As technologically advanced as today's sportbikes are, it's interesting to note that while even the most basic and bottom-rung econobox automobile comes standard with an anti-lock brake system, none of this seemingly basic safety technology has made its way to the supersport market. Of course, it could be said that ABS (anti-lock brake system) has barely made inroads into the motorcycle market in general, much less sportbikes. But with many sport-touring and standard motorcycles now being offered with ABS as an option, why hasn't it been even attempted with a supersport bike?
The two biggest reasons have been performance and weight. A sportbike is lighter, nimbler, smaller, and more powerful than your average motorcycle, and as such demands a more tactile approach to riding it. This is especially true when it comes to slowing all that performance; today's braking systems are highly-developed designs that are engineered not only to bleed off all that speed as quickly as possible, but also to provide the rider with maximum control over that deceleration via feedback and modulation. Any interference in that line of communication degrades the riding experience, and most ABS systems' threshold up to this point have been too low to avoid the disconnection that would inevitably occur on a supersport machine. And then there is the added weight of all the additional componentry and hydraulic fluid, of which there is very little room for on the compact and pared-to-the-bones build of a sportbike.
Leave it to Honda, then, to tackle the seemingly impossible task of engineering an ABS system specifically for supersport models that doesn't intrude upon their personality or performance.
We covered some of the primary aspects of Honda's new Combined ABS in a previous issue ("Honda Unveils Brake-By-Wire ABS for Sportbikes", Late Braking, September '08), but now that we've managed to get a CBR600RR C-ABS model for test (the C-ABS is also available as an option on the CBR1000RR), there are a ton of important details on the system that have come to light.
The biggest difference between conventional ABS and Honda's Combined ABS is that the Honda system is a true "brake-by-wire" design, meaning the brakes are electronically controlled--and that includes normal operation, when the ABS isn't triggered. Conventional ABS uses hydraulic pressure generated by the brake master cylinders from the rider pulling on the front brake lever/pushing on the rear brake pedal and redistributes it via a pressure control valve and/or pump to vary the hydraulic force at the point of wheel lockup. This often causes a loss of feedback at the lever (with many ABS, the lever feel becomes mushy and soft) due to the hydraulic pressure being rerouted through the various components when the system is activated.
These are the main components...
These are the main components of the Combined ABS: the two valve units on upper left and upper right measure the hydraulic pressure generated by the rider through the conventional brake master cylinders, and send data to the electronic control module in the center, which interprets the data and sends commands to the power units on lower left and lower right to apply pressure to each brake.
In order to make room for...
In order to make room for the C-ABS rear brake power unit located underneath the tailsection, Honda had to add a remote reservoir to the rear shock.
Both the standard and C-ABS...
Both the standard and C-ABS bike receive this lower fairing extension for '09 that completely covers up the engine. Its main purpose is to hide the C-ABS components that are mounted behind the engine.
Instead of using hydraulic pressure generated by master cylinders in the usual manner, the Combined ABS produces hydraulic pressure using an electric power unit for each wheel. The power unit consists of a DC stepper motor that spins a gear-driven ball screw (basically a screw riding in ball bearings that allows it to spin smoothly and quickly) attached to the hydraulic piston. These are controlled by an electronic control module (separate from the engine's ECU) that interprets data provided by valve units--again, one for each wheel--that measure the amount of pressure the rider exerts on the brake lever/pedal. The ECM tells the power units exactly how much hydraulic pressure to generate based on the data from the valve units; because the ECM is capable of hundreds of calculations and commands every second and the power units are able to adjust the hydraulic pressure just as quickly, there is no need for an inline pressure control valve as with a conventional ABS. This also eliminates the pulsing at the lever common with standard systems.
If the rider isn't controlling the brakes with hydraulic pressure, then won't the feel at the lever be non-existent? Another innovative idea in Honda's system called the "stroke simulator" handles that aspect. In order to simulate the brake feel in both normal and ABS operating modes, two rubber cushions of differing density in each valve unit provide increasing amounts of resistance as the lever/pedal stroke increases. This is designed to offer a familiar sensation to the rider that is claimed to be nearly identical to those generated by traditional hydraulic brakes.
Because there is a separate system for the front and rear wheel controlled by the ECM, Honda was able to incorporate its Linked Braking System philosophy--where actuating either brake also actuates the other (although using the rear brake does not automatically engage the front brake unless wheel lockup is detected; more on that later)--into the Combined ABS (hence the "combined" prefix). Instead of being constricted to a fixed ratio of front/rear brake power distribution as with the LBS, however, the Combined ABS is able to continuously and infinitely vary the braking power to each wheel, allowing the system to adapt to the CBR's more demanding handling characteristics and hopefully making the system much more transparent than its predecessor.
