My first experience with "The Weave"

Asking & talking to land speeders on 750 geometry Commandos told me they had no problems nor have I on decent surface non windy conditions but last Sunday ride on Trixie Combat going 90's moderate gusts on some waving asphalt she started the Weave while throtting a bee line so had to grit teeth and use body strength even more during the lowing of throttle that loads more of oscilating fork action backwards till 70's settled down again. This was not a fast action tank slapper event but whole bike and pilot wiggle wobble. Its the first time I've had Hinge onset going straight ahead no thought of lurking upset I know so so well to avoid on a clumsy Cdo. Its so rare I still prefer to live with the less effort to steer 750 rake. A fork damper would of prevented this wiggle wobble up to the point the whole bike reaction over comes the damper allowing free fork action for road following then may feel like trying to recover a crash with forks locked stiff off to one side or the other. Nothing wrong with 750's or 850's but their sloppy isolastics of which there is a solution one fellow enjoys to high heavens.

I believe a few thou movement at the swing arm spindle bearings translates to a lot of movement at the rear contact patch. On every bike I've ever owned, I've worked to get rigidity at the spindle, yet here we had a manufacturer who built in movement where traditionally it was studiously avoided to make bikes safer. The most dangerous road surface for motorcycle riders is when the bitumen is grooved in the direction of travel. Think about what the isolastics do in that situation.

I've talked to 3 Commando experts in the UK. The third guy said the later frame makes no difference at all, but the other two guys said it does. I suppose that is why I have an spare 850 frame and yokes sitting in my garage.

With my '71 750 frame, I never noticed any weave at speeds up to 100mph but it didn't feel super planted either.
On 19" rims.

Now that I'll be running a 18" rear, I'm thinking about the 850 frame again.

Wind eddies make a lot of difference on the isolastic side loading/unloading resonance with some mild suspension movement from road imperfections. The worse situation is free way speed seams that join together slightly diagonal to direction of travel with a gap about a tire with and traffic close behind and to each side. The tri-links made semi trailer blasts felt only as wind blast - pressure waves on pilot and a tremble through bike but no effect on easy line holding, yea.

If ya want to have a fast education on splashing forces together to study THE Hinge onset in each its components and likely survive, lower air pressure and go out on lumpy road in windy conditons while standing on pegs and wigger fork action or do zig zags in lane with some throttle blips in difference zones-phases of zinging. Its possible to get so wound up spring backs the tires start to pop off surface which is then way too much fun for me take thank you.

Check out the offset in the rear wheel. We chased this problem in a friends fastback for ages and tried everything until we discovered that the rear wheel had been re-laced with a new rim and whoever did the job never offset the rear wheel.

johno

' I'm kinda thinking rear shocks. As far as i know they are original to the bike and don't seem to have a lot of damping. "

They Dont have ANY Compression Damping , at all . :shock: El Cheapo etc , but were vastly better than Jap fish oil ones of the era . :lol: :lol: :x

Basic operation is the rear on bumpy bends holds low , therefore it steers . . As in ' Its got good rebound damping . Dosnt go up to fast .

Meanwhile , back at the ranch , the Girling Gas Shocks were on special , but came with the 110 Lb springs .
These , with two way damping , and the ' GAS ' actually just with a diaphram betwixt , kept the damper fluid
where it was best utilised ( as in Un Aerated 8 in the damper valves ) , Kept the BACK from ' pumping down ' ,
as a standard one is wont to do , at speed , on bumpy bends . Or with 5.000 lbs of luggage .

therefore the bar er right steered fairly nicely . But momentum & inertia were evident .400 Lb was a ' Big ' bike ! .

Asumeing the swing arm pin isnt totally hopeless , it steers pretty well , in the tip 7 catch - on the throttle pre unit principle .
the ' Never back off being merely DONT back off . More sensably , unless youre a adept rally driver , or M-X , on a motorcycle
you will realise wacking it into a bend so that as it settles its at its limits - doing something dramatic may well have some
repercussions .

