Skip to main content
000000 000003 000006 000009 000012 000015 000018 000021 000024 000027 000030 000033 000036 000039 000042 000045 000048 000051 000054 000057 000060 000063 000066 000069 000072 000075 000078 000081 000084 000087 000090 000093 000096 000099 000102 000105 000108 000111 000114 000117 000120 000123 000126 000129 000132 000135 000138 000141 000144 000147 000150 000153 000156 000159 000162 000165 000168 000171 000174 000177 000180 000183 000186 000189 000192 000195 000198 000201 000204 000207 000210 000213 000216 000219 000222 000225 000228 000231 000234 000237 000240 000243 000246 000249 000252 000255 000258 000261 000264 000267 000270 000273 000276 000279 000282 000285 000288 000291 000294 000297 000300 000303 000306 000309 000312 000318 000321 000324 000327 000330 000333 000336 000339 000342 000345 000348 000351 000354 000357 000360 000363 000366 000369 000372 000375 000378 000381 000384 000387 000390 000393 000396 000399 000402 000405 000408 000411 000414 000417 000420 000423 000426 000429 000432 000435 000438 000441 000444 000447 000450 000453 000456 000459 000462 000465 000468 000471 000474 000477 000480 000483 000486 000489 000492 000495 000498 000501 000504 000507 000510 000513 000516 000519 000522 000525 000528 000531 000534 000537 000540 000543 000546 000549 000552 000555 000558 000561 000564 000567 000570 000573 000576 000579 000582 000585 000588 000591 000594 000597 000600 000603 000606 000609 000612 000615 000618 000621 000624 000627 000630 000633 000636 000639 000642 000645 000648 000651 000654 000657 000660 000663 000666 000669 000672 000675 000678 000681 000684 000687 000690 000693 000696 000699 000702 000705 000708 000711 000714 000717 000720 000723 000726 000729 000732 000735 000738 000741 000744 000747 000750 000753 000756 000759 000762 000765 000768 000771 000774 000777 000780 000783 000786 000789 000792 000795 000798 000801 000804 000807 000810 000813 000816 000819 000822 000825 000828 000831 000834 000837 000840 000843 000846 000849 000852 000855 000858 000861 000864 000867 000870 000873 000876 000879 000882
English French German Italian Spanish

Wheel alignment

If both wheels are correctly aligned why should the bike head off to the left (on a flat road) when I let go the bars (on a private road of course!)? I have to lean to the right to maintain a straight line. George
Permalink

Previously George Phillips wrote:
If both wheels are correctly aligned why should the bike head off to the left (on a flat road) when I let go the bars (on a private road of course!)? I have to lean to the right to maintain a straight line. George
Camber of the road? Most of my bikes have drifted left with no steering input. I suppose if the steering damper was screwed down, it would hold it straight?Kevin
Permalink

The rear wheel not being centralised in the swing arm can cause that, if you make sure the forks are straight (see above) and the rear wheel is central then you can run a line or laser (or angle iron!) along both wheels the line should just touch both edges of both wheels, allowing perhaps for a fatter tyre at the back. The other possibility is a bent frame. But how bad is the pulling, can you feel it when you riding along?

As said it might just be the camber, have you tried another road?

Permalink

I would say the real difficulty here is checking the rear wheel is central to the frame, not actually central to the swinging arm as the arm is not symmetrical as far as I remember. so where would you measure ?

If the wheel is offset to one side, you will still be able to use the straight edge method to get the wheels in line but it will still not be in line with the frame. The 'not straight ahead' of the handlebars would be difficult to see unless it was really bad.

So how do you check the wheel is central to the frame ? There are methods to do it but I think it involves complete strip down and slate beds !

Anyone got any suggestions ?

By the way, I have ALWAYS had to lean slightly to one side to keep the bike straight when hands off.

Tony

Permalink

Previously George Phillips wrote:

If both wheels are correctly aligned why should the bike head off to the left (on a flat road) when I let go the bars (on a private road of course!)? I have to lean to the right to maintain a straight line. George

The answer is simple...It is caused by the CASTER ANGLE on the head-stock of the front fork. If we assume the frame is straight and the head-stock is undamaged the weight of the bike pushing down on the front will want to turn and keep the front forks pointing EXACTLY forwards and dead in line with the frame. ....However, when the rear wheel is NOT dead centre caused by incorrect offset or a bent swinging arm you will STILL be able to line up the rear and front wheels by canting over the rear wheel to point towards the front wheel but to fully achieve this pseudo alignment it will necessitate that the front wheel and forks are turned slightly from the dead ahead position to line up with the rear wheel being aimed at it. When on the move however, the caster angle will always be trying to return to the dead ahead position and when you release the handlebars grip it will do so and result in the non alignment re-occurring and steering the bike away from the dead ahead course.

