Product Photos: Ryan Palmer
Announced today, the SRAM Guide Ultimate is the new flagship model in SRAM’s Guide brake lineup. The idea behind the project was to throw everything the brake engineers had at this thing to make the best possible brake they could, without regard for cost. While the Ultimate’s lever is nothing more than a Guide RSC with a carbon blade and titanium bolts, there’s a whole lot of new stuff going on at the caliper.
SRAM GUIDE ULTIMATE | $290 EACH, ROTOR AND BRACKET NOT INCLUDED | SRAM.COM
Like most brakes, the Guides utilize a cup-seal timing-port system. Air bubbles rise to the top, escaping into a separate reservoir out of the pressurized side of the system. Notice the black cup seal on the left end of the spring, and the reservoir above it. Braking is initiated when the seal crosses over the timing port that connects the reservoir to the rest of the system. At this point, air on the reservoir side of the master will not affect braking. Also notice the swing link towards the left-most part of the cutout, which is responsible for controlling how fast and to what point in the lever stroke the pistons advance. This is what gives the Guide its superior modulation, pad clearance, and short dead band.
There’s a whole lot more to these new stoppers than carbon levers and fancy bolts. The real magic of the SRAM Guide Ultimate is in the all-new S4 caliper. Aside from needing to maintaining piston size and pad shape, engineers were given free reign to design the ‘ultimate’ caliper to mate with the already-impressive Guide master. SRAM’s main goal with the S4 caliper was to create a brake that feels exactly the same every time you pull the lever. This is accomplished by managing heat, creating super-consistent seal/piston rollback, and simplifying the bleed.
The redesigned piston tackles heat management and rollback. An micro-ribbed aluminum outer surface allows the piston to receive consistent lubrication from the DOT fluid inside the system, making piston rollback more reliable. The core of the piston is a phenolic compound designed to eliminate heat quickly. The pistons on other Guide models are made entirely of the phenolic material, but the aluminum cap allows for a much more controllable surface.
This little piece is a heat shield, and it’s responsible for significantly lowering the running temperature of the Guide Ultimate. SRAM experimented with heat shields around the whole pad opening, but found that the most significant gains were made in just the one location.
The black caliper on the left is the existing Guide caliper, and the one on the right belongs to the new Guide Ultimate. To make further reductions in the running temperature, engineers significantly increased the size of the pad pocket. You can barely make out the heat shield at the very upper part of the pad pocket. Between the new pistons, heat shield and wider opening, SRAM claims that the Guide Ultimate runs cooler than a Shimano XTR brake with both Ice-Tech and Freeza technology.
To simplify the bleeding process, there’s a new bleed port interface, with a new tool. The tool snaps into place and is held securely with a snap ring and rubber seal. After the connection is made, turn the knob counterclockwise to open the system for bleeding. There’s also a redesigned fluid path that allows bubbles to move through the system without getting caught up–as long as you have the pistons pushed back in, that is. To help remind you to do this, SRAM put the bleed port on the inside of the caliper so that you have to remove the wheel in order to do a bleed. Not only will it remind you to reset your pistons prior to bleeding, it’ll keep brake fluid off your rotors.
To round out this new flagship stopper, SRAM will be offering two-piece Centerline rotors in both six-bolt and Centerlock mounting and in 140-, 160-, and 180-millimeter diameters. They’ll retail between $72 and $78.
I had the opportunity to take the Guide Ultimates out for a test drive during Crankworx Rotorua in New Zealand. The Redwoods trail network offers nearly 100 miles of varied singletrack, from buffed-out jump lines to rutted downhill race runs.
We didn’t get the chance to get the Ultimates up to rotor-glowing temps on this particular ride, so I can’t speak to the heat management side of the equation quite yet–but I can say that consistency was top-notch. The lever threw to the same spot every time and braking power was predictable. I can’t wait to get a pair for long term testing–be on the lookout for that review in the coming months.
More on SRAM’s Guide brakes:
First Impressions: SRAM Guide Brake