Wheel Alignment

Previously wrote:

I've been riding my Norvil Commando for years(20K miles) during which timewith various improvements tothe front endI have achievedsuccessive improvements in handling and pointability to my ever increasing enjoyment.The bike has just passed its MOT for this year.

I had the new exprience this weekend of following it (I lent it to my daughter's BF and followed him on my rotary). To my consternation I could see an obvious wheel mis-allingment. On checking back home I discovered the centre lines of the front and back wheels to be about 17.5mm offset. Both wheels are parallelwith each otherand the frame (I think) but just offset from each other. When riding I am not conscious of this. The rear tyre appears to be roughly symetrical in the swinging arm but offset to the left compared to the frame.

So questions:-

1 - is this normal?

2 - in order to investigate further what is the datum to work from? How should the hub be centred (I think the chain run is in line)?

3 - could this be rectified by lacing the rear rim a little to the right?

4 - what else should I check?

Yes,it is so conceived by origin.

Hi Phil

You say you have checked the wheels are parallel,did you check this by the following method. You need a straight edge say a 6 ft piece of angle ironand 2 bricks. With the bike on its centre stand push the straight edge againsttheside of the back tyre using the bricks at either endto keep it high enough off the deck. Making sure you don't move the straight edge move to the front of the bike and adjust the steering so theside of the straight edgeis parallel with the edge of the front tyre. Carefully without moving the front wheel change the straight edge to the other side of the back wheel,the front tyre should betouching the side of thestraight edgethe sameas itwas on the other side if not adjustthe back wheelusing the chain adjuster until the wheels are parallel. To make up the17.5mm will only mean moving the adjuster by a few flats and could be an easy fix.

Peter

Thank you for the reference to the earlier submission, whoever provided it? 

I am satisfied I have measured the alignment correctly by using a pair of lengths of 40mm aluminium square section tube, clamped either side of the rear wheel and supported on blocks at front and rear wheels. The important point in my view is that the each beam needs to have a packer between it and the rear wheel. What you need at the front wheel is to be able to measure the gap between beam and wheel. If you work without a packer, you could have no gap to measure at the front wheel and wouldn't know whether it was just perfect alignment or the beam was bending a couple of mm over the 5ft length. So you create a known gap and then measure at both sides. 

So I'm fairly confident of my 7mm offset toward the drive side. What I have discovered however is what may well be the smoking gun. Although I had forgotten the event completely I discovered in my service record for the bike that I did once (30 years ago) snap a spoke in the rear wheel. The wheel went off to a reputable wheel builder and, when I collected it I vaguely recall that he remarked that he had trouble with the rim offset, claiming that the drive side spokes were almost 90 degrees from the hub axis! He had apparently restrung the wheel, but with more of an inclination to the drive side spokes which in his view was how it should be? Having read the debates in the forum I am prepared to believe that this was probably where the problem emerged?