use was to allow the fitment of a front derailleur without using a band clamp around seat tube. We remove this little spacer, and replace it with the chain device (or chain device adapter) and then clamp the bottom bracket assembly down my nice and tight, with the tabs aligned correctly (for which you should see your instruction manual delivered with the CD).

In order to be clear, let's just have another quick history lesson:

Waaay, back in the day... we used 'three-piece" cranks and BB, by which I mean you took a bottom bracket out of one box, and then took two crank arms out of another, and you made it all fit. Originally the axles on the BB were four sided (unsurprisingly, they were called square taper). In an effort to improve the interface, Shimano released a system they called Octalink. This was later copied/influenced by other crank by fractures who created the ISIS system.

Then, Shimano did something rather surprising, and they resurrected a 20 year old idea, and created a much more integrated approach to the whole BB and chain set debacle, this was called Hollowtech II. This meant that you now received the cranks and bottom bracket in one box, with the bearings for the bottom bracket now carried in cups that sit on the outside of the BB shell. Visibly, the biggest difference is that the cranks are now two piece, with the axle permanently connected to the drive side crank arm.

But, this system had some inherent disadvantages, most critically that because the axle is permanently fixed to the crank, it is not possible to swap axles to modify the bottom bracket length. Then there was also the problem of different bottom bracket widths, 68mm or 73mm (BTW: we always use 73 as wider = stiffer, right?)

In order to overcome this, Shimano simply pushed everything out board, increasing the chain line and the Q factor. By designing the bottom bracket widths around the widest possible use (73 mm shell also using E type) they simply added more and more of those little 2.5 mL spaces in order to make the bottom bracket work on "thinner" bikes.

They few years later, this new system was also copied/influenced by several other manufacturers, who jumped on board with something incredibly similar, which they decided to call X-Type.

So any of the cranks, up from any of the manufacturers, will therefore allow the fitment of a bottom bracket mounted chain device, as you simply remove all of the spacers, and bolt in the BB mount.

Now; back to the kilted skier's original question, as it would appear that he is NOT going to be using one of these newfangled X-Type crank sets...?

Now I am not as familiar with all the different BB's on the market as I used to be (it used to be my job, and I am glad not to have to deal with that headache any more..!) but as far as I'm aware, all of the major manufacturers still offer this option.

GUS: to finally (really) answer your question, I called Shimano / Madison in the UK, and they tell me that they have the BBES51 in stock (BBES51EC18) which will work.