Head shakes.

[bodgerbloke52]

My Commander is suffering head shakes from 40 to 50 mph unless hands are on the bars. I habitually use both hands to make adjustments to jacket vents, none of my other bikes have this vice. Useing BT45 tyres at reccomended pressure and sizes. Used these tyres for years, always found them to be first class, even cured wobbles on Earls fork BMW's.I have chased every single mechanical issue that could possibly contribute to the problem. Forks overhauld, steering head race pre load. Wheel alignment, wheel cetralisation, Up and down with fork legs in fork yokes, even changed the new rear tyre because it was just a tad out of true on the bead. Rear suspension units, clocked up wheel rims, ballance etc etc. Nothing has any effect on the issue. Convinced it is a built in feature, perhaps coming from the spindly Yamaha front forks??How many others have this issue and any cures? Any one know the designed rake and trail numbers?Roger in the Pacific NW

[johnbirchjar]

If memory serves, this problem has been discused befor,the only time I get "head shake" on the Classic is when the old girl is well loaded with camping gear, and then only if I take both hand off the bars,with one hand,? not even a tremble,ride safe,J.B.

[Ian]

My Commander did this on worn Avons, years ago. Since then only BT45s have been on and it's never done it since.You seem to have done all the obvious, so how about the less so; are the tyres fitted properly, and round? Is everything really fitted right, or just new - not always the same thing. Is anything just a bit loose or tight? And indeed, is there some badly placed or loaded luggage fitted?It's going to be something small...ian

[Dell Boy]

All my five Commanders have done this & my mates does to.I`ve just learnt to live with it. Worn tyre makes it a bit worse.My bikes have done it from new through to high milages.I think it is caused by the heavy front fairing but cant prove thats the cause.Derek.

[bodgerbloke52]

Thanks fellarsGood points Ian re checking the small stuff, done every one of em.Derek's experiance of ALL FIVE of his Commanders having the head shakes seems to be very conclusive. It would be intersting to try the bike with the front and/or rear Tupperware removed. As best as I can measure on the fully assembled bike, the rake and trail on mine are in the 27/28 degree 4.25" range which is well within the norm.I am most wary of the spindly Yamaha front forks. Small diameter legs, very small spindle and a fork brace that is not much more than a place to hang the flexi front mudgaurd.As it takes only a very light touch of the bars to prevent the shakes developing I am convinced the only cure is a small light steering damper, have looked at that but as yet can't see any way of mounting one.A old pal who spent his carreer with the West Midland police bikes came up with very interesting info. They had no problems with Police rotaries but not clear at present if that included the water cooled ones. They did however have the problem with thier ST 1300 Hondas. This was finally completly cured by changing the Timkin head races to push bike style cup and balls version. Very odd but John is a expert and knows his stuff. Makes yer think dunit.Roger

[bodgerbloke52]

PSMy ex West Midlands officer pal has just clarified that they were using only air cooled models that did not have the bar shakes. They have no experiance of the Commander. He is doing research as to why changing from Timkin taper had bearing on the Hondas to ball and cone type cured the problem, as it defies logic.Roger

[Ian]

Interesting point about the Honda head bearing change.What made somebody think to do it in the first place? Isn't the easiest assumption that Mr Honda knows his bikes pretty well and would fit competent parts to them? Why would anybody think that Honda would have got this wrong, or that such a simple thing would fix it?That being so, why would somebody suggest simply a different bearing, unless they had met this before, and what made them do it then?I think we should be told......

[kanonkopdrinker]

I think I have probably written this before, but I am pretty certain that 'head shakes' (aka low speed wobble) is a common feature on many machines across the manufacturers.Just the weight of the hands on the handlebars is enough to cure it.I remember being shown a film 'Wobble & Weave' (produced I think by Dunlop - or maybe Avon) using Murray Walker riding a whole range of machines, and yes, they all do that, sir. I believe this film was produced for those 'in the industry' rather than the general public.Has anyone else seen it?David

[Richard Negus]

It is an inescapable feature of any castered wheel, and responds well to damping. A supermarket trolley is a particularly good example of an undamped caster. In the late '70s, Dr Roe at Manchester Uni did a lot of research on the subject, which he referred to as 'flutter', producing papers suggesting what induced it, made it worse, and reduced it. His conclusion was that even minor damping, such as the riders hand contact, could stop the onset of flutter.I did similar work at Yamaha in Holland, riding various bikes up to speed, closing the throttle and taking hands off the bars, all the while being video'd from the back of an estate car. All the bikes and scooters had flutter to a lesser or greater degree, the worst being an XS1100 where the bars went from lock to lock and the tyre squealed before I lost my nerve and grabbed the bars again. In all cases, adding weight to the rear made it worse and weight to the front improved it. A flexible frame was easier to ride through flutter than a rigid frame (such as the XS1100). In every case, a simple hydraulic damper stopped the onset of flutter.The conclusion of these experiments was prototype step-thru scooter with a luggage compartment over the front wheel and a form of non-adjustable friction damper at the steering head.I suspect that front tyre choice (brand, type, size, pressure) can have an effect on flutter. Certainly, I feel more 'comfortable' on some tyres than on others - but that may just be prejudice.

