| Author | Message | ||
     Ben_jamminvfcc |
I've always wondered about the Buell's perimeter braking system, because it performs exactly opposite of the way I expected it to: I assumed that placing the rotor further out from the axis of rotation would dramatically increase the MOI of the front wheel. Much in the same way that you could swing a stone in a 2" circle and it'll have much greater momentum(and speed) than a stone swinging in 1" circle. Additionally, it is harder to swing. Yet it seems the Buell system is featherlight(at a standstill). Could this system become less beneficial as the speeds increase? Just a side note...anyone ever seen those pics of the '04 R1 with the dual perimeter braking system? That's hott....I wonder how hard it'd be to get dual perimeters on a Buell. Probably about half as hard as on the R1.  | ||
| Rigga  |
its lighter because the braking forces are transmitted through the rim instead of the spokes on a conventional braking system.....therefore the spokes can be made slimmer and thus a lighter wheel | ||
| Ben_jamminvfcc |
Well, I understand how that makes for a lighter system. But it seems that placing the weight of the rotor farther out from the axis of rotation would also increase the MOI of the front end as the speeds increased. I think I'm confused on my physics somewhere! BAH! | ||
| M1combat  |
Check out the ?third? issue of Fuell magazine for '04. It explains the benefits of the setup quite nicely. It doesn't go into the drawbacks, and they do exist from what I've heard. It's just that the benefits heavily outweigh any drawback I've heard of. I'm sure someone on the site could do the math... I'm curious to know whether there is more or less gyroscopic stability generated by our setup vs. a conventional dual disc setup. As far as the R1 w/ the dual perimeter brake... Anyone can get one. They are about $2100 as I recall for the base model. " Yet it seems the Buell system is featherlight(at a standstill). Could this system become less beneficial as the speeds increase? " That's a good question... Judging by the performance of the FX racing teams and really anyone racing a Buell... I would say "not really"  . The ZTL setup is "featherlight" though . Aint it great? | ||
| M1combat |
It "would" increase the moi of the front wheel assy., but the fact that the spokes are lighter and that there is only one rotor seems to make up for it. This leaves us with the obvious advantage that the entire unsprung assy. is a great deal lighter than anyone else's. | ||
| Ben_jamminvfcc |
Yea, I wonder why it isn't more widely copied...Patent infringement? I read it wasn't as advantageous in a racing application...but I fail to see how that's true... I've also heard though, that the Buell brakes aren't exactly SS literbike spec as far as stopping power....But, I bet if we went with another rotor, we'd have much more stopping power than a typical SS.....think of all that surface area. The only production bike I've seen(other than Buell) with perimeter's was a Ghezzi and Brian Furia...one race model with dual perimeters, and a hooligan model with a single perimeter brake(no rear). | ||
| Buells Rule! (Dyna in disguise)  |
There is a dual perimeter setup from the aftermarket for the tube frame Buells. Very pricey though. I also believe but have no proof that the perimeter brake on the XB's is also there for stability. It definitely serves more than 1 purpose. | ||
| Cataract2 |
Always wondered what would happen with two perimeter brakes on the Buells myself. Have a feeling it would be almost to much for the street. | ||
| Ben_jamminvfcc |
Yea...Buell hasn't actually revealed the secret behind the stabile feeling of their unstable "sounding" steering geometry. Though the rigidity of the frame is also responsible I'm sure. I'd venture that the frame is designed to flex laterally as well, while being very stiff horizontally. Buells Rule....is that an '04 R1 in your avatar? If its yours...I'm quite jealous. | ||
| Fullpower  |
Dyna pegged it there. The XB front wheel assembley, including the rotor weighs 21 pounds. putting the relatively heavy rotor way outboard on an otherwise very light wheel is the key to the stability of a bike with such radical geometry. that and the low hanging 20 pound muffler helps some. | ||
| Buells Rule! (Dyna in disguise) |
Not a pic of my actual bike, but I do have an 04 R1. Thanks. Here's mine  Ok now, back to the topic on unsprung weight & the perimeter braking. | ||
| Reepicheep  |