"And what if the Combined ABS system should suddenly develop an internal failure of some sort," question the luddites, "or if you move the bike when it is off? Would you have no brakes at all?" The elegant design of the Combined ABS also includes the fact that it is built in line with the standard brake system. The valve units that send data to the ECM measure hydraulic pressure generated by the rider operating the standard master cylinders via brake lever/pedal; a solenoid valve connects the two systems. When the engine is off or there is an electronic failure, the valve is open, allowing the rider to operate the brakes by the master cylinders in the conventional manner. Once the engine is running and the bike begins traveling over 3 mph, the valve closes and hydraulic pressure control is then turned over to the Combined ABS' components.
Oh, Right, There's The Bike, Too
Lost in all the hoopla of the Combined ABS is that the CBR600RR received some minor updates for '09. New crossover balance tubes on the exhaust header pipes and a muffler valve similar to the unit on the CBR1000RR, along with a new shot-peening process in the intake ports, are claimed to boost midrange power. The front brake calipers are the same monoblock design used on the bigger CBR (400 grams lighter) and the bodywork has been slightly revised, with the lower portion of the engine now covered with a fairing to hide the Combined ABS components mounted behind the engine. And amazingly enough, Honda finally updated the turn signals; the previous units were basically the same as those used on the original CBR600F Hurricane of '87.
The valve units measure the...
The valve units measure the hydraulic pressure exerted by the rider via the conventional brake master cylinders, and relay the information to the ECM, which tells the power units how much braking power to provide. The stroke simulator comprises two rubber cushions of differing density to replicate the resistive feel and feedback of a conventional brake system. When the engine is off or if there is a failure in the C-ABS, solenoid valves 2 and 3 close, isolating the system away from the brake system and allowing normal actuation of the brakes in the conventional manner.
The Combined ABS precisely...
The Combined ABS precisely and quickly controls hydraulic pressure using two electrohydraulic power units, one for each wheel. Based on data provided by the valve units, the ECM tells each of these power units exactly how much hydraulic pressure to provide and when. The electric stepper motor on the left spins the gear-driven ball screw that moves the modulator piston, precisely controlling braking force as often as hundreds of times per second.
This diagram shows the complete...
This diagram shows the complete layout of the Combined ABS, which is much simpler than conventional ABS that requires pressure control valves, pumps, and yards of extra brake line. Note that five main components are all located close to the engine to keep the weight as centralized as possible.
So How's It Ride?
Needless to say, we were a bit skeptical of the Combined ABS' ability to simulate a conventional brake system's feel at the lever, and we decided to take the standard '09 CBR600RR along for comparison purposes. Our testing ran the gamut of city traffic, highway drone, canyon carving, and even some closed circuit scratching (although the standard CBR wasn't available during that time).
Interestingly, Honda apparently decided not to promote C-ABS on the 600RR, as there are no logos or insignia anywhere on the bike. In fact, the C-ABS model looks identical to the standard model, and the only way you can tell the two apart (other than the sensor rings that are barely visible from the right side) is the gold-colored monoblock front brake calipers of the C-ABS version.
Pushing the C-ABS bike around with the engine off, and the brakes feel like any conventional system, which they should since you're actuating them in the standard fashion. Turn the ignition key on, and both bikes' dashes go through the same startup exercise, with the stepper motor on the tach running the needle to its full range and back, and the digital speedometer curiously running backwards from 180 mph to 0 mph in about two seconds. A small yellow ABS warning light on the lower left of the dash remains lit until you ease out the clutch and roll past 3 mph, which is basically anywhere with the clutch disengaged and the bike in motion.
Puttering along in city traffic, we were pleasantly surprised to find that the C-ABS brakes' feel is indeed nearly identical to a conventional brake system. Everything from lightly brushing the brakes while negotiating a tight space to moderate use while pulling up to stop or slowing to avoid a lane-encroaching automobile revealed no weird mushiness or numbness, with some "virtual" feedback actually being felt through the lever when you modulated the braking pressure at the lever in various situations. In fact, the response and feel is so seamless that there is no way anyone would be able to tell that they were riding the C-ABS bike.
Even during spirited canyon riding, there really isn't anything out of the ordinary that occurs when braking--except that the C-ABS bike remains impressively stable during situations where the standard bike might get a little out of shape. There is less front-end dive when braking on the C-ABS model, and this is because of the C-ABS' actuation of both front and rear brakes, with the rear brake acting to settle the chassis down on its suspension instead of letting the rear end jack up to full extension and cause excessive weight transfer to the front tire. Even more advanced riding techniques like trail-braking into corners were accomplished easily and comfortably with little fanfare and no weird issues. We also found that using the rear brake by itself in cornering situations worked very well without the annoying front brake application that would occur with the old LBS-equipped Hondas; this is because the C-ABS rear brake does not immediately activate the front brake unless rear wheel lockup is detected.
