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Weave issue

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In an effort to get the most out of my tyres I fitted a new 100-90-18 Roadrider to the front of my Fastback and the similar sized front that came off went on to the rear to be "used up" I have a WM2 rim on the front and a WM3 on the rear. A pronounced weave now starts at about 70. Yesterday I was testing my new trispark ignition taking it up through the gears and in third at 70 I got into the most frightening weave ever. Luckily I had the whole road to myself and I needed it. It took seemingly forever to subside, even my sh-t was scared. One issue that may contribute is that I only weigh 11 and a half stone now. More pies and a new rear tyre on order.

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Cant be anything to do with weight, Dave. I'm about 11 1/2 stone and the only problem is a bit of white-lining with a worn out rear tyre.

A worn rear tyre will have a larger footprint than new, given the same tyre pressure. Acceleration transfers weight to the rear tyre, again creating a larger footprint and also more rider weight will load the rear tyre and create a bigger footprint than less weight - so you'll possibly be experiencing similar symptoms. I would be very surprised if your frame/chassis is not, unfortunately, as badly mis-aligned as any other Commando.

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Check out Murray Walker on the subject:- 'Murray Walker talks about Wobble and Weave on Motorbikes' on Youtube. (I tried posting a direct link but, for some reason, the system wouldn't allow it. Worth a look though.)

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Sorry if this is a little off track. Is this common mis-aligned frame issue restricted to when the frames started to be made in Italy (I believe). I have a 68 Commando original frame that did not have horizontal tube under the main tube. I got round the frame cracking issue by strengthening the front end using tubes welded over tubes and welded brackets. It seems, from previous blogs,that adding the forementioned tube alonedid not 100% solve frame cracking. The alignment of my frame seems to be OK but whether that is just good luck I don't know.

Previously simon_ratcliff wrote:

Cant be anything to do with weight, Dave. I'm about 11 1/2 stone and the only problem is a bit of white-lining with a worn out rear tyre.

A worn rear tyre will have a larger footprint than new, given the same tyre pressure. Acceleration transfers weight to the rear tyre, again creating a larger footprint and also more rider weight will load the rear tyre and create a bigger footprint than less weight - so you'll possibly be experiencing similar symptoms. I would be very surprised if your frame/chassis is not, unfortunately, as badly mis-aligned as any other Commando.

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Well I thought the Norton Commandos Had 19 inch tires front and back Wm2 front and Wm3 rear both 19 inch and the Isolastics may need re adjusting too firm up the ride well have fun all yours anna j

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Previously harry_weaver wrote:

Sorry if this is a little off track. Is this common mis-aligned frame issue restricted to when the frames started to be made in Italy (I believe).....

I've so far checked and corrected Commando frames from 1971 to 1975 and they've all required significant work to square the swingarm axis to steering head axis and align the rear wheel to the frame centre line. Don't know what year(s) frames where made in Italy, but the U.K built ones are way out.

The "wobble and weave" clip appears to be an attempt to get people to keep below 70mph. A Commando that's been properly aligned does not wobble or weave - guaranteed.

18" wheels require wider tyres which are not necessary on a Commando. What messes up the handling is the factory built in mis-alignment.

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Previously david_evans wrote:

In an effort to get the most out of my tyres I fitted a new 100-90-18 Roadrider to the front of my Fastback and the similar sized front that came off went on to the rear to be "used up" I have a WM2 rim on the front and a WM3 on the rear. A pronounced weave now starts at about 70. Yesterday I was testing my new trispark ignition taking it up through the gears and in third at 70 I got into the most frightening weave ever. Luckily I had the whole road to myself and I needed it. It took seemingly forever to subside, even my sh-t was scared. One issue that may contribute is that I only weigh 11 and a half stone now. More pies and a new rear tyre on order.

Hi Dave.

