Guest ratchethack Posted August 7, 2007 Share Posted August 7, 2007 Radial brakes' bolts are slightly off from 90°. If the bolts were placed between the pistons in this image, they would be at 90° to the tangent, but the bolts are placed so that they are about 75° to the force. You are incorrect. In both radial and standard brake applications, braking force on the caliper retaining bolts is exactly 90 degrees to the bolt axis -- this would be true regardless of the distance between the bolts in the case of the radial caliper above. Link to comment Share on other sites More sharing options...
dlaing Posted August 7, 2007 Share Posted August 7, 2007 Darn, you may be right. <_>Each pair of piston's disk is being dragged along a different tangent. The average of the two is 90° to the bolts, but is that the force they are fighting? I need to think about this a bit.... EDIT OK, thought about it a bit and if you removed the lower bolt so that only the upper bolt remained, the upper bolt would not be a 90degree shear and likewise if you removed the upper bolt so that only the lower bolt remained, the lower bolt would not be under 90degree shear, but under more tensile force than upper bolt would be by itself. Do these forces balance out perfectly and create perfect 90 degree shear at each bolt? I am not shear sure Link to comment Share on other sites More sharing options...
dlaing Posted August 7, 2007 Share Posted August 7, 2007 No surprise, Algor has the answer http://www.algor.com/news_pub/cust_app/queensu/default.asp Still, one needs to understand the physics in order to understand how to find the answer with the software. Link to comment Share on other sites More sharing options...
docc Posted August 7, 2007 Author Share Posted August 7, 2007 Just a part number: "98 23 08 20" and description: "screw" What about for the caliper bolts, which are reported to be marked with a class? Is that specified in the parts guide? Link to comment Share on other sites More sharing options...
Guest ratchethack Posted August 7, 2007 Share Posted August 7, 2007 . . .if you removed the upper bolt so that only the lower bolt remained, the lower bolt would not be under 90degree shear, but under more tensile force than upper bolt would be by itself. Do these forces balance out perfectly and create perfect 90 degree shear at each bolt? I am not shear sure What's your vector, Victor? Dave, if you continue to be so unsure, why so many speculatory posts shooting off wildly in all directions? Settle down a little bit, and think. Consider the braking force applied to the caliper itself. Now consider the direction of shear force between the caliper and its carrier. That force is a force vector parallel with the force acting on the caliper. In other words, the force on each of the caliper bolts -- radial or conventional design -- is parallel to the plane described by the interface between the caliper and its carrier. This plane is tangent to, or at 90 degrees to the wheel radius. The bolts are exactly 90 degrees to this plane. Link to comment Share on other sites More sharing options...
dlaing Posted August 7, 2007 Share Posted August 7, 2007 What about for the caliper bolts, which are reported to be marked with a class? Is that specified in the parts guide? No, they show a drawing of the caliper bolts going through a washer, the caliper and into the fork, but no part number. But the do give the part number for the washer!!!! 19 14 98 00 description: washer EDIT that was from the 2000 parts catalog. The 2003 shows the bolt: part number: 98 68 35 30 description: Screw Link to comment Share on other sites More sharing options...
dlaing Posted August 7, 2007 Share Posted August 7, 2007 What's your vector, Victor? <_> Dave, if you continue to be so unsure, why so many speculatory posts shooting off wildly in all directions? Settle down a little bit, and think. Consider the braking force applied to the caliper itself. Now consider the direction of shear force between the caliper and its carrier. That force is a force vector parallel with the force acting on the caliper. In other words, the force on each of the caliper bolts -- radial or conventional design -- is parallel to the plane described by the interface between the caliper and its carrier. This plane is tangent to, or at 90 degrees to the wheel radius. The bolts are exactly 90 degrees to this plane. It is worth speculating about, because it is an important part of understanding physics and engineering design. I have been unsure about this one because it is complex. The force at one end of the caliper is different than the force at the other. Each bolt takes on different directional forces and yet they work together, supporting each other. Please answer this question: If the bolts pointed to the axle, would they be at 90° to the force? Link to comment Share on other sites More sharing options...
