Norvil 850 Roadster - high speed weave

Check that the wheels are accurately in line and also that the final drive chain has no tight spots in it. If you wear a loose jacket when riding and it starts to wag, that will be transfered to the bars. ( in helicopter flight its called " PIO or pilot induced osillation") If that's the case, relax your grip on one bar and see if it still happens. try to get your weight forward (full tank). The combination of wheel sizes should be ok but IMO the Commando benefits from a rear tyre that has a groove in the middle eg TT100, Road Runner. Check the isolastics are correctly adjusted and obviously the swinging arm has no play. Finally, borrow a 19inch rear wheel and try that.

If the tyres are ten years old, ditch them for new ones. tyres make a huge difference to how the bike runs. Firstly, you need to do this anyway and it's the simplest and quickest way to put you on the right path. As david E mentions, go over your wheel alignment. Then check your iso adjustments etc. Handlebar width shouldn't be a problem. I've had my Commando for over thirty years and in that time I've had all sorts of combinations of handlebars, wheels, tyres and forks. So long as everything is straight and in line you should be right, check all that. Tyres are really the big one if all else is good. Tyre choice is a personal thing, I've had Avon Road runners on a few bikes including the Commando and don't like them at all. For my riding and the way I do things I'm perfectly happy with Dunlop K81's. I had a '69 Roadster which was much better with the 3.60 front tyre, My '72 Combat has 4.10 19 on the front and a 4.10 18 on the rear. It doesn't weave, but becomes a bit light on at around 90mph, but i also have a handlebar mounted fairing and reasonably large panniers. Bottom line is, your bike should and will go better. Get a new pair of tyres. 32psi front, 36 - 42 psi in the rear. I've found that anything less than 32psi in the front makes the front heavey and lazy. What do you run for tyre pressures?

Bob

Back again, you say you have flanged rims. Check and make sure the front rim is absolutely in the middle between the front forks. It should have the same spacing between fork slider and rim on both sides. Sometimes when rims are relaced into the front of Commandos this is completely botched up and will be a big cause of bad handling if it is the case. The rear rim has a specific offset as well. If one or both of the rims have incorrect offset then you have a problem. If the front rim is on centre and the rear rim does not have the correct offset and is not on the centreline of the bike string lining the wheel alignement from front to back will not line the wheels up, but will make the rear wheel point slightly to one side. This means as you ride along the rear will be steering the bike across one way and then the front castor will try and correct, then it happens again and becomes a weave. This all needs careful measurement and you may need help from someone who knows with this one. Always a possability with re-laced wheels.

Bob

Hi Dave,

I had a slight wobble at speed on my 1972 750 Interstate.

Like others havesaid wheel alignment is very important.

Ive fitted Avon Roadrider 100/90tyres front & rear which has improved stability & eliminated wobbling over ruts & white lines. It also goes round corners better than it did with TT100's.

Ive fitted vernier iso's set fairly tightly & a Dave Taylor head steady which both added to stability.

One of my branch members had a twisted gearboxcradle which made handling frightening to watch when I followed him. Now its been straightend its a lot better.

Ive also been told to fit a hydraulic dampener to the forks to aid handling but thats my winter project.

It could have been dropped in the past & somthing may be bent, but when sorted you should be able to do 100mph without wobbling.

cheers Don

Previously wrote:

Just bought my first Commando, an eight year old Norvil 850. Very impressed with how smooth and comfortable it is but have found that at 60mph-plus it is easily provoked into rapid weaving that's hard to stop!

NOt sure what pertinent info to provide, but based on reading the technical section, the following may help.

The bars are USA type i.e. 5" high and 31" wide. However I found them to be too wide for me and have shortened each end by 45mm. The weave was there before and after.

The rims are flanged alloy: the front is marked 1.85 x 19 and the rear 2.15 x 18.

The front tyre is Roadrunner AM20 100/90 x 19 and the rear is AM21 110/90 x 18. The front tyre is eight years old and the bike has been idle for the lastfour years, so maybe tyres are the problem? Would appreciate your thoughts.

Hi David, another simple check you could have done is to take the bike to a garage and have the rear wheel checked for balance. I had a weave problem on a Yamahe R6 race bike and we tried all sorts to solve the problem and it turned out to be the rear wheel out of balance, we had it balanced up up and it solved the problem.

All the best Kev...