I had a similar heart stopping ride a year or so ago on a 72 Commando fitted with 18" wheels. It was at this time of year and i was dressed accordingly to keep out the cold.As i hit around 80mph (private roadof course) i went into an increadible weave and had to lay on the tank to get back under control.Mine was purly down to wind drag on myexcessive riding gear. I stream lined and have never endured this since. Hope this helps.

Mark

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The drag creates a negative pressure at the back of the rider who then pulls harder on the bars to compensate when the bike dosen't need any input to the steering. Factor in severe frame/chassis mis-alignment and it's not suprising the bike weaves.

Post frame alignment, I've toured with throw over panniers, tent and roll mat on the back seat and suffered no weaves or wobbles at speeds of 90 + . It really isn't surprising standard Commando's are so easily upset in the handling/steering dept.

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Just a thought on this, the original front tyre was fitted to the rear. 'Not trying to teach grandmother to suck eggs' - but was the direction of rotation of the tyre changed for the fact it has been fitted to the rear?

If there were no weave problems prior to the changing of the tyres , then I can't see it being a frame mis-alignment problem.

The make/type of tyre that was taken from the front may not be compatable with the Roadrider (stated to be 'similar' size).

Regards

Roger

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I should have added to my previous posting that head-on wind pressure has a much greater effect than turbulence. Effective streamlining would require a fairing or lying flat, that the problem was reduced through a change of clothing highlights the sensitive nature of a mis-aligned motorcycle chassis.

Dave has posted quite a bit of his trials concerning weaves and wobbles. I think I'm correct in saying the bike has a rod-end head steady, Lansdowne fork dampers, steering damper, 18" wheels and a new frame - all in an attempt to cure handling problems.

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Previously simon_ratcliff wrote:

Previously harry_weaver wrote:

Sorry if this is a little off track. Is this common mis-aligned frame issue restricted to when the frames started to be made in Italy (I believe).....

I've so far checked and corrected Commando frames from 1971 to 1975 and they've all required significant work to square the swingarm axis to steering head axis and align the rear wheel to the frame centre line. Don't know what year(s) frames where made in Italy, but the U.K built ones are way out.

The "wobble and weave" clip appears to be an attempt to get people to keep below 70mph. A Commando that's been properly aligned does not wobble or weave - guaranteed.

18" wheels require wider tyres which are not necessary on a Commando. What messes up the handling is the factory built in mis-alignment.

Thanks Simon for this additional information. Its depressing to think that Norton would allow adangerous mis-alignedframe set upto leave the factory.

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Hi

Attached a 70's Dunlop video on weaving. If / when it does happen to you I can agree that the suggestion of moving your weight forward and lying on the tank does work. My person experience is that wide back tyres do exacerbate the problem. When I raced a production fastback I did try a range of tyres and even managed to fit a 130 width tyre (it will fit without a chainguard) but it was a nightmare and would weave violently as if someone had thrown a switch. That said I wouldn't call a 100 tyre as particularly wide - I run a 110/90/18 on my 850 on the rear but a 90/90/19 on the front (the narrower front makes for much lighter steering and much more 'flickable' in my humble opinion). I suspect that fitting a used tyre on the rear is your problem and as I say the Commando appears to be very sensitive to back tyres.

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Bob,

Have you ever wondered why Commando's are so sensitive? There is no practical reason (as far as I'm aware) why a motorcycle should weave/wobble just because an oversized rear tyre is fitted - unless because of mis-alignment.

Mine used to get into cornering problems with 4.10 19 TT100's, 4.10 19 Avon RoadRunners and Bridgestone BT45's 110/80 18 (rear), 100/90 18 (front).

After alignment I used up the part worn Bridgestones for a few hundred miles, with no problems, apart from the usual white lining from a worn out rear. I now use 100/90 19 Roadriders front and rear. With hindsight, I wish I'd tried another set of new Bridgestones, but I had it in my head that the factory recommended 19" dia. rims where the way to go.

