high speed weave

Never experienced it myself, but only been near or over the ton once. Interesting, but I'm not interested at cruising at 80mph.

technically , if you ever find yourself in that situation , the correct proceedure is to PUSH Both Handgrips . Trying to steer the reaction time exagerates it .
Pushing locks the bars & the thing should be self damping .

Sitting to far back ( behind the rear axle ) accelerateing hard lent over & hitting a ripple / seam in the road can cause it . :x
The old friction dampers through the steering column were of some use too .
Unless you wound them down as hard as theyd go , then forgot to back it off as you hit the off ramp . :shock: :wink:
Letting go & useing both hands gets it off real quick though . 8) :mrgreen:

xbacksideslider » Thu Aug 22, 2013 2:23 pm
I weigh 250 lbs and I can provoke a weave on my '73 750 by sitting forward and upright and I can make it go away by moving my ass back or by entering a corner. When I ride fast, I ride with my weight forward but as the speed rises I move my weight to the rear. Coincidentally, that also results in the "laying on the tank" that the linked video recommends. Admittedly, my interpretation of "moving weight to the rear" may well be "laying on the tank"


Back in 1971 my '71 750 would weave on 4.10 Avon GPs and on 4.10 K81s as well. The best combo was 4.10 rear and 3.60 front - no weave but steering a bit quick. Nowadays I run a fat tires on both ends and put up with the threat of an occasional weave that I preemptively kill with weight shift/laydown as speeds rise.

The comment about modern bikes' forward weight bias is true but I differ a bit about why and the implications.

The main reason for designers taking weight off the rear and moving it forward is to enable more power to be put down by the rear wheel. The new bikes have wider wheels for the same reason - to put down their greater power and keep traction at far greater speeds/loads. The wider wheels, in turn demand quicker steering, greater mechanical advantage, so that means less trail and less head angle and less diameter as well.

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Exactomundo Exbackslider you do know. Fat tire is mainly for heat spreading so melt is delayed but the narrow patch is very similar to 110 size tire, especially at air pressure and speed fast cycles run. Fat tires loose a lot of foot print faster near edge than taller skinny ones. Anti-wheelie is main reason for modern front wt. bias. My un-tammed Trixie ran hands off no wobble/weave down to 20 mph, WHEN both tires were new and air balanced BUT some time before 2000 miles it became 35, and NOW front worn from brake and leans its dangerous to let go @40-45 or horrific fork slaps begin, UNLESS i move way back on seat then can roll down into 30's before sluggish fork occillations onset. Lay forward hands off coating down and see how much its wind eddie whipping front more than mass on it. The other reason moderns have more forward weight is they are so scary to really power around turns they have need to brake so much more or rear lets go, hehehe. The only real advantage of moderns is they can keep pull going longer and their tire compounds are softer and higher speed rated.

Notice how they tended to have the weave onset in slight leaning sweeper conditions. This is second worse state to put a cycle in, ie: constant held turn forces on constant throttle as gives time for resonance to build up. I've explored this as much as I will ever need to, to point I classify weave/wobble into two types or polarities, positive and negative. This requires going slightly insane to explore limits. While mostly up right it don't matter a whitworth if the bike is pulled or pushed from the side, it will behave the same. Put a bike on far over lean and a push down side impulse is not the same as a pull down one. Some cycles will fight to hold far down while others fight to fling back up, its those pilot efforts on forks to frame to over come the innate cycle character that can onset weave side ways and either low or high side depending on if the last straw was a pull down or push down vector and which end delivered it.

as stated I've explored weave wobble as much as I'll ever need to again, to point i've had foot flung off peg and I can flatly state when its pure force that removes foot the pilot first freak out instinct reflex is fast as possible get foot back on the FKing peg for stability and mass centering, but when the pilot is actually so freaked out by the sudden surprise of escalating oscillations the first fear reflex is to stick a foot down and if not instantly actually touched down its held out a bit longer wavering > just in case till either the weaving or the groin jabs calms down. Go look again at the groin pinching neuromuscular reflexes over the bike dramatic dynamics. Feels extra silly when pilot realizes what would happen if he actually did stomp a boot down firm with bike fall over pressure on top into tarmac at speed. Or tired it once or more to know for sure.

I put a set of '84 Honda CR 500 forks on a '79 XL500 (four stroke) and moved the lower mounting point of the rear shocks to give some lift in the rear. It had a terribly loose feel at around 65 mph. I had left the forks sticking out of the top of the triple clamps because the overall look was better. I was going to try lowering or raising the front end to see what affect it might have and decided to raise it by just putting the forks all the way down. Problem solved!! She was rock solid all the way to 80 mph. (As fast as it would go.)

I have read "the worlds straightest Commando" and plan to execute the ideas on mine as soon as I can, starting with the minimum recommendation and working up to the whole frame alignment mods.

