Steering pull to one side

There have been previous posts referring to this phenomenon, which can usually be fixed with wheel alignment, iso adjustments, symetrical handlebar furniture etc. I wondered if anyone had experienced more neutral steering when twin front discs are fitted rather than the lob-sided single disc arrangement.
Consider when the bike has the front wheel raised on it's centre stand. If the disc is right mounted, the handlebars will always want to bias over to the right due to the weight of the braking system. Conversely for left disc. Thus there must be a continual bias all the time whilst we are riding.
When riding we steer the bike left by pushing the left bar forward. In other words, to steer left we turn bars right and vice versa. Early Commandos with right discs tend to turn bars to right due to weight of disc and caliper. This surely must translate itself into a tendency to pull slightly to the left when riding.
Has anyone with a left mounted disc brake noticed a bias to the right?
Has anyone with a right mounted disc brake noticed a bias to the left?
Has anyone with a twin disc system experienced a more neutral steer?

I have always had a pull to the left on a std 74 MK2A with disc on right, that is until last year when the circlip let go in the rear brake drum and the bearing went walkies inside. Made for some interesting sounds.

I fitted a new circlip but also while I was in there put new sealed bearings in the drum and the rear wheel, plus fitted a new Roadrider rear tyre 100/90 19. Bike now tracks true hands off. Don't know if its the tyre or the new bearings that fixed the problem.

I have always had this problem with my '73 850 and wondered why? My single front disk is on right side and if riding/coasting with one hand (left hand) I find I must push outwards a bit to stay straight. In other words if I went "no hands" it would quickly veer to the left. I have it on my todo to explore how to fix.

Same. 72, Disc right. Drifts left. Think they all do this. If you view mine from the rear, the rear wheel isn't centered either, in the frame. So this may be designed in, or rather, due to some other aspect of the frame design/iso mountings etc, the drift happens. Read some website about someone who fixed up the "World's straightest...or best handling Commando" or some such title, and he said he fixed it, but hardly think going to all that effort is worth the result. Might not even make things better, but rather worse. Interested though in the results of your poll. I bet it's the norm.

Look on the positive side though...

Who waves to all the girls with their left hand?

:wink:

It would be interesting to hear from owners of left mounted discs to see if they wander to the right slightly.
As a slight aside it would also be interesting to learn what position most of us finally fix the rear wheel in the swinging arm after setting the tracking. Mine has to be set with rear wheel facing to the left, ie. spindle nut further forward on right side than left side.
Hewho - I seem to have perfected the left-hand crumpet wave, so not all bad news.

Crumpet Wave? Didn't they used to do the foot wave in France...or do they still? Here most use the left hand cause they don't have a cruise control on the throttle. Point taken though...matters not, as a wave is always better than a finger...or?

:wink:

I guess mine is a bit strange because it has no real pull to one side or the other but it does have a wobble when slowing down that starts about 30 or so and then goes away at 20? The first time I took my hands off the bars and it did this was a real treat. Mine is a MK III with the disc on the right. All other speeds are very solid and seems to handle very predictably, I guess they all have their own personality. Chuck.

Hortons Norton said:

I guess mine is a bit strange because it has no real pull to one side or the other but it does have a wobble when slowing down that starts about 30 or so and then goes away at 20? The first time I took my hands off the bars and it did this was a real treat. Mine is a MK III with the disc on the right. All other speeds are very solid and seems to handle very predictably, I guess they all have their own personality. Chuck.

Click to expand...

That's the standard handlebar flutter. As you say, quite a surprise the first time. I think that the oscillation is vibration frequency induced. I found that the Taylor headsteady helps.

My 2 cents here.
I don't think it has to do with the brake weight, but an alignment issue somewhere.
My logic stems from my Vespa, the front end clonks to one side with the wheel in the air because of the weight of single sided swing arm and shock - but it tracks straight-as-a-dime when riding,

Fastback-Phil

fastback,
Right you are. My Vespa is like yours, ( T4, 150cc, 1961), so heavy to one side that taking it off the center stand is a "watch out"... but the stinker tracks straight as an arrow while driving. Think you have a point.

Have you checked how Vespa have set the wheel alignment? If you ever get a free moment, wrap a long rope or string around the rear tyre and pull the two free ends tight towards the front of the bike (crouching in front of the front wheel - usual procedure)
Just wondering. It would also be interesting to find out how much torque is needed to resist the steering from pulling over to the side. On the lightweight Vespa steering it may only need a few foot pounds to counterbalance. I must try this on the Norton, too.
A small correction would have negligible effect on steering wander, in which case the Commando pull is probably more due to frame variances and inaccuracies.

It's 01:28 in the morning at the moment, so I will try to get to it in a few hours when I get under the son's car again and put the rest of the brake lines and the tank back in. I'm lucky I have a car lift where you can raise the car up and still put all the bikes under it in the garage...but working on the car requires pulling all the bikes out in the courtyard, so will have to move the Vespa anyway...remind me in the morning...and I will check... :wink:

Vespa alignment...
Two wheels on the trusty Vespa are in alignment and seem to be centered in the frame, so there seems to be no attempt by Piaggio to adjust the alignment to compensate for what must be a good 30/40 pounds difference between the weights on each side of the center of the frame. That would seem to blow away any suggestion that a tiny bit of weight difference on one side of the commando would cause a drift to one side or the other. If 30 or more pounds doesn't pull a scooter into a drift to the side...how can a measly 6 or 8 pounds do it to a Commando? My bet is you are correct and it is a fault in the frame design...or simply the front and back wheels being not in a straight line with each other...

Now it is time for the gurus to explain why I am wrong... :wink:

wow vespa talk on a norton forum

whats wrong with this picture.................. :roll:

If the bike is set up properly, it should track true, regardless of bike or tire manufacture.
On the Norton, the wheel is laced on a bias to counteract the weight of the disc. While it is true that the forks on a single disc bike will tend to flop over to the caliper side when on the centerstand, the weight of the caliper is minimal compared to the gyroscopic forces of a rotating wheel.
Drift to one side or the other is usually a function of tracking (how well the front and rear wheels are aligned with each other), tire wear, and 'crown' of the roadway.

My '74 MKII also suffered from low speed headshake and the infamous Commando "Left Lean". I'm the original owner, and it's done these things for as long as I can remember. Both conditions are now gone.

I replaced the front wheel with an eBay hub/rim and had it laced by Buchanans. There's about 1/8" difference in the offset between the OEM rim and my "new" one. The tire is now centered perfectly between the forks (it wasn't before). Also replaced the front tire with a new Avon AM21. Low speed headshake went away.

The left lean is a function of wheel alignment. You can't align the rear wheel with the frame, you need to align it with the front wheel. When I learned how to do that the left lean almost completely disappeared.

On my RH disc it always pulled left. Winter '06 I did a half hearted alignment according to the phantom oiler process and found front ISO offset at .31" and rear at .25". So the rear was pointing left. After I trimmed the front and added a .06" washer to the left it now tracks straight with both wheels inline. On an aside I just fitted my version of the Taglieri/Taylor head steady last weekend. Didn't notice any tracking change but it stopped that uncomfortable low speed flopping into turns feeling and seemingly no extra vibes.