This could be a great point of discussion. :). I also have raisers on my GSA. Find it more comfortable to stand long distances. Only thing it could have an effect on is balance. Weight is distributed different. More backwards than forward. Or is this splitting hairs ? Don't know. Previous...
What would the reason be when the rear tyre is changed from the following sizes :
Standard size 150/70 r 17 to 140/80 r 17. The two differences being the narrower tyre circumference is longer or the tyre bigger.
What is the advantage OR dis-atvantage doing this ?