The XB, like most litre bikes, has more then enough brakes to flip the entire bike with two finger braking. The only disadvantage to a single large rotor over dual rotors is heat dissipation. If you are riding aggressively on the track, you *may* overheat the rotor. I doubt it is possible to do this on the street and be alive for more then a 1000 miles of riding. So if you plan on doing 120 mph to 25 mph near panic stops 5 times every 95 seconds for an hour, you should consider a dual rotor setup. Note that to get the weight of the front wheel assembly back down to where stock is, you are looking at over $1000 worth of racing wheel. If, however, you don't plan on that type of sustained riding, you would be a fool (imho) to run anything but a single ZTL perimeter rotor. An insider posted a few years ago, Buell did not save much money going with a single 6 piston caliper versus two 4 piston calipers, but they did save a bunch of weight. | ||
| Brupska |
I know Josh Guyer's front brake what overheating at Homestead. I talked to his mechanic and he said that it may because they added a better master cylinder on the front. I talked to him every time he is in the shop. He is the greatest person to talk to. If you see him at the track and he is not busy I am sure he would talk to anyone about XB's and there strong points. I asked him about using different materials to use in making a racing front rotor and he told me all of the ins and outs. Carbon fiber is not legal. Titanium is questionable because of which pads to use. What is the factory front rotor made out of? | ||
| Outrider  |
Dyna...I can't believe you finally fessed up to the avatar. I have been keeping that secret for what feels like forever. Incidentally, the pic you just posted of your bike on the beach is Dyn-O-Mite! Your R1 gets better looking every time I see it. Kudos! | ||
| Hkwan |
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| Buells Rule! (Dyna in disguise) |
That bike looks positively evil. | ||
| Buells Rule! (Dyna in disguise) |
Bill, yep just like the pic in my profile because the lips of the rims are polished, looks good & thinking about having it done. Extra bling points.  | ||
| BadS1  |
Dyna the rims in your avatar look chrome to me and the black you see is shadow. | ||
| M1combat |
It does look good. Very good... | ||
| Buells Rule! (Dyna in disguise) |
Its possible, either way I like the look. Hmm maybe get me some spinners? Now again, back to unsprung weight. Who has a pic of peters S1 with the dual perimeter disc setup? | ||
| M1combat |
I do I do...  That one?? | ||
| Blake |
The perimeter brake is needed to stabilize the front end? Ever see a dirt track bike with a super-lightweight spoked front wheel and no front brake at all? Ghezzi and Brian are "production bikes"? Please point me toward the Ghezzi and Brian dealership in East Texas, I've been wanting to take a test ride.  Truth: A perimeter brake does provide superior stopping power compared to a single conventional disk, but without the lightened wheel is failing to exploit one HUGE benefit of such a braking system. Maybe someday we'll see the rear sprocket and brake done up in perimeter form too along with a frighteningly lightweight rear wheel just like the front on the XBs. The rotational or "polar" moment of inertia, a measure of an object's resistance to any change in rotational/angular velocity increases with the square of radius from teh rotational axis, the axle's centerline in our case. The tire si what governs the front wheel assembly's polar moment of inertia. It weighs more than any brake disk and is located further away from the rotational axis than any brake disk. The rim and outer portions of the wheel would be nest, then... the perimeter brake disk. What does polar moment of inertia of the front wheel assembly affect? Anyone? | ||
| M1combat |
Handling . How efficiently the suspension is allowed to work. | ||
| M1combat |
Also... Are you sure that our ZTL rotor weighs less than a front tire? I've never picked the rotor up, so I'm curious. | ||
| Trenchtractor  |