With the relatively low BHP of a Commando I'm convinced you don't need to go any wider than 100/90 but if you do, then, with a properly aligned bike, I wouldn't expect any problems. Regarding the video, I think they state, " all bikes weave/wobble", and then go on to mention the only way they got the Laverda to weave/wobble was with insufficient tyre pressure.

Harry,

It's also depressing they let bikes leave the factory with electric starts that didn't, insufficient camshaft hardening, porous cylinder heads, brakes that didn't, etc etc

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Interestingly, Velocette briefly tried using 3.50 tyres on the back of their singles. It turned out it adversely affect the handling, so the factory rapidly reverted to 3.25 rear tyres. A wider rear tyre may not always be a good thing.

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In the film clip that Bob has posted the presenter states in his summing up that worn rear tyres combined with a new front is a bad combination. I'll second that. I must admit that I failed to lie forward on the tank when my weave started. Schoolboy error.

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May I be the one to point out the blindingly obvious thing here? The bike was ok before you swapped over the tyres I assume, so, fit a new one to the rear and leave the front one where it was, on the front.

Why was the 18" rim fitted to the bike???? It is common knowledge that the 750 and 850 have different steering geometry with the addition of a steeper fork angle that gave quicker steering on the 850 and to reduce the quick steering you fit a skinnier front tyre. So it is very likely that the 18" rim will also effect the handling. Why not ask someone with a good knowledge of racing Nortons to give their opinion?

Also, is it realy worth the savings of a few extra miles on a tyre?

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New rear tyre fitted, so new at both ends now. still feels like it's going to weave at 70+ but busy traffic and distinct lack of b---s prevented me carrying out a full test.

The early 750 like mine has the steeper steering angle Boo. I believe the later 750 and 850 had the head angle changed from 26 to 27 degrees then the fork stanchions were steepened ie. not parallel the the fork spindle to reduce the trail

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Dave,

Are you now suggesting it's the steering head angle which is creating your weaves and wobbles - not lack of weight?

If so, it will be your latest theory in a long line of theories as to why your bike has handling problems. I think you've changed just about everything you can change, including a new frame.

Your problem is the same as every other Commando - factory mis-alignment.

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No Simon I'm just pointing out to Boo that I think he has the headstock angle facts the wrong way round. I think weight has a lot to do with the problem. Two up un Ireland in the summer posed no problems and travelling with luggage also caused no problems. I'm off to the market for a sack of spuds.

I'm happy with the frame alignment. The wheels are in line and the suspension is doing very little when cruising in a straight line on a smooth road.

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Dave,

I don't where you keep finding these smooth roads. Even so, a smooth road is not the same as a flat road, and at 70 mph the suspension will be moving, due to undulations if nothing else. With the swing-arm axis mis-aligned to the steering head axis the bike will act as if the swing-arm bushes are worn out, hence the weave.

What the extra weight does is alter the natural frequency of the motorcycle and alters the speed at which the weave will occur.

Frame alignment will cure your handling problems, solo, two up, with or without camping luggage, throw-over panniers, potatoes, etc.

If your 'parallelogrammed' frame is still up for sale, you've got a buyer, is it still £60.00?

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I spent quite a small fortune on my late departed Commando trying to cure a front end wobble at slow speeds. Despite a new rear cradle, vernier isolastics and uprated swinging arm it all made no difference. It always wore 4.10 x 19" TT100s front and rear.

I had a lengthy discussion with Norman White, regarding Commando handling, and he was of the opinion that 18" rear wheels were not a good idea. Neither were worn or old tyres and early swinging arms which twist permanently out of shape due to being unable to handle the engine power under serious acceleration. Poorly set Iso clearances are also know to affect handling.

The tubing used on Commando frames is known to bend easily and I wonder if a significant part of the handling issues are down to important chunks going out of alignment with ageing and not just from new.

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Previously david_evans wrote:

£50 to you Simon

O.k Dave, it's a deal.

