Yamaha R6 Forum: YZF-R6 Forums banner
1 - 8 of 8 Posts

·
Nothing Special
Joined
·
52 Posts
Discussion Starter · #1 ·
Floating Rear Caliper Mount vs Floating Disk: This is something that seems to be lost on so many people that it's nearly a lost fact.

Up to roughly the mid 1990s the full floating rear caliper mount was something commonly seen on nearly any bike that dared to wear the badge "high performance". Many top tier racers had them, many top tier builders used them. There's a skill set that goes along with the full floating rear brake caliper mount, together the two things create faster lap times, shorter/safer stops (10% to 15% more deceleration g-forces when the rear brake is used properly with the front brakes .. this is a measurable and repeatable thing), and more bike control mid-corner.

Before the advent of self throttling motorcycles (aka "traction control" and/or "anti wheelie") the rider was responsible for keeping the bike stable while accelerating or cornering. Today that responsibility falls mostly on the VCU's programmer, whether that person is the rider or someone else. Before digital TC, the rider would use the rear brake to hold the front wheel down on corner exit, mainly to keep it planted and prevent it from "getting light up front" and causing a front end washout. Proper application of the rear brake at apex can also "pull the bike in" towards the curb line as well. The rear brake also served to prevent high sides while still permitting acceleration on exit. On some of the more nasty/evil bikes the rear brake was used to smooth out the horrible throttle response or bad power delivery. In that hyper-sensitive area when you're at maximum lean angles and fully apexed at zero or trailing throttle, applying throttle at that time is the most surgical situation of each lap, and on some bikes that were poorly tuned or had peaky power curves the rear brake was the only thing that could provide some type of useful power delivery when attempting to tip up and begin exit. I mean when you have a power curve that is shaped like a friggin checkmark (abrupt power increase) and resembling nothing like any type of "curve" the rear brake was/is your only tool to tame that crappy delivery.

Today we have TC, "crossplane crankshafts" (another old but renamed concept, we used to call it "crank retiming" to create any number of funny sounding engine names like "twingle" or "screamer" or "big bang"), and anti-wheelie to control the exit drive.

With the shorter swingarms of the pre- "modern long swingarm" bikes the rear brake caliper needed to be floating ... that is to say "separately operating" from the swingarm's up and down motion. Why? If the swingarm and rear brake caliper are permitted to "float" independently on their own "moments" (so to speak) both may work far FAR more freely when the rear brake is applied. Non-floating rear caliper mounts tend to "bind up" the rear suspension when the rear brake is applied. No, it doesn't totally lock up the swingarm and prevent it from moving up and down at all. But, yes, a non-floating caliper mount will rob a good deal of compliance out of the rear suspension when the rear brake is applied. This loss of compliance does not permit the rear tire to maintain maximum grip because the rear wheel is not allowed to "comply" with the small irregularities of the road/track surface. The super long swingarms on today's homologation bikes (aka "sport bikes") somewhat reduce the need for the floating caliper mount, the extra swingarm length made possible by the modern engine designs that stack the transmission shafts on top of one another instead of putting them one after the other behind the crankshaft. Some swingarms on some modern sport bikes are over two feet long, eye-to-eye. That's about five or six inches longer than your pre-stacked-transmission era bikes were. Most early bikes' swingarms come in at just under 20 inches eye-to-eye compared to my 2003 Yamaha R6 which measures at just under 25 inches eye-to-eye.

Using the rear brake on corner entry is something still espoused by many hot shot riders today, even the MotoGP aliens.

The floating caliper mount is also very helpful at keeping the rear tire connected to the surface over stutter/braking/chatter bumps. It's sortof it's strong suit. So for those railroad crossings that have a STOP sign right after them where the road gets all bent out of shape, or "stutter bumps" approaching traffic signals (a super common thing out here in the southwestern desert, the streets become super hot during the day, and at night when they cool they buckle from severe expansion and contraction .... stutter bump city!).