It is also easy to check the rear wheels alignment but you will have to remove the rear mudguard. When done, stand the bike absolutely vertical by checking with a spirit level across the rear frames top tubes. Then set a straight bar across these tubes from one side to the other above the centre of the tyre. You will then need to find the centre of this bar either by running a line or laser down the frames top tube or measure the centre if the frame is a duplex Featherbed type. Then drop a short plumb line down to meet the tyre or better still the wheel rim without tyre fitted. The difference from the wheels centre gives the correction measurement (if needed) noting that you will halve this distance to true the wheel. Doing this will ensure the bike tracks straight hands free, assuming the steering head is not twisted sideways from the vertical plane.....Les

Permalink

Surely if the objective is to track straight, by far the easiest method is to pull over and adjust one side forwards and backwards a bit and a time until it's what you want?

Permalink

Hi David..this is fine if you want a bike that "crabs" and I have seen many when following them on ride outs....

Wheels, forks and frames and their steering geometry MUST ALL have their centres coincide perfectly in a straight line and in the vertical plane. If any one of these aspects is out, the bike will handle with a bias and no mucking about with the rear wheels chain tension adjusters will fix it. Obviously some riders will accept this and the way the bike needs constant correction by handlebar pressure or by body weight to offset a left or right steering bias even if it does make them wonder what is wrong and even be moved to ask a question on this forum why.....Les

Permalink

My MK2A Commando used to drift hands off to the left, I accepted it as,

1. With hands on the handlebars I did not notice

2. It was seen as being a problem with the disc brake which was cured on the MK3 by swapping the fork legs so the disc was on the other side. ref NOC notes page 29.

I fitted a new rear tyre, checked and adjusted the rear to front tyre alignment and checked and adjusted the iso's gaps.

Then I thought I would check the result and one, two or all of these cured the drift and I can now take my hands off and it steers straight on a flat uncambered road. As I never tested between each adjustment I cannot tell which one or combination made the difference.

Now the question is why does my bike not drift to the left like it should ;)

And no its staying as it is.

Permalink

Not sure it was Read or Hailwood who complained that the 650 ss would not go in a straight line and needed weight put on a footrest. It was decided that there was a weight bias and so the wheels were moved accross off center to counter this.Are you riding like them??!!.

Permalink

Les is spot-on here. It is very easy to let the the steering turn slightly and then align the the rear wheel with that. If front and rear rims or tyres are not the same width then it's even easier to be misled.

Some people have an inherrent ability to sit on any mis-aligned bicycle, make corrections automatically and effectively be happy with the handling of a camel. I rather envy them actually.

Permalink

Apols for the long silence guys but I've been driving round the south of England for the last day or two. Thanks for all your inputs. The slight drift to the left is not noticeable when riding normally, only when "hands off" (and on a flat road as I noted first off). I've got no intention of stripping it all down to get to the bottom of it but am very interested in the reasons given. Another project for next winter!
Permalink

Why would anyone want to ride "Hands Off" in the first place? For a start, it is a traffic offence, just as eating, while driving a car.

Permalink

This is an interesting subject George so thanks for airing it. I once owned a bought new Commando Roadster that pulled fairly strongly to the left if the grip on the bar was released and I was always baffled as to why it did this knowing that I had the rear wheel dead in line with the front one.. It's only in recent years the penny dropped when a Matchless G80 short stroke I own seems to have something very much out of line and even dishing the wheel over hasn't corrected it so I've given the subject quite some thought. In this case though I reckon the swinging arm is bent and hopefully it is rather than the frame.

By the way, the info I gave as regards correcting the wheel offset is wrong....I said halve the error distance of the centre measurement on the rim. Indeed, if you are dropping the plumb line to a KNOWN dead centre on the rim or tyre this measured difference is the TOTAL measurement that the wheel needs to be pulled across (assuming the frame and swing arm is all OK). However, If you are comparing rim EDGES to each other from the centre line the difference is in this case DOES have to be halved for your new correction of the rim position....Les

PS...You might want to correct the rear rim the following way. If you can get someone to hold the front wheel absolutely dead straight ahead (I know this is not easy but you can lock it there by using the damper knob if fitted) then using your straight edge adjust the rear wheel so that the edge is PARALLEL to the front wheel on both sides. You will probably notice that one side is perhaps bigger than the other which is the error on the rear wheels alignment as regards the centre line of the frame. So as said, halve this distance when correcting the rear rim. I would say if the bike pulls to the left the rear wheel for whatever reason is over to the left...REASON: If you have aligned your wheels perfectly to the the front you will be riding with the bar slightly to the right to get the front wheel to line up with the rear. As explained above, when you release the bars the wheel will return to the straight ahead position due to its caster action and this will now be turned to the left in relation to the previous alignment thus steering the bike to the left. Bare in mind these correction movements are tiny but enough to exert a small bias on where the bike wants to head for....

The problem with this method is getting the front wheel in an absolute front ahead position in relation to the frame which is why I favour the previous method where the rear mudguard has to be removed to get an accurate centre line through the bike from the headstock....Worth a try though I reckon....Les

PPS: Please note everything I have suggested is assuming the FRONT wheel IS DEAD CENTRE....well it is so easy to get this right no-one should have any excuse not to have it that way...IE: same gap either side of the rim to the forks sliders or tubes....