Informative list of factors that can strike almost any cycle. Maybe lowering the front fully in yokes was similar to film pilots laying out of the wind to settle cycle? Raised front choppers are known for bee line stability but the pilot is sat rather back and low, even if legs flaired out.

My wife's scooter is rated to mid 80's mph tops and automotive stable but can got it into mid 90's on long steeps but the combo of wind screen and small tires > gets too squirrlly to enjoy, so once was enough for me. Below the wind buffet onset it seems to self stabilize. Its a bit jerky in gusts too more than my realcycles though my flapping jacket slightly causes weave on my un tamed Commandos. I've been on a cycle that allows feeling the fork eddies spilling off and working out through tail end. Then started taking a closer look at the newbies fork steamlining for ideas.

I encourage perfection just for the pure sake of it but just straightening up and indexing all mating surfaces head steady mount flats to the innate .003" cant on top of cylinders to the swing arm and iso faces, will not help much to stave off un-tamed Cdo antics. Can put ya in touch with Ken Augustine or post his even deeper changes like Jim Comstock showed in the shortened racer in the Norvana post, for great Commando racer improvement he says. Some BMW and other makes issued models with front and rear out of line as much or more than some Cdo's yet no recall issues or reputation as widow makers, like the first Commandos. Safe returns exploring handling.

hobot said:

Feels extra silly when pilot realizes what would happen if he actually did stomp a boot down firm with bike fall over pressure on top into tarmac at speed. Or tired it once or more to know for sure.

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I did that once on the track and ended up setting sidesaddle- but at least I was still upright. Jim

I did that once on the track and ended up setting sidesaddle- but at least I was still upright. Jim

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HA what a silly way to learn fast, glad it didn't snatch foot/ankle underneath to high side off of and leave ya a gimp or a stump or like I found out it can sling your leg up over head way beyond natural joint range, ugh. I have been broken of that foot down reflex habit and if blown off the road like you I will do my best to stay upright and face impact like a man, maybe bail off depending what's ahead. Occasionally actually works out in a nothing to lose attempt.

I can't get over the weaves seen as IOM craft wheelie over crests so no tire conflicts inducing it. Seems they walk around, nay bound about, on the rear 8-9" width on a ~2" contact patch. This weaving onsets in far over leans too, some to me feel like being pushed off the ground by the devil, others feel like god shoving me away from heaven a positive negative sense but both induces tank slap. Positive kind tend to hi side to easy, negative kind low sides too easy. If ya can keep tires off ground long enough frame settles down on touch down its breath taking fun. Side weave feels like hitting a plowed field sideways then just lifting over it into smooth sailing. Solid mounts feel suddenly smoother while isolastics suddenly transmit most the engine vibes. Suspension motions felt as a yo yo like bungee cord sense. Ponder on it and my wee motto.

Talk about foot stomping . . . .

Long ago I bought an old Ossa 250 road racer, the thing was tiny, very light, and it came with dried out KR whatever Dunlop Trigonics, and after I got it running I took it for a test ride, not thinking that the front brake (from a Honda Superhawk) would be rusty and grabby, or that good. Well . . . . . I ran her through the gears and grabbed that brake and the front wheel/hard tire locked up big time and she was pitching me over the bars. I said "NO" and stuck my left foot out and slapped/stomped onto the asphalt and jerked up on the bars and picked that bike back up and put her back onto her wheels and we went straight. My foot hurt for a month.

The soles of my boots were leather - helped make it possible, that little bit of slip instead of rubber's grab.

I had an Ossa set up for flat track in the early 70's. That was a great bike, wish I had it back.

I raced indoor flattrack on it at our local fairgrounds. They would pour Pepsi syrup on the smooth cement floor for traction. What a gas, you could lean the bike till you had to drag one foot behind you as there was no room on the side for your leg. You just used two gears, one for the launch and the next for the rest of the race. Jim

ALRighty Jim, laying so low the peg folds up and spits your foot out and no knee room between tank and road the free foot ends up on rear axle rest. Sometimes on modern 17" cycle I will reflex a knee out then snatch back to seemingly jerk bike that way with some wind drag. With some ballistics inertia and controlled rear spin pretty easy to find the equilibrium to stay way low state of glee a good long ways. I can not do this on my un-tammed Combats, I got em to touch something now and then for an instant but not hold speed or accelerate longer turns w/o the hippity hoppity happening. Trixie has nothing special in her so counter productive to get into dangerous power band turning so once I found her and my limits [w/o much damage] its taboo. I still get caught out w/o trying having my buddy or strangers later tell me they enjoyed watching me try to tame the thing down while I'm about peeing in pants swearing I'm too stupid to ride.

Runing Codes Ninja in and out of crash like weave upsets about each turn got me banned to return but boy howdy did I get good learning in. My tool of choice for handling ease w/o any hint of weave or wobble even hands off at any angle, [short of break free] is otherwise one of the worst handling things i've ever tried not to crash.