crank,chain ring alignment ?

[steveb]

      i have a felt sector cruiser and have changed the stock gearing. the std chainring had a reducer/spacer fitted. when fitting the new chainring it was already at 19mm so i am presuming i will need spacers ?  is there a way of measuring the correct amount of spacing or is it trial and error? any help or diagrams much appreciated. thanx steve.

[HEYWOOD BMX]

  Pretty much trial and error.Try adding/removing spacers on the drive side of the bb until you get a better alignment.You can also get spacers to go behind the cassette/freewheel cog if that needs bringing out a bit...

[steveb]

thankyou for that,is it worth measuring the amount of axel to make it exactly central or is it good enough by eye ?  last time i did all this it was a 1 piece solid crank with a spider so none of this faffing around !!!!!!!! seems a strange design to have a floating axel that is not centred ?? 

[HEYWOOD BMX]

 Never heard of measuring the axle is centred.A floating axle can be pretty useful as you get plenty of adjustability.No good having a centred spindle if the rear sprocket is a bit+/- I`m running a 3 pc on my bike and the alignment is perfect with no tight spots at all.