Thus one adopts the ' notch or two ' incremental adjustment of controls , and holding the nose down / fronrt over . Steadying
balanceing on throttle comeing of the anchors , and bring up the power at / through / past the Apex ( of the bend ) .

Major factor I think as as operating speed increases the primary part of youre attention should be devoted to the task at hand . And
a brief divesting the grey matter of extraeneous influances 7 thoughts , before operation might well avoid a dissadvantageous event .

or in R.A.F. speak . keep your finger out .

[video]http://www.youtube.com/watch?v=01E_6oxvlQA[/video]

[video]http://www.youtube.com/watch?v=AsYR3KCfcaA[/video]

petejohno said:

Check out the offset in the rear wheel. We chased this problem in a friends fastback for ages and tried everything until we discovered that the rear wheel had been re-laced with a new rim and whoever did the job never offset the rear wheel.

johno

Click to expand...

What is the correct offset supposed to be?

elefantrider said:

petejohno said:

Check out the offset in the rear wheel. We chased this problem in a friends fastback for ages and tried everything until we discovered that the rear wheel had been re-laced with a new rim and whoever did the job never offset the rear wheel.

johno

Click to expand...

What is the correct offset supposed to be?

Click to expand...

Check this thread from the NOC. Vern Fueston is a frame expert, his posts are the ones to check for numbers. The bike on the last one is mine.

http://www.nortonownersclub.org/support ... el-offsets

So he says his rim is offset 1/8" to the right on his 850. Seems so small, it would be hardly noticable. Before I send my rim to Buchannans to check that. Can anyone else confirm this is correct for a 750 also?

elefantrider said:

What is the correct offset supposed to be?

Click to expand...

The correct offset will be whatever amount is necessary to get the centre line of the wheel (rim) set on the centre line of the frame (not central to the swing arm).

elefantrider said:

Seems so small, it would be hardly noticable. Before I send my rim to Buchannans to check that. Can anyone else confirm this is correct for a 750 also?

Click to expand...

It's always better to take your own measurements if possible.

About the most upseting thing to an isolastic rubbery baby buggy is the tire wear-age state. I'm a Half Fast expert on bad and worn old tire combo's and flat state you can not really set and judge isolastics for vibration or stability until both tires are in good shape and air balanced front to back, according to the pilot and cargo mass for the main road texture encountered.

All the Cdos I've ridden ,three 750's and two 850's all had some visible rear tire off centered to LH but they tracked and handled like "normal". Ridden normal ie: not getting police attention barreling into turns, none were upsetting no matter how loose the isos, swingarm or crappy tires. Press a bit beyond normal and your pilot skill and sense of security may be ruined, permanently.

The commando is heavier on the LH and the tires can take a set if left on side stand so maybe this compensates for factory to commonly issue em with rear off to the LH a tad. Looking into the importance of both tires in line, I found some famous brands like BMW with rear off set a tad from front. I personally do not think or find the rear offset amounts to matter a whitworth in stability but does make the regular Cdo a bit easier to toss to LH than RH. I want my tires in line like everyone else so Peel will be but I'm not bothering on Trixie which I know better than play racer games on.

The innate slack of swing arm loads pivoting through rear rubbers moves the front iso side to side, to point it can begin shoving or slapping the forks to oscillate, which then shudders back to swing arm-rear tire and so begins THE Weave THE HInge. Worn front tire can do this to rear too. With new tires I can ride hands off my sloppy Trixie Combat down to low 30's upper 20's with nil or mild weave onset but as they wear I have to watch out letting go in 40-50's or forks will begin a fast wobble that can tank slap if not re gripped in couple of seconds. The further back on seat I get the less this happens.

No matter how perfected you make your Cdo, no one races competitively w/o doing something to tame the isolastics rebounding. Without isolastics it is not a real Commando only a commando engine powered something else.

