different tyre sizes

[TracyPrier]

Hi all

 

I'm in the process of getting new shoes on the RT and have a question:

 

Are there any reasons to either get or not get slightly different size tyres?

 

The standard sizes for the RT are 120/70 17 & 160/60 18

 

For example, what about a 125/70 17 on the front? reasons for or against?

 

I'm asking because, for example I can get a great deal on this size.

 

Thanks

Tracy