I have just adjusted my rear chain and conventional wisdom says that a board or a taught piece of string should be used to check wheel the alignment after the chain has been adjusted. However, from all that I have read on this subject it says that the wheels and tyres should be the same size to ensure accurate alignment. This is all well and good, but very few bikes have the same size tyre front and back. A10's having 325X19 on the front and 350X19 at the back. Anyway, I opted for using the taught string method for checking the alignment because the centre stand would have got in the way if I had used a solid straight edge. How much error if any would have be introduced due to the fact that tyres are slightly different in size? The string is taught with no discernible evidence of it running other than true and straight. The string touches both tyres on the tyre walls and there is no evidence of any bending of the string. The rear tyre looks as if it is central in the mudguard when viewed from the rear. I am just a little concerned though because the drive side adjuster is screwed out just a little bit more than the timing side adjuster. I have not tightened every thing up yet, because I thought it prudent to check weather the method I have used is satisfactory and reliable. For the record the string is stretched across the wheels about 6" from the ground.