Up until today I didn't know what all the fuss was about... '74 850 MkIIa with 4.10 K81s front and back, Ikon rear shocks, Lansdowne forks, DT head steady, and running like a dream

I decided to try a 3.60 on the front, and all of a sudden I've got the weave!
I'm sure my height (6' 10") sitting bolt upright on a Roadster with US bars isn't going to help any, but it didn't do it before.

I'll stay with it for a while, until the tyre is half worn, then I'll take a view. Until now I was 100% happy with the tyres on the bike, but I couldn't recommend the latest set-up for an 850.

I know, I know... so why did I do it?! :roll:
Curiosity, I guess

Curiousity killed the cat ? Waiting for that new front to wear out not prudent ,maybe post it here for sale like new, then buy a wider tire.

elefantrider said:

So he says his rim is offset 1/8" to the right on his 850. Seems so small, it would be hardly noticable. Before I send my rim to Buchannans to check that. Can anyone else confirm this is correct for a 750 also?

Click to expand...

Buchanans knows all about the offset, they build all of CNW's wheels.

elefantrider said:

So he says his rim is offset 1/8" to the right on his 850. Seems so small, it would be hardly noticable. Before I send my rim to Buchannans to check that. Can anyone else confirm this is correct for a 750 also?

Click to expand...

This has come up before. When Vern is saying that the "offset" is 1/8", he is saying that that is how far you need to move the rim from center. To look at it, it would seem like the offset is 1/4" because when you measure it, one side is sticking out 1/4" more than the other. An example: If he was talking about the offset of the front iso brackets on the tube, he would say that the offset is 1/8". But when you modify a pre-MkIII front mount to take vernier iso's you cut 1/4" off the end on the right side because that's how much more it is sticking out on that side. To look at it you would say that the offset is 1/4". Vern would call it 1/8".

Snorton74 said:

Buchanans knows all about the offset, they build all of CNW's wheels.

Click to expand...

Vern used to work at Buchanans, he was their frame guy when they used to do that.

I do a good bit of mild off roading on factory Trixie and pretty happy w/o any weave as long as I don't get into sliding on Gravel or too bouncing on pasture. There's hand fulls of nice tight-ish sweepers I can take over 50-60 that does start a bit of crossed up slide and some weave onsets but only in slow rhytmic cycles that warn me & also practice me on using body [locked knees on tank, butt pressed in seat and death grip on bars] to dampen down the weaving, which with light throttle does. The strange thing is with that sense of weave onset ingrained in me on rough stuff Trixie will still surprise me at times on almost every ride in similar speeds on smoother pavement. I do not press un tammed Cdo into much G forces or speed and expect to make it home. With Patton's 'rump' rod and whimpy head and breast links on Peel allows 90 mph flully crossed up like flat traker on Gravel with reserves to change bike pitch and slide some [as long as no back off in the turn]. On rough hwy sharp turns she just stayed hooked w/o upset, till going too fast for me to take but not her. She has driven me insane like that.

I've got a long sweeper curve about 4 miles from home that always gives me the creeps. Both ways on it the bike starts to feel like it doesn't want to track right (45 zone, but you know), but I attribute it to the road surface, not sure. Cars don't seem to notice it. I'll have to inspect it a bit more, maybe do the tire pressure difference like Steve recommends. No houses around, so I can take it lots of times.

Dave
69S

Balancing each tires air comes after I've done my flat tire practice at each end then both ends till I get too scared that way before I will press isolastics on correct air at rather higher rates.

If its got two tires in line it pretty much behaves the same when the weave hits. Here's a sense of weave in the best there is which just ain't good enough for me no more. Even if my ole pos can't take turns as fast as this, she don't ever get that crazy so way more fun and I do believe can tolerate and spike more G's in direction changes. Do note the straight steering pilot or bike itself jerks just in time, time and again.

[video]http://www.youtube.com/watch?NR=1&v=xzB6KSlD6ec&feature=fvwp[/video]