| Author | Message | ||
     M1combat |
I read a statement made by I think Hal's that when they converted to dual hub mounted rotors that the tendency for the XB to stand up under braking went away... Can someone confirm, deny, or at least explain the physics of this to me?? Would it also go away if you went to dual perimeter mounted rotors? If so, can this be done with the stock rim?? | ||
| Bigj |
Me thinks the stand up business has all to do with the perimeter brake. Dual perimeter would be much worse. Sportrider mag did a test on moment of inertia btween an '02 R6 front wheel/brake setup, and an XB9 setup. Even the the XB9 setup weighed 4 lbs. or so less, the MoI was the same. All the weight is concentrated at outer edge of the wheel. If you've noticed, even though you see perimeter brakes on a lotta show bikes, there really haven't been many that have made it to production. No racing bikes run them(other than stock FB's). Actually the trend is going back to smaller lighter dual discs. I've even see a 4 rotor setup, with two very small discs per side.  | ||
| Skully |
Guys, Think about it: the location of the brake rotor has nothing to do with the bike tending to stand up under braking just like having only one rotor won't tend to make the bike turn under hard braking. (-5) The tendency to stand up during hard braking is more likely caused by the relatively steep rake of the front suspension. The very reason the bike handles so well may be the reason it tends to stand a bit during breaking. I have a race prepped Honda F3 that I only wish turned in like my little XB does. Regarding the Sportrider article and rotational inertia, lighter is still better. The less unsprung mass you have (wheels, brakes, fork sliders, fenders, etc.), the better the bike is going to handle. I have to wonder about the four rotor scenario. More brake pads, more calipers... more unsprung weight. Hope this helps, Keith edited by blake on December 03, 2003 | ||
| Kevyn |
someone please correct this if it's wrong... it's my understanding that the tendency for a bike to stand up under braking can be at least toned down if not eliminated with proper suspension set-up. if...you are braking in a corner, you may be coming in too fast?? | ||
| Daves |
Or you should be on a race track! To trail brake on the street/public roads is asking to crash. Ride to the edge! Dave Iowa HD/Buell (Buell Cycle Center) | ||
| Dynarider |
M1 is correct. Hals racing team did say that. The only reason they had to switch back to the stock style perimeter brake for this year was Buell told them to do so. Its for marketing & basically if they wanted to continue to get any funding...althought publically Buell will deny funding them...they had to use a stock style brake setup. | ||
| Azfirebolt |
Anyone have any shutter when the front brake gets hot. I've had a weird sensation every once in a while. Almost a warped rotor feel, but, it is seldom and unpredictable. Pads glazed? Fading due to heat? Anyone....? | ||
| M1combat |
Thanks Dyna, that's what I thought. As far as braking into a corner because I'm coming in too hot, that's not EXACTLY the case  . I have removed the chicken strips on my tires but only through the judicious use of tight corners and not hanging off the bike so as to use more lean angle. Don't worry, I ride safe . About the only time I notice it (because it's about the only time I brake in a turn) is on a downhill tightening right hander that starts out about 75 and the exit is about 55 (nowhere near the limit, I would estimate limit to be about 110 entry and 75-80 apex if you use the whole road, which I don't). The corner is marked 30, but I'm sure that's mostly because it's downhill and that plays havoc with cars in the wet. Anyway, back to standing... Here's my thoughts... The hub mounted rotor will be roughly what, 15 degrees from parallel to the center of the contact patch when you draw a line from patch to closest point where the rotor is attached to the hub? The perimeter mounted rotor would be more like 70 degrees? Could this be a factor? If so, dual perimeter brakes would move the average right back to the center of the wheel. As far as it being caused by rake, they didn't change the rake when they went to the hub mounted rotor at hal's... On the "proper suspension setup" issue, you may be right, it does tend to dive more than I like it to when I hit the brakes... Granted, it also stops VERY fast too . I have contemplated adding some spring preload and turning the damping up a 1/4turn for both bump and rebound, but I don't want to induce a headshake. It seems to handle VERY well as it is and if all I have to do is live with a little more dive than FEELS right to me... I will. | ||
| Sarodude |
