Shimano I-Spec A, B and II mounts explained

Mountain bike combination brake lever and shifters

If you’re a mountain biker and own a recent set of Shimano disc brakes and trigger shifters in Deore or higher, you’ll likely have seen the term ‘I-Spec’. This is Shimano’s wording for integrating the brake lever and shifter into one handlebar clamp. Where it gets confusing is that Shimano is now onto its third generation of I-Spec in just over four years.


I-Spec is an optional choice in Shimano’s line-up, and so you can still purchase standard clamp shifters in all of Shimano’s aftermarket groupsets. If your Shimano gear shifters feature their own bar clamps, then you do not have I-Spec.

I-Spec A

Original I-Spec (now called I-Spec A) was introduced with XTR M985 in 2011. It was designed as an answer to SRAM’s popular MatchMaker, system which provided a cleaner and lighter bar setup by placing the shifter and brake lever into a single clamp.

I-Spec a versus i-spec b shifters:

An ‘I-Spec A’ shifter can be easily identified by a hook-like nub at the attachment point.

I-Spec A brake levers remain compatible with newer I-Spec B shifters (use silver nut supplied with shifter). If you own I-Spec A shifters, these can unfortunately only be used with I-Spec A brake levers.

I-Spec B

Just over a year after I-Spec A, I-Spec B was introduced and aimed to make for a simpler, stronger and easier configuration.

Pictured is a i-spec b shifter lever. the lack of a hook at its mounting point is a clear sign this isn’t ‘i-spec a’:

I-Spec B shifter and brake lever

The key departure from the previous generation saw the hook attachment point removed. On top of this, the mounting hardware changed from a square nut, to a threaded pin and nut configuration that’s mounted within the brake lever.

I-Spec B remains in Shimano’s line-up and offers backward compatibility. If you buy a new I-Spec B shifter set, it will come with appropriate hardware for fitting to either I-Spec A or I-Spec B brake levers.

I-Spec II

Pictured is an i-spec ii shifter :

A new I-Spec II shifter

For XTR M9000 and recently launched XT M8000, there is a third iteration – I-Spec II. This latest version is the simplest to install of all three, and allows for a far greater range of angle adjustment than previous versions. It’s not at all backward compatible, however.

Newer i-spec ii brake levers come with a simple washer, remove this to fit a i-spec ii shifter. as you can see, there’s no facility given for an i-spec a/b bolt/nut:

I-Spec II shifters fit by replacing that plastic spacer on I-Spec II brake levers

I-Spec II does away with the bolt assembly and instead fits a semi-circle spacer inside the brake lever clamp. M9000 and M8000 brakes now ship with a simple plastic shim within the lever clamp; for I-Spec II use, you remove this shim.

It’s worth noting that I-Spec B compatible shifters are available in these new 11-speed XT and XTR group sets for backward compatibility with previous generation brake systems. 

SRAM and Shimano mix 

It’s worth keeping in mind that if you are buying Shimano aftermarket, you’re not being forced into I-Spec. You can still run clamp-type shifters and brake levers together if you wish. Furthering this, if you’re interested in mixing and matching SRAM with Shimano, ProblemSolvers offers a range of I-Spec-MatchMaker adapter options.


For a closer look at different I-Spec options, click or swipe through our gallery up top.