I'd liek to add here that I rode my KTM SM for a couple of months with the stock dirt 240mm disc while I was waiting on the arrival of the 320mm kit. I bolted on the 320mm kit, which consisted of the 320mm disc and REPLACEMENT Brembo caliper extention. The two discs weighed virtually the same, the 240mm dirt disc was definately more robust, while the 320mm disc was more lightwieght design. I noticed straight away two things... 1. the stopping (stoppie) power was immense compared to before... I had heard comments that unless I was going to ace the SM, not to bother with the 320mm kit as it was a waste of time for the road. BOLLOX. 2. the speed at which the bike turned in was reduced A LOT. I made no other set-up changes besided the brakes, and yet it was handled a lot slower, so much so i ran wide on the first corner I had a go at. Now if you asked me before I went out on that first ride how much difference it would make, I would have told you stuff all. Everyone was saying the only difference between the 320 and 240 kits was that the 320 cooled better. Not true. Now, when I ordered the new disc, I pulled the 240 and caliper off, checked pads, resurfaced them and decided that since they had very few hours work they would be fine on the new disc, they were still flat since the 240mm disc and pad set had done less than 30 hours. When I fitted the 320mm disc i simply resurfaced the pads again and we were away. | ||
| Blake |
A typical 120/70-17 front motorcycle street tire will weigh between 8 and 10 LBs when new. I'd be surprised if the 370mm diameter front brake disk weighs more than 2.9 LBs. So yes, I'm sure the disk weighs less than the tire. Even if the disk weighed the same as the tire the PMOI increases with radius squared, and the tire's radius of gyration is WAY larger than that of the disk, like 1.5 times as large (50% larger), thus even at the same mass the tire would contribute 1.52=2.25 times more to the PMOI than does the disk. More likely tire's mass is about three times that of the disk and so the tire overal contributes about 6.75 times more to the PMOI than does the disk. See, it gets less significant the further we go. | ||
| Blake |
Brad (Trench), I don't buy it. It had to be something else other than your disk upgrade that affected your perception of turn-in. Did you put on a new tire as well? Were you using the front brake while turning in? I cannot see any way for such a small disk to affect handling enough to notice at the speed you would be traveling, especially with a big front wheel/tire. | ||
| Trenchtractor |
Nope. The bike was essentially finished... wheels, tyres, suspension, pipe, plastics, the works... The only part that I was waiting on was the caliper bracket, I had the 320mm disc but could not use it until the bracket turned up. So out of frustration I mounted the 240mm disc and started using the bike... I'd had enough time (couple of months) to really get used to the bike as a SM with the 240mm disc... I was already using most of the front tyre. That's why I noticed it straight away, there was certainly a difference, it wasn't imagined, or are you gonna tell me there's a SOTP dyno equivalent to handling... I probably rarely turn in without brakes. But I could proly best explain it as 'needed more input on the 'bars to effect RAPID change of direction' with the 320mm disc compared to the 240mm disc. I could feel the front wheels reluctancy to change direction compared to before. I'd riden the bike that morning with the 240mm and rode it in the afternoon with the 320mm. I hadn't even changed the tyre pressure. Road surface temperatures here are fairly constantly hot, we are in the tropics. I HAD NOT EXPECTED ANY CHANGE IN HANDLING PRIOR TO RIDING THE BIKE that afternoon. So it's not like it was placebo effect... I wasn't imagining the difference, and I changed NOTHING else on the bike that day... The first ride I took was the same standard test loop I use and have used for the last 3 road bikes I've owned, so you could say I have a benchmark. And I continued to notice it. I'm not talking about the difference between a fatboy and the XB, I'm talking a subtle difference in handling that changed the charecteristics in a manner I noticed right away. It wasn't like it became notably physically harder to steer, more that it just required me to provide more input and a little sooner. I don't know if everyone would notice or not, but I did. Or maybe I just torqued the axle up a little too tight?? | ||
| Blake |
"I probably rarely turn in without brakes." Could that be a factor, what with the new more powerful brake an all? Possible? What diameter front wheel does the SM use? Big, no? | ||
| Rigga |
smaller than the off road wheel.....supermoto's generally use 17 inch wheels to take advantage off all the sticky road tyres about,bt i think trench was using the same wheel through out? just changed the brake disc diameter? |