The C-ABS' braking behavior is so seamless and its ABS threshold so high that it can be difficult to tell when the ABS is actually engaged. Even over rough pavement, braking action was just as smooth as any standard brake system, with none of the "free-wheeling" cycling tendencies common to more primitive ABS setups. The only time we were able to really notice the C-ABS activation was during very aggressive braking on the racetrack, or simulated panic stops on the street.
On racetrack pavement, the ABS actuation would be perceived as a slight numbness through the lever once past a certain braking threshold; even though you're asking for more braking power at the lever, the rate of deceleration remains the same (note that this is only at expert-level braking on a racetrack; most riders will probably never notice it). Think about that--this is an electronic braking system, yet feedback is good enough up to that point that any change in the brake behavior is only a slight numbness at the lever. Amazing.
|HONDA CBR600RR C-ABS |
|TEST NOTES |
|+ ||C-ABS brake-by-wire system works superbly |
|+ ||Same excellent CBR handling |
|+ ||Definitely will help most riders |
|- ||Adds 24 pounds of weight |
|- ||Adds $1000 to price |
|- ||Down on horsepower |
|+ ||Definitely the best ABS we've tested by far |
|SUGGESTED SUSPENSION SETTINGS |
|FRONT ||Spring preload: 10 turns out from |
full stiff; rebound damping—2 turns
out from full stiff; compression
damping—2 turns out from full stiff
|REAR ||Spring preload: position 5 of 9; |
rebound damping—2 turns out from
full stiff; compression damping—14
clicks out from full stiff
We conducted some simulated comparison panic stops on dry pavement, and again, the ABS engagement is so smooth that the only way to tell it was activated was a numbness at the lever. It took us a couple of tries before we were able to better the C-ABS' rate of deceleration, and note again that this was with an expert rider at the controls who is comfortable with the massive weight transfer that occurs on a standard bike and can use it to his advantage. Meanwhile, the more level chassis attitude and stable feel of the C-ABS bike will surely help the majority of riders stop more quickly and comfortably. And in the wet? Forget it. Even a pro-level rider wouldn't be able to reach the first-time stopping distances or deceleration rates of the C-ABS bike, because it is able to react to the changing grip levels of the wet brakes and tires far quicker than any human.
The only real drawbacks to the C-ABS are the additional $1000 on the sticker price, and the 24 pounds extra weight. To tell you the truth, even on a 600 like the Honda where that much weight would sound like a lot, we barely noticed it. Honda wisely positioned the C-ABS components as close to the engine as possible for mass centralization.
Oh right, the bike. Since most of the CBR is unchanged from the previous model, we found the '09 CBR600RR C-ABS bike to possess the same sharp handling and impressive performance of its predecessor. We felt like there might be a slight bump in midrange power around 9000 rpm, but nothing earth-shattering. Otherwise, the CBR is the same great bike that has won our last two middleweight shootouts.
Which One, C-ABS Or Standard?
Honda has made a quantum leap forward in anti-lock brake systems with the Combined ABS. That it works so transparently and superbly on a high-performance machine like the CBR is a testament to its well-thought-out design. But the big question is, would we buy the C-ABS version over the standard model? We figure that would depend on where you intend to ride most of the time, and your riding skill level (and you'd better be honest with yourself). If you do a lot of track days and are an intermediate to expert level rider, you'd probably prefer the standard CBR. But for everyone else, there's no doubt in our minds that the extra $1000 would be money well spent.
| ||Indicated Speed ||GPS MPH ||Stopping Distance ||Max Long Gs ||Average Gs ||Deceleration Rate |
|C-ABS ||50mph ||49.09mph ||122.97 ||-1.38 ||-0.97 ||21.077f/s^2 |
|Standard ||50mph ||49.09mph ||105.32 ||-1.31 ||-1.04 ||24.610 f/s^2 |
We used our Racepak G2X datalogger to record braking performance of both the standard CBR600RR and the C-ABS model during three simulated panic stops from approximately 50 mph using El Jefe as the test pilot, with the numbers averaged for both bikes. Just looking at the raw numbers chart on top would lead you to conclude that the standard CBR stops much quicker than the C-ABS bike; for instance, the standard bike stops in a shorter distance and has a higher deceleration rate, and while the C-ABS bike generates a higher max braking G force, it doesn't sustain it as long. Looking at the deceleration graph shows that the standard bike is able to gain a higher deceleration rate quicker and sustain it during the first portion of the graph. Note that although the standard bike's graph tails off, it still stops in a shorter distance; both of these advantages are because of the standard bike's weight transfer, allowing Kento to use more traction for stopping. Looking at the longitudinal G over time graph, however, you can see where the C-ABS is able to generate a significant spike in power during initial braking, because he doesn't have to squeeze the brake to keep the front end from diving suddenly. However, once the system detects lockup, it quickly intercedes, and you can see where the cycling adds distance as the bike slows to stop. It should be noted that with some practice, we could most likely get the C-ABS to stop quicker by modulating pressure more, and these are results obtained by an expert rider. And in the wet, we're confident that the C-ABS will always stop or slow in a shorter distance.