[bodgerbloke52]

I hace found basically the same results as Richard. I was once involved with testing at MIRA with Tony Mills and the two Dunlop test riders. We were testing half a dozen popular bikes of the mid seventies including BMW, Kawasaki, Honda and Laverda. We were not exploring low speed shakes but high speed weaving and shakes on a flat out curve. After a mix of differing tyres we noticed that the taller heavier Dunlop tester had somwhat more high speed control compared with his much smaller lighter collegue.We then strapped a divers belt on both riders and started adding lead weights to the leather pockets incorporated in the belt for that purpose. Each time we added weight, the bikes handling got better. The Laverda could manage a flat out full thottle run through the curve with only a cople of weights. The Kawa and BMW, although much improved could not be taken thru the corner at any where near the Laverda speed. In the end we were hoisting the smaller feller on and off the bikes because of all the lead he had on. Also found that riders had to sit forward and well tucked in.Before retiring I was US importer for Marchesini magnesium road race wheels. The weight saving over stock alloy wheels was astonising but the main reason for fitting the wheels on race and road bikes was the considerable improvement in handling as all levels. I have personaly cured low speed shakes by changing to magnesium front wheel. Once the very heavy stock alloy wheels start to oscillate the weight acts as a pendulem and magnifies itself into a full blown tank slapper as Richard descibed.It is true that it only takes a light touch on the bars to prevent the problem. However I have habitually used both hand to do other jobs momentorily so I am not happy until it is cured. Especialy as my other bikes do not have the problem. Tooks like a damper is the only practical answer but where does one hook it up on a Commander?Roger

[kanonkopdrinker]

Found it!It's on YouTube!! Search for "Murray Walker talks about Wobble and Weave on Motorbikes "

[bodgerbloke52]

I have a steering damper assembly off a BMW R90S, It might fit the Commander. Keep you posted.Roger

[Bob]

Not all Norton’s did this, it was part of our pass off test to check the Head Shake, to see if it would self start, if it did not we would thump the handlebar to get it started and see if it self stopped, at MIRA we would hands off at 100 mph and study when the shake started, some at around 70 mph down to 15 mph, we found that we could steer the bike if gentle leg pressure was applied, but the brake pads would need pumping back to the discs, so do not try this on the road.What helped?Ribbed front tyre, ribbed continually that is, a ribbed with lateral cuts will almost certainly be worse, but this slowed the front end response at speed (slight lag in direction change), a damped front tyre can be tested by fitting a spring balance to the handlebar ends, with rider sitting normally, the resistance to move the steering measured, not to be confused with headstock climb.On the MK3 830 cc Norton we introduced faked rake to aid higher speed stability and reduce the shake, with faked rake the trail reduced under heavy braking so changing direction when driving less than gently was improved for spirited riding.On any machine an Interestingly fact is that if you drive over a strip of low friction road (stretch of oil on road, or low friction track) whilst in the middle of the shake, it stops almost immediately.Whilst doing high speed test on the Rotary with Dunlop, the best combination that I tried was a Radial front and a Cross ply rear, this was over 20 years ago and whilst being perfectly safe in my opinion, we could not if my memory is correct proceed with this combination for road legal reasons. I was not the best person to select for high speed weave as my size was more forgiving, but I developed my own ways to find the threshold, such as sitting poorly, starting the weave and seeing if / when it stopped. If I can dig out some test reports I will post them.Bob

[bodgerbloke52]

BobMost interesting experiences. Particularly your findings of a Radial on the front stopping the problem, I may try that. I have used the Bridgestone B45 pairs for years on all sorts of older bikes not designed for radials. Always found them very good, they often will cure a head shaking bike of the problem. I am new to the Commander so have no previous experience of tyre choice. It came with Pirelli "Match" MT80. 100/90 and 120/90. When we raced Laverdas in the seventies we found that the ribbed front Pirelli would actually cause the rider to crash under high speed cornering such as Gerards at Mallory Park. Roger Winterborn crashed there very heavily because I had failed to realise he was using this tyre so I could not advise him to remove it. Since then I have had a aversion for the make in general. Sadly I did not try a hands off test with the MT 80's on the Commander before replacing them with the BT45's.Roger

