Wheel alignment

George, how do you align your wheels i run a string around to check mine.

Barry

Are the forks twisted?

Try this https://m.youtube.com/watch?v=vSunBRB6-r8

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

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?

How'd you get on George?

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

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

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?

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

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.

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??!!.

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.

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.

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....

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

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.

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

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!

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!

.....Or make one of these.............

http://www.realclassic.co.uk/techfiles/wheelalignment.html

Designed this many years ago but still think its better than any conventional straight edge device....

Les

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