Here's a silly retort WRT Hal's statement about less standup without the perimiter brake... What if the effect of standing up is lessened by the greater rotational inertia of the heavier tire / wheel / rotor combo? Put another way, the same attributes that make the XBs more willing to change direction may make them more susceptible to certain type of direction change. Just a completely unsubstantiated, uncalculated shot in the dark. -Saro | ||
| Englishman119 |
My experience as an XB racer for what its worth.... Any handling problems with my XB have ALL been self inflicted. Either poor riding position or the dreaded death grip on the bars. Unintended Stoppies are due poor riding position. Scully is on the money, the bike is short with a steep steering angle which just helps to lift the rear wheel. That’s the down side. The up side is a bike that flicks through corners like no other. There is a natural tendency under heavy breaking to lock your arms straight to brace yourself, or hold on, as you experience the breaking forces. This then transfers more of your bodyweight to the front wheel as you are effectively pushing down on the bars from above. Result is a Stoppie. All my unintended stoppies have been due to locked arm, sitting upright type breaking. Look at the best road racers. Even under the most spirited of breaking their arms are at least bent or better, parallel to the tank. They are taking most the breaking forces via their legs and crutch gripping the tank. By not pushing down on the bars under breaking, rather, but by pushing straight ahead you are also perfectly balanced for counter-steering the bike. I was under the impression Hals tried the dual disc to combat brake fade ! My $0.02 Mark edited by englishman119 on December 03, 2003 | ||
| Paulinoz |
"I have removed the chicken strips on my tires but only through the judicious use of tight corners and not hanging off the bike so as to use more lean angle." I hang of the bike to reduce lean angle or maintain the same angle at a higher speed, unless you are refering to hanging of in the opposite direction, I might be confused but then I am Australian. | ||
| Blake |
There may be something to the added gyro effect of the larger front disk causing the front wheel to want to turn-in as the bike leans, thus necessitating additional counter-steering input. Solution? Drill a bunch of lightening holes in your rotor a' la wave rotor. Would be interesting to try. The lighter front stock tire would seem to reduce that effect, so if you have mounted and aftermarket tire and not noticed a difference, that effect is probably not a factor. If you do notice a difference after putting on a new heavier aftermarket front tire, that would tend to support the idea that the added rotational inertia is contributing to the tendency to stand up under braking. | ||
| M1combat |
Englishman... I am referring to the tendency to "un-lean" itself, not stoppies. I don't think I've used the brakes hard enough to even worry a tiny bit about stoppies. I try to keep everything a LONG ways under the bikes limits and a good bit under my own limits. One thing I have learned out of a couple times of surprising myself is that I really just need to trust the damn bike... It'll do it. I won't be even really attempting to learn either of our limits until I can catch a track day in Phoenix. I am just trying to catch one in the winter time. You are correct about the brake fade. They just ended up with an added bonus. Paulinoz - I too lean off the inside to reduce lean angle, but mostly just for practice as I don't think I "need" the extra traction. I was leaning a tad outside just so I could use more lean angle and scrub the chicken strips. My reasoning was that I didn't want to have to use un-scrubbed edges when I really needed the edges and all that they could give me. The whole rotational inertia idea... I think I read somewhere that someone did a comparo on the rotational inertia of a GSXR600 and the Buell. Even though the Buell setup was lighter, the weight of the large rotor and it's greater distance from the center made the difference in inertia negligible. I would really like to talk to one of the M2 owners who have converted to two perimeter rotors about their experience with the setup. They have more rake and trail, but I would appreciate their input. Taking a look at the forest though, what Englishman said is probably the case even though he was referring to stoppies. I bet that some more preload and damping will help tremendously. Can anyone offer insight as to the handling effects that would take place? What would be the effect from fast bumps (not high speed bumps)? | ||
| Anonymous |