Regarding Phil's ageing frame comments, I bought my Mk3 with 17,500 mile on the clock in 1987 and it didn't handle then. The strength in a Commando frame is in the spine and the triangulation/bracing which encompasses the rear iso mount. Fair enough, the down tubes which then go under the engine are a weak area, but do not contribute to the frames strength, as far as I'm aware.

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Previously simon_ratcliff wrote:

The drag creates a negative pressure at the back of the rider who then pulls harder on the bars to compensate when the bike dosen't need any input to the steering. Factor in severe frame/chassis mis-alignment and it's not suprising the bike weaves.

Post frame alignment, I've toured with throw over panniers, tent and roll mat on the back seat and suffered no weaves or wobbles at speeds of 90 + . It really isn't surprising standard Commando's are so easily upset in the handling/steering dept.

well I do not recall feeling any drag doing 87 mph down the M62 in the poring rain and my bike has 8 inch rise bars on has Standard , But I do remember lots of Steam coming of the engine has it was being water cooled by the heavy rain Buy she did not miss one beat, that;s what you call a good competition magneto made by Lucas K2FC now hit high prices , your anna j
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Previously anna jeannette Dixon wrote:

Previously simon_ratcliff wrote:

The drag creates a negative pressure at the back of the rider who then pulls harder on the bars to compensate when the bike dosen't need any input to the steering. Factor in severe frame/chassis mis-alignment and it's not suprising the bike weaves.

Post frame alignment, I've toured with throw over panniers, tent and roll mat on the back seat and suffered no weaves or wobbles at speeds of 90 + . It really isn't surprising standard Commando's are so easily upset in the handling/steering dept.

well I do not recall feeling any drag doing 87 mph down the M62 in the poring rain and my bike has 8 inch rise bars on has Standard , But I do remember lots of Steam coming of the engine has it was being water cooled by the heavy rain Buy she did not miss one beat, that;s what you call a good competition magneto made by Lucas K2FC now hit high prices , your anna j

Anna you're a hooligan. Its wild reckless youth like you that give us gentle ageinglaw abiding motorcyclists a bad name. 87 mph that's obscene. :)

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I've had some success today by removing the windscreen, raising the rear suspension from soft to middle and filling the petrol tank. Looks like my Abus security chain and lock will be coming along for the ride a lot more now. (looks a bit better than the spuds)

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Previously mark_chapman2 wrote:

Previously anna jeannette Dixon wrote:

Previously simon_ratcliff wrote:

The drag creates a negative pressure at the back of the rider who then pulls harder on the bars to compensate when the bike dosen't need any input to the steering. Factor in severe frame/chassis mis-alignment and it's not suprising the bike weaves.

Post frame alignment, I've toured with throw over panniers, tent and roll mat on the back seat and suffered no weaves or wobbles at speeds of 90 + . It really isn't surprising standard Commando's are so easily upset in the handling/steering dept.

well I do not recall feeling any drag doing 87 mph down the M62 in the poring rain and my bike has 8 inch rise bars on has Standard , But I do remember lots of Steam coming of the engine has it was being water cooled by the heavy rain Buy she did not miss one beat, that;s what you call a good competition magneto made by Lucas K2FC now hit high prices , your anna j

Anna you're a hooligan. Its wild reckless youth like you that give us gentle ageinglaw abiding motorcyclists a bad name. 87 mph that's obscene. :)

Well that was going slow in third gear at 3600 rpm i have a big sprocket on the engine to try slow it down And only on half throttle at that I did say these Norton Manxmans had a habit of going fast she just wants to go go go and I have a job of holding her back when she go the bit between her teeth , No really there fast bikes and you do not seam to feel the wind ether and passing just about every thing on the M62 , the police were no were too be seen maybe it was too wet for them , yours Anna J
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Now then Anna, you are having a laugh! 3600rpm in TOP would give a road speed of 60mph! You must have put a rear wheel sprocket on the gearbox!! If you could reach 7000rpm in top you would be doing about 210mph at that rate...... you would have to get your chin on the tank to achieve it though; a bit tricky with your apehangers..... boy, those Manxman's are quick....