Don's comment about a twisted cradle is a definite contributor. Mine was out by 060" at the front compared to the rear with the cradle and wheel pointing left by at least that multiplied by the distance between rear mount and rear axle centre. Engine offset is supposed to be 3/16" to the left. Mine was 0.25" rear and 0.31" front. I had to machine the rh front ISO tube by 060" and add equivalent spacer to the lh. It completely stopped my weave at any speed. Tyres and condition, pressures and wheel alignment of course play a major part. IME the AM20/AM21 combo were poor for tramlining. I ran BT45's for a couple of years and these were the best I ever experienced on a Commando. In an attempt to keep Jap parts off the bike I went back to Avons with AM26. They're OK but nota patch on the Bridgestones, especially in the wet.

Previously wrote:

Just bought my first Commando, an eight year old Norvil 850. Very impressed with how smooth and comfortable it is but have found that at 60mph-plus it is easily provoked into rapid weaving that's hard to stop!

NOt sure what pertinent info to provide, but based on reading the technical section, the following may help.

The bars are USA type i.e. 5" high and 31" wide. However I found them to be too wide for me and have shortened each end by 45mm. The weave was there before and after.

The rims are flanged alloy: the front is marked 1.85 x 19 and the rear 2.15 x 18.

The front tyre is Roadrunner AM20 100/90 x 19 and the rear is AM21 110/90 x 18. The front tyre is eight years old and the bike has been idle for the lastfour years, so maybe tyres are the problem? Would appreciate your thoughts.

Hello - there's one answer, ditch the frame and get a Featherbed frame Commando frames were a lash up from day one that why I will not buy a Commando! yours Anna J Dixon

That's a really helpfull suggestion Anna. If you want to exploit the power of a larger Norton engine, the Commando frame allows this without your fillings falling out. Peter Williams didn't seem to have much of a problem with them in the early seventies. The Atlas is particularly unpleasant due to vibration.

With all due respect, this type of comment is not at all helpful on a club website. If you have such a problem with Commandos then I'd suggest ignoring this section of the forum entirely.

The Featherbed versus Commando debate was surely done to death in 'Roadholder' at the time.

Previously wrote:

hello theres one answer dich the frame and get a featherbed frame Commando frames where a lash up from day one that why I will not Buy a Commando ? your Anna J Dixon

These replies don't seem to be in chronological order but I think we get the drift.

Dave Evans

Dave,

It may seem a stupid suggestion however sometimes when new tires are fitted they dont pop out all way round the rim, this can lead to quite a wobble. also the rim lock somtimes holds the tire in more at its area and gives an out of round condition. putting the bike on the center stand and spinning the wheel with a fixed guage on theswingarm or framewill show either of these conditions right off.

My experience concurs with Norman White's avice that the commando is very sensetive to tyre choice. He recommends TT100s on original 19" rims or for the best handling 18" rims WM2 front and WM3 rear with bridgestone BT45s.

I tried Avons a long time ago and didn't like them and went back to TT100s but still experienced weave on fast sweeping bends. I them fitted one of Normans isolastic head steadies and that sorted the problem.

He is critical of the 19" front and 18" rear combination.

Hi David

Another vote for tyres here. I've had my 850 for 13 years, and whenever the handling has gone off it's been a tyre issue. I always change bike tyres when I feelthe profile has gone off. On the Commando this is always well before the tyre is worn to 2mm, which is as far as I like to take them anyway.

Once the back tyre squares off significantly, I get the famous Commando weave. This only happens at about 80 and above though.Last year the front started to shake its head a bitat 20 to 40mph (another well documented Commando trait). The handling was back to rock solid with new tyres.

I've always run AM20/21's and been very happy with them. I put Roadriders on this time as everybody was telling me they're much better. I ran them at the pressures recommended by a technical guy I spoke to at Avon - 28/31. I hated them, and had a few slides in the wet as well. I'm now running them at around 26/28 and they've behaved much better. I asked a few people runningRoadriders if they've had any bother, and it seems it's just me!

Cheers

Jeff

I'd like to add that I have run two different Commando's with 18" rear rims, one of the bikes weaved badly when cornering at 70mph and above, the other didnât. The bike that weaved is Interstate 750 with standard seat/footrest/handle bars setup. The weaving stopped when I refitting the 19â wheel rim and tyre. The bike that doesnât weave is in cafÃ?-race style (clip-ons/rear-sets/single seat).