[Bob]

Hi,Check if the use of Radial and Crossply tyre is road legal a I did not think that it it was 25 odd years ago.Bob

[bodgerbloke52]

BobThere is no legal requirement over here, just recommendations not to mix from the tyre (TIRE manufactures. Some Triumphs come new with Bias rear, radial front.Harley have some bikes with Radial rear bias front.What was your experience with radial front and rear?? I will certainly try a radial front on the commander.Roger

[Bob]

Hi,We was conducting high speed stability test, and had a machine set up that developed self start weave, this was in part due to a small radio case being placed on the rear behind the Pillion seat, from memory the weave self started at 90 mph but never went critical up to a maximum sat up unfaired speed of around 120 mph, but still weaving, the shape of the box had as much to do with the weave as the weight of the Radio inside.With this example bike it was cured of weave by fitting Radial front, the hands off shake was also cured.Also not that you should do it, lowering the front tyre pressure in say 5 psi steps until the hands off shake stopped ( if it did ) gave me a feel for the energy involved, but most times lowering the pressure stopped the hands off shake from developing, but it is not a good idea to run at 15 psi, this was just a calibration method normally conducted on the test track/s.Note that hands off shake was a known issue and deemed acceptable if one handed ( any) it would not develop whilst closed throttle rolling from 70 mph in top gear, and then 50 mph. I used to find that on most machines just a gentle thumb and finger grip on the handle bars was all that was required.The shake never spat me off and in fact we used it to good effect to test the fairing bracket and horn brackets and the like, as the shake would develop lock to lock and act like an accelerated pave test.This was of particular benefit when testing water cooled radiator mounts and the like.Incidentally the AC police bike also had this problem and on most machines in service, and I remember the Chief Riding Instructor for WM police sending out a MEMO that any officer riding no handed would be deemed to be not under proper control of the machine and will be subject to discipline investigation, the problem reports stopped just as quick as they had began. Having a slight pre-load on the head race bearings reduced the self start hands off shake zone ( lowered the MPH ) and in some cases eradicated it, but I never liked nipped up head race bearings or heavy steering dampers a it for me lost some front end feel, especially in the wet.Bob

[bodgerbloke52]

BobMost instructive, thanks for your wisdom.I have tried more pre load on the head bearings a few weeks back, it raised the commencement speed by 5mph but as pre load was too high it was only a experiment. 20 psi in front cured it but bike handled like a heard of cows. The West midland police fellow you mentioned was probably my pal John Hacket who advised that changing to crowded roller bearings on their ST Hondas was effective. Had to revert to OE bearings when Honda waved a big stick.I have a radial Michelin on the way, will report findings.Roger

[Dell Boy]

Have not experienced weave on the Commanders but was bad/dangerous on Commando`s not really cured by steering dampers but sorted by fitting flat bars that pushed the weight forward. After riding featherbeds I found Commando handleing most disconcerting.None off the featherbeds I have owned has either wobbled or weaved.I found Commando`s fitted with 3.60 front tyres handled better than those fitted with 4.10 tyres.Even the Vincent engined featherbed didn`t do it though it wouldn`t go round corners unless you forced it too.Hands off & no shakes at any speed on the featherbeds. Any one know why? I use narrow, 3.00x 19 ribbed tyres which I think is why.Currently, as an emergency, I have a fat 120 front tyre on the Commander currently in use & that shakes from 35 to 65 m.p.h. Much worse than usual. Narrow tyres are currently on order so will report back when fitted.Derek.

[bodgerbloke52]

DerekAll the Egli framed bikes worked very well at any speed. He was adamant that good handling required that both wheels were very firmly connected and in perfect alignment with inflexible means. The standard Vincent had nice rigid front and rear ends but were connected together by just a couple of small bolts which led to all sorts of high speed problems. Fritz even made his own front forks with three large diameter tubular "axles" as he found that front fork flexing allowed the front wheel to wander about. The Commando he claimed could never be expected to handle properly where the front and rear were held together with a few bits of rubber. Perhaps Richard N might advise us all how he got his Commando to average over 100 mph in the 24 hour race at Spar. Roger

[Richard Negus]

Two fearless riders !