And, the rear brake was also used to keep engine RPM in check when down shifting, this obviously in a time before slipper clutches were nearly "the norm". But this stuff was back in a time when your right foot did more than hold up the right side of your ass when you stand up. Your right foot was your Traction Control, your Slipper Clutch, your handling correction device, your Anti Wheelie, your anti-highside unit, your throttle response tuner, your "manual crossplane crankshaft", your oversteer initiator (especially on bikes with lesser amounts of on-tap closed throttle BHP needed to break the back end loose and get it to come around and back the bike in to the corner) ..... as well as that thing that gives you something to put your right boot on. ;)

I think that for modern short course racing (aka AMA PRO, and so on) that there's not much need for a floating caliper mount since the tracks are so well groomed and taken care of. However if you're a "real roads" racer (aka Isle of Man, Pike's Peak, Macau) the floating caliper mount might be something to consider. Hell, even some of the airport tracks that are so friggin rough might be candidates for floating rear calipers. Public roads are total shit compared to pampered and primped short courses. At 150mph+ on poorly kept public roads that have irregularities, launch points and dips that dead-bottom the suspension at full revs in top gear ... I'd sure like to know that I have that floating caliper mount to help keep the rear tire on the surface .... especially when those 165mph mailboxes and fireplugs whizz by!

TODAY'S FLOATING DISKS ..... ok now these little goodies are designed for a completely different purpose. Well, not really I suppose .... I mean all of these things are aimed at the same general purpose which is to reduce speed safely. But the fact that today's disks and yesterday's rear caliper mounts both contain the word "floating" is the only other thing that the two have in common with one another (other than better decel). Today's floating disks operate by allowing the rotor to self-align between the brake pads when the disk begins to warp (from heat). Those little floating "buttons" permit the actual disk rotor to "float" separately from the rotor center a little bit from side to side. When the disk rotors heat up, they warp out of shape. When that happens the pads only have contact with the rotors for a reduced amount of rotation instead of the pads being in contact for the full 360 degree circle that the rotors turn in, since the rotor is warped the pads only contact it .. let's say .. 180 degrees ... or HALF of the amount of time. The pads are held very tightly in the caliper when the brakes are applied, they cannot move or "float" along with the shape of the warped disk as the rotor heats. Since the pads cannot move in their calipers while also remaining in proper contact with the heated and warped rotor, the rotor is designed to move permitting the pads to maintain a far better grip .... the design effectively increases "swept area" after the rotors warp from heat distortion. So when the rotor heats up under braking and begins to warp, it can shift or "float" on those little buttons ... just enough ... so that the rotor remains better aligned between the pads as they grip the spinning (and warped) rotor. As the rotor cools it straightens back out, all is well.

SO, CAN THE FLOATING REAR CALIPER MOUNT BE USED WITH A FLOATING REAR ROTOR? Absolutely, yes. Since they both perform different functions that are both aimed at the same end (better braking) they work fine together. There are no conflicting effects or odd side effects from combining a floating rear caliper mount and a floating rear disk.

As far as me? Well, I come from dirt track and MX racing. The rear brake is an essential item there, from TT tracks all the way to the mighty mile tracks. It's something I use every time I stop or slow down, street or dirt, I don't think of it as the rear brake, or the front brake ...... they're just THE BRAKES and they are both to be used at whatever state of front/rear balance I .. as the rider ... chooses. It's a skill I've developed over 40+ years of riding and racing and to be honest it's a skill that nearly anyone my age (54 years) that raced will have within their set of experiences. I'm one of those that believes it's better to loose twenty pounds of ass-fat and use the rear brake rather than spend $3k on pipes and other 0.1 second per lap expenses ......... (think about it folks, on a 400 pound 150hp bike loosing 20 pounds of ~fat ass~ equals roughly 4 or 5 hp when the power-to-weight ratios are figured up! All for eating right and taking care of yourself. A funny sight is the guy in overly tight leathers with a bike dripping with titanium crap. Learn to use the rear brake and pick up 15% per corner entry .... loose twenty pounds and pickup another chunk from the stopwatch. All for free. Or .... keep up with the Crispy Cream cheeseburgers and spend another $3k on crapola to obtain the same result. Just a thought......)