Man I hate the BS that circulates. Just ran a bunch of testing at VIR, and no, the single disc does not make the bike stand up. Fact...the XB race bikes turn better with the single disc because it has less inertia, and far less unsprung weight. Fact...the dual disc works Nissin systems run by Hal's were extremely special...you can't even buy them, and you sure wouldn't want to if you knew the price. Fact...these systems did have more stopping power with less lever effort than the single disc stock system...also far better than any OEM dual disc system. Fact...they did NOT handle as well, so the riders want a system with the best of both worlds...now there's a surprise. Will it happen...we'll see. But think of these two things: 1) Running a stock XB system with race pads, Cicotto repeatedly outbraked Matt Wait's Yamaha at Daytona this year while vying for the lead...do you need more brake than this? 2) The racers want more bite with less lever effort...ie. much lower effort to get stoppies and lock the wheel...do you need that when the road may be wet, oily, bumpy? Reminds me of when at the first Lightning race in Daytona a rider came over bitching that he needed more brake on his motorcycle, and asking why we wouldn't allow dual discs but required stock singles. I asked him what lap times he was turning, and he was about 15 seconds per lap slower than Higbee, who was running the same single disc. Now tell me, did that rider need a dual disc set up, or did he need to work on some other things? | ||
| M1combat |
I'm not looking for more brake power. I understand that the lighter the unsprung mass the more compliant the front system will be. I have personally noticed that with even just a bit of an application of the front brake (I don't tend to use the rear) the bike seems to want to stand up a LITTLE bit (enough to make me want to countersteer a little). I assume that if I were to hit the brakes a good deal the bike would stand up quite nicely although I haven't tried that. I have already mentioned that it could be my setup (Out of the book for my weight but I haven't actually checked the sags) and quite frankly am perfectly willing to accept that it may be technique as well. The fact that others have noticed this leads me to believe that I am not causing it. Don't worry, that doesn't lead me to believe that I am doing everything right. All I am asking is for someone to explain the physics of the situation to me. In case you were wondering, I also understand that braking in a straight line is the best thing to do unless you are in a short to medium length tightening radius corner. Which is where I notice it. It could very well be that it's caused by the fact that I'm NOT leaned over to the limit for that radius of turn and the bike isn't at home. I'm not blaming anything on the bike, I like it (to say the least). I'm asking for input. I've heard that the more you learn about your tools the more able you are in using them. I seem to remember Micheal Schumacher at least repeating it. "But think of these two things: 1) Running a stock XB system with race pads, Cicotto repeatedly outbraked Matt Wait's Yamaha at Daytona this year while vying for the lead...do you need more brake than this? 2) The racers want more bite with less lever effort...ie. much lower effort to get stoppies and lock the wheel...do you need that when the road may be wet, oily, bumpy?" 1) No. 2) Certainly not. I want to know exactly how my front brakes work (or as close as I can get). If Hal's team hadn't noticed the ZTL brake attempting to stand the bike up under braking why did they mention that it went away when they swapped to the works setup? Personally though, I would think that an astute pilot would be able to use this to his advantage on a racetrack... I'm not sure how, but I'd bet there's a way. As far as your last paragraph... I'm betting I'd be a good 20 or so seconds behind. I believe I need to work on pretty much everything. I also didn't say I thought I needed a dual rotor setup. I said I would like to hear some rants or raves from people who have tried it, especially if it was on an XB. I would also like to hear from someone who has used dual hub mounted rotors AND a single ZTL rotor on an XB. | ||
| Rsh |
All sport bikes have the tendency to stand up in corners when braking, some to a higher degree than others. For me suspension adjustments have made the most difference. I use the Battle2win Shawn Higbee settings as my baseline, which has changed my XB9R into an extremely flickable go where you point it type bike, these settings seem to have lessoned the stand up under braking issues. The manuals suspension settings gave me the feeling I had to fight the bike to get it leaned over and any thought of trail braking was questionable. The XB just wasn't nearly as much fun as it is now. | ||
| Opto |
