I ran a 23 front and 28 rear for a while. My bike did not explode. The bigger rear is actually nice. A bit more comfortable. I did feel faster with a 23 in the rear as compared to the 28 but I could have just been playing mind games with myself but a mind is a terrible thing to waste... really though the lower pressure could be the difference. The 28 was very stable and huged the pavement.