Throwback? Oh hell yes I am. I mean, I like the rear brake (along with the front of course) enough that I'm even going as far as installing a left hand operated rear brake, like the supermoto freaks use, along with the buck standard foot operated rear brake (they use independent calipers on the better designed systems, one caliper for the foot brake and one caliper for the rear hand brake, each on it's own hydraulic system). I wish I'd had that when I raced TT and/or MX, there were SO many times that having the advantage of using the rear brake while turning right would have been a race-winning move. I've also found need for rear brake while right foot was otherwise "busy" on street bikes (parking on hills, using loading ramps, and so on).

But then again, that's just me, the throwback. :)

(I'm also using a thumb throttle instead of a twist throttle, but don't tell anyone, I'd hate to start a rukuss! I discovered many years ago that the thumb throttle is far superior for road bikes, at least for me it is. And there is simply no better throttle design on Mother Earth for doing wheelies! .... end of sentence, nothing to even argue about there. Tons TONS safer, far better handlebar purchase in corners when hanging off the bike, and no stuck-open throttle when the bike falls on it's side (something track marshals would come to appreciate!) If there are any bumps to deal with, as in MX racing or other off road two-wheeled riding the thumb throttle is not ideal and should not be considered. But as long as you're not dealing with "whoops" and jumps the thumb throttle is a superior device. The fact that your right hand is clinging to a nice and solidly mounted non-moving grip, just like the left side is, is mega-helpful, especially when getting physical on the bike in corners. Just watch a You Tube of flat track racing quads, you'll see the same body position as knee dragging. Note their effortless throttle control, at no time is there any concern about properly "cocking" your hand or wrist before entering a corner. If you've never flat-tracked a quad you most likely won't agree with this. It's a learned skill, one I've years of honing. It's a skill much easier learned by two-wheeling beginners rather than veterans .... newbs have nothing to "unlearn" or reteach themselves. If you're a seasoned rider, I might suggest trying it .. but be very careful at first and learn the device properly. Once learned, it's superior design for street/road bikes becomes clear.)

SO THAT'S ALL I GOT.... : My best effort to explain the difference between a full floating rear caliper mount and a floating rotor. As well as their functions and uses. Perhaps that will help a few folks better understand the engineering between their legs.

Thanks ..... :)
 

·
pin it to win it
Joined
·
8,087 Posts
Tldr. I don't use the rear
 

·
Nothing Special
Joined
·
52 Posts
Discussion Starter · #5 ·
This guy doesn't seem to mind not having one:

At least not in that several second video clip he's not. Better research his interviews, along with piles of other MGP racers. The "super-racers don't use the rear brake" is a myth. A bad one. There are even articles all about that exact topic (how MGP riders brake from 200mph+ was the most recent one I saw ... nothing but actual quotes from MGP riders, if that's what one needs to help convince them).

In my mind, since I'm not the ultra talented Stoner (insert ~whomever~ hero worship here) I would require every advantage I can get to compete. I only possess about 4.5:1 power to weight ratio of talent anyhow, so any advantage is worth investigating. Rear brake adds around 15% of stopping power ... this is a known fact, a measured fact. Why oh why would I ever want to leave 15% of braking power on the table for other riders to take from me?

Think about it.

No, there's no floating rear caliper kit for the R6 or any other sportbike I know of. As I said in my article TC and long swingarms have negated the need.

However that does not mean the rear brake is a boat anchor. Squids insist that "they never use it". Fine, I'll take that 15% more braking g-force and corner control over the guy unwiling to even learn how to use it. It's a great tool, obviously it's something that a LOT of riders leave there for YOU to take advantage of and beat them. They brag about it all the time ... "I never use mine" ... so TAKE IT FROM THEM!!!!! It's FREE! Imagine up to 15% more braking force at every single corner entry. If I were promoting some "new" gadget that promised that, they'd be lined up at my door throwing money at me to obtain it.

Well, it's right there fellas. Free. Or not. It's up to you.

"Get it" ..... those sponsors that you want most certainly do!
 

·
Reads the rulez
Joined
·
2,255 Posts
Oh look, the R6 resident, Shervin, is back.

We missed you.
 
1 - 8 of 8 Posts
Top