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Previously ian_cordes wrote:

Now then Anna, you are having a laugh! 3600rpm in TOP would give a road speed of 60mph! You must have put a rear wheel sprocket on the gearbox!! If you could reach 7000rpm in top you would be doing about 210mph at that rate...... you would have to get your chin on the tank to achieve it though; a bit tricky with your apehangers..... boy, those Manxman's are quick....

Hello I have Not got Apehangers On , The Apehanger bars are well over 12 inch high , too be just that Apehangers , The Manxman has only 8 inch high bars there only half the size of a Apehanger , there just Comfortable handle bars and nothing like a Commando Chopper or Harley Davidson's Bars and with a 23 tooth engine sprocket and 20 t on the gearbox sprocket in third gear your doing 60 mph at 3.600 or there about a 23 engine sprocket the biggest you can get on the big twin it drops the revs and gives you big legs so your up 4 teeth from standard gives a ratio around 3.2/3 third to one but the power out put can handle all this, not problem and you do not need to get your head on the tank ether there is very little in wind resistants that the point I was making even in the up right comfortable position you can achieve these speeds and in heavy rain too . I was not hanging around believe me, And Doug Hele tested the 650 motor to rev and run too 9000 rpm and run in safety at that revs this is why it won 3 years in a row at Thruxton 24 hour races and the only weaving in the race was thought the chicane they made and you all called me a hooligan well you should of been with me when i was younger That Model (99SS) Special Cafe racer did well over ton 120 it had a five speed Shaftlighter gearbox twin Garner Flat side carbs and only weigh in at 378lb it had drops on A double sided four leading shoe up front alloy rims alloy tank oil tank and short seat and rear sets sweeped back pipes and Manx Short Megaphone silencers back then the Cops did not bother you much there were No speed limits on the new motorways so you could give it a fist full . I have seen me go to a race meeting and enter the Bike and race and ride all the way home over some 120 odd miles but I was young back then , that was over 40 years ago Yours Anna J
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If a 100/90 18 front is used in combination with a 110/80 18 rear, the bike is lowered by approx. 15mm front and rear. This reduces the trail and should allow the bike to turn quicker. Therefore the steering is more sensitive. Dosen't explain why the bike would weave. On Mk3's the trail is actually increased, which slows the steering.

With 18" rims, on my Mk3 Commando, the handling was worse than when using 19" rims. Through right hand corners the front end would seemingly under steer with out warning. It was so bad I actually stopped after one worrying moment, to walk back to the corner to check what made the tyre 'slip' whilst leaned over. The road surface was clean and dry.

Post frame/chassis alignment, using the part worn 18" Bridgestones, the bike never showed any signs of the unpredictable 'understeer'. Gone also was the typical Commando weave, which was worse the higher the frequency of road bumps, experienced using 18" (front and rear) and 19" (front and rear) dia. rims.

I now use 19" front and rear without any problems, which I think is the best overall combination for any Commando - which has had the frame/chassis correctly aligned.

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It may not be of relevance but I had serious weaving problems on my 72 Roadster. I wouldn't take it over 60 mph, it was all over the road.

I finally found that the swinging arm could be swung sideways by about 5-6 mm. Everybody said its the bushings but they were fine.

The shaft was a poor fit in the frame tube, could be moved 0.5 mm radially. The silly little bolt on top couldn't begin tostop the shaft moving in the tube.

I bought 2 split shaft collars (1-1/8 inch id), drilled and tapped a hole in one half of each, drilled two holes in the frame tube and can now lock the shaft firmly in place.

Handling is a lot better but nowhere near as good as my Dominator.

 

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