Why does any bike stand up? (This is a simplified description.) You're leaning hard into a right-hander, the contact patch of the front tyre is slightly to the right of the steering centerline, i.e. a line drawn down through the center of the steering head bearings. You grab a handfull of front brake, the front wheel tries to turn to the RIGHT, to center the contact patch closer to the steering centerline - you guess the result of that. Nothing to do with brakes. Something to do with front tyre profile, rake, trail. One BWB'er mentioned that Metzeller something tyres near eliminated this effect on a XB9, as did a German mag who fitted 208's to the 12S. Other riders aren't affected I guess because they don't put the bike in that position, but they still go very fast. Just my 2c. | ||
| Glitch |
I'm not sure how, but I'd bet there's a way. Not on a track mind you...but...in the twisties, I've found that when you get to a turn that ends in another turn going the opposite direction (ie: hard right to hard left) I just feather the front brake a little, and it helps the transition from one lean angle to the other. | ||
| Reepicheep |
Geesh. Why on earth would you not want to have to push hard to turn hard? Or push harder to turn hard while breaking? Until I get arm pump from my local set of twisties, I consider this a plus. I love the handling characteristics of my Cyclone, and loved the 9s characteristic on my one cruelly short test ride. I want the bike to want to stand up while breaking... ITS A STREET BIKE! AND ON A STREET BIKE YOU PROBABLY WANT TO BE STARTING TO STAND IT UP WHILE YOU START BRAKING. Um. imho.  | ||
| Chainsaw |
Amen, brother. | ||
| Kcfirebolt |
Someone mentioned the shuddering from the front brake pads during hard riding. I had that happen to me in Arkansas a couple of months ago. Does anyone know what going wrong when that happens? My mechanic said they were glazed. I roughed them up some and the problem went away until I went to a track day and the problem resurfaced. When the bike went in for its 15k, the mechanic discovered that they had spilled fork oil on the front pads during the 10k and he said that may have caused the shuddering. They replaced the pads for free. What do you guys think? It is pretty spooky when that shudder appears, particularly when I'm charging around Arkansas. | ||
| Blake |
How can you possibly say your suspension is set up per the book if you haven't even checked the sag????? Sag settings affect handling SIGNIFICANTLY. Suggest you check your sag. You know that sag thing? You might want to check it. Checked your sag lately? Got sag? Know what it is? Don't be sagfoolish. Sag, it's your friend. | ||
| Paulinoz |
Dont ever remeber seeing actual figures for sag on The XB12 just spring settings for different weight ranges, but I am probaly mistaken. A link to these figures would be good | ||
| M1combat |
Those are the setting I'm referring to. Daves had it setup for my weight when I bought it. I am just referring to fine tuning it just right instead of a generic "close enough" based on my weight. I'll get to it. Still though, others with far better setup skills than me have noticed it. Keep in mind, I don't really mind the fact that it happens, I just want to know how it works. I'll go grab my service and owners manual and take a look around for SAG settings. | ||
| M1combat |
Nothing, I'll look around on the web. I know I've read something about it the value. I was thinking 35mm vehicle sag. | ||
| M1combat |
Alright, so Sportrider says between 25mm and 35mm of rider sag. Of course, after they say that, they say that it really depends on geometry. I was waiting for that. I guess I'm still left with setting it based on table 15 in the owners manual and then tune to preference. I'll be sure to record where it's at. | ||
| Trojan |
We changed our front brake from the single disc to the dual radial setup because we found that the front brake was just getting too hot and fading very quickly. This may be due to the fact that a lot of our race tracks in the UK are quite short and technical, and in some races the brakes would last only 3 laps before fading badly due to heat. We improved it slightly by using Castrol response DOT 4 plus brake fluid, but still not enough to be able to take full advantagge of the 'Bolt's brilliant handling against the Duc's and Aprilias. The other 'imponderable' is rider feel. Jonathan was never confident enough to brake hard right up to the apex of turns with the ZTL brake, (a problem which should not occur on public roads!)but did feel a lot better with the dual disc setup as far as feel and confidence went. The dual disc was ultimately more powerful in the end for us, although we have no figures to prove this. The factory tested both types of brakes with all sorts of telemetry, so when they say that the single disc performed better then I certainly wouldn't argue. I think in the end it comes down to what you as the rider feel more comfortable with. | ||
| Glitch |
Being confident can be the deciding factor in a lot of things. | ||
| M1combat |
That's a wise statement Glitch. | ||
| Trusty748 |
"Its physics, Jim" Dr 'Bones' McCoy |
