Wheel alignment

[oval57]

On a recent ride a fellow club member came up to me and said that my wheels weren’t tracking the same. I have since ran a straight edge along the bike and found the following. With the straight edge on the left side of the bike it touches both side walls on the rear wheel and the same on the front, when I put it on the right side against the rear wheel side walls there is about a 20mm gap to the front side walls.the wheels are obviously tracking in the same direction but the centre line of the front wheel is off centre. I checked the  distance from the rim to the centre of the plunger on the rear and this measurement is with in 5 mm with the wider side being on the left, the front wheel is sitting centre to the forks , I wouldn’t imagine that this would be right ... the bike is a 1951 A10 Any thoughts  on centralising the wheel .. cheers

[Jules]

2 things come to mind Oval, firstly I'm not familiar with plunger frames but I think that the wheels are the same widths as the s/a models which means the front is smaller than the rear?? if so, then your straight edge shouldn't actually touch the front wheel on either side but should have equal clearances (ie be parallel)…..
Secondly, again unfamiliar with plungers, so could the frame be bent, or maybe more likely, the rear wheel is not sitting "square" in the rear fork ie slightly angled due to a different spindle location each side? I'm assuming (as you are I think) that plungers didn't have an offset at all, but maybe another member can answer that.....

[Rex]

I'm a little unsure what you mean there.
The front wheel sits central to the fork legs, and the  rear rim sits central to the rear frame spine. The rear frame lower members aren't symmetrical, so the distance from rim to those wouldn't be correct.
It points to your rear wheel either having wrong/missing spacers etc or the off-set being wrong on the wheel.

[Swarfcut]

  Bit of a mystery here, with several possible causes, but firstly I would make sure it is not a trick of a  twisted rear mudguard.   

  The front and rear tyress have different profiles, so the straight edge should not touch either side of the front tyre as Jules correctly states.

 Each wheel should be located centrally, on the imaginary datum line passing along the central spine and steering head, in other words, centrally between the forks and rear chainstays.  Moving the rims sideways is a case of adjusting the offset of the rim to the hub centre by spoke adjustment.

  The hub position sideways is governed by the fitment of the correct bearings, hub spacers and internal sleeves.

  If the front wheel is considered to be OK, then the rear wheel must be slightly off the vertical when viewed from the rear. As a first check I would try removing the rear wheel, and reassemble the spindle and see that it lies horizontally. If it is not level the fault is in the plunger assemblies, or the position of the plunger mountings themselves, due to a misalignment in the frame.

  It may be that the plungers have mis matched springs or one side is binding.  Whatever you find, the easiest fix will probably be making custom spacers to return things to normal.

 Somewhere on the forum are details of frame dimensions, which will help you determine if you have a major mis alignment. The upper chainstays should be symetrical on each side of the seat lug at the top of the vertical frame tube.  The through stud here passes within a sleeve which is not listed as a spare part. The sleeve ensures correct alignment between the front and rear sections of the frame. 

  Hope this is some help.

  Swarfy.



  Rex, I have always thought the lower tubes were symetrical, well on my frames they  always looked that way.

  Swarfy

[Rex]

Maybe mine have been pushed in or pulled out through side-car pulling or whatever, but the chain-side tube is further in than the off-side one. Not a huge amount, but enough to nause up the wheel off-set if someone was to rely on those dimensions. Always the frame spine for me though.

[Swarfcut]

 Rex... A good point there.  Like you I would always take measurements from the most central and stable frame component.

      Considering the original post, I have it in my mind that the rear wheel is running in line with the front, but the tyre footprint is offset to one side, either due to mis alignment of the bearings, spacers, hub assembly, or that the rear spindle is not horizontal.  There is no mention of being out of track which would be a simple rear wheel fore and aft spindle adjustment.

   Swarfy.

[duTch]

 Rex, sorry to disappoint you but I'm with Swarfo re the frame- the rear frame should be symmetrical,as per attachment. In my rebuild, I had trouble aligning my rear wheel, but the frame was bent as....at both ends, had it professionally straightened. If left out of shape you'll be running the chain out of alignment on the sprockets....
  oval- provided your frame is straight and all the correct spacers are in there and the rim offset is right (can't remember the magic figure, but ~5/16" comes to mind- I have WM3 rim so had to re-calculate ), maybe as suggested your rear axle may be slightly out of parallel....doesn't take much.

 I did some measuring a while ago, and calculate the rear chaincase cover screw and rear outer G-box cover screw are *very close*  to the same distance from the mainshaft (but on a different horizontal plane by about an inch or so from memory),  so can be used for a quick check to rear axle- should be same distance (I think about ~440mm + depending on adjustment **edited).

 **edited; NB- ^Tip^  only useful for Plunger models

 I'm sure you're aware that the axle lug slots are different lengths, hey ?.....