Guest ratchethack Posted August 7, 2007 Share Posted August 7, 2007 It is worth speculating about, because it is an important part of understanding physics and engineering design.. . . OK, as long as you have a legit interest and aren't just thrashing -- I reckon getting to the physics behind engineering is part o' what we attempt to cover here. . . .If the bolts pointed to the axle, would they be at 90° to the force? Yes. If you haven't studied vectors before this may be a little difficult. . . but it's really quite simple, actually. A vector is simply a force with a particular direction assigned to it. In your photoshopped photo, the axis of each of the bolts is now aligned with the radius. However, in this case the force vector on each of the retaining bolts is STILL 90 degrees, since the braking force on the caliper is now described by a CIRCLE rather than a straight line in the actual case of the real radial brake. Again, in both cases, the direction of force described by the vector at the bolts is the same. Link to comment Share on other sites More sharing options...
dlaing Posted August 7, 2007 Share Posted August 7, 2007 OK, as long as you have a legit interest and aren't just thrashing -- I reckon getting to the physics behind engineering is part o' what we attempt to cover here. Yes. If you haven't studied vectors before this may be a little difficult. . . but it's really quite simple, actually. A vector is simply a force with a particular direction assigned to it. In your photoshopped photo, the axis of each of the bolts is now aligned with the radius. However, in this case the force vector on each of the retaining bolts is STILL 90 degrees, since the braking force on the caliper is now described by a CIRCLE rather than a straight line in the actual case of the real radial brake. Again, in both cases, the direction of force described by the vector at the bolts is the same. You can't have it both ways. The bolt is taking the primary force from only one angle. Describing it one way rather than the other does not allow the bolt to be withstanding two primary vectors of force. I am open to the possiblity that either of the bolt scenarios is at 90 degrees to the force, but not both. I am inclined to think the bolts facing the axle are taking the direct 90 degree force. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted August 7, 2007 Share Posted August 7, 2007 You are again incorrect, Dave. There's no having it "both ways". It's only one way in each of 2 scenarios. I again emphasize that in the actual radial caliper situation, the shear vector force on the bolts is defined by a straight line, where the caliper has no option but to move in a straight line defined by its relationship with its carrier should the bolts fail. The caliper CANNOT follow a curved path when the bolts fail. In the hypothetical photoshop scenario, the caliper is forced in the direction of a CIRCLE defined by its relationship with the caliper carrier. The caliper CANNOT follow a straight path when the bolts fail. In BOTH cases, as mentioned previously, the shear vector force on each bolt is 90 degrees to the bolt axis. There are no two ways to interpret the Physics here. NOTE: There are also secondary vector forces at work, having to do with the offset of the center of the brake pad force relative to the orientation of the pads and the geometry of the caliper, the carrier, and the mounting bolts. These secondary vector forces dictate tensile strength requirements on the bolts, as well as yield (shear) strength. For purposes of this discussion, these secondary forces are best left alone, lest we open up discussion far far far beyond the scope of the most basic underlying principles at work. I won't argue this any further. Please get help elsewhere if you need further confirmation. Link to comment Share on other sites More sharing options...