I have always put the weave down to weight distribution, but I am convinced for best handling the original rim and tyre size is the best setup. I choose to use Avon roadrunner universals on my Interstate, on my own its great,BUT two-up and fully loaded it suffers a sort of frame flexing weaveONLY when I hit a bump while cornering at 70 and above. This goes away if the handle bars are held very lightly (you have to stay calm and not panic) the bike always sorts itself out. Too much weight on rear of bike is the cause.

If my Commando ever starts to feel like it wants to weave itâs usually because the rear tyre pressure is on the low side or the rear tyre is nearly worn out. By increasing the tyre pressureI can usea half worntyre until it's down to its limit without any fear of weaving. This is only my unprofessional opinion and NOT a recommendation.

PS: Does anyone want to swop a 18" Alloy rimcush drive rear wheel for an original 19" Dunlop rim rear wheel(as fitted to 1972 750 Commando)?

Previously wrote:

Previously wrote:

I'd like to add that I have run two different Commando's with 18" rear rims, one of the bikes weaved badly when cornering at 70mph and above, the other didnât. The bike that weaved is Interstate 750 with standard seat/footrest/handle bars setup. The weaving stopped when I refitting the 19â wheel rim and tyre. The bike that doesnât weave is in cafÃ?-race style (clip-ons/rear-sets/single seat).

I have always put the weave down to weight distribution, but I am convinced for best handling the original rim and tyre size is the best setup. I choose to use Avon roadrunner universals on my Interstate, on my own its great,BUT two-up and fully loaded it suffers a sort of frame flexing weaveONLY when I hit a bump while cornering at 70 and above. This goes away if the handle bars are held very lightly (you have to stay calm and not panic) the bike always sorts itself out. Too much weight on rear of bike is the cause.

If my Commando ever starts to feel like it wants to weave itâs usually because the rear tyre pressure is on the low side or the rear tyre is nearly worn out. By increasing the tyre pressureI can usea half worntyre until it's down to its limit without any fear of weaving. This is only my unprofessional opinion and NOT a recommendation.

PS: Does anyone want to swop a 18" Alloy rimcush drive rear wheel for an original 19" Dunlop rim rear wheel(as fitted to 1972 750 Commando)?

Alan, yes I can relate to your experience. There does seem to be a lightness to the front end that quickly turns into a wobble/weave when I hit bumps on the turn. This makes it an "exciting" ride and I am learning to stay calm and get more weight forward! Therefore it seems the high bars and upright riding position also don't help. I'm not up for changing rim sizes but as previously posted, am in the process of getting new tyres.

I have an 18" rear on my '72 Interstate and I'll go along with all of the above. Weight distribution is a big thing with the Commando. I'm sure people misinterpret frame flex for iso problems. When you look at a stripped Commando frame there is not much of it, very light. I was standing beside a mate's son's Honda race replica wizz bang RR wotzit, looking at the swing arm. This giant alloy single sided monstrosirty probably had the weight of a Commando frame by itself. No wonder modern bikes handle with the metalwork that goes into making their frames and swing arms. The old Norton frames, featherbed included, are not a scrap on modern constructions.

Back to weight distribution, it's amazing the difference in an Interstate when you swap tank, seat etc for Roadster items. Not only do you move your weight forward, when getting into the twisties, moving right up on the little tank also makes a difference and suddenly the bike becomes fun again.

Load the interstate up with your fat mate on the pillion seat, carton of grog and a few other camping essentials in the panniers and the same bike becomes almost unrideable. When I had the '69 Roadster at the same time as I had the Interstate, I rode the Roadster most of the time because it was more fun. As I outlined in an earlier post, the front tyre on the Roadster was a 3.60 X 19 and was much sharper in the front end compared to the Interstate with the standard 4.10 X 19. You just need to work out which way you want to go. At the moment I stick with the interstate tractor, because I can load up and do overnight runs. Mind you, the trouble and strife won't get on the thing, she's been spoilt by a much bigger and much more comfortable cruiser pillion seat. Thats not bad either.....

Previously wrote:

That's a really helpfull suggestion Anna. If you want to exploit the power of a larger Norton engine, the Commando frame allows this without your fillings falling out. Peter Williams didn't seem to have much of a problem with them in the early seventies. The Atlas is particularly unpleasant due to vibration.

the vibration only cut in above 4000 rpm becuse of the balance facter , commandos vibrate as well ? the BRM Norton 4 from 1950 would have been a better bet ? but Norton hadNo cash too develop it ?