GuzziMoto Posted September 18, 2009 Share Posted September 18, 2009 Some change the rake with the clamps as Greg states. Changing rake on the clamps has a greater affect on trail than just altering the rake alone. Remeber trial is the difference between the point that the steering axis and the tires contact patch meet the ground. In racing changing the offset was a early solution to the increased rear ride height needed to get correct squat during acceleration. This also benefited of decreasing the rake, but often decreased trail to an unacceptable level, reducing the offset of the fork would remedy that. Some motorcycles already have a very good squat angle, raising the rear ride height can disturb this, adjustable rake & offset triple clamps can allow you to decrease the rake of the forks but still keep the trail accpetable, this quickens the initial steering input but will still maintain a acceptable amount of stability. I think we are using different definitions for "rake". In my experience the common definition of "rake" is the angle of the steering axis. You can not change the rake angle of the steering axis with triple clamps. You can change the trail by changing the offset or you can change the fork angle if you were to bore the top and bottom clamps offset from one another or some adjustable clamp set allow you to change the offset of the top and/or bottom separately to some extent and this would change the fork angle (the steering stem would still pivot at the same angle). The effect on trail of this would vary as the forks are turned and as the suspension compresses. Talk about piss poor engineering. How hard could it have been to just have them weld on the steering head to the frame at a 25.5 degree angle? Link to comment Share on other sites More sharing options...
Greg Field Posted September 18, 2009 Share Posted September 18, 2009 Guzzimoto: Which forks on your wife's bike? (Axle nut or not?) Link to comment Share on other sites More sharing options...
GuzziMoto Posted September 18, 2009 Share Posted September 18, 2009 Guzzimoto: Which forks on your wife's bike? (Axle nut or not?) As I recall the forks have an axle nut. If I understand you correctly then this means they are the earlier forks without the funky offset. I will have to check this evening to confirm. Link to comment Share on other sites More sharing options...
Greg Field Posted September 18, 2009 Share Posted September 18, 2009 Read the part number on the underside of the lower triple. As I said before, there're lots of combos of parts possible, and some retrofitting was done, but in general, the ones with an axle nut have the non-canted triples. Link to comment Share on other sites More sharing options...
GuzziMoto Posted September 18, 2009 Share Posted September 18, 2009 Read the part number on the underside of the lower triple. As I said before, there're lots of combos of parts possible, and some retrofitting was done, but in general, the ones with an axle nut have the non-canted triples. Thanks. Link to comment Share on other sites More sharing options...
Guest ratchethack Posted September 18, 2009 Share Posted September 18, 2009 For all those subscribing to the idea that some (but not all!) short frame Guzzi's (and long frames too!) are INEXPLICABLY possessed by The Extremely Twitchy Demon -- with no way to tell the difference -- as introduced and lately made infamous on this and a prior thread by Yoo No Hoo -- you can rest assured that the idea of demon possession of motos is not without precedent! No, siree! In fact, lacking any evidence for that which remains UNEXPLAINED and UNSUBSTANTIATED (as demonstrated so spectacularly on this thread and others) -- and all the way up to "modern times", if mid-last century may be included -- we have fairly good documentation that demonic possession was still considered the best possible explanation for moto handling behaviors as recently as a half century ago by a soon-to-be WORLD DOMINANT moto company! You just gotta love the translation in this exerpt from a 1962 Honda Cub owner's manual (note demonic reference in the last point below): 1. At the rise of the hand by Policeman, stop rapidly. Do not pass him by or otherwise disrespect him. 2. When a passenger of the foot hooves in sight, tootle the horn trumpet melodiously at first. If he still obstacles your passage tootle him with vigour and express by word of mouth, warning, "Hi, Hi!" 3. Beware of the wandering horse that he shall not take fright as you pass him. Do not explode the exhaust box at him. Go soothingly by. 4. Give big space to the festive dog that makes sport in the roadway. Avoid entanglement of dog with wheel spokes. 5. Go soothingly on the grease mud, as there lurks the skid demon. Press the foot brake as you roll around the corners, and save the collapse and tie up. The ever-so-very Nasty Wheel Skid Demon, kissing cousin of the Short Frame Extremely Twitchy Demon No, Gents! Unsubstantiated Old Wive's Tales of the Short frame Extremely Twitchy demon possessed Short Frame Guzzi clearly ain't a unique concept -- nor, apparently, are they goin' away any time soon -- at least in the mind of possibly only one? hereabouts. . . Link to comment Share on other sites More sharing options...
Greg Field Posted September 18, 2009 Share Posted September 18, 2009 I wonder if Pavlov ever tired of his dogs? Link to comment Share on other sites More sharing options...