[andy588tt]

Hi AllHead shakes sounds like a gig in the park with Status Quo they were the days Well riding a bike with with the front end doing its own thing is every bikers night mare I was always told open the throttle to get out of trouble not much good when heavy breaking the Tiger Cub had a blown oil seal in one fork leg I cured it with replacing oil seal and proper amouts of oil in each leg.When I purchased the wife Thunderbird new it was fine until the large side car was fitted and it handled like a pig. A different riding style I fitted different forks because of the dive and fitted leading link under braking the front came up and low speeds uneven ground the Head shakes I fitted a damper from a car "Polo" two feet long from bottom of fork with a Rose fitting to the side car now very stiff no shaking and handles like a bike on rails at all speeds and corners .Ride safeAndy

[Dell Boy]

Hello Roger,After two years of near death experiences on fast bends the featherbed frame was sold & an Egli chassis purchased & the vincent engine installed.A transformation took place.I only now have to think that I want to go round a bend/roundabout & that is where it goes with virtually no input from the pilot. Best £500.00 I have ever spent [1980 price] & so light.Built from 531 tubing with superb sif bronze welds. Beautifull.I have an ex-racer Laverda 750SF [1971] & that doesn`t shake or weave either so some manufacturers could design it out I think.Derek.

[bodgerbloke52]

RichardPete Davies, one of the nutters on your Commando, and I were giving a talk recently to a large Laverda owners meeting. Pete was asked how he went so fast. He replied that he had a zip installed in his head which allowed him to swap brain for a pork chop.DerekThe Laverdas we raced did have rigid, read heavy, chassis but they could be seriously upset by tyre choice. The most stable was 410 Dunlop TT100 F & R but rear grip was poor. Faster lap times came with Dunlop endurance pairs but high speed handling suffered somewhat. On certain circuits, Pete sometimes asked for a rear slick which was very good for lap times but I hated it because how bad it made the bike shake rattle and role, it just did not look good at all.Ray Knight was on one of our triples in the Island production bike race. Ray is a master of the TT circuit. His course knowledge allows him to sweep very smoothly through the many very fast tricky parts in one high speed flow. In practice Ray said he could lap considerably quicker if bike did not weave at high speed. I knew that it would be spot on with the pair of 410 TT100's but I feared the rear would not do the three lap race as its speed rating was below the speeds Ray was using. We went ahead and swapped out the Endurance race Dunlop rear for the TT100 anyway. Ray shot round at hell of a pace in the race but the tyre would not have done another lap as it was in shreds with chunks ripped out of it. I still have the tyre as a keep sake.Roger

[bodgerbloke52]

CURED ITI fitted a Michelin 110/80 Road Pilot 2 on the front. Pressure 32psi. Within a few feet the bike felt pleasantly different.Wanging round the lanes I found handling was better than ever, light and 100% neutral. Took it up to 6500 in top going up my test hill. Coming down, I let it coast with no hands from 100 to 20 mph, rock steady all the way, just my knees kept it on the narrow but straight road.The radial is so successful that I am tempted to try the same on the rear. Any caveats Bob???As this tyre is different section to the 100/90 BT45 it replaced, there is the posability that the improvement could be related to that fact and not the construction. The general "feel" suggest it is the construction that is the issue.Anyroadup, thanks Bob for your sage advice, I am dead chuffed.Roger

[Dell Boy]

I have had a new narrow tyre, COUGAR 90/100 on the Commander for two weeks now.Hands off it shakes a small amount at 45 mph but otherwise is stableWith the 100/120 fitted it shook,hands off, from 30 to 65 m.p.h. quite severely.Conclusion; narrow,triangulated profile is the best option to limit the head shaking.Derek.

[bodgerbloke52]

DerekIntersting but my findings were opposite to yours.The BT45 Bridgestone got better the lower the pressure, it did not shake at all at 20 psi but of course otherwise handled like a herd of cattle. Not sure if shake cure was due to greater foot print or more flex in the wall. All radials have more flexible walls than bias ply and my Michelin choice was wider than OE at 110m instead of 100m.It is no exaggeration to say the Commanders handling is now transformed. It is rock steady at any speed hands off. So neutral it can be steered by knees only, bars are now simply somewhere to place ones hands just like a Feather Bed framed Norton as in my 61 Easy two.Roger

[wust588]

I can attest to Bob's riding and technical skill during my time at Norton, and rode with him quite a few times.I used to watch aghast (and of course with admiration) at some of his antics, and usually got the impression that he was hardly trying.Three of us were out on Interpols on one ride, somewhere in Devon, when we came up to a humped back bridge. My mate and I slowed right down, but not Bob, he accelerated of the bridge about thirty degrees from the vertical, and executed a perfect "landing" the other side.I used to have fun (and still do, thankfully) but I was always grateful to be just a humble speedo tester.John.