raz Posted August 7, 2007 Share Posted August 7, 2007 While you two are at it, please take the opportunity to educate us in why radially mounted calipers are so hyped in magazine reviews. When I first read about them I thought it was just some esthetic nonsense, but I have been told there might be some real advantage. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted August 7, 2007 Share Posted August 7, 2007 While you two are at it, please take the opportunity to educate us in why radially mounted calipers are so hyped in magazine reviews. When I first read about them I thought it was just some esthetic nonsense, but I have been told there might be some real advantage. Indeed there is a legitimate advantage! If you routinely apply your brakes to the limit of their stopping power at speeds of 180 mph , you might have a genuine concern about the amount of flexing of your fork lower castings, tubes, and stanchions, twisting of the calipers relative to the rotors, etc. -- and the detrimental effects all of this has on handling with a peg dragging the tarmac, while nicely drifting through a 120 mph sweeper under heavy late braking as the fork is binding under such kinds of flex with non-radial brakes!! However, for those who aren't riding to quite that level on the road , IMHO all the hype has ANOTHER VERY IMPORTANT purpose -- and that, my friend, IMHO would be it's PRIMARY PURPOSE! -- of course that would be to separate FOOLS from their cash! For every World Class racer riding ultra-fast, hyperpowered, ultra-lightweight track missles bristling with exotic unobtanium components, how many idiot newbies with more money than sense d'you figure there are who will eagerly pay the outrageous markup on some of this crap so they can bolt it onto their tarted-up commuter/boulevard cruiser/barges?! In today's competitive marketplace, not only is advertizing hype CRITICAL -- but one has to take some care to understand one's target market demographics and the mentality of the target consumer, n'est-ce pas? After all, there's a burgeoning high-dollar "race bling/farkle" cottage industry out there that depends nearly entirely on glowing magazine reviews fueled by many nice "race bling/farkle" freebie kickbacks for reviewers, that offer nice glossy photo's of bolt-on blingery that is, for all practical purposes, IMHO very often entirely useless on the road. I reckon far more of this stuff -- and the bulk of the target market -- is sold to rank beginners exclusively for parking lot parading/posing purposes than to guys who actually make anything approaching actual use of it on the track. . . Can you be convinced that you really NEED radial calipers? How about wave rotors? Radial levers? How inadequate can you be made to FEEEEEEL about your as delivered stock front set o' Brembo's, which I find can be made to howl a sticky front tire on a 550 lb. motorcycle with 2 fingers -- and very controllably at that?! For the life of me, I can't. . . But then, I'm merely a Road Geez with an overweight pushrod motor twin with a boat-anchor bevel drive in it's rear hub, with a far-less-than-Tonti-rigid, flexi-spine frame with a rear weight bias problem and a short swingarm -- so wot do I know? I reckon if you have an ego that requires putting some glossy lipstick on y'er pig to "feel good about yourself" whilst riding it, you just gotta have it and nothing else will do. . . BAA, TJM, & I seriously doubt 99.9% of riders will find that their MMV. Link to comment Share on other sites More sharing options...
raz Posted August 7, 2007 Share Posted August 7, 2007 If you routinely apply your brakes to the limit of their stopping power at speeds of 180 mph , you might have a genuine concern about the amount of flexing of your fork lower castings, tubes, and stanchions, twisting of the calipers relative to the rotors, etc. -- and the detrimental effects all of this has on handling with pegs on the tarmac, while nicely drifting through a 120 mph sweeper under late braking while the fork is binding under such kinds of flex with non-radial brakes!! So the distance between the wheel axle and the caliper mount on my Sporti could make that part of the fork flex when braking hard. That's the idea in short? But... but... that's my natural anti-dive system! Link to comment Share on other sites More sharing options...
Guest ratchethack Posted August 7, 2007 Share Posted August 7, 2007 So the distance between the wheel axle and the caliper mount on my Sporti could make that part of the fork flex when braking hard. That's the idea in short? But... but... that's my natural anti-dive system! I like it, Raz. Works just peachy f'er Yours Truly also! I can't imagine anyone wanting to give up "natural" anti-dive for parade/poser blingery, can you? -- err, on second thought, cancel that. . . I reckon I can well imagine this -- and worse -- after all. . . Link to comment Share on other sites More sharing options...
dlaing Posted August 8, 2007 Share Posted August 8, 2007 While you two are at it, please take the opportunity to educate us in why radially mounted calipers are so hyped in magazine reviews. When I first read about them I thought it was just some esthetic nonsense, but I have been told there might be some real advantage. Radial brakes on upside down forks are more rigid and maintain better pad alignment. And disputably the bolts exhibit less shear force This results in real world differences for street bikes, but the differences may not be perceptable. There are certainly alot of sceptics out there. They probably have no benefit on up side up forks as the caliper brackets are normally shorter. I think in ten years 90% or more of new motorcycles with USD forks will move to radial calipers as there should be little increase in production cost. However as an aftermarket purchase, you won't get much bang for your buck by upgrading. Link to comment Share on other sites More sharing options...
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