John in Leeds Posted September 18, 2009 Share Posted September 18, 2009 You just gotta love the translation in this exerpt from a 1962 Honda Cub owner's manual (note demonic reference in the last point below): 1. At the rise of the hand by Policeman, stop rapidly. Do not pass him by or otherwise disrespect him. 2. When a passenger of the foot hooves in sight, tootle the horn trumpet melodiously at first. If he still obstacles your passage tootle him with vigour and express by word of mouth, warning, "Hi, Hi!" 3. Beware of the wandering horse that he shall not take fright as you pass him. Do not explode the exhaust box at him. Go soothingly by. 4. Give big space to the festive dog that makes sport in the roadway. Avoid entanglement of dog with wheel spokes. 5. Go soothingly on the grease mud, as there lurks the skid demon. Press the foot brake as you roll around the corners, and save the collapse and tie up. Delightful - honest and unsophisticated Link to comment Share on other sites More sharing options...
GuzziMoto Posted September 18, 2009 Share Posted September 18, 2009 Just when I thought this was digressing into an informative thread...... Link to comment Share on other sites More sharing options...
Greg Field Posted September 18, 2009 Share Posted September 18, 2009 What? You don't like a slobbering dog? Link to comment Share on other sites More sharing options...
raz Posted September 18, 2009 Share Posted September 18, 2009 Good one, Ratch I'm always very careful not to explode exhaust boxes at horses but I must admit I have been ignorant regarding the risk of dogs getting entangled with my wheel spokes. And advice #2 should be forwarded to docc's horn thread. Hi! Hi! Link to comment Share on other sites More sharing options...
GuzziMoto Posted September 18, 2009 Share Posted September 18, 2009 Greg, the number on the underside of the lower clamp is 502 481B. The last part of the vin # (I assume that's what you are calling frame #) is 112434. It was bought as a 2000 in early '01. What does that tell you? Link to comment Share on other sites More sharing options...
emry Posted September 19, 2009 Share Posted September 19, 2009 I think we are using different definitions for "rake". In my experience the common definition of "rake" is the angle of the steering axis. You can not change the rake angle of the steering axis with triple clamps. You can change the trail by changing the offset or you can change the fork angle if you were to bore the top and bottom clamps offset from one another or some adjustable clamp set allow you to change the offset of the top and/or bottom separately to some extent and this would change the fork angle (the steering stem would still pivot at the same angle). The effect on trail of this would vary as the forks are turned and as the suspension compresses. Talk about piss poor engineering. How hard could it have been to just have them weld on the steering head to the frame at a 25.5 degree angle? I apologize, you are quite right. The problematic part is when the fork axis and the steering axis are no longer on the same plane. The definition for rake is rather old, forks and steering stems were always parallel, no issue. By definition changing the angle of the fork does not change the steering axis angle 'rake', as long as the vertical height of the steering head is constant. To be honest the jury still seems to be out on what and how (modern) rake should be calculated. Some consider the steering axis angle plus the fork axis (such as most custom chopper makers) or a variable of the two as effective or overall rake, some still say ignore it. In reality it boils down to the unknown of slip angle, camber angle, steering rotation (steering drop), and the transistion between normal and 'counter steering'. Effects of riding - a bump in the road or a dip how that relates to tire size plus changes of COG. Altering the fork axis relative to the steering axis has noticable effects on how a motorcycle behaves even when its trail is keep constant, I have to side with the custom chopper folks at this point (It might not be technically accurate, but it does a better job of mathmatically evaluating how a motorcycle will steer). But I am still waiting for a clear explaination of the forces and changes due to this 'misalignment'. When this is done right some very desirable handling characteristics can be achived without some of the short comings of the twitchy red frame demons...... sorry I just had too. Find me a demon Ratch... Sorry if I have caused any confusion folks. Link to comment Share on other sites More sharing options...
GuzziMoto Posted September 19, 2009 Share Posted September 19, 2009 That's fine, as you said it is not a clear cut issue. Chopper guys usually (or at least used to) list both the rake of the steering stem (as rake) and the extra angle the clamps add. In my opinion the problem with adding angle in the clamps is that while the forks are pointed straight ahead the extra angle is in line with the steering stem. But as you turn the forks that angle kicks the front wheel off to the side. It is no longer adding its angle to the steering stem rake entirely. The more you turn the forks the more of that angle goes off to the side instead of in line with the steering stem. This is not a big deal on choppers (they handle poorly to begin with) but on a sportbike anything more then a small bit causes wonkey steering geometry as the forks turn. This not only would kick the front wheel off to one side but would cause the trail to change as well. That is why it is used on choppers and drag bikes mainly. In fact, Kosman, who make them for drag bikes goes so far as to point out that it changes fork tube angle, not rake. But again, that is splitting hairs. The important part is that it is a crude wonkey patch that should have been done differently if at all. Guzzi engineering, gotta love it. Link to comment Share on other sites More sharing options...
Greg Field Posted September 19, 2009 Share Posted September 19, 2009 Greg, the number on the underside of the lower clamp is 502 481B.The last part of the vin # (I assume that's what you are calling frame #) is 112434. It was bought as a 2000 in early '01. What does that tell you? GM: Sometimes the US VIN corresponds to frame number but more often to engine number, so I'm not sure how useful it is. Sorry, but I meant under the upper clamp. Does it read "01493100" or "01493130" (both early) or "501452" (most late)? Axle nut or not? Link to comment Share on other sites More sharing options...
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