'09 Honda CBR600RR C-ABS
Type: Liquid-cooled, transverse inline-fourValve arrangement: DOHC, four valves/cyl., shim-under-bucket adjustment
Bore x stroke: 67.0 x 42.5mm
Compression ratio: 12.2:1
Induction: PGM-DSFI with 2 injectors/cyl., 40mm throttle bodies
Front suspension: 41mm inverted cartridge fork, 4.7 in. travel; adjustments for spring preload, compression and rebound damping
Rear suspension: Unit Pro-Link single shock absorber, 5.1 in. travel; adjustments for spring preload, compression and rebound damping
Front brake: Two, four-piston calipers, 310mm discs
Rear brake: Two-piston caliper, 220mm disc
Front wheel: 3.50 x 17 in.; cast alloy
Rear wheel: 5.50 x 17 in.; cast alloy
Front tire: 120/70ZR-17 Dunlop Sportmax Qualifer PT
Rear tire: 180/55ZR-17 Dunlop Sportmax Qualifer PT
Rake/trail: 23.7 deg./98mm (3.8 in.)
Wheelbase: 53.8 in. (1367mm)
Seat height: 32.3 in. (820mm)
Fuel capacity: 4.8 gal. (18L)
Weight: 436 lb. (198kg) wet; 407.2 lbs (185kg) dry
Instruments: Analog tachometer, LCD panel display for digital speedometer, coolant temperature, fuel level, odometer/dual tripmeters, clock; warning lights for neutral, high beam, turn signals, EFI problem, C-ABS problem
Quarter-mile: 10.84 sec. @ 129.23 mph
Top speed: NA
Roll-ons: 60-80 mph/4.00 sec.; 80-100 mph/3.61 sec.
Fuel consumption: 39 to 48 mpg, 42 mpg avg.
Honda almost got it right in regards to the C-ABS. Don't get me wrong, kudos to the Honda engineers for designing a very advanced ABS specifically for a sportbike. And the CBR600RR is a fantastic middleweight, featuring an engine with enough torque that it feels more like a small literbike rather than a 600, and the suspension is compliant without compromising its cornering ability.
But that's where there's also the compromise with the ABS. To start with, the standard Honda non-ABS brakes work awesome. Easy to feel and modulate with excellent power. Riding aggressively, you lose some of this finesse with the ABS. It's not too intrusive, but it does affect the ride and front-end feel nonetheless. Technically, I could bore you with the dynamic rake changes and why the standard bike has a better feel, but it is the rider experience that suffers--albeit slightly. For less aggressive riding and novice to intermediate riders, it's a great rider aid. I would really like to have the security of the ABS around town, but I wouldn't want to compromise the little Honda's awesome canyon and track performance for it. Maybe an on/off switch for the ABS next year?
Before I rode the new CBR600RR C-ABS, Kento explained how the Honda engineers designed their braking system to be completely "ride-by-wire". Since I understood about half of his explanation, I was skeptical about how it was actually going to work; another OEM doing something just because it can. After testing the C-ABS, I was surprised that it actually works really well. What's so fascinating is that at regular speeds, it was hard to tell the ABS version from the non-ABS version when we switched back and forth between the two CBRs. Exerting light to medium pressure on the brakes had a similar lever feel to the standard hydraulic units.
Under heavy braking the ABS version worked very well. I compare the feeling to hard braking on new tires; a little greasy but nothing scary. The ABS model had very little front-end dive, and under stressful situations the C-ABS would be a nice thing to have. However, I would rather have the feel and feedback of a standard hydraulic brake system and I think that most sport riders would too.
I have to tip my cap to the engineers at Honda for the overall performance of the C-ABS. It really is a well-designed system that is transparent enough for most riders that it won't be an issue at any time. And having the security of ABS in a panic situation (especially in wet conditions) is something that will be worth the price to many people. Most anyone who asks me which bike to pick between the two would get the C-ABS answer.
Of course, the key word is "most". For some expert riders who do a lot of track days, you might notice some intrusiveness under very heavy braking. It's nothing scary or demanding, but for those riders who really like braking deep into corners, you'll sometimes find yourself asking for just a bit more braking power.
The extra 24 pounds of heft isn't really much an issue either, because the Honda was the reigning featherweight of the 600 class. And the mass is kept close to the engine so that its effect on handling is minimal.
Would I fork out the extra $1K for it? If I mostly rode on the street, I probably would.