Permalink

You've certainly given this some thought, Les. Removing the rear mudguard is too much trouble for the size of the problem but your second option is do-able. To answer John's valid query - because it's the only way to find out of the bike has a steering bias. Cheers - George
Permalink

Previously Tony Ripley wrote:

I would say the real difficulty here is checking the rear wheel is central to the frame, not actually central to the swinging arm as the arm is not symmetrical as far as I remember. so where would you measure ?

If the wheel is offset to one side, you will still be able to use the straight edge method to get the wheels in line but it will still not be in line with the frame. The 'not straight ahead' of the handlebars would be difficult to see unless it was really bad.

So how do you check the wheel is central to the frame ? There are methods to do it but I think it involves complete strip down and slate beds !

Anyone got any suggestions ?

By the way, I have ALWAYS had to lean slightly to one side to keep the bike straight when hands off.

Tony

Hello Tony, I used a 3 plumb line system when I rebuilt my dommie, briefly : ensure the bike is vertical, I used a spirit level (good quality), then I fixed a slack piece of cord logditudinally above the bike front back, from this slack line I used 3 shorter plumb lines hanging down, using a bit of ingenuity ensur the lines are centred on the centre of the front wheel and the middle plumb on the centre of the headstock,when it has all settled down and stopped moving, the rear most plumb will give you the what should be the centre of the rear wheel, measure offset if it exists, an correct the discrepancy on the spokes,. The three plumbs will always hang in line,basic science, I used a longish spirit level from a mate who is a builder, and placed tha vertically on the side of the front wheel/tyre,time consuming I suppose but works well, Jim hill

Permalink

Picking up on Jim's final sentence, maybe it's a design feature - what we might call "character"! George
Permalink

George, you haven't told us what model of Norton we are dealing with here. Something to think about and try and establish is, despite the wheels being in line where you check them, probably about 4 inches above the floor, the wheels may not be lined up in the vertical plane. I have seen this on a Commando where the frame had been parallelogramed (made up word) The headstock is very hard to bend on a Commando but the two frame loops under the engine and at the rear Iso mounts can easily be bent to one side. This leads to the rear wheel not being vertical compared with the front one. This is very difficult to measure because the error can be masked by turning the handlebars so the front wheel appears to line up with the rear. If your front Iso bolt does not slip straight through the Iso sleeve without twisting the sleeve to line up with the frame lugs then the frame is bent. If we are not talking about a Commando here then you could look for a similar misalignment at the swinging arm of other types of frame. e.g.. swinging arm twisted.

Permalink

Quite right, David. When I posted the query I glibly thought it was a general wheel alignment problem. It's a '55 ES2 but your comment is valid re the vertical alignment of the wheels. I'll try and check that. Cheers, George
Permalink

George. You did not tell us if this problem appeared only after you re-set the wheel alignment, removed and replaced a wheel, or after you rebuilt the forks, etc, or has it always been like it? Ian

Permalink

Ian - the problem has always been there since I bought the bike. Briefly letting go the bars is my way of checking alignment. Despite aligning the wheels it always drifts left unless I lean to the right. My thinking is that for the back to drift left, the rear wheel must be pointing to the right (at the front of the wheel), but it won't go any further left without hitting the inside f the mudguard where it steps out to miss the chain-case so there's little I can do about it. Not a major prob - just interesting.
Permalink

George. Yes, I do the same. My Featherbed, despite what Mike the Bike (or Phil Reed!) said about having to weight up one footrest for it to steer straight, does steer straight without doing that. Often bikes are restored without a thought to checking alignment, and, given the age of these bikes, and who know how many times they have been down the road in all those years, it is not surprising that something may be a little out of line.

Having said that, I have had machines which display this trait, only for it to be cured by a change of tyres.

For wheel alignment, I have 2 long box section dural tubes, and I clamp them either side of the rear wheel with bungee cords for and aft of the wheel, as high up the wheel as centre stands etc will allow. I then, having checked them for parallel, measure the gap between them and the front tyre, at two points, front and back of the tyre, which there should be, given that it is narrower than the rear tyre. I then simply wind the rear wheel to one side or the other until the gaps are equal. As has been previously stated, that will not compensate for a bent frame, twisted swinging arm or out of line headstock, of course.

Or, keep both hands on the bars! Remember what happened the last time you took a hand off.... ouch!Cry

Permalink

Remember? How can I forget - the twinges are still there! Your alignment method is similar to mine except that I use a single length of angle iron.
Permalink

I bet they are!!

The benefit of two is that you can instantly see when the front wheel is central between the box sections. When you check one side then the other with a single bar, the front wheel can move a little whilst changing sides. Also, being light, the ali ones will remain horizontal when just held by bungee cords, leaving your hands free to measure and adjust. Good old Trago Mills!

Permalink

I think the issue is to do with gyroscopic precession of the front wheel. This takes place at 90 degrees to where the input is applied. something is applying a force to the front wheel trying to turn it to the right in your case. Precession takes place at 90 degrees in the opposite direction pushing the bike over to the left. Look carefully at your headstock bearings and then the vertical wheel alignment if you are sure both wheels are correctly aligned in the horizontal axis

 

Norton Owners Club Website by White-Hot Design

Privacy Policy